COMFORT and DESIGN Principles and Good Practice

COMFORTand DESIGN

Principles and Good Practice

2830_C00.fm Page ii Tuesday, November 2, 2004 8:58 AM

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Peter Vink

COMFORTand DESIGN

Principles and Good Practice

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p. cm.Includes bibliographical references and index.ISBN 0-8493-2830-6 (alk. paper)1. Human engineering. I. Vink, P. II. Title.

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Foreword

We are accustomed to the idea that our technology, our work practices, and our dailylives are changing at a sometimes frightening pace. One of the most ancient, com-monplace, but important indicators of our compatibility with new developments isour notion of comfort.

Comfort

and

discomfort

are terms widely used and specificallyunderstood, but lacking the sort of generally acceptable definitions that make themeasy to account for in the design process.

Discomfort is known to be a good predictor of musculoskeletal problems andis thus an obvious target for design effort, and comfort, as a competitive advantage,is becoming increasingly important in the battle for market share across a wide rangeof consumer and industrial products.

The fact that there is no such thing as an agreed paradigm of comfort ordiscomfort makes design focused on improving comfort or reducing discomfort achallenging exercise. This book provides valuable insight into the issues. Examplescome from Japan, the United States, Sweden, Germany, and The Netherlands andfor the first time, case studies of good practice plus the latest theories on the topicare included in one book. It provides support for managers, designers, researchers,and all those who are concerned with designing products and work situations toincrease comfort or reduce discomfort.

This book gives me great satisfaction. In 1999, in cooperation with TNO, Iinitiated a new chair of Participatory Ergonomics at Delft University of Technology.Professor Peter Vink was appointed to the chair and his energy and achievementsin the position are demonstrated in this book.

Bill Green

Emeritus Professor, Applied Ergonomics and Design,University of Canberra

Former Head of Industrial Design,Delft University of Technology

Acknowledgments

Alstom

France

Arbouw

The Netherlands

ASPA Kantoorinrichting

The Netherlands

Bahco Tools

Sweden

Bombardier

Canada

Creative Box Inc.

Japan

CRFiat

Italy

Dutch Bricklayers Association

The Netherlands

Dutch Ministry of Home Affairs

The Netherlands

ETEC

The Netherlands

Faber Electronics BV

The Netherlands

Finland Post

Finland

FIOH

Finland

Ford

United States

FOSAG

The Netherlands

GTI

The Netherlands

Grammer AG

Germany

Inalfa Roof Systems

The Netherlands

Interior Centre

Japan

JAFIKA

Japan

Kaiser AG

Liechtenstein

Karimoku

Japan

Koninklijke Ahrend NV

The Netherlands

Kosuga

Japan

Long Island RailRoad

United States

Multina

United States

Nissan

Japan

Paus GmbH

Germany

Philips DAP

The Netherlands

RET

The Netherlands

TwinSeal

The Netherlands

Tytecker

The Netherlands

Volvo Car Corporation

Sweden

Yamatake

Japan

About the author

Peter Vink

is head of the department of ergonom-ics and innovation at TNO in The Netherlands.(TNO is the Dutch acronym for The NetherlandsOrganization for Applied Scientific Research.) Hisgroup conducts research in product and systemdesign that contributes to greater comfort or to areduction of physical workload. Products thatresult from their research range from hand toolsand seats to vehicle interiors and construction-sitetransport devices. Professor Vink has written morethan 200 papers on these topics. He is past presi-dent of the Dutch ergonomics association. He isalso a professor of industrial design of Delft University of Technology, where heteaches on participatory design principles and contributes to the overall knowledgebase in the field of ergonomics.

Contributors

J.C. Beckers

RET, The Netherlands

T. Bosch

TNO Work and Employment, The Netherlands

R.E. Bronkhorst


F.K. Cheung

Delft University of Technology, The Netherlands

R.C. Davies

Lund University, Sweden

M.C. Dekker


P.M.A. Desmet


J. van Deursen

TNO Industrial Technology, The Netherlands

J.H. van Dieën

Vrije University, The Netherlands

J.P. Djajadiningrat

Eindhoven University of Technology, The Netherlands

S.M. Eikhout


G. Fujimaki

Waseda University, Japan

M.P. van der Grinten


L. Groenesteijn


M.D. Hagedoorn-de Groot


B.J.A. van Haperen


A.M. de Jong


S. Kishi


M.A.J. Kompier

University of Nijmegen, The Netherlands

T. König

Tytecker, The Netherlands

E.A.P. Koningsveld


F. Krause


L.F.M. Kuijt-Evers


S.H. Lee

University of Tsukuba, Japan

M.P. de Looze


R. Mitsuya


H.F. van der Molen

Arbouw, The Netherlands

S. Nichols

University of Nottingham, United Kingdom

K. Noro


D.S.C. Osinga


C.J. Overbeeke

Eindhoven University of Technology, The Netherlands

K. Reijneveld


J.W. van Rhijn


I.A. Ruiter


N. Schoenmaker


J. Stahre

Chalmers University, Sweden

T. Tereoka


G.H. Tuinzaad

TNO Industrial Technology, The Netherlands

A.A. Visser


J. Visser


L. Vormer


Abstract

Comfort is increasingly important in sales of cars, hand tools, seats, earth-movingmachines and airplane tickets. Discomfort is a predictor of musculoskeletal injuriesand should be reduced in situations that consume a significant part of our time.However, there is no such thing as a general notion of comfort or discomfort.

Therefore, the end user of a product must be involved in research on comfort.If managed correctly, this end-user involvement leads to profitable results, which isdemonstrated in several cases in this book.

This book supports managers, designers, and researchers in designing productsand work stations to increase sales (by increasing comfort) and to reduce muscu-loskeletal injuries (by reducing discomfort). Both theory and good practice in regardto comfort and discomfort are described for the first time in one book. Examplescome from Japan, the United States, Sweden, Germany, and The Netherlands.

The reader is introduced to the latest developments in theories on comfort andwhich factors should be studied in order to optimize comfort in the workplace(Chapters 1, 2, and 3). The reader also benefits from the latest knowledge on howto involve participants in comfort research and set up a project (Chapter 4). InChapters 5 through 22, eighteen cases that are described in detail illustrate howdiscomfort is reduced in a design process, or how comfort is improved. The costsand benefits of comfort products are discussed in Chapter 23.

Contents

Theory

Chapter 1

Comfort Experience...................................................................................................1

P. Vink, C.J. Overbeeke, and P.M.A. Desmet

Chapter 2

Theory of Comfort...................................................................................................13

P. Vink, M.P. de Looze, and L.F.M. Kuijt-Evers

Chapter 3

A Theory on Pressure Distribution and Seat Discomfort.......................................33

K. Noro, G. Fujimaki, and S. Kishi

Chapter 4

Participatory Ergonomics and Comfort...................................................................41

P. Vink, S. Nichols, and R.C. Davies

Cases on Reducing Discomfort in Work

Chapter 5

Discomfort and Productivity in Improved Bricklaying ..........................................55

P. Vink, A.M. de Jong, and E.A.P. Koningsveld

Chapter 6

Reducing Discomfort in Work with New Products for Glaziers............................73

A.M. de Jong, H.F. van der Molen, and P. Vink

Chapter 7

Reducing Discomfort in Installation Work .............................................................85

A.M. de Jong and P. Vink

Chapter 8

Reducing Discomfort in Office Work .....................................................................95

P. Vink and M.A.J. Kompier

Chapter 9

Productivity and Discomfort in Manual Assembly Operations............................111

J.W. van Rhijn, M.P. de Looze, L. Groenesteijn, M.D. Hagedoorn-de Groot, P. Vink, and G.H. Tuinzaad

Chapter 10

Productivity and Discomfort in Assembly Work:The Effects of an Ergonomic Workplace Adjustment at Philips DAP.................129

M.P. de Looze, J.W. van Rhijn, N. Schoenmaker, M.P. van der Grinten, and J. van Deursen

Cases on Chair Comfort

Chapter 11Comfort in Furniture at Home ..............................................................................137T. Teraoka, R. Mitsuya, and K. Noro

Chapter 12Discomfort and Dynamics in Office Chairs..........................................................147M.P. de Looze, P. Vink, and J.H. van Dieën

Chapter 13Designing Comfortable Passenger Seats...............................................................155R.E. Bronkhorst and F. Krause

Chapter 14Comfort through an Emotion-Aware Office Chair ...............................................169C.J. Overbeeke, M.P. de Looze, P. Vink, and F.K. Cheung

Cases on Hand Tool Comfort

Chapter 15Toward a Comfortable Paint Scraper ....................................................................181S.M. Eikhout, R.E. Bronkhorst, P. Vink, and M.P. van der Grinten

Chapter 16Development of a Handheld Steel-Fixing Tool ....................................................193J. Visser, T. König, I. Ruiter, and P. Vink

Chapter 17Comfort Effects of Participatory Design of Screwdrivers....................................207S.M. Eikhout, P. Vink, and M.P. van der Grinten

Chapter 18Comfortable Manual Bag Sealing.........................................................................219M.D. Hagedoorn-de Groot, T. Bosch, S.M. Eikhout, and P. Vink

Cases on Vehicle Interior Comfort

Chapter 19Comfortable View in an Earth-Moving Machine of 2015....................................229L. Vormer, M.C. Dekker, A.A. Visser, F. Krause, and P. Vink

Chapter 20Tram Drivers’ Comfort ..........................................................................................239D.S.C. Osinga, P. Vink, and J.C. Becker

Chapter 21Redesign of Earth-Moving Machines: It’s Also in the Details ............................247F. Krause, M.P. van der Grinten, K. Reijneveld, and R.E. Bronkhorst

Chapter 22Concept of a Future Nissan Car Interior ..............................................................263B.J.A. van Haperen, P. Vink, C.J. Overbeeke, J.P. Djajadiningrat, and S.H. Lee

Cost/Benefits

Chapter 23Costs and Benefits of Comfort Products for Professional Use ............................281E.A.P. Koningsveld

Index......................................................................................................................289

1

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

1

Comfort Experience

P. Vink, C.J. Overbeeke, and P.M.A. Desmet

CONTENTS

1.1 Importance of Comfort ....................................................................................11.2 Importance of Discomfort................................................................................11.3 Striving for (Dis)Comfort ................................................................................21.4 Comfort Knowledge Is Needed .......................................................................31.5 Aspects of Comfort in an Airplane .................................................................41.6 Aspects of Comfort in the Literature ..............................................................51.7 Aspects of Discomfort in the Literature..........................................................71.8 Comfort Is for Everyone..................................................................................81.9 Comfort and Ergonomics.................................................................................81.10 Comfort and Emotion ......................................................................................91.11 Conclusions ....................................................................................................11References................................................................................................................11

1.1 IMPORTANCE OF COMFORT

Everyone pays attention to comfort. When buying a bed or a car, or flying acrossthe ocean, comfort comes into play. Therefore, manufacturers of products such asseats, cars, beds, hand tools, and production lines strive for comfortable products inorder to stay ahead of competition.

Comfort is influenced by many factors in the environment. That means that itis not easy to design, market, or manage with a focus on comfort. However, knowl-edge about comfort is a requisite when designing an airplane interior, working inthe marketing department of a hand tool manufacturer, managing the optimal per-formance of office workers, or trying to measure discomfort as a precursor of backcomplaints.

1.2 IMPORTANCE OF DISCOMFORT

Reducing discomfort — another issue discussed in this book — is not a luxury. Tostimulate optimal human performance, discomfort should be prevented. The tramcabin should in fact be built around the driver in order to accommodate his perfor-mance. The same applies to the environment of the assembly worker and to thesoftware system of the office worker. Optimal human performance is needed to stayahead of competitors, and reducing discomfort can be a great help in this regard.

2

Comfort and Design: Principles and Good Practice

Also, discomfort is a precursor of complaints in the back, neck, and arm and shouldalso be prevented for that reason. Discomfort can lead to musculoskeletal problems(Proper et al. 1999) that cost society a lot of money. In a longitudinal study where1789 subjects were followed for 4 years, a high score on postural muscular discom-fort resulted in a significantly higher percentage of sick leave due to musculoskeletalinjuries such as back and neck pain. This is a serious problem in Europe (Fig. 1.1),which makes preventing discomfort very important.

1.3 STRIVING FOR (DIS)COMFORT

However, at least three problems face us in striving for comfort:

• The exact cause of discomfort or comfort is unknown. There is no

model

available that describes the cause of comfort.• Every individual has his or her own meaning for comfort. Comfort is a

subjective phenomenon

.• The comfort design process is not described, and the

approach

is unknown.

These three problems that will be discussed in this book are interwoven, but forclarity the model, the subjective experience, and the approach are separated. Themodel and the subjective experience will be described in Chapter 2 and the approachin Chapter 4. Chapter 3 describes a theory on sitting comfort. The theory explainedin Chapters 1 through 4 will be applied to actual cases in Chapters 5 through 22.Chapter 23 concerns costs and benefits.

The present chapter describes aspects related to comfort and the way it is linkedto other fields of study and applications.

FIGURE 1.1

Percentage of workers in the EU having pain in the back, legs, arms, or neckand shoulder during more than 25% of the working time, based on 1000 workers in each EUcountry (Merllié and Paoli 2000).

0%

10%

20%

30%

40%

back legs arms neck/shoulder

Comfort Experience

3

1.4 COMFORT KNOWLEDGE IS NEEDED

There are of course manufacturers who claim that their product increases comfortbecause they say that they have a special sensor for that or because an expertlooked at it. Of course to some degree everyone has some knowledge of comfortthat can be generalized, and some predictions can be made. However, for profes-sional situations or in buying beds (which are used about one-third of our lives)it is not wise to base it just on beliefs. Discomfort in an earth-moving machineor along an assembly line could lead to mistakes or back complaints. A lowerlevel of comfort in an airplane could result in fewer bookings because nowadaysvarious data for comfort ratings are easily obtainable on the Internet (Table 1.1).Therefore, design approaches involving experiments with the real end users arepreferable. This is not simple, however. Just asking end users “Do you think itwill be comfortable?” or “Is it comfortable when you use it?” won’t give enoughinput for a design. In this book, several methods are used to link the comfortexperience with the design.

Many studies show the positive effects of a design process in which end usersplay an important role (see Chapters 5 to 22). Two of these studies are

• An approach including user tests that led to a more comfortable paintscraper (see Chapter 15), which resulted in higher sales ratios

• An improved assembly line (see Chapter 9) that led to higher productivityand more satisfied workers

TABLE 1.1Example of an Internet Seat Comfort Rating of Airliners

AirlinerSeat comfort

rating

Finnair 8.2Singapore Airlines 8.2British Airways 7.5Austrian Airlines 7.2Malaysia Airlines 7.0Cathay Pacific 6.9Continental Airlines 6.8Delta Airlines 6.8South African Airways 6.8Air France 6.7Iberia 6.7KLM 6.6United Airlines 6.6US Airways 6.5Lufthansa 6.3

Source:

www.vliegtarieven.nl (August 2003).

4


1.5 ASPECTS OF COMFORT IN AN AIRPLANE

Comfort or discomfort is often noticed during a long-distance flight in economyclass (Fig.1.2). Many aspects of discomfort and comfort play a role during the flight.

•

Thermal comfort.

One could experience dry air, cold feet, or a draft.This not only influences skin temperature, but could also result in expe-rienced discomfort in the respiratory system.

•

Acoustic comfort.

Noise could cause some inconvenience. However, a lothas been done to reduce acoustic discomfort in airplanes. Better materialsthat deaden the noise, or even active antinoise systems, have been applied.

•

Visual comfort.

Sometimes the screens are of poor quality, resulting invisual discomfort.

•

Physical comfort.

Restricted leg space, the position of the screens, andreduced movement possibilities could result in back and neck discomfort,but also in problems such as deep vein thrombosis.

• Discomfort due to

vibrations

and

shocks

does not often play a majorrole during a flight, but it could be experienced as well.

FIGURE 1.2

In airplanes the hip–knee space often results in discomfort.

Comfort Experience

5

Apart from the influence of the environment, our perception also plays animportant role (Fig. 1.3). The way we perceive the environment is influenced by ourhistory and mood. We could experience this flight more comfortably because it isbetter than previous flights, or we could experience a comfortable flight because thecare provided by the flight attendant puts us in a good mood.

1.6 ASPECTS OF COMFORT IN THE LITERATURE

The above-mentioned aspects of comfort are also described in the scientific liter-ature. The MEDLINE database lists 261 papers with

comfort

in the title betweenApril 1993 and April 2003. By far most of these (140 out of 261) concern climateor thermal comfort (Fig. 1.4), which means that this is an often-studied area. Anaspect of comfort not mentioned in the example of the airplane is comfort relatedto the treatment of sick persons. Measurements of the effects of medicine or nursing(pain/patient comfort) are seen in these papers. Research on this aspect is mentionedin 28 out of the 261 papers. The third most often mentioned issue is physicalcomfort (28 out of 261 papers). It concerns research regarding seating, posture,physical loading, and foot pressure measurements. Only six studies mention morethan one aspect (within the

others

category of Fig. 1.4), so most of the studies aremonodisciplinary.

FIGURE 1.3

Emotional aspects do play a role in the comfort experience and are not forgottenin the exterior design of this plane.

6


Another search in the Swetsline database for the word

comfort

in a title resultedin 44 papers (Fig. 1.5) published between April 1993 and April 2003. Again, thermalcomfort is most often mentioned, but so are vibration and shock. Acoustic comfortand physical comfort are third and fourth, respectively.

FIGURE 1.4

Aspects of comfort mentioned in the titles of 261 scientific papers (database

Medline, Applied Ergonomics

).

FIGURE 1.5

Aspects of comfort mentioned in the titles of 44 scientific papers (database

Swetsline, Ergonomics

).

0 20 40 60 80 100 120 140 160

others

pain/patient comfort

perception

physical comfort

visual comfort

vibrations/shock

acoustic comfort

thermal comfort

0 1412108642

perception

physical comfort

visual comfort

vibrations/shock

acoustic comfort

thermal comfort

Comfort Experience

7

1.7 ASPECTS OF DISCOMFORT IN THE LITERATURE

Several aspects of discomfort are also found in the scientific literature. BetweenApril 1993 and April 2003, 109 papers with

discomfort

in the title are listed in theMEDLINE database. Most of these papers concern pain studies (43 out of 109) andmusculoskeletal aspects of physical discomfort (35 out of 109). These 35 studiesconcern the effects of postures or assembly tasks on musculoskeletal discomfort,but they also discuss pressure during seating (Fig. 1.6).

It is interesting to note that comfort is mentioned more in climatic studies orstudies regarding thermal comfort, whereas discomfort is mentioned more in thetitles of studies regarding pain and musculoskeletal loading. To some extent thisrelationship is also found in the research among nonexperts. Chapter 2 refers to astudy by Zhang et al. (1996) in which discomfort is related to clustered descriptorssuch as fatigue, restlessness, pain/biomechanics, strain, and circulation. Comfort ismore related to clustered descriptors such as impression and relaxation.

Recent research (Kuijt-Evers et al. 2004) showed that the important aspects forthe end user differ according to the product. For handheld tools,

functionality

and

reliability

are important aspects closely related to comfort (Kuijt-Evers et al. 2004),while in seats comfort is strongly related to the terms

relaxed

,

at ease

, and

happy

(Zhang et al. 1996). Because of the fact that knowledge is available on the experienceof comfort related to handheld tools, seats, vehicle interiors, and work stations, thesefour areas are described separately in this book. A description of the theory andexamples are given for each area.

Chapters 1, 2, 3, and 4 describe the theory, and Chapters 5 to 10 discuss thereduction of discomfort in work. Chapters 11 to 14 concern comfort in seat design,

FIGURE 1.6

Aspects of discomfort mentioned in the titles of 109 scientific papers (database

Medline, Applied Ergonomics

).

0 10 20 30 40 50

others

pain/patient discomfort

perception

physical discomfort

visual discomfort

vibrations/shock

acoustic discomfort

thermal discomfort

8


Chapters 15 to 18 in handheld tool design, and Chapters 19 to 22 in vehicleinteriors.

1.8 COMFORT IS FOR EVERYONE

Everyone has an opinion about comfort. After reading this text, some readers willexperience discomfort due to the lack of lumbar support in their chair. Others willfeel incredibly comfortable and enjoy the fascinating text in combination with theexcellent figures. It is difficult to predict if someone will experience discomfort, orcomfort, or nothing at all. This book views comfort as a subjective phenomenon;the comfort of a product can be evaluated only by the user. A product in itself cannever be comfortable. That is why this book pays much attention to how a usershould be involved in the design process. The end user should be involved becausehe is the expert on his task and work. This end-user involvement is studied in thearea of participatory ergonomics (see Chapter 4). With the help of participatoryergonomics, the design process can be structured with special attention on how totake the participants into account, especially the end user.

1.9 COMFORT AND ERGONOMICS

There is a strong connection between ergonomics and comfort.

Ergonomics (or human factors) is the scientific discipline concerned with the under-standing of interactions among humans and other elements of a system, and theprofession that applies theory, principles, data and methods to design in order tooptimize human well being and overall system performance.

www.iea.cc/ergonomics (December 2003)

In fact, ergonomics is the discipline that studies how the environment should beadapted to strive for optimal human performance. One of the outcomes of anergonomic design is comfort, or reducing discomfort. Accordingly, ergonomics isthe discipline that is crucial in optimizing the environment to arrive at an experienceof comfort. Therefore, much of the knowledge in this book overlaps with ergonomics.

One difference between comfort and ergonomics could be that in comfort moreattention is paid to the experience of the end user and to affective behavior. However,attention to experience and affective human behavior is also growing among ergo-nomists, which is proven, for instance, by a conference organized by ergonomistson this subject (Helander et al. 2001). Dul and Kahmann (2001) state that it is notexpected that many ergonomists will become specialists in emotional experience.

As a consequence of the statement mentioned above, that the comfort of aproduct can be evaluated only by the user, much attention should be paid to how auser should be involved in the design process. As noted earlier, this end-user involve-ment is dealt with in the area of participatory ergonomics — the adaptation of theenvironment to the human (that is, ergonomics) together with the proper persons inquestion (participants) (Vink 2002).

Comfort Experience

9

1.10 COMFORT AND EMOTION

Given the fact that the concept of comfort has an experiential component, it can beconsidered to be related to our emotions. In recent years, the design community hasshown a growing interest in these emotions.

Because comfort is also influenced by the state we are in, it has a relationshipwith emotions. Kansei engineering is one method used to incorporate and studyhuman emotions in an early stage of the design process. One of the founders of themethod is Nagamachi (1998) from Japan. Kansei is a Japanese concept and difficultto translate into one word. It has to do with the human emotions. In an example ofKansei engineering, designs of parts of the vehicle interior of a Mazda were shownon a computer screen to future users (Nagamachi 1998). The users attributed wordsto what they saw in various designs. Speed indicators were shown in various designs:round, long, with gothic numbers, and so on. In this way the emotions of car drivers,measured as reactions on speed indicators in the dashboard, could be recorded andused as input in the design. Using Kansei engineering, data were also gathered onreactions to beer cans (Ishihara 1998). A group of 16-year-old women that had neverdrunk beer before could describe the taste.

A similar but opposite study was performed by Smets and Overbeeke (1995).Students of industrial design were asked to design 3D models of bottles for energydrinks. The emotion caused by the taste was to be expressed in the bottle design.The drinks were tasted and based on the taste, the bottles were designed. Thesebottles were shown to naïve subjects, which means that the subjects did not knowwhich taste was coupled with which bottle. The subjects were asked to match thebottles and tastes, and the accuracy of matching appeared to be very high. Thismeans that it is possible to incorporate emotion experiments into the early stages ofthe design process.

For the development of comfortable products it could be wise to have someknowledge of emotion and design. The emotional content of design is also importantin a work setting. Manufacturers of professional products and machines anticipatethis trend, which was also featured in a conference on affective human factors design(Helander et al. 2001).

Researchers at the Delft University of Technology aim to develop approachesand instruments that offer designers handles for discussing the emotional impactof the product design with the intended users. Desmet et al. (2001), for example,developed the

emocard

method, a nonverbal self-report instrument. It was devel-oped because Desmet and Hekkert (1998) found that emotions are difficult toverbalize, especially the type of subtle, low-intensity emotions elicited by products.Furthermore, asking users to describe their emotional responses requires cognitiveinvolvement, which may influence the responses themselves. Therefore, theemocard method was designed to enable users to express their emotional responseswithout the use of words.

The instrument consists of 16 emocards that depict cartoon faces with 8 distinctemotion expressions on 8 male faces and 8 female faces. These expressions varywithin the dimensions of

pleasantness

and

arousal

. With these two dimensions

10


Russell (1980) created a “circumplex of emotions,” which was used as a visualstructure for the set of emocards (Fig. 1.7).

In a discussion, the emocards help the participants to express their emotionalresponses. For instance, participants can select a card that best expresses theiremotional responses to a product. Participants can also put the cards in order ofrelevancy. In this way, the cards can be used both as an aid to objectify emotionalresponses and as an aid for starting a conversation on these responses with a designeror researcher.

Recently, Desmet (2003) developed a new nonverbal self-report instrument thatmeasures a set of 14 distinct emotions: the Product Emotion Measurement instrument(PrEmo) (Fig. 1.8). Each emotion in this set is portrayed by an animated cartooncharacter employing dynamic facial, bodily, and vocal expression and is presentedon a computer interface. Participants can report their responses by selecting thoseanimations that correspond with their felt emotion(s). The unique strength of PrEmois that it combines two qualities: it measures distinct emotions and it can be usedcross-culturally because it does not ask respondents to verbalize their emotions. Inaddition, it can be used to measure mixed emotions, that is, more than one emotionexperienced simultaneously.

Instruments such as emocards and PrEmo are not only worthwhile for productdesign, but they can also be used by management and employees in participatoryworkstation optimization.

FIGURE 1.7

The 16 emocards developed by Desmet et al. (2001) that support findingemotional reactions to products.

Comfort Experience

11

1.11 CONCLUSIONS

Knowledge of comfort and discomfort is important in designing chairs, beds, handtools, and working environments. A long-distance flight could make us aware of thedifferent aspects of comfort. Every passenger could experience a different comfortaspect during the flight because comfort is a subjective phenomenon. The fact thatit is a subjective phenomenon and the fact that various aspects influence comfort,make it difficult to study. A lot is known about the thermal aspect of comfort, anaspect that is most frequently mentioned in the literature.

This book is more focused on the aspects of comfort related to product design,which is a rather new area. It is closely related to ergonomics and emotional aspects,so these issues will also be described in this book. The part of ergonomics thatstudies user involvement in the design process (participatory ergonomics) is espe-cially interesting because comfort is a subjective phenomenon. Therefore, a separatechapter will be dedicated to this topic.

REFERENCES

Desmet, P.M.A. (2003) “Measuring emotion; development and application of an instrumentto measure emotional responses to products.” In M.A. Blythe, A.F. Monk, K. Over-beeke and P.C. Wright, eds.,

Funology:

From Usability to Enjoyment

, Dordrecht:Kluwer Academic Publishers.

FIGURE 1.8

PrEmo interface.

12


Desmet, P.M.A. and Hekkert, P. (1998) “Emotional reactions elicited by car design: a mea-surement tool for designers.”

Automotive Mechatronics Design and Engineering, 31stISATA Conference Proceedings

, 237–244.Desmet, P.M.A., Overbeeke, C.J. and Tax, S.J.E.T. (2001) “Designing products with added

emotional value: development and application of an approach for research throughdesign.”

The Design Journal

, 4(1): 32–47.Dul, J. and Kahmann, R. (2001) “Ergonomie in de belevingseconomie.”

Tijdschrift voorErgonomie,

26(5): 15–20.Helander, M.G., Khalid, H.M. and Ming, T. (2001)

Proceedings of the International Confer-ence on Affective Human Factors Design

, Singapore, June 27–29, 2001.Ishihara, S., Ishihara, K. and Nagamachi, M. (1998) “Hierarchical kansei analysis of beer can

using neural networks.” In P. Vink, E.A.P. Koningsveld and S. Dhondt, eds.,

HumanFactors in Organizational Design and Management IV

, Amsterdam: Elsevier,421–426.

Kuijt-Evers, LFM, Groenesteijn, L, Looze, MP de and Vink P. (2004) “Identifying factors ofcomfort in using hand tools.”

Applied Ergonomics,

35(3): 453–458.Merllié, M. and Paoli, P. (2002)

Working Conditions in the European Union

, Dublin: EuropeanFoundation for the Improvement of Living and Working Conditions.

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, Amsterdam: Elsevier, 399–404.Proper, K.I., Bongers, P.M. and Grinten, M.P. van der (1999)

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discomfort in sitting.”

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, 38(3): 377–389.

13

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

2

Theory of Comfort

P. Vink, M.P. de Looze, and L.F.M. Kuijt-Evers

CONTENTS

2.1 Introduction ....................................................................................................132.2 General Theory...............................................................................................14

2.2.1 Comfort in Dictionaries...................................................................142.2.2 Comfort in the Scientific Literature ................................................142.2.3 Comfort Is a Subjective Phenomenon.............................................142.2.4 The Comfort Model.........................................................................152.2.5 Elements of the Comfort Model .....................................................16

2.3 Theory per Product ........................................................................................192.3.1 Preventing Discomfort at Work.......................................................192.3.2 Factors Influencing the Comfort Experience ..................................20

2.3.2.1 Theory of Herzberg...........................................................202.3.3 Theory of Seat Comfort ..................................................................20

2.3.3.1 Chair Elements’ Relative Contribution to Comfort and Discomfort..................................................................23

2.3.4 Theory of Hand Tool Comfort ........................................................232.3.5 Theory of Vehicle Interior Comfort ................................................24

2.3.5.1 Comfort Aspects in Earth-Moving Machines...................262.3.5.2 Scientific Knowledge about Vehicle Interiors ..................262.3.5.3 A Study to Find Out End-User Opinions.........................27

2.3.5.3.1 Current Machine ..............................................292.3.5.3.2 Improvement Possibilities................................29

2.4 Conclusions ....................................................................................................30Acknowledgment .....................................................................................................30References................................................................................................................30

2.1 INTRODUCTION

In Chapter 1 it was shown why knowledge of comfort is important. This knowledgecould support the design of products such as seats, vehicles, and hand tools andincrease sales, but it could also help prevent injuries of the back, shoulders, andarms. In this chapter the knowledge available in the literature on comfort related toseat, hand tool and vehicle interior design is described. The first sections concernthe general theory, including an overview of what is under debate in the literature

14


and on the consensus found in research. After that a model is described, followedby the theory applied to products related to sitting, hand tools, and vehicle interiors.

2.2 GENERAL THEORY

2.2.1 C

OMFORT

IN

D

ICTIONARIES

The meaning of the word

comfort

differs among different dictionaries and in differentcountries. It is described as “freedom from pain; well being” in most dictionaries (e.g.,the New Penguin English Dictionary 2000; Van Dale 2000). In these dictionaries,comfort is also translated as “convenience of the interior, or things which bring bodilyease.” Many people probably associate comfort with the interior or with visible thingssuch as footwear and clothing. However, comfort research is also focused on climate(Chapter 1), and in several languages you can be ahead of your competitor and havea comfortable advantage. In this case, comfortable means that you don’t have to worryso much. So it seems that the interior is not the only area of comfort research.

2.2.2 C

OMFORT

IN

THE

S

CIENTIFIC

L

ITERATURE

In the scientific literature the definition of comfort is under debate. Slater (1985)defines comfort as a pleasant state of physiological, psychological, and physicalharmony between a human being and his or her environment. Richards (1980)stresses that comfort is the state of a person that involves a sense of subjective well-being, in reaction to an environment or situation. Regarding discomfort, mostlymedical patients or physical discomforts are mentioned. Discomfort scales are alsooften used in biomechanical or musculoskeletal research (Marras 2003). It isassumed that more local discomfort (sometimes described as local postural discom-fort) means a higher loading and a higher chance of getting musculoskeletal injuries.

Despite the ongoing debate on the meaning of comfort, there are some issuesthat are generally accepted (Looze et al. 2003):

• Comfort is a construct of a subjectively defined personal nature.• Comfort is affected by various factors (physical, physiological, psycho-

logical).• Comfort is a reaction to the environment.

2.2.3 C

OMFORT

I

S

A

S

UBJECTIVE

P

HENOMENON

So, these three points are not under debate. One of them — comfort is a subjectiveexperience — is of special importance because it strongly relates to how to copewith comfort in design. A product in itself can never be comfortable; it becomescomfortable (or not) in its use. The user decides whether or not a product iscomfortable, or leads to discomfort, by using the product.

This complicates the construct of comfort because it is not known how everyindividual will react to a product. For instance, for Passenger 1 on a long-distanceflight, back discomfort is of great importance. Passenger 2 wants a reduction in noiseand Passenger 3 needs more space. This complication is one of the reasons whydesigning comfortable products is difficult.

Theory of Comfort

15

However, it is not impossible to design comfortable products such as a train interior.Recently, a train interior was designed that was described as comfortable by 83% ofthe passengers (Bronkhorst and Krause 2002; see also Chapter 13). During the designof the interior, experiments were performed in a setting that was as naturalistic aspossible to find the optimum comfort experienced by end users (Fig. 2.1).

In this book, comfort is defined as

convenience experienced by the end userduring or just after working with the product.

The product can be a building, ameans of conveyance, a utility article, a work station, clothing, or furniture.

2.2.4 T

HE

C

OMFORT

M

ODEL

Comfort could have three manifestations:

• Discomfort. The participant experiences discomfort because of physicaldisturbances in the environment.

• No discomfort. The participant is not aware of discomfort or comfort, orthere is no discomfort.

• Comfort. The participant experiences noticeably more comfort than expectedand feels comfortable.

The comfort model is shown in Fig. 2.2. It is a simplification of a more detailedmodel developed by Looze et al. (2003). The output is located on the right side ofthe model: comfort, no discomfort, and discomfort. The experience of discomfort orcomfort is partly due to ourselves: (1) the history of our comfort experiences deter-mines our expectations of a product, based on what we are used to; and (2) our statecould be excited or relaxed, which influences our mood and thereby our continuingstate. And of course all of this takes place in a certain environment.

The experience of comfort and discomfort is also caused by external stimuli(input). The inputs are shown on the left side of the figure. For example, our sensorsreceive the pressure and after this input the selection and weighing processes start.

FIGURE 2.1

An experiment establishing discomfort and comfort in the design phase of atrain interior (Bronkhorst and Krause 2002).

16


Our state of arousal or experiences in the past influence these weighing processes.Based on these processes, the product causes comfort, discomfort, or nothing thatwe are aware of.

The output is also influenced by the environment, in which case the input isnoticed in our mind. This is an important factor and it is unknown how the environ-ment influences the comfort experience. A consequence is that a product shouldalways be tested in an environment that is as close to reality as possible.

2.2.5 E

LEMENTS

OF

THE

C

OMFORT

M

ODEL

In this section each element of the model is described separately, but in reality theseelements are not separated. It is not known how the elements are related to eachother and what the contribution of each element is to the total experience. That iswhy it is important to analyze the user situation (e.g., during a task analysis) and toperform experiments with products in the design phase in an environment as closeto the naturalistic setting as possible.

1.

History

influences the experience. This is important for product designers.Products should have at least the level of comfort people are used to. A nonadjustableoffice seat will be experienced as not comfortable in western European countriessuch as Sweden and the Netherlands. A caveman would not have this problem(although the opinion of the caveman is now difficult to verify in an experiment).We always evaluate the appearance and styling of a product with our past as areference. That means that a product designer should know the history and socialbehavior of the target group. Drivers of earth-moving machines are used to the

FIGURE 2.2

The comfort model. The feeling of (dis)comfort is determined by the inputrecorded by sensors and the information processing that is influenced by the history and stateof the participant.

Environment

visual input

smell

noise

temperature/

humidity

pressure/touch

posture/movement

comfort

nodiscomfort

discomfort

history + state

Theory of Comfort

17

comfort of their personal automobiles. They expect a comparable level of comfortin the vehicle interior of their earth-moving machine (Fig. 2.3).

2. Our

state

also influences whether we experience discomfort or comfort. Aftera few hours of heavy physical exercise, a relaxed seat is more comfortable than aftersitting for 3 hours in a car. Picard (1997) showed in her research that emotions, feelings,and mood play a role in the way someone evaluates a product. A mock-up in a cleanlaboratory may receive a different evaluation than a mock-up evaluated on the shopfloor. The environment or situation, therefore, influences the state of people.

3. The

visual input

also influences our experiences. Visual information plays amajor role; it is the first impression of comfort. In the design world, visual informationis important. The first ideas of a product are often communicated visually (Lugt 2001),and later on in the design process drawings (Fig. 2.4) or computer pictures are also

FIGURE 2.3

The comfort experienced in the interior of an earth-moving machine (

A

) isinfluenced by the previous experiences in car (

B

).

FIGURE 2.4

Drawings used in discussions with users: (

A

) design De Groot, TNO; (

B

) designCheung, TU-Delft.

18


used (Fig. 2.5). It is important to realize that comfort is not influenced by stylingor appearance alone. Kuijt-Evers (in Bronkhorst et al. 2001) showed that 49experienced office workers evaluated 1 out of 4 office chairs negatively based onthe visual information (a brown traditional chair). Contrary to what was expected,this chair was evaluated positively after actually using it.

4. The sense of

smell

also has an influence. Different authors (e.g., Theimer1982) report that smell influences our experiences, and mostly we are not aware ofthis effect. It even influences our sexual activity, aggression, and territorial behavior.In some ways we all know that: when your neighbor is flatulent, you involuntarilymove your body to the other side to avoid the smell. As with other inputs, everyperson will react differently to the smell associated with a product. Most people likethe scent of a new car, but some do not.

5.

Noise

is a type of input that can influence comfort positively or influencediscomfort negatively. The noise of the engine while working in an earth-movingmachine can lead to discomfort (Vink et al. 2001), whereas the sound of a Harley-Davidson is a kind of music to some of us.

6.

Temperature and humidity

are also related to (dis)comfort. Searching for

comfort

on the Internet leads you mostly to temperature and climate issues. Air condi-tioning, office temperature, drafts, and humidity are often associated with comfort. Apleasant climate is often not noticed, but a high or low temperature attracts attentionand the discomfort is perceived. According to Carrier, one of the largest manufacturersof indoor air-quality systems, indoor air quality is the most important reason why officerental contracts are not extended (www.carrier.com, June 2001). This is certainly notan objective source, but it indicates that the issue has some importance.

FIGURE 2.5

Example of a picture made by a computer and used in discussions with usersto design the work stations.

Theory of Comfort

19

7. Various studies show the relationship between

pressure

and discomfort insitting (Goossens et al. 1998, 2002). Goossens (1998) increased the force appliedto a buttock by a circle 30 mm in diameter. He found a clear correlation betweenthe level of pressure (force increase) and the perceived discomfort. To feel pressurewe have sensors located in the skin. Generally, a better distribution of pressure betweena seat or handle and the human body leads to less discomfort. A literature survey(Looze et al. 2003) showed that of all objective measures, the distribution of pressurehas the clearest relationship to discomfort in sitting. In this area Goossens et al.(2002) have done some impressive work. They showed that participants are able toperceive small differences in pressure on their bottoms and could translate this todiscomfort. In addition to pressure we also have touch. A thick carpet is experiencedas different from a concrete floor by our bare feet, and the textures of handles havean influence on the feeling of comfort. Sonneveld (2002) describes how we can takethese feelings into account during the design process.

8. The

posture and movements

determined by the product can also lead todiscomfort. In the long run, local perceived discomfort could even result in musculo-skeletal disorders (Proper et al. 1999; see also Chapter 1). Back pain is found in one-third of all European workers. Neck and shoulder pain is found in almost one-quarterof European workers. Not only is the human factor a problem, but also the costs. Inthe Netherlands, musculoskeletal injuries cost

€

8 billion each year (Bongers et al.2000). Thus, the problem is large enough to require that something should be doneabout it. This is an opportunity for designers: design products that reduce musculo-skeletal injuries. In other words, use experiments during the design process to avoiddiscomfort and as a result prevent musculoskeletal injuries.

In designing a product, all sensory modalities should be considered. This couldbe a lot of work. Therefore, it is often wise to think about the use of the productand to derive the sensors that have priority. Recently, at Delft University of Tech-nology, a study was done to assess each modality’s potential contribution to overallproduct experiences (Schifferstein and Cleiren 2004). An approach was used inwhich subjects experienced real-life products through one modality: either vision,touch, audition, or olfaction (smell). Visual and tactual information appeared to bemost detailed and resulted in the clearest memories of past events and associationswith other products. Because vision may have an advantage over touch by virtue ofthe speed with which visual information is processed, vision is likely to dominateproduct experiences in real-life situations (Schifferstein and Cleiren 2004).

2.3 THEORY PER PRODUCT

2.3.1 P

REVENTING

D

ISCOMFORT

AT

W

ORK

To stimulate optimal human performance, discomfort should be prevented. Anassembly work station should, in fact, be built around the operator to accommodatehis performance. The same applies to the software system of the office worker.Optimal human performance is needed to stay ahead of competitors, and reducingdiscomfort can be of great help. Therefore, striving for discomfort reduction is veryimportant.

20


Musculoskeletal discomfort is often measured in a work environment (Marras 2003)in order to optimize the work station layout. Establishing the reduction of discomfortin experiments during the design process is needed to prevent musculoskeletal injuries.A method often used to study discomfort is the LPD (local postural discomfort) method.The way this method can be applied to optimize work stations will be discussed inChapters 8, 13, and 15.

2.3.2 F

ACTORS

I

NFLUENCING

THE

C

OMFORT

E

XPERIENCE

The way comfort, discomfort, and no comfort are related differs according to thetype of product, but the factors influencing comfort also differ. In this section thefactors influencing comfort are described for seats, hand tools, and vehicle interiors.The motivation theory of Herzberg et al. (1993) is described first because of itssimilarity to this framework discussed here.

2.3.2.1 Theory of Herzberg

In the late 1950s, Herzberg was considered by many to be a pioneer in motivationtheory. He interviewed employees to find out what made them satisfied and dissat-isfied on the job. Physical factors, according to Herzberg, cannot motivate employees,but they can minimize dissatisfaction if handled properly. In other words, they canonly dissatisfy if they are not all right. Dissatisfaction is related to company policiesand salary (Table 2.1). Motivators, on the other hand, create satisfaction by fulfillingindividuals’ needs for meaning and personal growth. These are issues such as thework itself and advancement, and they are related to satisfaction.

2.3.3 T

HEORY

OF

S

EAT

C

OMFORT

In the areas of comfort and discomfort a similar division can be made. If we considercomfort and discomfort during sitting, absence of discomfort does not automaticallyresult in comfort. Comfort will be felt when more is experienced than expected.This is supported in research by Zhang et al. (1996) and by Helander and Zhang(1997). Based on questionnaires, they found that discomfort is more related to pain,ache, and heavy legs (Table 2.2). When there is absence of discomfort, nothing isexperienced. To notice comfort, more should be experienced. Comfort is related toa sense of well-being and to the plushness of the chair.

TABLE 2.1Factors Influencing Satisfaction or Dissatisfaction

Dissatisfaction Satisfaction

- Company policies - The work itself- Administrative procedures - Achievement- Salary - Recognition- Working conditions - Advancement

Based on Herzberg et al. (1993).

Theory of Comfort

21

Zhang et al. (1996) did cluster the descriptors. Discomfort is related to clustereddescriptors such as fatigue, restlessness, pain/biomechanics, strain, and circulation.Comfort is more related to impression, relief/energy, well-being, and relaxation(Table 2.3).

Looze et al. (2003) described a more refined theoretical model based on theaforementioned findings of Zhang et al. (1996). In this model (Fig. 2.6) differentfactors underlying sitting discomfort and comfort are described, as well as therelationships between these factors. Also, discomfort and comfort are seen as sep-arate entities in this model.

The left part of this theoretical model concerns discomfort. The physical pro-cesses underlie discomfort, agreeing with comparable models on the etiology ofwork-related physical complaints (Winkel and Westgaard 1992; Armstrong et al.1993). These authors consider

exposure

,

dose

,

response

, and

capacity

as the mainissues. According to Armstrong, exposure refers to the external factors producing adisturbance of the internal state (dose) of an individual. The dose may evoke a

TABLE 2.2Factors Influencing Comfort or Discomfort during Sitting

Discomfort*

Comfort*

Pain 0.81 Relaxed 0.82Sore 0.81 At ease 0.82Ache 0.81 Happy 0.81Circulation to legs cut off 0.79 Content 0.81Hurting 0.79 Pleased 0.81Dull ache 0.78 Pleasant 0.79Swollen ankle 0.76 Well-being 0.76Numb 0.71 Restful 0.76Stiff 0.71 Safe 0.73Heavy legs 0.68 Calm 0.73

*The factor loading after varimax rotation. (The higher the number, the better the relationshipto discomfort or comfort.)Based on Zhang et al. (1996).

TABLE 2.3Cluster of Factors Influencing Comfort or Discomfort during Sitting

Discomfort Comfort

- Fatigue - Impression- Restlessness - Relief/energy- Pain/biomechanics - Well-being- Strains - Relaxation- Circulation

Based on Zhang et al. (1996).

22


cascade of mechanical, biochemical, or physiological responses. The extent to whichexternal exposure leads to an internal dose and responses depends on the physicalcapacity of the individual. With regard to sitting, it could be said that the physicalcharacteristics of the office seat (product level, e.g., form, softness), the environment(context level, e.g., table height), and the task (context level, e.g., the performanceof VDU activities) expose a seated person to loading factors that may involve forcesand pressure from the seat on the body and joint angles. These external loads mayyield an internal dose in terms of muscle activation, internal force, intradisc pressure,nerve and circulation inclusion, and skin and body temperature rise, provokingfurther chemical, physiological, and biomechanical responses. The perception ofdiscomfort may be established by exterocepsis (stimuli from skin sensors), propri-ocepsis (stimuli from sensors in the muscle spindle, tendons, and joints), interocepsis(stimuli from internal organ systems), and nocicepsis (stimuli from pain sensors).

The right part of the model concerns comfort, that is, feelings of relaxation andwell-being. Again, the influential factors are presented on human, seat, and contextlevels. At the context level, not only the physical features are assumed to play a role,but also psychosocial factors such as job satisfaction and social support. At the seatlevel, the aesthetic design of a seat in addition to its physical features may affectthe feelings of comfort. At the human level, the influential factors are assumed tobe individual expectations and other individual feelings or emotions. The dominantfactor of discomfort, as suggested by Helander and Zhang (1997), is illustrated bythe horizontal arrows pointing from the left (discomfort) to the right (comfort) partof the model.

FIGURE 2.6

The comfort model for sitting described by De Looze et al. (2003).

COMFORT MODELSITTING DISCOMFORT

(= feelings of pain, soreness,numbness, stiffness)

SITTING COMFORT(= feelings of relaxation,

well-being)

phys

ical

cap

acity

physicalfeatures

Product

Contextphysical

environmenttask

Human emotionsexpectations

physical environmenttask

psychosocial factors

physical processes

physical featuresaesthetic design

Theory of Comfort

23

2.3.3.1 Chair Elements’ Relative Contribution to Comfort and Discomfort

In designing a chair it is important to know what elements of the chair are majorfactors determining the level of discomfort and comfort. In an unpublished study of15 contemporary office chairs by Looze, the levels of comfort and discomfort weremeasured by use of the chair evaluation checklist of Helander and Zhang (1997). Thismethodology is based on the theory of seat comfort mentioned earlier. On a 1-to-9scale subjects had to rate their opinions (1

=

I completely disagree; 9

=

I completelyagree) about 14 statements (Table 2.4) addressing the underlying factors of comfortand discomfort. The sum of the ratings yielded separate ratings for comfort anddiscomfort. In addition, the same subjects gave their ratings for separate chair elements.By a multiple regression analysis, we found the following regression equations:

discomfort

=

38,175

−

2,743 backrest uniformity

−

2,431 seat pan uniformity (

R

2

= 0,273)

comfort

=

13,158

+

3,247 backrest comfort

+

2,741 seat pan uniformity

+

1,442 armrest comfort (

R

2

=

0,511)

This indicates that the uniformity of pressure distribution on the backrest andseat pan are the main factors determining discomfort, whereas comfort is mainlydetermined by the comfort of the backrest and the uniformity of pressure distributionof the seat pan and, to a lesser extent, by the comfort of the armrest. Other elementssuch as softness of the seat, armrest material, and texture of the seat appear to beof a lesser importance.

2.3.4 T

HEORY

OF

H

AND

T

OOL

C

OMFORT

Most theories of comfort concern seating. However, comfort also plays an importantrole in the use of hand tools. Based on studies where users were asked to describetheir experience with screwdrivers, Kuijt-Evers et al. (2004a) showed an important

TABLE 2.4The Statements Used in the Chair Evaluation Checklist

Discomfort statements Comfort statements

-I have sore muscles -I feel relaxed-I have heavy legs -I feel fit-I feel uneven pressure -The chair feels soft-I feel stiff -The chair is spacious-I feel restless -The seat looks nice-I feel tired -I like the chair-I feel uncomfortable -I feel comfortable

The 79 office workers gave their ratings for each statement on a 9-pointscale (1

=

I complete disagree; 9

=

I completely agree). From Helander and Zhang (1997).

24


difference between the construct of comfort/discomfort in using hand tools (such asscrewdrivers and pliers) and comfort/discomfort in seating. In seating, comfort anddiscomfort are different entities with different underlying determinants. Comfort isassociated with feelings of relaxation and well-being and discomfort is associatedwith pain, tiredness, soreness, and numbness (Zhang et al. 1996). However, in the useof hand tools adverse body effects, like cramped muscles, blisters, and inflamed skin,underlie both comfort and discomfort. Additionally, comfort is mostly determined byfunctionality and physical infraction using hand tools (Kuijt-Evers et al. 2004b). Thiscould be explained by the different nature of seats and hand tools. Unlike sitting, theuse of hand tools is mostly accompanied by discomfort. Helander and Zhang (1997)argue that when discomfort factors are present, comfort factors become secondary inthe perception of comfort/discomfort. Because discomfort factors are present in handtool use, comfort may be dominated by discomfort. Therefore, respondents may alsothink of comfort while using hand tools in terms of the absence or reduction ofdiscomfort.

These results are supported by several hand tool evaluation studies in whichcomfort is measured in terms of discomfort (Chao et al. 2000; Fellows and Freivalds1991). From this perspective, comfort and discomfort in using hand tools can beseen as two opposites on a continuous scale, as supported by Vergare and Page(2000), Jianghong and Long (1994), Wilder et al. (1994), and Jensen and Bendix(1992). The factors having the closest relationship with comfort are

good fit in hand

,

functional

,

easy to use

, and

reliable

(Table 2.5).Clustering these factors is also possible. Descriptors such as

good fit in hand

,

functional, reliable, and safe have a strong relationship with comfort in using handtools. Descriptors such as solid design, professional looks, styling, and nice colorare slightly related or not related at all to comfort. Based on statistical analysis,six comfort factors could be distinguished (functionality, posture and muscles,irritation and pain of hand and fingers, irritation of hand surface, handle charac-teristics, and aesthetics; see Table 2.6). These six factors explain 53.8% of thevariance and can be classified into three meaningful groups: functionality, physicalinteraction, and appearance. We can conclude that in the use of hand tools thesame descriptors are related to comfort as to discomfort; descriptors of function-ality are most related to comfort, followed by descriptors of physical interaction;and descriptors of appearance become secondary in determining comfort whenusing hand tools.

2.3.5 THEORY OF VEHICLE INTERIOR COMFORT

Vehicle interiors are found, for example, in earth-moving machines, trains, streetcars,cars, and airplanes. In a vehicle, a seat and often controls (more or less related tohand tools) are found among other elements that influence comfort, such as view,climate, noise, and vibration. This complicates the decision on how to improve thecomfort in a vehicle interior. The theory of comfort and discomfort in seating and inusing hand tools does not give us enough support to make a decision on how an idealcomfortable interior should be designed. Based on theory, we may know how todesign a comfortable seat and comfortable controls, but comfort in such a complicated

Theory of Comfort 25

environment as a vehicle interior is determined by more factors than these. Therefore,information is needed about all the aspects that influence comfort in vehicle interiors,as well as about the relationships between them.

Because comfort is a subjective phenomenon, the end user plays an importantrole in the specification of the aspects of comfort that need improvement. The next

TABLE 2.5Ranking of Descriptors in the Study of Kuijt-Evers et al. (2004a)

DescriptorMean rating* Descriptor

Mean rating*

1 Good fit in hand 1.10 21 Sharpness 1.422 Functional 1.10 22 No slippery handle 1.443 Easy in use 1.14 23 Pleasurable 1.444 Reliable 1.14 24 No irritation 1.485 Force exerted from tool 1.16 25 No numbness in fingers 1.516 Safe 1.20 26 No inflamed skin 1.527 Handle feels comfortable 1.22 27 Handle size 1.588 No peak pressure on hand 1.24 28 Relaxed working posture 1.629 No blisters 1.24 29 Roughness of handle surface 1.6410 High-quality tool 1.24 30 No sore muscles 1.6411 No pain 1.24 31 Handle doesn’t feel clammy 1.7012 Task performance 1.26 32 Easy to take along 1.7413 No body part discomfort 1.27 33 Weight of tool 1.7814 High product quality 1.28 34 No pressure on hand 1.8015 Lack of tactile feeling 1.29 35 No sweaty hands 1.8016 Low handgrip force supply 1.34 36 Handle hardness 1.8217 No muscle cramp 1.36 37 Solid design 2.7818 Handle shape 1.38 38 Professional looks 3.0819 Friction between hand and handle 1.39 39 Styling 3.3820 Comfortable working posture 1.41 40 Nice color 3.68

* The lowest score has the closest relationship to comfort.

TABLE 2.6Cluster of Factors Influencing Comfort or Discomfort during Hand Tool Use

Discomfort Comfort- Nonfunctional - Functional- Bad posture/high muscle activity - Good posture/relaxed muscle activity- Irritation and pain in hand/fingers - No irritation and pain in hand/fingers- Bad hand surface - Good hand surface- Bad handle characteristics - Good handle characteristics- Bad aesthetics - Good aesthetics

The upper factors are of greatest importance.Based on Kuijt-Evers et al. (2004a)

26 Comfort and Design: Principles and Good Practice

section presents an example of how end users give their opinions on what shouldbe improved in an earth-moving machine.

2.3.5.1 Comfort Aspects in Earth-Moving Machines

Comfort in earth-moving machines has improved dramatically in the last 4 yearsand is seen as an important sales argument. A study among 84 designers andmarketers employed by manufacturers (Vink et al. 2003) showed that 80 of themanufacturers will pay attention to comfort during the coming years. Comfort, then,is an issue. Most priority will be given to seat improvements, followed by noise andview issues (Fig. 2.7). The attention given differs somewhat if the answers ofdesigners and engineers are compared with the answers of sales and marketingmanagers. Sales and marketing focus more on noise, whereas designers and engi-neers give priority to seats and controls.

It will be interesting to see whether the emphasis of the manufacturers really fullfilsthe needs of end users. Therefore, the results of this study will be compared with theoperators’ needs. The conclusion is that comfort cannot be left out of the machineanymore. The automotive industry paid attention to comfort for more than 10 years,although a lot remains to be improved there, too. In fact, operators of earth-movingmachines are used to comfort in their own cars and have similar demands for theinteriors of their machines.

2.3.5.2 Scientific Knowledge about Vehicle Interiors

Some information is also found in the scientific literature regarding comfort inearth-moving machines. Many studies refer to vibration (Kittusamy 1999) and

FIGURE 2.7 Attention to the comfort aspects by 80 representatives of manufacturers in thecoming years.

0 10 20 30 40

seat

controls

noise

vision

climate

vibration

cab dimensions

steering wheel

design/engin.

sales/ market.


noise (Brambilla et al. 2001). Zimmerman et al. (1997) show that the mainproblems of earth-moving machinery operators concern physical complaints in theneck/shoulder and low back region, as well as general fatigue and feelings ofdiscomfort. This might be attributed to a combination of static load during pro-longed and often awkward sitting postures, exposure to whole-body vibrations,and handling and steering the machine (Zimmerman et al. 1997; Tola et al. 1988;Looze et al. 2000).

A comfortable, well-designed vehicle interior may improve postures and providean environment stimulating optimal operator performance. Based on a literaturereview about musculoskeletal disorders and their risk factors, Zimmerman et al.(1997) recommended four guidelines for reducing work-related musculoskeletaldisorders among operators:

• Minimizing the magnitude and frequency of vibration reaching the operator• Optimizing the location of controls so that reach distance, trunk flexion,

and rotation are minimized• Providing maximum operator visibility from an upright, supported, seated

posture• Taking regular breaks to minimize the effects of sustained postures

Improvements in cab comfort are very often based on reducing the risk factorsfor work-related musculoskeletal disorders (Zimmerman 1997; Attebrant 1997).Aspects that have to be improved are mentioned in only a few studies. Nakada (1997)describes the desirability ranking defined for dump trucks and wheel loaders by agroup consisting of a product creator, designers, design engineers, operators, andyoung people. Nakada (1997) shows that from a design perspective much attentionis paid to the instrument panel monitors and meters and the operator seat.

Unfortunately, the operators’ opinions cannot be distinguished in Nakada’s study(1997). In order to design a comfortable vehicle interior, the opinions of the operatorsare important, as they are the end users of the machines. Their experience as usersmay be of great help in designing a comfortable cab. Therefore, Kuijt-Evers et al.(2003) defined aspects mentioned by wheel loader and excavator operators that canbe used to improve the comfort of vehicle interiors in the future.

2.3.5.3 A Study to Find Out End-User Opinions

In the study by Kuijt-Evers et al. (2003), 336 operators were interviewed at aBAUMA trade fair, the world’s largest exhibition of construction equipment. Mostof the participants were wheel loader operators (n = 61) and excavator operators(n = 212). Only the results for excavator operators are presented here, as they accountfor 62.7% of the respondents. Figure 2.8 is an example of an excavator and a wheelloader is shown in Fig. 2.9. The interview questions considered characteristics ofthe population, evaluation of the current machine being operated, and futuredemands. Kuijt-Evers et al. (2003) assumed that if more than 20% of the operatorsrated a part of the machine “average” or “poor,” then comfort improvements werepossible in the vehicle’s interior.


FIGURE 2.8 An excavator.

FIGURE 2.9 A wheel loader.


2.3.5.3.1 Current MachineAmong the excavators, 50% appeared to be less than 4 years old. Of the excavatoroperators, 55.9% rated the overall cabin comfort as “good” or “very good.” To findaspects that can increase cab comfort in the future, only the data of newer machinesis analyzed.

As seen in Table 2.7, several aspects of the excavators are rated “average” or“poor” by more than 20% of the operators, including seat, vibration and damping,dashboard and displays, and climate control.

2.3.5.3.2 Improvement PossibilitiesThe operators also generated 467 ideas to improve the machine’s comfort. Theseaspects were classified into 15 categories, of which seat comfort, climate control,cab design (cab design, dimensions, ingress/egress), and accessories are most oftenmentioned (Fig. 2.10).

TABLE 2.7Aspects Rated “Average” or “Poor” by More Than 20% of the Operators for Excavators Less Than 4 Years Old

Aspect Operators (%) Seat comfort 29.5Vibration and damping 27.0Dashboard and displays 26.0Climate control 24.1What the machine looks like 24.0Cab dimensions, interior space, ingress and egress 22.3Noise reduction 21.9View 21.9Adjustability of seat and controls 21.0Reliability 20.9

FIGURE 2.10 Categories of items most mentioned by operators to improve vehicle interiorcomfort.

seat comfort21%

climate contro19%

cab design19%

accessories12%

others29%


When the results of Kuijt-Evers et al. (2003) are compared with the results ofNakada (1997), both studies rank the operator seat high. The instrument panel,monitors, and meters are also ranked high in the study by Nakada (1997). In thestudy by Kuijt-Evers et al. (2003) the dashboard and displays are high on the listof parts rated as “average” or “poor” by more than 20% of the operators, but theyare not seen as aspects that can improve cab comfort. Kuijt-Evers et al. (2003) alsomention vibration but Nakada (1997) does not, probably because experienced oper-ators played a larger role in the Kuijt-Evers study (2003) compared to Nakada’ssubjects, and because Nakada was focused on the interior design. This study showshow information from end users can be gathered to set priorities for improvingcomfort among the parts of a vehicle interior.

2.4 CONCLUSIONS

In this chapter the theory of comfort has been described in relation to design.Comfort/discomfort is a construct of a subjectively defined personal nature. It isaffected by various kinds of factors (physical, physiological, and psychological),and it is a reaction to the environment. A theoretical model of comfort/discomforthas been proposed, based on literature review and experiments and specified forseats, hand tools, and vehicle interiors. The subjective character of comfort/discomfort implies that the opinion of end users is needed when designing com-fortable products.

The study concerned with earth-moving machinery showed that end users as wellas manufacturers could give important information on how to design a more comfort-able product. These may help focus attention on the major aspects that need improve-ment in order to achieve our goal: the design of comfortable products and workplaces.

ACKNOWLEDGMENT

The authors want to thank the Koninklijke Ahrend NV for supporting part of thisstudy.

REFERENCES

Armstrong, T.J., Buckle, P., Fine, L.J., Hagberg, M., Jonsson, B., Kilbom, A., Kuorinka,I.A.A., Silverstein, B.A., Sjøgaard, G. and Viikari-Juntira, E.R.A. (1993) “A concep-tual model for work-related neck and upper limb disorders.” Scandinavian Journalof Work, Environment and Health, 19: 73–84.

Attebrant, M., Winkel, J., Mathiassen, S.E. and Kjellberg, A. (1997) “Shoulder-arm muscleload and performance during control operation in forestry machines; effects of chang-ing to a new armrest, lever and boom control system.” Applied Ergonomics, 18(2):85–97.

Bongers, P.M., et al. (2000) Risicofactoren voor lage rugklachten: resultaten van een longi-tudinaal onderzoek, Hoofddorp: TNO Arbeid.

Brambilla, G., Carletti, E. and Pedrielli, F. (2001) “Perspective of the sound quality approachapplied to noise control in earth-moving machines.” International Journal of Acous-tics and Vibration, 6(2): 90–96.


Bronkhorst, R.E. and Krause, F. (2002) “End-users help design mass transport seats.” InHuman Factors in Seating and Automotive Telematics (SP-1670), SAE World Con-gress, Detroit, Michigan, March 4–7. Warrendale (PA): SAE, 1–6. SAE TechnicalPaper Series 2002-01-0780.

Bronkhorst, R.E., Kuijt-Evers, L.F.M., Cremer, R., Rhijn, J.W. van, Krause, F., Looze, M.P.de and Rebel J. (2001) Emotie en Comfort in Cabines: Rapportage TNO Basisfinan-ciering 2000, Team 40, Hoofddorp: TNO Arbeid.

Chao, A., Kumar, A.J., Emery, C.T.N.D., Nagarajarao, K. and You, H. (2000) “An ergonomicevaluation of cleco pliers.” Proceedings of the 14th Triennial Congress of the Inter-national Ergonomics Association, San Diego: 4–441 (on CD-ROM).

Fellows, G.L. and Freivalds, A. (1991) “Ergonomics evaluation of a foam rubber grip for toolhandles.” Applied Ergonomics, 22(4): 225–230.

Goossens, R.H.M. (1998) “Measuring factors of discomfort in office chairs.” In P.A. Scott et al.,eds., Global Ergonomics. Proceedings of the Ergonomics Conference, Amsterdam:Elsevier Science.

Goossens, R.H.M., Teeuw, R. and Snijders, C.J. (2002) “Sensitivity for pressure differenceon the ischial tuberosity.” Ergonomics (submitted).

Helander, M.G. and Zhang, L. (1997) “Field studies of comfort and discomfort in sitting.”Ergonomics, 40: 895–915.

Herzberg, F., Mausner, B. and Snyderman, B.B. (1993) The Motivation to Work, Somerset,NJ: Transaction Publishers.

Jensen, C.V. and Bendix, T. (1992) “Spontaneous movements with various seated-workplaceadjustments.” Clinical Biomechanics, 7: 87–90.

Jianghong, Z. and Long, T. (1994) “An evaluation of comfort of a bus seat.” Applied Ergo-nomics, 25: 386–392.

Kittusamy, K. (1999) Subjective Response to Whole-Body Vibration among Operators ofConstruction Equipment, Huntington, WV: Marshall University.

Kuijt-Evers, L.F.M., Krause, F. and Vink, P. (2003) “Aspects to improve cabin comfort ofwheel loaders and excavators according to operators.” Applied Ergonomics, 34(3):265–272.

Kuijt-Evers L.F.M., Groenesterjin, L. Looze, M.P. de, and Vink, P. (2004a) “Identifying factorsof comfort in using hand tools.” Applied Ergonomics, 35(5): 453–458.

Kuijt-Evers L.F.M., Twist, J. Groenesterjin, L. Looze, M.P. de, and Vink, P. (2004b) “Iden-tifying productors of comfort and discomfort in using hand tools using the comfortquestionnaire for hand tools (CQH).” Ergonomics (submitted).

Looze, M.P. de, Kuijt-Evers, L.F.M. and Dieën, J.H. van (2003) “Sitting comfort and discom-fort and the relationships with objective measures.” Ergonomics, 46: 985–997.

Looze, M.P. de, Roetting, M., Vink, P. and Luczak, H. (2000) “Towards comfortable andefficient man–machine interaction in the cabins of vehicles.” Proceedings of the 14thTriennial Congress of the International Ergonomics Association, San Diego: 3–340(on CD-ROM).

Lugt, R. van der (2001) Sketching in Design Idea Generation Meetings, Delft: TU Delft(Proefschrift).

Marras, W.S. (2003) “The future of research in understanding and controlling work-relatedlow back disorders.” In Ergonomics in the Digital Age, Proceedings of the 15thTriennial Congress of the International Ergonomics Association, Seoul (on CD-ROM).

Nakada, K. (1997) “Kansei engineering research on the design of construction machinery.”International Journal of Industrial Ergonomics, 19: 129–146.

Picard, R.W. (1997) Affective Computing, Cambridge, MA: MIT Press.


Proper, K.I., Bongers, P.M. and Grinten, M.P. van der (1999) Longitudinaal onderzoek naarrug-, nek- en schouderklachten. Deelrapport 5: Lokaal ervaren ongemak. De relatiemet en de voorspelling van klachten aan het bewegingsapparaat, Hoofddorp: TNOArbeid.

Richards, L.G. (1980) “On the psychology of passenger comfort.” In D.J. Oborne and J.A.Levis, eds., Human Factors in Transport Research, vol. 2. London: Academic Press,15–23.

Schifferstein, H.N.J., Cleiren, M.P.H.D. (2004) “Capturing product experiences: a split-modalityapproach.” American Journal of Psychology (submitted).

Slater, K. (1985) Human Comfort, Springfield, IL: Charles C. Thomas.Sonneveld, M.H. (2002) “Tactiele beleving van de gebouwde omgeving.” In R.N. Pikaar, ed.,

Ergonomie van de gebouwde omgeving, congresboek 2002, Enschede: ErgoS, 157–164.Theimer, E.T., ed., (1982) Fragrance Chemistry: The Science of the Sense of Smell, New York:

Academic Press.Tola S., Riihimaaki, H., Viderman, T., Viikari-Juntura, E.H. and Tanninen, K. (1988) “Neck and

shoulder symptoms among men in machine operating, dynamic physical work andsedentary work.” Scandinavian Journal of Work, Environment and Health, 14: 299.

Vergara, M. and Page, A. (2000) “System to measure the use of the back rest in sitting-postureoffice tasks.” Applied Ergonomics, 31: 247–254.

Vink, P. and Hark, T.A. ter (2003) “Future demands on comfort in construction vehicles’interiors according to manufacturers.” In F. Krause, R.E. Bronkhorst and M.P. de Looze,eds., Comfortable Earth-Moving Machinery: Knowledge and Experiences from theEurocabin Project, Hoofddorp: TNO Work and Employment, 99–105.

Vink, P., Hark, T.A. ter and Krause, F. (2001) Future Demands on Comfort in ConstructionVehicles’ Interiors According to Manufacturers, Hoofddorp: TNO Work andEmployment.

Wilder, D., Magnusson, M.L. and Pope, M. (1994) “The effect of posture and seat suspensiondesign on discomfort and back muscle fatigue during simulated truck driving.”Applied Ergonomics, 25: 66–76.

Winkel, J. and Westgaard, R. (1992) “Occupational and individual risk factors for shoulder-neck complaints: Part II—The scientific basis (literature review) for the guide.”International Journal of Industrial Ergonomics, 10: 85–104.

Zhang, L., Helander, M.G. and Drury, C.G. (1996) “Identifying factors of comfort anddiscomfort in sitting.” Human Factors, 38(3): 377–389.

Zimmerman, C.L., Cook, T.M. and Rosecrance, J.C. (1997) “Work-related musculoskeletalsymptoms and injuries among operating engineers: A review and guidelines forimprovement.” Applied Occupational and Environmental Hygiene, 12(7): 480–484.

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0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

3

A Theory on Pressure Distribution and Seat Discomfort

K. Noro, G. Fujimaki, and S. Kishi

CONTENTS

3.1 Pressure and Discomfort ................................................................................333.2 General Discussion ........................................................................................333.3 Explanation in a Specific Case ......................................................................343.4 Conclusions ....................................................................................................39References................................................................................................................39

3.1 PRESSURE AND DISCOMFORT

As described in Chapter 2, pressure distribution has a clear relationship with dis-comfort during sitting. It is among all objective measurement techniques, it is perhapsthe most convincing (Looze et al. 2003). Several studies are concerned with thisrelationship (Ebe and Griffin 2000; Ebe and Griffin 2001; Kamijo et al. 1982; Parkand Kim 1982; Vergara and Page 2000). This chapter describes a theory of how thisrelationship can be explained. The relationship is developed based on years ofresearch at Waseda University and ErgoSeating Co., Ltd. In particular, the changein pelvis angle and body pressure distribution and their relationship will be describedin this chapter, and an explanation for the importance of pressure distribution willbe given.

3.2 GENERAL DISCUSSION

Fujimaki (2002) has shown that there is a relationship between discomfort in timeand pressure distribution. A higher pressure resulted in more discomfort, which is inalignment with other studies (e.g., Looze et al. 2003). This chapter concerns thechange in time of two objectively measurable factors that are closely connected withthe sense of discomfort. These two factors are pelvis angle and body pressure distri-bution. Both are graphically demonstrated Fig. 3.1 — the seated human model.

34


On earth, human bodies are under the influence of gravitational forces. Thismeans that the body is pulled downward due to its weight. Pressures on the bottomand under the feet carry most of this weight. To change these pressures it is possibleto move the pelvis in three directions: yaw, roll, and pitch (Fig. 3.1). The theory inthis case is that this movement is experienced when the discomfort rises above acertain threshold. The pressure distribution under the buttock can be measured.Figure 3.2 is an example of a pressure map measured between buttock and seat pan.

3.3 EXPLANATION IN A SPECIFIC CASE

In Fig. 3.3 a model is shown that describes the relationship between pelvis positionand pressure (a specific case is shown in Fig. 3.10). The position of the pelvisinfluences pressure distribution under the buttock and a pressure also influencesthe position of the pelvis. In this study the relationship is described during a period

FIGURE 3.1

The seated human model.

FIGURE 3.2

An example of body pressure measured between the buttock and the seat.Pressure is measured in mmHg.

A B C D E F G H I J K L M N O

123456789101112131415

200

180

160

140

120

100

80

60

40

20

0mmHg


35

of sitting. With this model, information as to posture changes in the pelvis rotationcaused by the pressure changes between buttock and seat pan can be understoodover time. The assumption is that the sense of discomfort is affected by this pressureand influences the pelvis position.

To describe the relationship, pressure on the seat pan and the pelvis angle weremeasured during 50 minutes of computer work. Figure 3.4 shows a chair used inthis measurement, and the environment of the experiment is shown in Fig. 3.5. Thecomputer displayed at the lower left of this picture shows the body pressure of thesubject. Figure 3.6 and Fig. 3.7 present the changes in roll and pitch, respectively,observed in the pelvis movement over time.

FIGURE 3.3

A model showing the relationship between pelvis angle and pressure distribution.

FIGURE 3.4

A chair used in this study.

36


Figure 3.8 presents the fluctuation in average pressure on the seat pan observedduring 50 minutes of work, and changes in the maximum pressure on seat pan forthe same period are shown in Fig. 3.9. If we compare Fig. 3.6 with Fig. 3.9, causalrelationships can be described: The pelvis position changes abruptly the momentbody pressure on the buttock exceeds a certain value. Figure 3.10 shows the syn-chronized movement of pelvis angle and pressure map when the subject is resetting.In previous experiments these phenomena were frequently seen after working morethan 30 minutes in one posture. Point A is just before the subject started movement,point B is when the subject was resetting, and point C is just after the subject finished

FIGURE 3.5

Environment of the experiment.

FIGURE 3.6

Changes in the roll angle of the pelvis during 50 minutes of seated work.

0

10

20

30

40

50

0 10 20 30 40 50

Time (min.)

Rol

l ang

le (

deg.

)


37

FIGURE 3.7

Changes in the pitch angle of the pelvis during 50 minutes of seated work.

FIGURE 3.8

Changes in the average pressure on the seat pan during 50 minutes of seated work.

FIGURE 3.9

Changes in the maximum pressure on the seat pan during 50 minutes of seatedwork.

–30

–20

–10

0

10

20

0 10 20 30 40 50

Time (min.)

Pitc

h a

ng

le (

de

g.)

02468

1012141618

0 10 20 30 40 50

Time (min.)

Ave

rage

pre

ssur

e (m

mH

g)

020406080

100120140160180200

0 10 20 30 40 50

Time (min.)

Max

imum

pre

ssur

e (m

mH

g)

38


the move. There was high pressure on the buttock at point A, and the uncomfortablefeeling of the high pressure caused the subject’s macro movement. This macro move-ment reduced the high pressure on buttock, and the subject was able to maintain thesitting posture for a while longer. From the result, it can be said that the pressuremaps at points A and B represent the uncomfortable condition, and the pressure mapat point C is the comfortable condition.

FIGURE 3.10

The relationship between pelvic roll angle and body pressure distribution.

FIGURE 3.11

Discomfort accepted (full line) and discomfort not accepted (dotted line) inthe pressure on the buttock.

A

B

C

A B C

–20

–10

0

10

20

30

36:00 36:10 36:20 36:30 36:40

Rol

l ang

le (

deg.

)

Time (min. & sec.)

0 10 20 30 40 500

50

100

150

200

Max

imum

pre

ssur

e (m

mH

g)

Time (min.)

Discomfort zoneComfort zone


39

The aforementioned analysis provides a reasonable basis for categorizing thebody pressure into two zones: discomfort accepted by the human body and discom-fort not accepted (Fig. 3.11).

3.4 CONCLUSIONS

This chapter has described a theory of the relationship between pressure under thebuttock and pelvis position, and a relationship was found between pressure andpelvis position. Also, an explanation and a conclusion as to what could be acceptedas discomfort by the human body were given.

REFERENCES

Ebe, K. and Griffin, M.J. (2000) “Qualitative models of seat discomfort including static anddynamic factors.”

Ergonomics

, 43(6): 771–790.Ebe, K. and Griffin, M.J. (2001) “Factors affecting static seat cushion comfort.”

Ergonomics

,44(10): 901–921.

Fujimaki, G. and Mitsuya, R. (2002) “Study of the seated posture for VDT work.”

Displays

,23: 17–24.

Kamijo, K., Tsujimura, H., Obara, H. and Katsumata, M. (1982) “Evaluation of seatingcomfort.”

SAE Technical Paper Series

820761.Looze, M.P. de, Kuijt-Evers, L.F.M. and Dieën, J.H. van (2003) “Sitting comfort and discom-

fort and the relationships with objective measures.”

Ergonomics

, 46: 985–997.Park, S.J. and Kim, C.B. (1997) “The evaluation of seating comfort by the objective measures.”

SAE Technical Paper Series

970595.Vergara, M. and Page, A. (2002) “Relation between comfort and back posture and mobility

in sitting-posture.”

Applied Ergonomics

, 33: 1–8.

41

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

4

Participatory Ergonomics and Comfort

P. Vink, S. Nichols, and R.C. Davies

CONTENTS

4.1 Why Participatory Ergonomics? ....................................................................414.2 Participants in Design ....................................................................................424.3 Definition of Participatory Ergonomics.........................................................434.4 Approaches.....................................................................................................434.5 The Opinion of Experts .................................................................................444.6 Essence of the Approach................................................................................444.7 Participating Groups ......................................................................................454.8 Stages Towards Implementation ....................................................................46

4.8.1 Stage 1: The Initiative........................................................................464.8.2 Stage 2: Problem Identification and Setting Goals ...........................464.8.3 Stage 3: Solution Choices..................................................................474.8.4 Stage 4: Implementation ....................................................................474.8.5 Stage 5: Evaluation ............................................................................47

4.9 Some Problems in Participatory Ergonomics................................................484.10 Participatory Ergonomics Methods and Design ............................................484.11 Advantage of Using Envisioning Tools .........................................................484.12 Virtual Reality and Participation ...................................................................494.13 Example of Using an Envisioning Tool ........................................................504.14 The Participatory Design Process..................................................................51References................................................................................................................53

Part of this chapter is based on Vink, P., Lourijsen, E., Wortel, E. and Dul, J. (1992)“Experiences in participatory ergonomics: Results of a round table session duringthe 11th IEA congress.”

Ergonomics

, 35(2): 123–127. See also: http://www.tandf.co.uk/journals/tf/00140139.html

4.1 WHY PARTICIPATORY ERGONOMICS?

As stated before, comfort is seen in this book as a subjective phenomenon. Thecomfort or discomfort of a product can therefore be evaluated only by the user. Aproduct in itself can never be comfortable. That is why much attention is paid to

42


how a user should be involved in the design process. End users should be involvedbecause they have unique insights into their tasks, work, or activities. This involve-ment of stakeholders such as end users is addressed in

participatory ergonomics

,and a separate chapter is devoted to this topic. With the help of participatoryergonomics, the design process can be designed with special attention on how totake the participants into account, especially end users.

The positive effects of participation have been demonstrated before and arealso a reason to pay attention to this topic. The European Foundation for theImprovement of Living and Working Conditions (1999) reports that direct partic-ipation in production organizations most often leads to quality improvements (90%of the cases), to reduction of throughput times (60% of the cases), and to reductionof costs (60% of the cases). Several cases in this book, discussed in subsequentchapters, prove that this is also true for the involvement of participants in productdesign.

4.2 PARTICIPANTS IN DESIGN

In work situations the end user is the worker. This is an advantage compared tostudies of consumer products because the target group is more homogeneous andclearly defined. A design is made specifically for a bricklayer, a pilot, or a glazier.In participatory ergonomics this employee is often heavily involved in the designprocess (Vink et al. 1992), but there are other stakeholders and experts involved aswell. More and more design processes have design teams.

According to Palacios of Steelcase, a large office furniture manufacturer inthe United States, such a team is needed at a very early stage (Palacios and Imada1998). Figure 4.1 shows why several participants should be involved at an earlystage of the design process. Facility management is the part of the team thatsupplies information on the demands of buyers. Ergonomists, human movement

FIGURE 4.1

In an early stage of the design process data are needed, which compels a designteam. In this figure the several kinds of data are described according to Palacios and Imada(1998). Workplace items are organization, used methods, and techniques in the work, aes-thetics, culture, etc.

designspecifications

data on ergono-mics and posture

demands ofthe buyers

health & safety,industry standards

workplaceitems

data oncompetitors


43

specialists, or other health and safety executives can provide ergonomics andposture data. Guidelines on production possibilities can be delivered by productionmanagement and engineers. Health and safety experts or labor inspectors couldbe included to supply guidelines on working conditions. Marketing specialistshave information, or have access to information, on competitors. Managementand employees could supply information on the work that is done and theworkplace. Consequently, for a product like an office chair a rather large teamis needed.

4.3 DEFINITION OF PARTICIPATORY ERGONOMICS

Participatory ergonomics is the discipline that studies how different parties shouldbe involved in a design process. Participatory ergonomics is the adaptation of theenvironment to the human (i.e., ergonomics) with the involvement of the properpersons in question (participants) (Vink 2002). Defined in this way, participatoryergonomics is more an umbrella term under which various approaches are found.That is also described in the literature. Kuorinka (1997) describes participatoryergonomics as “practical ergonomics with necessary actors in problem solving.”Wilson (1995) puts it into a wider perspective: “It is the involvement of peoplein planning and controlling a significant amount of their own work activities,with sufficient knowledge and power to influence both processes and outcomesin order to achieve desirable goals.” Thus, Wilson stresses the fact that theemployee should have control over his task, emphasizing that participatory ergo-nomics is an umbrella concept.

The common characteristic is that during the design process attention is paidexplicitly to the role of designers, employees, end users, and others involved. Inthis book, the available knowledge regarding participatory ergonomics is appliedto design.

4.4 APPROACHES

Among others two approaches are often seen in the design practice: (1) a partici-patory design process led by a manufacturer of products; and (2) a participatoryprocess led by the end users, usually those at the managerial level. Illustrations ofboth approaches are found in the next chapters. Chapter 7, on installation workers,is a typical example of an approach led by management of end users. The paintscraper chapter (Chapter 15) is a typical example of a design process led by amanufacturer.

There is an important difference between these approaches in terms of settinggoals. When the process is guided by the manufacturer, the manufacturer definesthe goal of the design process. Often this is a product that anticipates a forthcomingcustomer need for comfort. In the second approach, it is important that the manage-ment and employees of the company define the goal.

44


4.5 THE OPINION OF EXPERTS

Participatory ergonomics is a combination of different approaches. However, com-mon themes can be distinguished that are interesting both for designers of comfort-able products and for management. In order to review experiences of participatoryergonomics and to identify common themes, a roundtable was organized in one ofthe international ergonomics meetings (Vink et al. 1992). Eighteen ergonomists(Table 4.1) with experience in participatory ergonomics attended the session. Theyapplied the approach mostly in large companies (10 out of 18) and less frequentlyin smaller companies (6 out of 18) or sectors of trade (7 out of 18). The roundtablediscussion addressed the following questions:

• What is essential in the approach?• Who should participate?• What are the elements of an ideal process?• What problems are seen most often?

The results of the session with the 18 experts are summarized in the next sections.

4.6 ESSENCE OF THE APPROACH

Participatory ergonomics focuses on an ergonomic strategy that can be applied indifferent ways in different fields of ergonomics. An essential part of this strategy isthat direct participation of the stakeholders involved should be strived for in animprovement process. In this process (Fig. 4.2), different stages can be discerned(Vink and Kompier 1997; Noro and Imada 1991). Once the process is initiated,problems should be identified and solutions selected and developed. Then the solu-tions should be implemented and the effects, as well as the process itself, should beevaluated, with the results feeding back into the process.

The 18 experts mentioned several approaches to involve workers. The two mostfrequently mentioned are one in which the workers are trained to select improve-ments themselves, and one in which the workers generate ideas and the ergonomistadvises on final selection.

TABLE 4.1 List of Participants in the Session on Participatory Ergonomics

R. Akselsson (Sweden) M.J. Costa (Canada) Etienne (France) P. Hasle (Denmark)M. Hedman (Sweden) M. Helander (U.S.)C. Hurts (Netherlands) M. Joyce (U.S.)G. Jungetag (Sweden) A. Kamp (Denmark)E.A.P. Koningsveld (Netherlands) J. Kloosterboer (Netherlands)I. Kuorinka (Finland) M. Launis (Finland)H. van der Molen (Netherlands) A. Oginski (Poland)L. Patry (Canada) B. Silverstein (U.S.)


45

According to the 18 experts, essential elements in the participatory ergonomicsapproach are

• Explicit attention on adapting the environment to human capabilities• Striving for direct involvement of the participants• Using a stepwise approach

4.7 PARTICIPATING GROUPS

People from many different levels of the company can be involved in the partici-patory ergonomics strategy (Table 4.2). Involvement depends strongly on the par-ticular way in which groups have to play a role. If the program of improvement isnot too radical, only workers and the lower level of management need participate.But in many cases, for example where decisions on budgets or organizational

FIGURE 4.2

Different stages of a participatory ergonomics program.

TABLE 4.2 List of Possible Parties Involved in Participatory Ergonomics

Employees/workersEmployers/managementMaintenance engineersDesign engineersHealth and safety workers (e.g., occupational physician)Low-level management (e.g., foreman, supervisor)Trade unionsBranch organizationsCentral purchase unitsIn-company health and safety committees

1. initiative

5. evaluation

4. implementation

3. selection of solutions

2. problem identification

46


structures are involved, middle management or even top management should alsoparticipate, given their decision-making power. One review (Cotton et al. 1988)argues that involving a group that is only representative of workers in a workinggroup, rather than the workers themselves, will not lead to successful participation.It is also vitally important to have workers develop ideas for improvement incollaboration with managers.

4.8 STAGES TOWARDS IMPLEMENTATION

4.8.1 S

TAGE

1: T

HE

I

NITIATIVE

To begin a participatory ergonomics program an initiative should be taken some-where, either within or outside the organization. Different potential starting pointswere mentioned by the 18 experts during the roundtable session. For example,workers, occupational physicians, sector organizations, or unions could be aware ofa problem and initiate the approach. Of course, successful implementation is morelikely when the workers take the initiative or are in need of the improvement andthus

desire

improvements.In one example mentioned during the session, the occupational health service

initiated the process (Patry et al. 1991). Thereafter, a joint committee of workersand management was formed and started discussions at different levels within thecompany. In this case, the role of the ergonomists was to stimulate discussions toallow the workers to formulate improvements. An initiative can also be created bymanagement (Chapter 10) or from outside the company, for example by the laborinspectorate, a union, or a sector organization (Chapter 6). Starting the project willthen be difficult because the attitude of potential participants inside the companymay be indifferent or even hostile.

4.8.2 S

TAGE

2: P

ROBLEM

I

DENTIFICATION

AND

S

ETTING

G

OALS

The involvement of both workers and management in the problem identificationstage was stressed. If the identification of the problem is done without participationof any one group within the company, implementation could become a problembecause some people might not be aware that there

was

a problem!It was also emphasized that in the early stages of the project, goals and a general

framework (a common concept) agreed to by all groups should be formulated. Thisis essential because in a later stage decisions that have unfavorable consequencesfor one or another of the parties might be necessary. It is quite common that workersand management have different, even conflicting, interests. Having defined a com-mon concept, unity of purpose rather than division is the result.

The concept should also be formulated in a language with which the company iscomfortable. This could be an improvement in product quality or in the efficiencyof the production process. Having such a concept makes it clear to all parties whycertain meetings or training programs are necessary. Various tools can be used toidentify problems, among them self- or corporate assessment training for workersand management, checklists, work analysis, feedback by video or slides, mock-up


47

(Chapters 13 and 20), simulation systems (Chapter 9), Ergomix (Chapter 13), andso on.

4.8.3 S

TAGE

3: S

OLUTION

C

HOICES

Another essential stage in the participatory process is the selection of solutions andimprovements. Again, the 18 experts felt that the workers should always play a rolebecause they are most familiar with their work content. Testing the improvementsis very important. Workers should also be informed about other activities needed tomake the product so as to establish their contribution to the product. This is neededto achieve better improvements and to avoid worsening the situation for otherworkers.

Two approaches were mentioned for the selection of improvements. In the first,workers are trained to participate in a process of improving the working environmentand to set priorities themselves. This recognizes the fact that the workers know theirwork best. An advantage is that the implementation will be easier; disadvantagescould be that the management is neither convinced nor committed, or ineffectiveimprovements are selected. In most situations, workers are not capable of actuallydesigning the product, which makes a next step necessary: the design. Collaborationwith product designers is therefore inevitable.

The second approach calls for workers to formulate improvements and forexperts to make the final selection. The advantage of this approach is that the optimalimprovement is chosen. In the discussion it was noted that experience showed thatworkers and experts commonly selected similar improvement strategies.

As mentioned earlier, decisions can lead to conflict and disagreement on appro-priate improvement strategies. Therefore, a decision-making structure is needed. Toavoid conflict, the improvement strategy should align with the earlier-stated concept,so that everyone can at least understand why the actual improvement is chosen.Consensus on criteria for choosing improvements, such as financial limitations,employment security, and production rates, is also important and should be statedat the beginning of the process.

4.8.4 S

TAGE

4: I

MPLEMENTATION

Using a participatory strategy, implementation can be easy because workers andmanagement have selected the improvements themselves. Of course, attention isneeded to facilitate technical realization, promotion, training, and instruction. Toachieve implementation of improvements such as optimal workplaces, a permanent,embedded participatory process could be necessary. For example, workers in thecompany can be trained to work towards ergonomic improvements continuously(train the trainee stage).

4.8.5 S

TAGE

5: E

VALUATION

In this stage the process can be evaluated to improve the implementation or to learnfor future cases. It could also be an opportunity to evaluate the effect of the process,to look for new possibilities of improvement, and to learn. Too often this step is

48


underestimated (Chapter 7). It can yield valuable information that can be used inmarketing (Chapter 15) or to increase knowledge.

4.9 SOME PROBLEMS IN PARTICIPATORY ERGONOMICS

During the session, various problems in applying participatory strategies were dis-cussed. The three most frequently mentioned problems are listed below.

• Management is not yet convinced of the need for ergonomic improvement.When management does not take the improvement initiative, they willneed to be convinced as to the need for improvements, which may bedifficult. A solution to this problem is to address the managers in theirown language, as described by Kogi (1985). This can mean stressing aneconomic goal or benefit and giving concrete examples.

• Workers deny the need for improvement. In this case the starting point should not be the improvement itself; theworkers should first be aware of the problems. Starting with training theworkers on work problems is essential; thereafter the workers shouldgenerate improvements themselves.

• Conflict between workers and management. As suggested above a common concept should be agreed and set by allgroups involved from the start. During the project realization, the unifyinggoal should be stressed, rather than the divisory one. This makes a com-promise understandable and acceptable.

4.10 PARTICIPATORY ERGONOMICS METHODS AND DESIGN

The previously mentioned approach is rather general and not specifically focusedon design. In designing an interior, seat, hand tool, or assembly line, specific toolsare often used to involve end users actively in the design process. Tools that havepreviously been used in participatory workplace design projects, in a variety ofcontexts, include round-robin questionnaires, focus groups, drama, democratic meet-ings, virtual reality, layout modeling, and mock-ups and full-scale laboratory mod-eling (Davies 2000).

4.11 ADVANTAGE OF USING ENVISIONING TOOLS

Participatory design is a learning process for all participants (Ehn 1988; Ehn et al.1996). New understandings are created and refashioned, aided by the designer’stacit, nonverbalized design knowledge and augmented by the participant’s engage-ment with the environment. Activating design tools can serve to animate and enlivenusers (Ehn et al. 1996). The tool becomes part of the design activity, helps in verbalizingthe participants’ expectations, and stimulates their creativity (Stoeckli et al. 1993).


49

Tools can allow both the contemplation of the design problem in an abstract wayand the ability to relate solutions to reality (Hornyánszky 1998).

A vital prerequisite to allowing participants to be involved in a meaningful wayis that they experience being in control of the tools (Ehn 1988; Schön 1983). Theinsight that the tool gives depends mostly on how easily it can be understood.Successes have been achieved in projects where full-scale objects, mock-ups, andprototypes have been used (see also Chapter 13 and 20). These achievements canbe explained by the similarity of the tools to the devices that participants use in theirdaily lives. The deployment of this type of design method means that the situationand environments that are forged are not merely attempts to verbally describe andimagine the future use of an environment, but instead serve as a method of experi-encing that world through direct physical involvement.

4.12 VIRTUAL REALITY AND PARTICIPATION

In addition to the achievements of physical prototyping, another strand of researchcomes from recent work on the use of virtual reality (VR) (Fig. 4.3).

According to a previous overview of virtual reality and systems design (Davies2001), VR is well suited for the design of large and complex systems that constitutea vehicle. In such designs, many people with diverse areas of expertise are involvedover a long period of time (Östman 1998). Among the companies using VR for vehicledesign are Volvo, John Deere, Ford, Chrysler, General Motors, British Aerospace,Aerospatiale, and Boeing, to name a few. It saves time and can increase qualitybecause tests with real subjects are replaced by model work.

Design in this area includes concept formulation (perhaps looking at the outerform of a car: Is it pleasing to the eye? What is the wind drag coefficient?); planningthe actual construction sequence of the final product; and testing issues, such asorder of assembly and part fit. People may also be included in the VR design, perhapsas drivers or machinery controllers to ensure that there is enough standing room orthat controls can be reached and activated. In some cases, reaching a control —

FIGURE 4.3

A scene from a virtual reality movie to support discussion on the design of thework station.

50


perhaps a lever — can result in a body position that does not allow enough torqueto be applied to actually perform the required action. In other situations, the factorof interest is more obscure, such as sitting comfort over a long period of time oraccess to driver controls for people of varying body dimensions.

Another problem is putting many parts together into small areas, such as in theengine bay, where they compete for space with other elements. The arrangement ofwires and pipes has to be drawn in a way that is physically possible, that keeps theamount of material used to a minimum, that allows mounting in the first place andfixing at later stages, and (in many cases) that is not in the way, or is completelyhidden.

Sometimes the use of a vehicle within a certain environment is of interest, inwhich case the vehicle is modeled as well as a suitable place for it to be driven in.This allows ergonomic testing in an ecologically valid situation. Combining virtualenvironments with physical artifacts can further heighten the sense of realism,particularly if the physical controls are coupled to the computer system. In Fig. 4.4 aplan for a town is discussed with end users (citizens) with the support of VR andmock-ups. VR is a worthwhile system to be used before testing comfort with realend users as well.

4.13 EXAMPLE OF USING AN ENVISIONING TOOL

One of the envisioning instruments is the Ergomix (Fig. 4.5). It uses blue screentechnology, a system that is widely used in the film and television industry tosuperimpose video images of a person on any background image. Blue screen hasalso been used in design environments, for example in the design of work stationsby research institutes and automotive companies. The use of blue screen technology

FIGURE 4.4

A VR system used in combination with a model to discuss town planning withend users — in this case, citizens. (Photo courtesy of REFLEX, Lund University.)


51

allows links between design drawings (on paper or on the computer) and realworkers. Video images of a worker going about his or her normal tasks are super-imposed on a drawing of the proposed setup. In other words, the Ergomix linksCAD design drawings with real users. Drawings come to life at an early stage ofthe design process, with people testing the effects of various dimensions.

Using this technology, the supply systems for the assembly of car roofs weredesigned for Inalfa Roof Systems (Tuinzaad et al. 2000). Inalfa is one of the worldleaders in roof systems for cars and trucks, and they aim at a healthy, productive, andhigh-quality assembly line. Next to the logical order of parts and tools, the positionand dimensions of the racks for supplying roof parts to the assembly line play a rolein the efficiency of the assembly process. Various forms and heights of

virtual

racks(only drawings of the racks were available) were tested by assembly workers in theErgomix (Fig. 4.6). The optimal design could be fine-tuned before the mock-up stage.The various designs of the racks and their respective consequences in terms of workerpostures and ease of handling were shown on a video. As a result, the workers weremotivated to work with the improved racks. Some of the workers were involved in thechoice, and most of them were convinced of the increase in productivity (fasterhandling) and reduction in physical load (less time in awkward postures).

4.14 THE PARTICIPATORY DESIGN PROCESS

Based on the five stages of participatory ergonomics described earlier and on recentliterature (Noro 1999; Haines et al. 2002; Vink et al. 2002), a new design processcan be described that could be of use in participatory design. The aim of a participatorydesign process is to allow users to have a large amount of input into product design.Users have tacit knowledge as a result of their high level of familiarity with a

FIGURE 4.5

The Ergomix applied to the design of a bus cabin.

52


FIGURE 4.6

The height at which the glass panel is supplied is simulated in the Ergomix.(Pictures taken from video recordings made during the Ergomix session with workers scaledat different heights working with several racks.)

TABLE 4.3

Step 1. Preparation

Participants are informed about the project during a central meeting. The aim of the project, strategy (step-by-step approach), members of a steering committee, and possible outcomes are discussed.

Step 2. Analysis of tasks, work, and health

The tasks, handlings, and work are studied with the use of interviews, questionnaires, observations, or simulation studies.

Step 3. Selection of improvements and design

Based on the analysis, user requirements are made focused on the goals set in Step 1. These user requirements indicate the design attention points that should be taken into account. A solution session, can be used to generate ideas. Essential in the method is that based on the user requirements where the problems are visualized (e.g., by mixed reality systems), the participants report ideas for improvement. Based on the first ideas, first versions of design could be made, which could be tested in mixed reality systems and adapted.

Step 4. Pilot study with the improvements

The new design is again tested in a mixed reality environment or in reality, and a prototype could be made.

Step 5. Implementation

In this stage the new designs are implemented in the actual workplaces. Instruction videos can be added showing new working methods or new ways of operating, and training could be added. In a central meeting all participants are also informed about the new situation.

Step 6. Evaluation

This step provides information about the effectiveness of the new design. After some time working the effects can be studied with the same techniques used in the step analysis to ensure that any benefit gained is long term. If necessary an adaptation could be added.


53

workplace or piece of equipment, which means that they will be more aware of anyproblems experienced and more able to give advice regarding design modifications.

Essential in the participatory design approach is that all participants (end users,designers, and other stakeholders) progress step-by-step toward the end result (amore efficient, healthful, and comfortable design). After (or during) every step inthe process, all participants are kept informed. Tools such as those described abovecould improve the efficiency of this process and ensure consistency in the informationpresented to participants to keep them informed. This approach contains the stepsdescribed in Table 4.3.

REFERENCES

Cotton, J.L., Vollrath, D.A., Froggatt, K.L., Lengnick-Hall, M.L. and Jennings, K.R. (1988)“Employee participation: Diverse forms and different outcomes.”

Academy of

Man-agement Review

, 13(1): 8–22.Davies, R. (2000)

Using Virtual Reality for Participatory Design and Brain Injury Rehabili-tation

, Lund: Lund University (Ph.D. thesis).Davies, R.C. (2001) “Applications of systems design using virtual environments.” In Kay

Stanney, ed.,

The Handbook of Virtual Environments

, Mahwah, NJ: LawrenceErlbaum Associates, 1029–1100.

Ehn, P. (1988)

Work-Oriented Design of Computer Artefacts

. Stockholm: Arbetslivscentrum.Ehn, P., Brattgård, B., Dalholm, E., Davies, R.C., Hägerfors, A., Mitchell, B. and Nilsson, N.

(1996) “The Envisionment Workshop — from visions to practice.”

Proceedings of

theParticipatory Design Conference,

Cambridge, MA: 141–152.European Foundation for the Improvement of Living and Working Conditions (1999)

Com-munique July/August, 1999

, Dublin: EFILWC, 2.Haines, H., Wilson, J.R., Vink, P. and Koningsveld, E.A.P. (2002) “Validating a framework

for participatory ergonomics.”

Ergonomics

, 45(4): 309–327.Hornyánszky Dalholm, E. (1998)

Att forma sitt rum. Fullskalemodellering i participatoriskadesignprocesser

, Lund: Akademisk avhandling vid institutionen för byggnadsfunk-tionslära.

Kogi, K. (1985)

Improving Working Conditions in Small Enterprises in Developing Asia

,Geneva: ILO.

Kuorinka, I. (1997) “Tools and means of implementing participatory ergonomics.”

Interna-tional Journal of Industrial Ergonomics

, 15: 365–370.Noro, K. (1999) “Participatory ergonomics.” In W. Karwowski, ed.,

The Occupational

Ergo-nomics Handbook

,

New York: CRC Press, 1421–1429.Noro, K. and Imada, A. (1992)

Participatory Ergonomics

, London: Taylor & Francis.Östman, J. (1998)

Virtual Reality and Virtual Prototyping — Applications in the American

CarIndustry

. Swedish Office of Science and Technology: Overseas Report USA 9806 (inSwedish).

Palacios, N. and Imada, A.S. (1998) “A macroergonomic approach to product design.” InP. Vink, E.A.P. Koningsveld and S. Dhondt, eds.,

Human Factors in OrganizationalDesign and Management IV

, Amsterdam: Elsevier, 439–444.Patry, L., Cote, M. and Kuorinka, I. (1991) “Participatory ergonomics of two work stations:

Warehouse employees and police officers.” In Y. Quéinnec and F. Daniellou, eds.,

Designing for Everyone:

Proceedings of the 11th Congress of the

InternationalErgonomics Association,

Vol. II, London: Taylor & Francis, 1747–1749.

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Schön, D. (1983)

The Reflective Practitioner — How Professionals Think in Action

, New York:Basic Books.

Stoeckli, H.P. and Weber, B. (1993)

Zum Unterricht im LEA 1985–1993. DA-Informations149

, Lausanne: Ecole Polytechnique Fédérale de Lausanne.Tuinzaad, G.H., Rhijn, J.W. van, Deursen, J. van and Koningsveld, E.A.P. (2000)

EfficientFlow and Human Centered Assembly: The Success of an Interactive

Approach

,

Eind-hoven/Hoofddorp: TNO Industrial Technology/TNO Work and Employment.

Vink, P. (2002)

Comfort

, Delft: Delft University of Technology (inaugural address).Vink, P. and Kompier, M.A.J. (1997) “Improving office work: A participatory ergonomic

experiment in a naturalistic setting.”

Ergonomics

, 40(4): 435–449.Vink, P., Lourijsen, E., Wortel, E., and Dul, J. (1992) “Experiences in participatory ergonomics:

Results of a round table session during the 11th International Ergonomics Associationcongress.”

Ergonomics

, 35(2): 123–127.Vink, P., Miedema, M., Koningsveld, E. and Molen, H. van der (2002) “Physical effects of

new devices for bricklayers.”

International Journal of Occupational Safety and

Ergo-nomics

, 8(1): 71–82.Wilson, J.R. (1995) “Solution ownership in participative work redesign: The case of a crane

control room.”

International Journal of Industrial Ergonomics

, 15: 329–344.

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0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

5

Discomfort and Productivity in Improved Bricklaying

P. Vink, A.M. de Jong, and E.A.P. Koningsveld

CONTENTS

5.1 Introduction ....................................................................................................565.2 The Bricklayer................................................................................................56

5.2.1 A First Redesign ................................................................................565.2.2 The New Devices ...............................................................................58

5.3 Methods..........................................................................................................595.3.1 Experienced Loading .........................................................................605.3.2 L5/S1 Maximum Loading..................................................................615.3.3 Observing ...........................................................................................61

5.4 Results ............................................................................................................625.4.1 Experienced Physical Loading Results..............................................625.4.2 L5/S1 Maximum Loading Results.....................................................635.4.3 Observing ...........................................................................................63

5.5 Discussion ......................................................................................................655.6 Conclusions ....................................................................................................665.7 The Bricklayer Assistant................................................................................66

5.7.1 Innovations .........................................................................................675.8 Research Question..........................................................................................675.9 Methods..........................................................................................................685.10 Results ............................................................................................................685.11 Discussion ......................................................................................................695.12 Conclusions ....................................................................................................705.13 Evaluation by Employers...............................................................................705.14 General Conclusion........................................................................................71Acknowledgment .....................................................................................................71References................................................................................................................71

56


5.1 INTRODUCTION

Approximately 20,000 bricklayers and 7000 bricklayer assistants are involved inbricklaying in the Netherlands (Jong et al. 2003). They make new houses, offices,and industrial structures and renovate older buildings. Discomfort during this workis very high (Arbouw 1994): 38% of the bricklayers and 36% of the bricklayerassistants in the Netherlands reported back complaints during work (Arbouw 2000in Jong et al. 2003). Each bricklayer handles manually about 800 to 1000 bricks perday. A bricklayer assistant transports manually about 2400 to 3000 bricks per day(Miedema and Vink 1996). The general agreement is that there is certainly room forimprovement, so the total process of bricklaying was improved. The Dutch brickmanufacturers’ alliance (KNB), the Dutch bricklayers’ employers alliance (NMPB),the employers’ alliance in the Dutch construction industry (NVOB), and the second-largest applied scientific research institute in Europe (TNO) developed a new methodof laying and transporting bricks. In this chapter a distinction is made between theimprovements for bricklayers and those for bricklayer assistants.

5.2 THE BRICKLAYER

The bricklayer’s main task is to lay bricks using mortar and trowel. The work isdone with care according to a prescribed pattern to ensure that all joints have auniform thickness and the rows are straight. Actual bricklaying consumes 90% ofthe time. The

waal

type of brick (weight 17 N) is used most often and is laid byone hand, with the trowel in the other hand. Other tasks such as setting out material,transportation, and communication consume the other 10% of the time. Traditionally,the bricks are set out at ground level behind the bricklayer, and therefore thebricklayer bends and rotates his back about 800 to 1000 times a day.

As far as the frequency of lumbar injuries is concerned, bricklayers belong to thetop four trades in the construction industry (Arbouw 1994). The financial and socialconsequences of sick leave and work disability are large. In 1993, the time lost dueto sick leave was 13.3%, and the incidence of new cases of disability in 1 year was4% of the total number of bricklayers (Arbouw 1994). Of this sick leave, 55% is dueto musculoskeletal complaints (Arbouw 1994). The major problem experienced bybricklayers is working between 0 and 0.5 m above the floor (Vink et al. 1996).

5.2.1 A F

IRST

R

EDESIGN

The idea was that a raised stack of bricks would reduce the back load as well as thediscomfort because the degrees of frequent forward bending would be reduced.However, raising the stack of bricks could cause more discomfort in laying the lowerrows. Therefore, the musculoskeletal load factor in raising the height of the brickswas tested in a laboratory experiment. The goal was to find the exact ideal heightthat resulted in postures with the least discomfort. Figure 5.1 shows three heightsfor the bricks and mortar. Oxygen uptake, discomfort, and back loadings were testedin each of the three situations (Vink and Koningsveld 1990).

The effects of increased height of the set-out bricks and mortar on the energeticworkload, discomfort, and biomechanical back stress were investigated. Ten healthy


57

subjects between 25 and 30 years of age, with at least 3 years of bricklaying expe-rience, were observed during the building of a wall measuring 2

×

1.5 m. Oxygenuptake was recorded during the bricklaying. A questionnaire on locally experienceddiscomfort was used directly after bricklaying under the different working conditions,and posture was estimated from photos to provide input for a static biomechanicalmodel. If the other tasks remained similar, the energetic workload decreased 2 to 8%with a 0.3 m higher level of set-out bricks and mortar. However, this difference wasnot significant because the oxygen uptake was influenced by the height of the set-outbricks and mortar, as well as by the height at which the bricks had to be placed inthe wall (Fig. 5.2). The Turkey contrast test showed that the oxygen intake wassignificantly lower during bricklaying at the 0.3 and 0.5 m levels for rows 12, 17,and 22, with respect to normal bricklaying (p < 0 to 0.5). So the heightened set-outof bricks and mortar appeared to lower the energy consumption, especially whenbricks were placed in higher rows in the wall (Vink and Koningsveld 1990).

FIGURE 5.1

The situation of traditional bricklaying on a scaffolding (

A

) and on the ground (

B

).

58


The experienced back load was lowest for the upper rows at the 0.5 m level.However, in comparing the three levels for building a complete wall, raising theset-out to 0.3 m created the least experienced discomfort. Working in the higherrows, the 0.5 m set-out showed the best results in terms of experienced discomfort.Biomechanical analysis of a photo of a subject showed the least lumbar back stresswhen the bricks and mortar were set out at a height of 0.5 m. Because thecombination of working in the higher rows and having bricks and mortar at aheight of 0.5 m consumed the least energy, created the best-experienced discomfortresults, and produced the least lumbar back stress, the upright position should bepursued.

5.2.2 T

HE

N

EW

D

EVICES

Before implementing innovations, it is essential to have support from the participantsand to test the innovations. Therefore, different products were developed and testedin cooperation with the sector organizations. Since 1990, several products designedto raise the bricks and mortar have been developed in order to reduce trunk flexion,but user tests showed that several products were not feasible. An aluminiumheight-adjustable folding table was developed and tested by bricklayers, but itappeared that the control mechanisms in these tables were too fragile. Malfunctionswere caused by mortar on the mechanical parts or by damage during transport. Irontables turned out to be too heavy to transport between workplaces, and especially fortransport to other building sites. Foam boxes used to raise the bricks were lightweight,but they appeared to be unstable in the field tests and were even blown from thescaffoldings by strong winds. User friendliness, safety, implementation possibilities,and discomfort were evaluated in the field tests. After several tests and brainstormingsessions two devices were evaluated as feasible, and the effects of these devices onlumbar loading were investigated in this project.

One improvement was a split floor in scaffolds. The traditional scaffolds wereadjusted to enable raising of the bricks or to lower the floor where the bricklayerstands. By adding extra mounting provisions to the pipes of the scaffolding, boards

FIGURE 5.2

Working conditions of the bricklayer, with the set-out bricks and mortar inwhich the load was measured. (

A

) the old situation; (

B

) the set-out bricks and mortar wereraised to 0.3 m; and (

C

) were raised to 0.5 m.


59

could be positioned at various heights by the scaffolders. This increases the possi-bilities for lowering the level of the boards for the bricklayer 0.5 m, or for raisingthe level of the boards where the bricks and mortar are positioned (Fig. 5.3). Theso-called HC scaffolding, which can be set up by a crane, facilitates this loweredbricklaying and reduces the workload of the scaffolder. From the research mentionedabove, it turned out that, ideally, the position of the bricklayer is lowered 0.5 mbecause he starts higher on the wall and the bricks are set out at 0.5 m.

Another improvement involved the use of shores. A few bricklayer companiesuse very simple shores of wood and iron or aluminium that can be placed on thescaffold (Fig. 5.4). This solution also raises the bricks and mortar 0.5 m. The totalweight of these shores was 100 to 200 N, depending on the materials used. Forheavier shores, the boards and supports can be split to simplify transport.

5.3 METHODS

To study the effects precisely, measurements should be taken in the actual situation.However, measuring effects in a naturalistic setting is difficult, and a laboratory studydoes not guarantee the same effects in practice, especially in the construction industry.Every building is different, every building site is different, and several factors such as

FIGURE 5.3

Bricklaying with a split-floor scaffolding. The floor of the brick layers (twopersons on the left in the picture) is lowered causing the bricks and mortor raised 0.5 m.

60


body space do influence postures. Valid and reliable measurements are, in fact, impos-sible. In this study it was also impossible to find enough situations in practice toobserve both devices separately in exactly the same situation. From the first observa-tions, the impression was that the working methods applied did not differ muchbetween working traditionally and working with raised bricks. The effects that wereevident were assumed to be caused by the raising of set-out bricks and mortar.Therefore, in this study a combination of three indicative experiments was used to finddifferences between working traditionally and working with the bricks raised 0.5 m:(1) questioning about

experienced loading

immediately after the work done; (2) esti-mating the

maximum loading

of lumbosacral junction L5/S1 from field recordings;and (3)

observing

the specific bricklaying task.

5.3.1 E

XPERIENCED

L

OADING

To get an indication of the perceived loading, the design for the study had to takevarious aspects into account. Since short-term effects, such as getting accustomed,should be excluded, a group was needed that had been working with the raised bricksfor a longer period. Nevertheless, experience with the traditional way of workingwas also essential and had to be fresh in mind. Therefore, out of all bricklayers agroup was defined that had worked for more than 2 years traditionally and that hadbeen working with the raised bricks for approximately 50% of their time over the

FIGURE 5.4

Bricklaying with a shore, with bricks and mortar raised 0.5 m.


61

past year. By interviews in the sector, one bricklaying company was found that metthese criteria. All 25 bricklayers from this company were asked to complete aquestionnaire on experienced loading with the 2 systems. Questions were askedabout their preference for traditional working or for working 0.5 m raised, theinfluence of each system on their work pace, and the discomfort they experiencedin the different body regions after a day of working. Differences were tested withthe t-test for paired comparison (p < 0.05).

5.3.2 L5/S1 M

AXIMUM

L

OADING

To estimate the L5/S1 peak loading in the traditional and in the 0.5 m raised wayof working, the postures were estimated and the forces on the L5/S1 segment werecalculated. As mentioned earlier, most of the working time is consumed by brick-laying itself. To make a comparison possible, an average task with

waal

bricks wasrecorded in the traditional situation and with the materials raised 0.5 m. Threebricklayers were found who worked one day in the traditional situation and one daywith the bricks raised 0.5 m, performing comparable tasks.

The three bricklayers were videotaped during the 2 days. For each subject andeach condition, seven images were selected from the videotapes where the torsoflexion was highest. The average angles of each body segment were calculated fromthese selected images, tested with the t-test for paired samples (p < 0.05), and putinto the 2-D static strength prediction program model (Chaffin and Andersson 1991)to calculate the L5/S1 load.

5.3.3 O

BSERVING

Using existing studies and interviews with specialists in bricklaying, the averagework was defined: working with the

waal

bricks; some windows, some corners;working with teams of three bricklayers and one assistant; and so on. Constructionsites were then located where this average bricklaying work could be found. Tensubjects were observed using both the old and the new working methods and werevideotaped during 1 day of work. Additional measurements were performed on theweights of the bricks and on handling distances. The time spent on several tasksand the frequency of handling were measured with a stopwatch. From the videotapes,the angles of some body segments compared to the vertical were estimated (trunk,upper arm, lower arm, and head). Also, estimations were made of the horizontal distancebetween ankle and hand, the vertical distance between ground and hand, and theasymmetry in trunk posture.

These data were analyzed and evaluated according to the guidelines on physicalworkload for the construction industry (Table 5.1). The NIOSH equation was usedfor lifting; the Mital guidelines for pushing, pulling, and carrying (Mital et al. 1993);and for posture and repetitive work the ISO/CD 11226 (1995), NF X 35–106 (1985),and prEN 1005-4 (1996). The assessments, therefore, are based on available interna-tional guidelines and on consensus among Dutch ergonomists and the constructionindustry (Molen and Delleman 1997).

62


5.4 RESULTS

5.4.1 E

XPERIENCED

P

HYSICAL

L

OADING

R

ESULTS

Twelve bricklayers completed the questionnaire, a 48% response. Six respondentshad no history of back complaints, but others had suffered from back complaintsduring at least some time over the past 12 months. All respondents preferred bricksand mortar raised 0.5 m, a significant difference. The handling time did not differsignificantly (nine bricklayers reported no difference and three reported that quickerwork is possible in the raised situation). The raised situation resulted in less dis-

TABLE 5.1 Abstract of Guidelines Used to Evaluate the Workload

Evaluation

Activity Source Criterion Green Yellow Red

Whole body judgment

Lifting NIOSH* Various <MPL MPL–3xMPL >3xMPLOne-handed lifting Mital** Max force >P90 male P25–P90 male <P25 malePushing/pulling Mital** Max force >P90 male P25–P90 male <P25 maleCarrying Mital** Max force >P90 male P25–P90 male <P25 male

Posture

(static as well as repetitive movements, more than 2 per minute)

Upper arm ISO/CEN*** >60

°

Elevation<1 hour 1–4 hours >4 hours

Low back 1 ISO/CEN*** >60

°

Flexion <1 hour 1–4 hours >4 hoursLow back 2 ISO/CEN*** >0

°

Rotation <1 hour 1–4 hours >4 hoursLow back 3 ISO/CEN*** Overextension <1 hour 1–4 hours >4 hoursNeck 1 ISO/CEN*** >25

°

Flexion <1 hour 1–4 hours >4 hoursNeck 2 ISO/CEN*** >0

°

Rotation <1 hour 1–4 hours >4 hoursOther joints ISO/CEN*** Extreme

angles<1 hour 1–4 hours >4 hours

Repetitive handlings

(with the hands)

>2/min NF X**** Force >85N <1 hour 1–4 hours >4 hours>3/min NF X**** Force >60N <1 hour 1–4 hours >4 hours>4/min NF X**** Force >35N <1 hour 1–4 hours >4 hours>5/min NF X**** Force >20N <1 hour 1–4 hours >4 hours

Green = Safe. (For lifting, this means that in applying the NIOSH 1991 equation the maximumpermissible limit [MPL] should not be exceeded. Pushing is considered safe if more than 90% [P90 =90 percentile] are able to perform the task.) Yellow = Improvements will be needed over time.Red = Improvements are needed immediately.

* NIOSH equation described in Waters et al. (1993).** Mital et al. (1993).*** ISO/CD 11226 (1995) and prEN 1005-4 (1996).**** NF X 35–106 (1985) and Kilbom (1994).


63

comfort. The effects on body segments were largest for the lower back. In the raisedsituation, the discomfort in the lower back decreased significantly (the mean for olddiscomfort in the low back was 4.2, and 2.4 for new discomfort, p = 0.03) (Fig. 5.5).

5.4.2 L5/S1 M

AXIMUM

L

OADING

R

ESULTS

The measured angles are shown in Table 5.2. All angles were influenced by theworking method (Table 5.2), especially in regard to the trunk. As could be expected,the trunk is significantly more upright when working with the 0.5 m raised bricks(difference 69.8

°

). This resulted in an estimated decrease of 56% in the meancompression force (2.3 kN traditionally and 1.6 kN with raised bricks).

5.4.3 O

BSERVING

The observations made several aspects clear. The time consumption of the differenttasks was not significantly different. The most important difference in posture wasfound in trunk flexion (Table 5.3). In the traditional situation (three to four times perminute for more than 4 hours a day) the bricklayer will bend his back more than 60

°

.This is evaluated as a high health hazard (red

in the system of Table 5.1). In workingwith 0.5 m raised bricks the back is bent in the same frequency, but the flexion mostlydoes not exceed 20

°

. Working with

waal

bricks of 17 N is acceptable in this situation(green). However, working with bricks heavier than 20 N, with a frequency of fivebricks per minute during a period of 2 hours, creates a yellow hazard.

FIGURE 5.5

The body region where 12 bricklayers report discomfort reduction while work-ing with bricks and mortar raised 0.5 m.

0

2

4

6

8

10

12

neck upper back lower back shoulder elbow wrist/hand

64


Although observed in only 2 subjects in this study, the best results were obtainedin the situation where the floor on which the bricklayer stands is 0.5 m lower thanusual. This is in alignment with the experienced discomfort.

5.5 DISCUSSION

All experiments indicate that bricklaying with bricks and mortar raised 0.5 m isfavourable. The bricklayers experience the work better, the lumbar peak load esti-mation on L5/S1 is lower in the raised condition, and observation of the work showsthat working with raised bricks reduces the risk. However, the conclusions shouldbe drawn with care because this study had only a limited number of subjects observedunder nonstandardized conditions at construction sites.

Each part of these experiments had its drawbacks:

TABLE 5.2 Average Angles of Three Subjects (Defined in Figure)

Angle working traditionally (sd) Angle working 0.5 m raised (sd)

Shoulder –88.9 (6.4) –66.6 (7.4)Elbow –74.9 (5.0) –38.1 (9.8)Trunk –5.9 (10.3) 63.9 (2.4)Knee 116.8 (5.6) 99.9 (3.2)Ankle 83.3 (3.1) 84.7 (1.3)

sd = Standard deviation of the 21 recorded angles (3 subjects

×

7 measurements). All differencessignificant (p < 0.05).


65

• It was impossible to study the effects of each product (split scaffoldingand shores) separately.

• The questionnaire had a low response.• Bricklayers completing the questionnaires could be biased because the

new devices were promoted by management with the motive to reducemusculoskeletal load.

• Only three subjects could be found that had comparable work for biome-chanical analyses.

• Dynamic work was analyzed with a static biomechanical model.• Only ten subjects were observed.• Observations were evaluated with guidelines that still have weak bases.

This study illustrates that experimental measurements in a naturalistic setting dohave constraints. It is clearly not always possible to follow the rules of the experimentalparadigm (controlling certain factors and at the same time manipulating others). Fur-thermore, the validity of the evaluation of the loadings is uncertain. However, all threeexperiments trend in the same direction, and therefore the results from these studiesare used to advise bricklayers positively on implementing the better way of working.

Comparison with other studies on bricklayers strengthens the outcome. The factthat bricklaying is heavy work is described by Jørgensen et al. (1991). The findingthat bricklayers bend three to four times per minute is comparable to a study amongGerman bricklayers (Luttman et al. 1991). Although there are large differences inthe working methods, Luttman et al. (1991) established a handling frequency of2.9 times per minute. Also in Germany, Jäger et al. (1991) calculated the compressionforces and concluded that the compression forces are more acceptable when bricksare grasped from the minimal height of 0.5 m. The previous laboratory study (Vinkand Koningsveld 1990) showed a decrease of 21% in biomechanical loading (from1.9 kN traditionally to 1.5 kN with materials raised 0.5 m at lumbar segment 3 and4), whereas in this field study a reduction of 30% was found.

Other measurements such as oxygen uptake and electromyography readings alsosupport our results. Jørgensen et al. (1991) stated that the large number of repetitivetrunk flexions resulted in muscular fatigue that could be found in the electromyographypattern. Oxygen uptake was also significantly lower in a 0.5 m raised situation (Vinkand Koningsveld 1990).

TABLE 5.3 Number of Observed Trunk Flexions during a Day Working with

Waal

Bricks, Averaged over Ten Observed Bricklayers (Sd)

Trunk flexion >20

°

>60

°

Working traditionally 912 (112) 842 (128)Working with bricks raised 0.5 m 211 (45) 12 (2)Bricklayer standing 0.5 m lower 42* 2*

* Values based on observation of only two subjects.

66


However, regardless of the improvement created by using raised bricks andmortar, there is still room for further improvement. The frequent handling in bricklaying(three to four times per minute) and other tasks such as setting out, carrying, andcleaning offer many possibilities for improvement. Also, the situation in which thebricklayer positions himself 0.5 m lower is preferable, which means that the scaf-folding with the split floor should be promoted in combination with training as tohow the scaffolding should be used.

5.6 CONCLUSIONS

The major discomfort experienced by bricklayers is related to working between 0and 0.5 m above the floor level. This study indicates that the problem can be partiallyreduced by raising the stack of bricks with shores or by using scaffolding provisionsthat allow bricklayers to stand 0.5 m lower than usual. Experiments and literaturesupport this finding, and bricklayers experience the reduction in discomfort. Esti-mations of lumbar back load show a significant reduction. Observations evaluatedwith appropriate guidelines show a shift from

not acceptable

to

acceptable

. Furtherimprovements to reduce the bending frequency and to improve the other tasks ofthe bricklayer are advised.

5.7 THE BRICKLAYER ASSISTANT

The bricklayer assistant’s main task is to prepare the work for the bricklayers. Some-times scaffoldings have to be made, and transport of bricks and mortar to two or threebricklayers is always the case. An assistant transports approximately 2400 to 3000bricks a day (Fig. 5.6). He spends 46% of his daily working time on transportingbricks, 13% on transporting mortar, 4% on removing scaffolding, and 37% on generalactivities such as servicing tools, cleaning, deliberation, and so forth (Meijer 1994).Traditionally, assistants perform their tasks manually. This includes the manual loadingof the wheelbarrow (repetitive lifting), trundling the wheelbarrow (lifting, carrying,pushing), and unloading (repetitive lifting). For loading and unloading a cramp issometimes used, with which five to eight bricks can be picked up together.

The objective of this study was to establish the differences in physical load forthe bricklayer assistant between the traditional and the new way of handling bricks.The traditional working method was analyzed in 1993. The development of newaids took 4 years, and this work was evaluated in 1998.

5.7.1 I

NNOVATIONS

Several devices have been developed to eliminate the manual loading, unloading,and transport of bricks. A pincer device (Fig. 5.7) is available with which 200 to400 bricks can be picked up and transported with a crane. Because of this mecha-nization, the physical load on the assistant has almost been eliminated.

Traditionally, the bricks are delivered in bulk or as indivisible packs. In the newway of working the packs of bricks can be picked up by a kind of forklift mountedon a crane and moved from and to the truck. This brick pack can be transported by


67

crane directly to the place where the bricklayer works. It was a big effort to convincethe supplying industry (companies that have the brick ovens and transport companies),the bricklaying companies, and general contractors to make these investments. Aparticipatory approach was needed in which the management and representatives ofsector organizations from all of the mentioned industries participated. Prototypeswere tested and adapted on several sites.

FIGURE 5.6

A task of the bricklayer assistant: transporting bricks.

FIGURE 5.7

Two pincer devices for transporting 200 to 400 bricks with a crane. This is thecompletely mechanized working method to eliminate manual lifting by the bricklayer assistant.In part A a device is used for scaffolds that can be reached from above. In part B the deviceallows workers to place the bricks from the side.

68


5.8 RESEARCH QUESTION

To convince participants to invest, the effect of the improvements on musculoskeletalloading was studied. Most companies were not convinced of the positive effect.Therefore, our hypothesis was that the mechanized and partly mechanized way ofworking have no effect. Also, if the new way of working should be promoted itwould be of great help if the costs were reduced. In this study, therefore, the costsof the old and new methods were estimated.

5.9 METHODS

Two conditions were observed: traditional working and mechanized working. Fivebricklayer assistants were observed and videotaped during a full day of work undereach set of conditions. As mentioned earlier, loading and unloading the wheelbarrowand transport with the wheelbarrow consumed most of the time. Therefore, con-struction sites were selected where these activities constituted most of the work. On-site estimations were made in the following areas:

• Forces exerted on the hand by carrying and lifting the wheelbarrow, eight-packs of bricks, and aids. These measurements were recorded by a dyna-mometer (accuracy 1 N).

• Frequency of handling and durations of the tasks were recorded by stop-watch.

• Experts selected the three most demanding tasks (which appeared to beloading, unloading, and transport), and these tasks were sagittally video-taped to record body postures.

Several distances visible on the videotape were measured: the horizontal distancebetween ankle and hand; the vertical distance between ground and hand; the asym-metry and the posture of the trunk (angle between vertical and trunk); and the upperarm in space. These data were analyzed and evaluated according to the guidelineson physical workload for the construction industry (Table 5.1).

The financial consequences of the two methods were roughly estimated basedon a situation in which 6000 bricks (a medium-sized building site) should be setout. A calculator employed by a bricklaying company that makes bids as a subcon-tractor to the general contractors calculated the costs.

5.10 RESULTS

Most activities in the traditional way of working are considered red, according toTable 5.1. In loading and unloading the wheelbarrow, two bricks (

waal

type, 17 N;and

maas

type, 31 N) were usually lifted in each hand, for a total weight of 68 Nor 124 N. Sometimes a cramp was used, in which five to eight bricks could be pickedup by one hand (85 to 248 N for the bricks + 5 N for the cramp). A wheelbarrowcarrying 80 bricks was usually loaded or unloaded in approximately 5 minutes. Thetotal loading and unloading time was 5 hours out of the 8-hour work day.


69

Working with the wheelbarrow also resulted in unacceptable postures duringloading and unloading. The estimations of the most flexed position of the trunkvaried between 60 and 80

°

(70

°

average). Loading and unloading bricks positionedat 0.5 m above the ground resulted in trunk flexions of 0 to 20

°

per minute. However,this range was unacceptable because of its high frequency (3 to 4 times per minute).Lifting and pushing the wheelbarrow was unacceptable due to the high weight ofthe bricks and wheelbarrow together — approximately 1300 N (1190 to 1410 N).From the force estimates it appeared that 500 N (varying from 462 to 541 N) iscarried by the hands and 800 N by the wheel. The initial required pushing force is200 N (165 to 230 N) followed by 60 N (48 to 77 N) continuously, which is notconsidered to be the major problem.

The new way of working included positioning the bricks directly onto the scaf-foldings from the truck. The number of bricklayer assistants needed is thereby reduceddrastically. Activities that still require bricklayer assistants are preparing the scaffold-ings, planning which bricklayer needs the bricks, transporting mortar (which is stilla heavy task), resetting packs of bricks (a highly variable workload), and craneoperating. More effort is now needed for planning than in traditional bricklaying.

The bricklaying company’s cost estimate for setting out 6000 bricks traditionallyis $440 (16 hours of bricklayer assistant time). Under mechanized conditions, thecost estimate is $248 (2 hours of bricklayer assistant time, $110; renting a craneand crane operator, $138).

5.11 DISCUSSION

Regarding the research question, the hypothesis that the innovations have no effectis false. The innovations described earlier should be promoted in the constructionindustry. Tasks with the highest musculoskeletal demands, such as loading, unload-ing, and pushing a wheelbarrow, are eliminated in the new way of bringing bricksto the bricklayers. This type of work consumed 46% of the traditional working day.Promotion of these innovations will not be too difficult because the financial advantagesare shown to the bricklaying company for medium-sized jobs. The traditional trans-port of 6000 bricks requires 2 days’ work by the bricklayer assistant, which costsapproximately $440. Transporting 6000 bricks completely mechanically (30 chargesof 200 bricks each in the pincer device) costs $248 (2 working hours and 1 hourrenting a crane and operator).

To build one house the system is not cost-effective; the financial advantage existsif brick transport is required only once in 2 days. This is normally the case at abuilding site of more than four houses. Of course, other costs such as rebuilding theovens and making special devices for transport are not included. These costs areborne by the brick manufacturing companies, but they did raise the brick price andwill have a return on their investment in a few years.

The transport of mortar still needs attention. In the old situation it didn’t consumemuch time (13% of the working time), but as the brick is transported faster and thenumber of bricklayer assistants decreases, mortar transport might have to be donemore frequently.

70


The method of evaluation can also be discussed. All evaluation methods haveweaknesses, and in fact our knowledge is not far enough advanced to come to asolid conclusion of

acceptable

or

not acceptable

. Even for the red–yellow–greenguideline applied in this project, the knowledge is in fact scarcely available.

A major point on this study is the fact that only observations are used. No exactrecorded data are available, and no perceived or experienced loading is measuredin this study. Other studies (Arbouw 1994) show that the work of the bricklayerassistant is perceived as heavy, with a high discomfort level that is in alignment withour results. Also, bricklayer assistants have a high frequency of sick leave (17.7%)compared to the Dutch construction industry as a whole (12.1%) (Arbouw 1994).The same situation is found in other countries. In the United States the injury rateis 14.7%, compared to 3.1% in all construction occupations (Hsiau and Fosbroke1996). All told, a large number of studies support the findings of unacceptableloading for the bricklayer assistant.

5.12 CONCLUSIONS

This study indicates that the major problems in the work of bricklayers and bricklayerassistants can be improved. For bricklayers a lowered floor in the scaffolding is agood improvement, reducing the discomfort. For the assistants, loading and unload-ing the wheelbarrow created an unacceptably high load. The work of the bricklayerassistant is more acceptable if this part of the job is eliminated. The innovationstested eliminated the wheelbarrow work, thereby promoting the innovations. How-ever, the task of manually transporting mortar by the wheelbarrow is still too heavyand also needs innovations.

5.13 EVALUATION BY EMPLOYERS

A few years after introduction of these innovations a study was done regarding theirimplementation (Jong et al. 2003). This study shows that more than half of the sectoruses the new devices. Also, 25 employers were interviewed (Jong et al. 2003), andthe results from this study show that important reasons for buying the new system(Table 5.4) are improvement of working conditions, a positive cost–benefit ratio,and increase in productivity. The difficulty in using it on some construction sitesand the dependency issue of whether or not to use the crane of the main contractorare reasons for not adopting the system.

Other positive aspects seen as important by the employers are the involvementof many parties and many tests in the field. In this project the bricklayer sectororganization, unions, main contractors, researchers, and suppliers were all heavilyinvolved (the participatory ergonomics approach). Negative aspects mentioned byJong (2003) included perceptions of an unstructured process and no direct employeeinvolvement. This shows that the reduction of discomfort is very intensive. Also,the importance of the combination of discomfort reduction and cost–benefit improve-ments has been shown to be profitable.


71

5.14 GENERAL CONCLUSION

This large project shows that discomfort reduction can be achieved by firm efforts,which can prevent musculoskeletal problems in the future. More than half of thesector has implemented the improvements, which can be seen as a success. Analysisof the parts of bricklayers’ bodies that experienced much discomfort in the traditionalsituation was important in order to focus the development of ideas. Collaborationwith different parties as well as combination of work-improvement results withfinancial benefits are important success factors. On the average, employees notice theimprovements and employers are satisfied as well. Perhaps a more structured designprocess and more direct employee involvement could have led to even better results.

ACKNOWLEDGMENT

The authors want to thank Arbouw, Mr. Jac de Kroon, the Dutch brick manufacturers’alliance (KNB), the Dutch bricklayers employers’ alliance (NMPB), and the employ-ers’ alliance in the Dutch construction industry (NVOB) for supporting this study.

REFERENCES

Arbouw (1994)

Work and Health in the Construction Industry

, Amsterdam: Arbouw (inDutch).

Chaffin, D.B. and Andersson, G.B.J., eds. (1991)

Occupational Biomechanics

,

2nd ed

.

,New York: Wiley & Sons.

Hsiao, H. and Fosbroke, D. (1997) “Determining research focus for reducing overexertioninjuries in the construction industry.” In

Proceedings of the 13th Triennial Congressof the International Ergonomics Association,

Tampere, Finland: Vol. 6, 118–120.ISO/CD 11226 (1995)

Ergonomics — Evaluation of Working Postures (ISO/TC159/SC3)

,Osaka: JISC.

Jäger, M., Luttman, A. and Laurig, W. (1991) “Lumbar load during one-handed bricklaying.”


, 8: 261–277.Jong, A.M. de, Vink, P. and Kroon, J.C.A. de (2003) “Reasons for adopting technological

innovations reducing physical workload in bricklaying.”

Ergonomics

,

46(11):1091–1108.

Jørgensen, K., Jensen, B.R. and Kato, M. (1991) “Fatigue development in the lumbar paraver-tebral muscles of bricklayers during the working day.” International Journal ofIndustrial Ergonomics, 8: 237–245.

TABLE 5.4 Reasons for Adopting the New Way of Working, According to Employers

Improvement in working conditions (37%)Positive cost–benefit ratio (74%)Productivity increase (26%)


Kilbom, Å. (1994) “Repetitive work of the upper extremity, part I: Guidelines for the prac-titioner.” International Journal of Industrial Ergonomics, 14: 51–57.

Luttman, A., Jäger M. and Laurig, W. (1991) “Task analysis and electromyography forbricklaying at different wall heights.” International Journal of Industrial Ergonomics,8: 247–260.

Meijer, J.G. (1994) Analysis of Bricklaying, Ede: SAOB (in Dutch).Miedema, M. and Vink, P. (1996) Risk Assessment and Evaluation in Bricklaying, Amsterdam:

Arbouw (in Dutch).Mital, A., Nicholson, A.S. and Ayoub, M.M. (1993) A Guide to Manual Materials Handling,

London: Taylor & Francis.Molen, H. van der and Delleman, N.J. (1997) “Arbouw guidelines on physical workload for

the construction industry.” In Proceedings of the 13th Triennial Congress of theInternational Ergonomics Association, Tampere, Finland: Vol. 6, 197–199.

NF X 35-106 (1985) Ergonomie — Limites Défforts Recommandées pour le Travail et laManutention au Poste de Travail, Paris: AFNOR.

PrEN 1005-4 (1996) Safety of Machinery — Human Physical Performance, Part 4: Evaluationof Working Postures in Relation to Machinery (CEN/TC122/WG4), Delft: NNI.

Vink, P. and Koningsveld, E.A.P. (1990) “Bricklaying: A step by step approach to betterwork.” Ergonomics, 33(3): 349–352.

Vink, P., Munnik, M.J. and Voorde, J.A.W. ten (1996) “Bricklaying company Van Berkumimproves bricklaying.” In M.A.J. Kompier, R.W.M. Gründemann, P. Vink and P.G.W.Smulders, eds., Aan de Slag!, Alphen aan den Rijn: Samsom, 105–115 (in Dutch).

Waters, T.R., Putz-Anderson, V., Garg, A. and Fine, L.J. (1993) “Revised NIOSH equationfor the design and evaluation of manual lifting tasks.” Ergonomics, 36: 749–776.

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0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

6

Reducing Discomfort in Work with New Products for Glaziers

A.M. de Jong, H.F. van der Molen, and P. Vink

CONTENTS

6.1 Discomfort among Glaziers ...........................................................................736.2 Design of Mechanical Aids ...........................................................................746.3 Steps in the PE Approach for Glaziers..........................................................746.4 Diffusion at the Sector Level.........................................................................756.5 Results at the Sector Level ............................................................................766.6 Results ............................................................................................................76

6.6.1 Results of Step 2: Analysis................................................................766.6.2 Results of Step 3: Selection of Improvements..................................776.6.3 Results of Step 4: Pilot Study with Improvements...........................786.6.4 Results of Step 5: Implementation ....................................................796.6.5 Results of Diffusion at the Sector Level ...........................................796.6.6 Results of the Effects Study at the Sector Level ..............................80

6.7 Discussion ......................................................................................................826.8 Conclusions ....................................................................................................83Acknowledgment .....................................................................................................83References................................................................................................................84

Parts of this chapter are reprinted from Jong, A.M. de and Vink, P. (2000) “Theadoption of technological innovations for glaziers;

Evaluation of a participatoryergonomics approach.”


,

26:939–946. (Copyright 2000, with permission from

Elsevier)

6.1 DISCOMFORT AMONG GLAZIERS

Among glaziers, discomfort is high. Some years ago, studies of this sector level(Arbouw 1996) showed that glaziers had a physically demanding job. Windowpanesweighing from 50 to 200 kg are often lifted manually to the second floor.Transporting the windowpane manually is frequently observed, and the sector

74


organizations recognize the problem of high musculoskeletal load resulting indiscomfort and perhaps even back injuries in the long run.

Therefore, most companies agree that there is certainly room for improvementin working methods. However, changing working methods can be very difficult, anddesigning new methods consumes energy and time. Sometimes the workers do notsee the necessity, sometimes the improvements are too costly, or sometimes theworkers may refuse to use new working methods. Besides the difficulties in imple-menting them, it is of course important to find the most appropriate improvementsaimed at reducing the major problems.

6.2 DESIGN OF MECHANICAL AIDS

To redesign the working methods in the most appropriate way and to increase thechances of successful implementation, a special approach was developed based onthe participatory ergonomics (PE) approach described in Chapter 4. In the presentstudy this PE approach was applied to three small glazier companies to find themost optimal improvements. For the purpose, mechanical aids that reduce the majormusculoskeletal loadings were designed. These were developed with the understand-ing that they should be appropriate for use by all glaziers.

After the PE approach, a campaign was organized to promote use of these aidsin the glazier sector. A few years after promotion, the effects in the sector wereevaluated. Those effects are described in this chapter, especially with respect to theadoption of new methods of work. To understand the role of the different steps inthe PE process, the final result of the approach is studied, as well as the separateeffects of each step followed in the campaign.

6.3 STEPS IN THE PE APPROACH FOR GLAZIERS

As described in Chapter 4, one of the important elements in the PE approach is thatall participants (of the companies, sector organizations, and advisors) progressstep-by-step toward the end result (reduction of physical workload). In this project,all participants in the three companies were kept informed after every step in theprocess. Glaziers from these companies completed checklists, developed suggestionsfor improvements, tested improvements, and gave their preferences. These resultswere discussed with them.

A steering group discussed the headlines, costs, and benefits. Members of thisgroup included one glazier; management representatives of the three companies;representatives of Arbouw (the Dutch institute for improving working conditions inthe construction industry), FOSAG (the glaziers’ sector organization), and TNO (thesecond largest applied scientific research organization in Europe). A steering groupdecision, for example, was to determine which improvements could be used in themajority of companies within the sector.

The following steps were followed in this project.

•

Step 1: Preparation

All glaziers of the three companies were informed about the project duringa central meeting. The aim of the project (reduction of physical workload),


75

the step-by-step approach, members of the steering committee, and pos-sible outcomes were presented by the consultants from TNO.

•

Step 2: Analysis

In previous studies (Arbouw 1996) the work and health problems hadalready been studied. Pane lifting and pane transport, horizontally as wellas vertically, were experienced with a lot of discomfort, and objectivedata showed comparable results. Experts made additional observations inthe three participating glazier companies. In a meeting with glaziers ofthe three companies, these results (older studies, recent observations) werediscussed. The main problems were defined based on these discussions.

•

Step 3: Selection of improvements

User requirements were made for the main problems defined in Step 2.These user requirements indicated the solutions that should be developedand selected. Ideas for improvements were generated in solution sessions,following a procedure described in detail elsewhere (Urlings et al. 1994a,1994b). Essential to the solution session is that a good description of thesituation around the problem is presented to — in this case — a groupof glaziers, ergonomic experts, product designers, and management of thesector organization and of the participating glazier companies.

Inspired by the description of the problem, everyone draws or describesa solution on paper (silent round). The papers are collected and thechairman discusses the ideas without knowing whose they are. After this,additional solutions are asked, inspired by the previous ideas. Then thegroup estimates the effect of the ideas on discomfort and efficiency, aswell as the feasibility of the ideas. In two meetings of the steering group,solutions are further prioritized based on feasibility, user friendliness,costs, and estimated effects on health.

•

Step 4: Pilot study with improvements

Various companies making comparable products were asked to designproducts based on drawings and descriptions from the solution session.These were discussed with experts (ergonomists and product designersfrom TNO), and prototypes were made of the new mechanical aids. Threeglazier companies worked one day using these aids. The work was observedby ergonomists from TNO and partly by members from the sector orga-nization Arbouw. Based on these observations and on interviews with theglaziers and Arbouw, a list of improvements was made. The mechanicalaids were adapted and tested again by two glazier companies.

•

Step 5: Implementation

In the three glazier companies, the experience with the mechanical aidswas discussed. Management and the glaziers together decided which aidswere needed and should be purchased by the companies.

6.4 DIFFUSION AT THE SECTOR LEVEL

The previous steps were input to set up a campaign that was organized to promoteunderstanding and use of the improvements.

76


Guidelines were made and agreed upon by employers and employees of the sector.These Arbouw guidelines were based on measurements of what was acceptable interms of physical load and contained elements such as the maximum acceptableweights of windowpanes.

A brochure and a videotape were made to explain the several solutions, and all2050 companies of the Dutch glazier sector were invited to attend a demonstrationday. All mechanical aids were demonstrated there, and influential representatives ofthe glazier industry explained why it is important to innovate. Every visitor receivedthe videotape and the brochure, and the same information was also published in thejournals of the sector and Arbouw. Companies that were members of the sectororganization FOSAG and were not able to attend the demonstration day received avideotape by mail.

6.5 RESULTS AT THE SECTOR LEVEL

In the long run, this approach to reducing musculoskeletal discomfort and the use ofsick leave is rather expensive and time consuming. Therefore, it is interesting to knowwhat the effects of the stepwise approach and the campaign are. The effects amongglazier companies were evaluated. A year after the demonstration day a questionnairewas sent to the 2050 glazier companies in the sector. It contained questions on theawareness of the mechanical aids, the number of products that were purchased, andtheir use and expected effect on reduction of the musculoskeletal load. The same datawere also gathered from the three participating companies as a reference.

To determine differences between variables, a chi-square test with 95% confi-dence interval was used (Pearson’s test p < 0.05). It was applied to find relationshipsbetween

• The size of the company and level of investments• The size of the company related to the adoption• The opinion of users on physical load reduction

The satisfaction of regular users was determined at three levels: (1) satisfactionwith the use of the device itself; (2) satisfaction with the new working method; and(3) satisfaction with the final result of the work.

The 2050 glazier companies that received the questionnaire were members ofFOSAG. The exclusion of nonmembers had a practical reason: we only had addressesof the members.

6.6 RESULTS

6.6.1 R

ESULTS

OF

S

TEP

2: A

NALYSIS

The three main problems identified by the three glazier companies appeared to beloading and unloading panes on the car, horizontal transport and vertical transport,and removing putty. These issues were confirmed by the ergonomists who observedthe work.


77

6.6.2 R

ESULTS

OF

S

TEP

3: S

ELECTION

OF

I

MPROVEMENTS

A large list of solutions was developed in the solution sessions. Some were notfeasible because of the large impact they would have. One solution that had largeeffects was to require architects to reduce the use of large windows. Some solutionswere too costly, and some had only a minor effect. From the total list of solutions,the following were chosen to be tested in the three companies.

• An agreement was made with the glass manufacturers that all panes wouldbe marked with a sticker to show the exact weight (in kg) of the pane, sothat glaziers would not have to estimate the weight.

• For loading and unloading the pane from the truck, a special glass hoistwas developed (Fig. 6.1).

• A glass cart (Fig. 6.2) was developed to reduce the loading during hori-zontal transport from the truck to the building.

• To reduce the loading during horizontal transport inside a building, a glasssledge was developed (Fig. 6.3).

• To reduce manual vertical transport, a special lifting device was designedthat could be used in combination with scaffolding (Fig. 6.4).

• To eliminate all manual transport (vertical as well as horizontal), anexisting truck with crane was adapted to transport both the glass and theglazier (Fig. 6.5).

• A mechanical putty remover was developed that reduced forceful handling(Fig. 6.6).

FIGURE 6.1

The glass hoist is a device that can be mounted on the glass truck to lift thepane from the truck onto the glass cart. (Photo courtesy of Muyen BV.)

78


6.6.3 R

ESULTS

OF

S

TEP

4: P

ILOT

S

TUDY

WITH

I

MPROVEMENTS

Glaziers from the three pilot companies were satisfied with the solutions. Someminor revisions had to be made on handles and the position of the suckers. Withrespect to the truck-crane (Fig. 6.5), there was uncertainly regarding its safety. Thequestion was whether it was stable and strong enough to carry the load of a panetogether with a glazier in positions far away from the base of the truck. Therefore,it was decided to study this proposal further. Among the experts there was alsouncertainty about the possibility of breaking glass with the transport devices. How-ever, the response of all glaziers after the test was “We are used to working withglass, so we also know when to be careful.” The strength of the participatoryapproach was evident here.

FIGURE 6.2

The glass cart is a device that enables horizontal transport without manuallycarrying the glass. (Photo courtesy of Muyen BV.)

FIGURE 6.3

The glass sledge is a device to transport glass on galleries and other flat surfaces.(Photo courtesy of Muyen BV.)


79

6.6.4 R

ESULTS

OF

S

TEP

5: I

MPLEMENTATION

All three companies decided to buy mechanical devices and paid attention to thepreparation for using them. For instance, it was agreed that the transport of thedevices to the construction site should be organized.

6.6.5 R

ESULTS

OF

D

IFFUSION

AT

THE

S

ECTOR

L

EVEL

About 80% of all companies visited the demonstration day. Most of them felt thatthe event and the mechanical aids displayed were useful (the impression of FOSAG,Arbouw, and TNO representatives who were there). A videotape given to the com-panies that attended was also sent to other members of FOSAG who did not visitthe demonstration day. The solutions and a report of the day’s activities werepublished in several journals, including specialized publications of the constructionindustry.

FIGURE 6.4

To prevent manual lifting on two regular ladders, a special device to lift glassup the wall of a building has been developed. (Photo courtesy of Piet Ridder.)

80


6.6.6 R

ESULTS

OF

THE

E

FFECTS

S

TUDY

AT

THE

S

ECTOR

L

EVEL

The sector questionnaire was completed by 412 glaziers (response 20.1%), and 88%of the respondents were aware of the fact that new glazing devices were available. Oneor more of the devices was bought and used by 55% of them. The same groupmentioned that the devices were not only bought (234 glass carts, 105 glass sledges,66 glass hoists, and 50 vertical transport devices), but actually used as well. Two devices(truck with crane and mechanical putty remover) were not included in the research.

FIGURE 6.5

For vertical and horizontal transport of glass, as well as mounting the pane,this truck with crane can be effective. (Photo courtesy of Arbouw.)

FIGURE 6.6

To reduce forceful handling, a mechanical putty remover is advised. (Photocourtesy of Fein GmbH.)


81

The resources of companies to invest in new technologies have been determined.There appears to be a strong relationship (p = 0.000) between the size of a companyand the number of devices bought, that is, the amount of the investment. Thus, smallcompanies in general invest less than larger companies. However, larger companiesneed to buy relatively more devices than small companies because they employ moreglaziers who use them.

The three participating companies adopted a total of five glass carts, eight glasssledges, four glass hoists, and six vertical transport devices. Figure 6.7 shows acomparison between the adoptions of the three participating companies and the otherrespondents. The glazier companies that adopted one or more of the devices areshown as a percentage of the total number of respondents.

The participating companies have all adopted at least one of each type of device,which is not true for the respondent group. The adoption rate for respondents variesfrom 10 to 41%. Reasons for these differences can be found in open questions ofthe questionnaire. The companies that did not buy the glass hoists or vertical transportdevices reported that they did not have enough volume of business to invest in thesedevices.

Among the companies that used the glass sledge, 44% used it weekly and 39%used the glass cart weekly. Large differences are found in the frequency of use ofthe glass hoists and vertical transport devices. Reduction of physical load andincreased satisfaction has been determined for frequent users of the devices (31%of the respondents); 91% indicated a reduction of the physical load as a consequenceof the mechanical devices used. Often (47%) a reduction in back loading is men-tioned, but 92% report that this load reduction does not result in reduced sick leave.Furthermore, the significance of the reduction of physical load as a consequence ofregular use of the devices has not been demonstrated (p = 0.23).

With respect to the three levels of satisfaction (satisfied with the device, satisfiedwith the working method, and satisfied with the result of the work), significantimprovement was demonstrated at all levels (Table 6.1).

FIGURE 6.7

The percentage of participating companies adopting the PE approach comparedto companies that were informed. At least one means at least one of the devices is bought and used.

0

20

40

60

80

100

at least one glass cart glass sledge glas hoist device to lift

412 companiesPE companies

82


Satisfaction at all three levels by regular users has been demonstrated. In theopen questions, the reason “handy to use” is often reported. However, use of thedevices is difficult in some situations, such as on a rough ground or around trees infront of a building.

6.7 DISCUSSION

Musculoskeletal discomfort among glaziers has been reduced because it is esti-mated that more than half of the glazier companies use one or more mechanicaldevices specially developed for reducing the musculoskeletal load. Also, thevarious partners, including FOSAG and Arbouw, consider the project to be suc-cessful. Since the participating companies regularly use the glass-handlingdevices and are highly satisfied with their use, the participatory approach seemsto have succeeded in developing devices that are also suitable for nonparticipatingglass companies. In our opinion, there were three major success factors (see alsoBernoux 1994):

1. The fact that employees defined the needs and cooperated in finding andtesting solutions

2. The fact that solutions were very simple to implement, visible, and easyto understand in their use (see also Rogers 1995)

3. The fact that a sector group was responsible for the process, including acampaign at the sector level

Nevertheless, this study has three major weaknesses:

1. The efforts were great, and the question arises whether this is the mostefficient way (including roles of the participants) to reduce musculoskel-etal loading in a sector.

2. There was a low response on the evaluation questionnaire. In fact, weonly know for sure that 11% of the glazier companies that are FOSAGmembers use the devices.

3. More adoption is possible because 45% of the respondents had not yetbought a device.

TABLE 6.1 Satisfaction with the Devices

Satisfaction about % of users indicating

very

or

sufficiently

satisfied Pearson’s p

Use of the device 86.3% .001New working method 87.7% .026Result of the work 92.6% .020


83

Furthermore, it was not possible to carry out this study according to the rule ofthe

experimental paradigm

. Ideally, a control group of glazier companies that wereexcluded from the campaign would have been formed, but experiments in a natu-ralistic setting often have these constraints (Vink and Kompier 2003).

Discussions with other the glazier companies revealed that important reasonsfor buying the new devices included better working conditions and (sometimes)efficiency improvement, partly due to the expected reduction in sick leave over thelong term and partly because of lower direct costs (Koningsveld et al. 2004). Forinstance, the glass cart enables some work to be done by only two glaziers insteadof three, which reduces labor costs.

In a previous evaluation 3 months after ending the PE project (before thecampaign), the participants reported moderate use of the devices (Jong et al.2000). When this was again evaluated more than a year later, adoption by par-ticipating companies had increased significantly. All companies bought moredevices. Furthermore, the frequency of use had decreased for the glass sledgeand the glass hoist, but increased for the glass cart and the vertical transportdevice. Apparently, the devices that were adopted as a result of participation inthe project pleased the glaziers in practice. As a result, more devices were bought.This shows that an evaluation should not be performed too early in the processbecause the time required for evolution in the use of the devices should be takeninto account.

The low level of response on the questionnaire could be improved by individualinterviews or by stimulating the company management. However, the costs of theseefforts are high and the results based on 412 questionnaires returned are alreadyindicative.

The number of companies not using the mechanical aids could be increased.The three companies actively involved in the PE approach received

extra treatment

,which may have led to a better adoption rate in those three companies (100% vs.55%). This strengthens the power of PE approaches found in other studies (Bernoux1994; Wilson and Haines 1997; Vink and Kompier 1997; Vink et al. 1997; Noro andImada 1991). It appears that more direct involvement of employees is advisedbecause it results in greater adoption of improvements.

6.8 CONCLUSIONS

This case shows that a thorough, planned design process could lead to reduction ofdiscomfort in an employment sector. More than half of the glazier sector works withat least one of the new devices. Important success factors include the employeesdefining the needs and testing the solutions, the solutions being clearly stated andhighly visible, and the sector playing a large role in implementing the solutions.

ACKNOWLEDGMENT

The authors want to thank FOSAG and SVEG for their support.

84


REFERENCES

Arbouw (1996)

Risk Assessment in Transport and Mounting Glass Panes

, Amsterdam: Arbouw(in Dutch).

Bernoux, P. (1994) “Participation: A review of the literature.” In M. Gold, ed.,

The Economicsof Participation

, Dublin: European Foundation for the Improvement of Living andWorking Conditions, 6–11.

Jong, A.M. de and Vink, P. (2000) “The adoption of technological innovations for glaziers:Evaluation of a participatory ergonomics approach.”

International Journal of Indus-trial Ergonomics

, 26: 939–946.Koningsveld, E.A.P., Dul, J., Rhijn, J.W. van and Vink, P. (2004) “Enhancing the unpact of

Ergonomic interventions.” In

Ergonomic in the Digital Age

.

Proceedings of the 15thTriennial Congress of the International Ergonomics Association

, Seoul (on CD-ROM).Noro, K. and Imada, A. (1991)


,

London: Taylor & Francis.Rogers, E.M. (1995)

Diffusion of Innovations

,

New York: The Free Press.Urlings, I.J.M. (1996)

Guide to Lighten the Load of Glaziers

, Amsterdam: Arbouw (in Dutch).Urlings, I.J.M., Vink, P. and Wortel, E. (1994a) “A technique for finding solutions.” In

Proceedings of the 12th International Ergonomics Association

Congress

, Toronto,Vol. 3: 352–354.

Urlings, I.J.M., Vink, P. and van der Molen, H.F. (1994b)

Scaffolding Guide to Lighten theLoad

,

Arbouw: Amsterdam (in Dutch).Vink, P. and Kompier, M.A.J. (1997) “Improving office work: A participatory ergonomic


Ergonomics

, 40(4): 435–449.Vink, P., Urlings, I.J.M. and van der Molen, H.F. (1997) “A participatory ergonomics approach

for redesign work of scaffolders.”

Safety Science

, 26(1/2): 75–85.Wilson, J.R. and Haines, H.M. (1997) Participatory ergonomics.” In G. Salvendy, ed.,

Hand-book of Human

Factors and Ergonomics

, 2nd ed., Chichester: Wiley, 490–513.

85

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

7

Reducing Discomfortin Installation Work

A.M. de Jong and P. Vink

CONTENTS

7.1 Introduction ....................................................................................................857.2 The Company Studied in This Case..............................................................857.3 Health and Safety...........................................................................................867.4 The Approach.................................................................................................867.5 The Method ....................................................................................................877.6 Results ............................................................................................................887.7 Discussion ......................................................................................................917.8 Conclusions ....................................................................................................92References................................................................................................................93

Parts of this chapter are reprinted from Jong, A.M. de and Vink, P. (2002) “Partic-ipatory ergonomics applied in installation work.”

Applied Ergonomics

, 33: 439–448.(Copyright 2002, with permission from Elsevier)

7.1 INTRODUCTION

Incidence of sick leave and musculoskeletal discomfort among installation workersis high (Jong and Vink 2002). Installation work is done as part of construction andmaintenance, and it could involve installing central heating, installing electricalsystems, plumbing, or making regulation systems for the process industry. Part ofthis work is done in work stations at the company location, but mainly it happensat the construction sites. Conditions at these sites vary greatly. Often the work isdone under time pressure because clients want to use the installed systems as soonas possible.

7.2 THE COMPANY STUDIED IN THIS CASE

In the case discussed here, an installation company wanted to reduce workers’ mus-culoskeletal discomfort and also improve work efficiency. This is one of the largestcompanies in the Benelux, with a staff of 7000 employees. The company intends to

86


be the best in regard to quality and safety, and it is well equipped to do the morecomplex installation work. The strategy of the company is to acquire the more complexprojects as well as the average projects. Another part of the strategy is to pay muchattention to the workers because of their importance in the production process.

The consequence of this strategy is that experienced and highly educated instal-lation workers are needed, as well as a group of employees equipped to do theaverage projects. Attention is paid to training employees in new working methodsbut also to health and safety issues. The company has locations spread across severalEU countries in order to serve the clients in the different regions and to have localemployees close to the clients. Each location has a manager responsible for planning,product quality, and health and safety. This manager can employ specialists in thefield of health and safety, and, in fact, a health and safety manager is working atalmost every company location.

The various locations often have work stations where the company’s work isdone. If new systems are introduced, the work stations in the local workshops areredesigned. At construction sites the installation company’s influence on workingconditions is very low because other companies own the site. The only influencemanagement has is to pay attention to the optimal tools required to improve thework done by their installers.

7.3 HEALTH AND SAFETY

Work stations in the local offices and the work preparation stations are ergonomicallywell designed to speed up the work and increase quality. At the construction sites,the working conditions are worse because of the lack of company influence. Trans-port of materials and tools from and to the van is often done manually. Employeesmay have to work in a kneeling position, in limited space, or reaching above thehead in a static posture.

The major risks on these construction sites involve safety issues and concernsabout excessive musculoskeletal loading. Safety risks include slippery surfaces andfalls, as well as accidents involving electricity. The heavy manual lifting and carrying,static postures, and repetitive handling often seen on construction sites can createproblems in regard to musculoskeletal loading.

Before starting to reduce worker discomfort, a campaign designed to improvesafety was conducted for 2 years.

7.4 THE APPROACH

In a meeting, the president of the company emphasized the importance of improvingworker discomfort levels to the company management and to health and safety man-agers. That session discussed a change of priority: After 2 years of paying attentionto improving safety conditions, the next 2 years would focus on improving workers’physical loading conditions. The president said, “For our company there are two mainissues: making money and care for our employees that make the money. Therefore,in improving the physical discomfort and load we will have to look for those improve-ments that reduce the loading on our employees and increase efficiency in work.”

Reducing Discomfort in Installation Work

87

The idea was that improvements were needed, especially in the work done onconstruction sites. After this session the staff was asked to develop a stepwiseapproach to implement improvements applicable at various construction sites. Thiswas a positive consequence of the strategy to do both complex and average instal-lation work and to pay attention to the employees. This chapter describes the designprocess and the effects of the project.

7.5 THE METHOD

The design process consisted of six steps, based on previous experience (Vink andKoningsveld 1990; Jong and Vink 2000; Looze et al. 2001).

•

Step 1: Preparation.

The goal of the project was defined in this step,and a steering group responsible for following the process was formed.All employees were informed in the journal published by the companies,and every employee received a postcard specifying the project.

•

Step 2: Analysis.

In this stage the main musculoskeletal risks and haz-ardous tasks were defined. Those definitions were based on sick leavedocuments already available at the health and safety institutes; interviewswith management, health, safety, and environment (HSE) managers, andemployees; and previous studies.

•

Step 3: Idea generation.

Group sessions were planned to develop newideas for improvements in the most hazardous tasks, according to proce-dures described in detail elsewhere (Urlings et al. 1994; Chapter 6). Threegroup sessions were planned: one on heavy lifting and carrying, one onkneeling work, and one on static work. The groups consisted of approx-imately 20 subjects, mainly employees, middle managers, and foremen,with some staff and an external ergonomist.

In the group sessions, the main problems were explained with videos and picturesfirst, and then all attendees wrote a solution on paper. These solutions were collectedand presented (nobody knew who wrote which idea). After that process, a newsolution round was introduced and additional ideas were collected. An estimate wasmade of the effect each solution might have on productivity, health, and feasibility.

•

Step 4: Testing.

The most promising ideas were assembled by employees,staff, or external experts. These were tested by a group of employees whowere used to working together, and tasks were observed by the ergonomist;postures were videotaped and time of handlings was recorded under boththe old and the improved working conditions. Musculoskeletal discomfortand worker productivity were estimated by observations and analyzingthe videotapes.

•

Step 5: Implementing.

Solutions with positive effects were communi-cated throughout the entire company. This was done by making a solutionbook containing all the solutions, which was presented in meetings withthe employees. Solutions particularly applicable to their work were given

88


special attention. If a solution had a negative effect on at least one of theissues —

musculoskeletal loading

or

productivity

— it was not included inthe book. Also, additional improvement ideas were requested and wereadded to the book when a commission (an external ergonomist, HSEexperts, staff and management) approved the solution. This idea genera-tion was promoted by giving prizes for the best solutions.

•

Step 6: Evaluation.

Based on interviews with health and safety executivesin all parts of the company, the number of solutions bought was calculated.Also, the number of additional solutions and the the actual use of theimprovements were estimated. The company then estimated costs andbenefits of the total project.

7.6 RESULTS

This section describes the results observed for each step.

•

Results of Step 1 (Preparation).

The defined goal of the project was notsurprising: to reduce musculoskeletal discomfort and improve efficiencyat construction sites. A more specific goal was needed, and it was decidedto focus the goal more on the

analysis

step. Top management and the staffmembers involved in safety and health and communications agreed onthis goal.

•

Results of Step 2 (Analysis).

The main problems were transport (heavymanual handling) to and from the van, working in a kneeling position,and working in static postures. The staff members mentioned in the

FIGURE 7.1

A draw-out workbench that eliminates working on the floor and reduces backflexion.


89

previous step joined the TNO advisors to agree on the specific goal ofreducing musculoskeletal discomfort and improving productivity in thesethree tasks.

•

Results of Step 3 (Idea generation).

Ideas were generated by 25 employeesfrom various parts of the organization. From a large list of solutions, ninewere chosen that were feasible and were estimated to contribute most toimproving the problems. Four examples of these solutions are shown inFigs. 7.1 to 7.4.

FIGURE 7.2

A transport device to eliminate manual lifting and carrying.

FIGURE 7.3

A sitting device to eliminate kneeling during installation work on the floor.

90


•

Results of Step 4 (Testing).

The results of the tests on productivity andmusculoskeletal loading are shown in Table 7.1. Most improvementsresulted in a productivity increase; doing the same work with fewer employ-ees in the new situation is seen as a productivity improvement. Mostimprovements also reduce the work load. It is assumed that reducing theduration of carrying, lifting, or an awkward posture reduces the risk andthe discomfort.

FIGURE 7.4

An easy-roll gets the spool onto a buck without lifting.

TABLE 7.1 Number of Employees Needed in the Old and the New Situations and Percentage of Time Spent Carrying and Lifting (Lift); in a More Than 60

°

Flexed Back Posture (Flex); or in a Kneeling Position (Kneel)

Number of employees

% of time lifting/flexed/kneeling

Solution Old New Old New

1 4 2 34% lift 6% lift2 2 2 6% lift 0% lift3 4 2 32% lift 3% lift4 4 4 14% lift 4% lift5 3 3 45% flex 7% flex6 2 2 23% flex 8% flex7 2 2 34% flex 12% flex8 2 2 45% kneel 2% kneel9 2 2 31% kneel 4% kneel


91

•

Results of Step 5 (Implementing).

The nine solutions were included ina solution book, and every part of the company received copies that wereused in meetings. Additional improvements were asked for in these meet-ings, which yielded another 60 proposed solutions. Twelve of these wereexpected to have a positive effect on productivity and health and wereapplicable in more than one part of the company, so these twelve ideaswere added to the solutions book.

•

Results of Step 6 (Evaluation).

The number of additional solutionsproposed was estimated to be 60, as noted in the previous step. In total,at least 138 devices were in use throughout the company. All of the ninechosen solutions were used at least weekly, and seven were used on adaily basis.

The cost/benefit ratio for the project was positive, according to the company.The investment consisted partly of man-hours (

€

50,000) and partly of buying newequipment (

€

14,060), for a total investment of

€

64,060. The benefits were espe-cially favorable in solutions 1, 2, 3, and 4 (Table 7.2). The total reduction in costsgenerated by the first four solutions could be as much as

€

167,150. However, theexperience of the company is that in practice, only roughly half of these reductionsare realized. This means that the actual benefit is approximately

€

16,000 in 1 year,apart from the reduction in musculoskeletal discomfort and the improved well-being of employees.

7.7 DISCUSSION

As a result of this project, worker discomfort should be reduced by using the newdevices, and financial benefits will be felt within a year. From the company’s pointof view, therefore, the project was a success. The company purchased 138 newdevices and found 60 additional improvements. Probably more improvements couldbe found, but the solutions presented in this chapter were the only ones traceableby interviews. The implemented solutions contribute to reduction in discomfort andwork load and improve well-being, as is mentioned by some workers, and the

TABLE 7.2 Estimation of the Benefits within 1 Year from Each of the First Four Solutions

SolutionNumber of

solutions in useReduction in

man-hours/week

Reduction inman-hours(40 weeks)

Cost reduction(

€

45/hour)

1 3 16 1,920 86,4002 73 0.25 730 32,8503 3 8 960 43,2004 35 0.08 117 5,265

total, 1–4 167,150

92


company estimates that there is a productivity increase with a return on investmentof 25% (

€

16,000/

€

64,000).From a research point of view, however, the study is not a success. Only 198

solutions were generated by 7000 workers — a yield of just 3%. According to Rogers(1995) 2.5% of a group are innovators and adopt an improvement anyway. In thiscase, we could have reached only the early adopters. Also, the real effect of theimprovements on musculoskeletal discomfort was not measured, and the effect ofonly the minimal number of improvements is known. For a good estimate, more in-depth observations are needed.

Furthermore, the evaluation was done within half a year after the project wascompleted. As noted in Chapter 5 and by Jong and Vink (2002), most improvementsare implemented after 2 years because investments in new equipment first have tobe put into a budget for the following year. A proposal for conducting a thoroughevaluation was discussed with the company but did not interest them. It is not partof the company’s strategy to sponsor further scientific research. Such questions maybe of more concern to governments.

A previous study (Jong 2002) showed that six factors play an important role insuccessfully implementing improvements:

1. User tests by employees2. Improvements focused on the specific tasks3. Active participation of management in keeping more employees informed4. Direct participation of employees and opinion leaders in the improvement

process5. Good cost/benefit ratios6. Usable products (without changing the work drastically)

In this project all six factors played a role because the tests were performed byemployees and the improvements were focused on the actual work. Costs andbenefits were explicitly mentioned, and management supported the improvements.Perhaps the weakest point in this project was the direct participation. Of the 7000employees, only 3% were directly involved.

A thorough evaluation was not conducted, although it could have been helpful tothe company as well as to the research. Such an evaluation could show that only apart of the company is involved in solutions and that more activities could be neededto spread the knowledge further. However, the company was not interested in a furtherevaluation because the project was seen as successful. Perhaps ergonomists shouldtrain themselves to be better change agents — better able to convince companies ofthe need for evaluation and further implementation of solutions.

7.8 CONCLUSIONS

By using a participatory process, various improvements were implemented to reducemusculoskeletal discomfort and increase productivity in the installation company.The company evaluated the project as successful because it contributed to thecompany’s overall strategy. From a scientific point of view, it is difficult to draw


93

conclusions as to the effects. More thorough research is needed, especially concern-ing the evaluation.

Among the lessons learned from this project are: (1) that user tests by employeesthemselves are very important; (2) that the involvement of HSE managers is impor-tant; and (3) that explicit attention to costs and benefits is essential. Perhaps ergon-omists should be better trained as change agents in order to convince companies ofthe usefulness of evaluation and further implementation of solutions.

REFERENCES

Jong, A.M. de (2002)

Improving Working Conditions at the Construction Site

, Delft: DelftUniversity of Technology (Ph.D. thesis, in Dutch).

Jong, A.M. de and Vink, P. (2000) “The adoption of technological innovations for glaziers:Evaluation of a participatory ergonomics approach.”

International Journal of Indus-trial Ergonomics

,

26: 939–946.Jong, A.M. de and Vink, P. (2002) “Participatory ergonomics applied in installation work.”

Applied Ergonomics

, 33: 439–448.Looze, M.P. de, Urlings, I.J.M., Vink, P., Rhijn, J.W. van, Miedema, M.C., Bronkhorst, R.E.

and Grinten M.P. van der (2001) “Towards successful physical stress reducing prod-ucts: An evaluation of seven cases.”

Applied Ergonomics

, 32: 525–534.Rogers, E.M. (1995)

Diffusion of Innovations

,

New York: The Free Press.Urlings, I.J.M., Vink, P. and Wortel, E. (1994) “A technique for finding solutions.”

Proceedingsof the 12th International Ergonomics Association Congress,

Toronto: Vol. 3: 352–354.Vink, P. and Koningsveld E.A.P. (1990) “Bricklaying: A step by step approach to better work.”

Ergonomics

, 33(3): 349–352.

95

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

8

Reducing Discomfort in Office Work

P. Vink and M.A.J. Kompier

CONTENTS

8.1 Reducing Discomfort in Office Work............................................................968.2 Ergonomic Interventions: Not Only

What

You Do, but Also

How

.................................................................................................968.3 The Case Company........................................................................................968.4 A Participatory Approach ..............................................................................978.5 Three Studies and Three Research Questions...............................................988.6 Methods and Procedures................................................................................98

8.6.1 Study 1 ...............................................................................................988.6.2 Study 2 .............................................................................................. .998.6.3 Study 3 ...............................................................................................99

8.7 Results of Study 1: The Old Workplace (n = 45) .......................................1008.8 Results of Study 2: The Ergonomic

Experiment (n = 12).....................................................................................1018.8.1 The Self-Chosen Workplace ............................................................1028.8.2 Comparing the Old Workplace and the Recommended

Workplace.........................................................................................1028.8.3 Comparing the Old, Recommended, and Self-Chosen

Situations..........................................................................................1038.9 Results of Study 3: The Follow-Up Study (n = 45) ...................................104

8.9.1 Comparing the Self-Chosen Situation and the Old Study (n = 45) ..................................................................................105

8.9.2 Comparing Two Subgroups: Twelve and Thirty-Three Employees (n = 45) .........................................................................105

8.9.3 Answers to the Research Questions ................................................1078.10 Conclusions ..................................................................................................108Acknowledgment ...................................................................................................108References..............................................................................................................109

96


This chapter is based on Vink, P. and Kompier, M.A.J. (1997) “Improving office work:A participatory ergonomic experiment in a naturalistic setting.”

Ergonomics

, 40(4):435–449. See also http://www.tandf.co.uk/journals/tf/00140139.html

8.1 REDUCING DISCOMFORT IN OFFICE WORK

Work station design, the work tasks involved, and work–rest schedules (e.g., thescheduling of breaks) contribute to the type and prevalence of physical discomfortin offices. Physical discomfort in office work is quite common, as was demonstratedin a study by Fogleman and Lewis (2002). These authors studied discomfort invarious body regions (head and eyes, neck and upper back, lower back, shoulders,elbows and forearms, and hands and wrists) and the way such discomfort was relatedto keyboard use and monitor and keyboard position.

Fogleman and Lewis demonstrated that discomfort increased as a function ofthe number of hours the keyboard was used. They also showed that improper monitorand keyboard position were related to head/eye and shoulder/back discomfort,respectively. These results emphasize the importance of work station ergonomics,well-designed work tasks, and well-designed work–rest regulations. From these andcomparable studies it also follows that ergonomic interventions in office work maybe indicated as a means of increasing comfort (see also Mehkora et al. 2000).

8.2 ERGONOMIC INTERVENTIONS: NOT ONLY

WHAT

YOU DO, BUT ALSO

HOW

Implementing ergonomic improvements is more than choosing the right ergonomic

technical

design solution. It is well known from ergonomic studies (e.g., Ong et al.1988; Grandjean et al. 1983) that employees do not automatically adopt well-designed office furniture, such as adjustable seats and desks. From studies in par-ticipatory ergonomics (Chapter 4) it may be concluded that ergonomic improvementsare best implemented when employees themselves, as well as other company parties,are actively involved (Noro and Imada 1992; Imada 1994). Positive results havebeen obtained by using a stepwise participative approach (Chapter 4). This approachis based on the assumption that employees ought to be recognized as experts withrespect to their own work situation and that organizational change is best developedin a participative and systematic way.

8.3 THE CASE COMPANY

Against this background, an ergonomic intervention study in order to reduce physicaldiscomfort was carried out at the Department of Salary Records in a Dutch nationalministry. This department is responsible for paying salaries to all employees in thisministry, and the work is both mentally and physically demanding. It consists mainlyof visual display unit (VDU) work (data entry, data control, word processing, datasearching, reading documents, and so forth). Around the 15th of each month, all


97

necessary changes need to be put into data files to enable proper payment of salaries.This resulted in an elevated work pace, especially in the 2 weeks preceding thedeadline. Management of this department wanted to improve the work situation andchose to start an ergonomic project.

8.4 A PARTICIPATORY APPROACH

In the first phase of the project a steering committee was formed consisting of thehead of the department (chairman), a representative of the health and safety com-mittee, the company doctor from the ministry, an ergonomist, a representative of thepersonnel department, a representative of the union, and of the central occupationalhealth service of the government. In addition, a small team (chairman, ergonomist,and employee) was formed to ensure daily progress. The ergonomist was an externalconsultant who also undertook the research and prepared the questionnaires andtests (Vink and Kompier 1997).

From a LOQUEST questionnaire study (Hildebrandt 1992) it appeared that 39%of the 45 employees had neck complaints and 31% had shoulder complaints duringthe previous 12 months (Vink and Kompier 1997). These scores were significantlyhigher than those in two large reference groups of about 1000 Dutch employees(Fig. 8.1).

These results were discussed in regular work consultation meetings. In thesemeetings it appeared that the employees preferred to focus on the improvement ofthe workplace in order to reduce neck complaints because these bothered them mostduring work.

FIGURE 8.1

Percentage of the 45 employees in the study population reporting complaintsduring the last 12 months in the study population, compared to Dutch reference groups inmaintenance work (n = 436) (Hildebrandt et al. 1996) and in agricultural work (n = 1634)(Hildebrandt 1995).

0

10

20

30

40

50

60

shoulders elbows wrists/hands neck upper back lower back

study population maintenance workers agricultural workers

98


8.5 THREE STUDIES AND THREE RESEARCH QUESTIONS

This participatory ergonomics project consisted of three parts:

1. Ergonomic study of the old workplaceFirst, the old workplace — that is, the work situation as it was at the startof the experiment — was investigated in the areas where all 45 employeesworked. Research question 1 was: What is the ergonomic quality of theold workplaces in the department?

2. Ergonomic experimentSecond, a sample of 12 employees participated in an ergonomic experi-ment. According to ergonomic guidelines, each of them was instructed tochoose his or her

ideal

workstation and, after 2 weeks, was allowed todeviate from those recommendations. Objective and subjective effectswere recorded. Accordingly, research question 2 included: (a) What dif-ferences can be shown between the recommended workplaces and the oldworkplaces? and (b) What differences can be shown between the recom-mended and self-chosen workplaces, and why would employees want todeviate?

3. Study of 45 employees (follow-up study)Third, on the basis of this experiment, all 45 employees received thoroughand individual instruction in constructing their ideal workplace. Theirworkplaces and subjective reports were recorded 5 months later. Note thatthere was a difference between the 12 employees who participated in theergonomic experiment and their 33 colleagues who did not. The lattergroup received thorough individual instruction and training only. It maythus be argued that the other 12 participating employees received an

extra

treatment. Accordingly, research question 3 included: (a) Is the workplace in the

self-chosen condition a better workplace, compared to the old workplace?(b) Do the 12 employees who also participated in the previous experimentchoose a better ergonomic design for the workplace compared to their 33colleagues? and (c) Why do employees in the self-chosen workplacedeviate from the recommendations?

8.6 METHODS AND PROCEDURES

8.6.1 S

TUDY

1

Anthropometric data were collected for each individual. In addition, various criteriawere recorded for the old workplace: desk height; chair height; VDU screen position;keyboard position; availability of document holder; availability of an inclined desk;percentage of time carrying out VDU work; the position of the VDU screen withrespect to light sources; foot space and foot rests; user-friendliness of software anddocuments to be handled; and the position of telephones, reference books, and records.


99

8.6.2 S

TUDY

2

Next, 12 employees (7 men, 5 women) were selected. Criteria for inclusion werevariation over workrooms, employees frequently performing “normal and representativetasks,” performing the same tasks over a period of at least 30 minutes, and motivationto participate in the experiment. Each of these 12 employees took part in the ergonomicexperiment that was performed at the actual workplace. The subjects were recordedduring normal VDU work, which included 30 minutes continuously sitting in a staticposture in the traditional workplace, in the recommended workplace, and in a self-chosen workplace adjustment (2 weeks later).

Lateral photographs were used to study the influence of the workplace adjust-ments on the neck and back position with respect to the vertical. The camera (135-mm focus) was positioned at shoulder height, 0.2 m posterior to the table edge andapproximately 3 m lateral to the subject. Three lateral photographs were made ofeach subject, in each condition, while the subjects were watching the screen (e.g.,data controlling) in cases where this was the major part of the task. In cases wherethe major part of the task was looking at the document holder (e.g., data entry), thephotograph was made during that part of the task.

A vertical reference (doorpost or windowframe) was established in the back-ground of the photograph. A line was drawn between the point of the nose and themiddle of the ear cavity (the angle between the head and the vertical: neck flexion)and a line was drawn between the middle of the shoulder and the middle of the hip(flexion of the back). The average angle for the 12 subjects was calculated for boththe old and the recommended conditions, and the differences were tested (t-test forpaired observations, p < 0.05). This was also done for those subjects for whomdetailed data were available in all three conditions.

Six subjects were recorded in the old situation in the morning and again in theafternoon in the recommended situation. The other six were recorded in the recom-mended situation in the morning and in the old situation in the afternoon. The self-chosen workplace was recorded 2 weeks later, half of the subjects in the morningand half in the afternoon.

Local musculoskeletal discomfort in 40 different body regions (summing up toseven cluster scores) was recorded in all three conditions (old, recommended, and self-chosen), using local postural discomfort (LPD) (Chapter 2). Before and after workingfor 30 minutes, subjects had to rate their perceived discomfort on a category ratio scaleranging from

no discomfort

(score 0) to

extreme discomfort

(score 10). For eachemployee, the difference in scores between

before

and

after

were calculated by sub-tracting the before scores from the after scores. The differences between the conditionswere tested by the Wilcoxon signed-rank test for paired observations (p < 0.05).

8.6.3 S

TUDY

3

There were 45 subjects in the follow-up study (19 men, 26 women). The men’saverage height was 1.78 m (SD = 0.08) and their average weight was 76 kg (SD =7.6). For the women, the average height was 1.63 m (SD = 0.09) and the averageweight was 63 kg (SD = 8). All of these employees received tailor-made instructionsand training with respect to their ideal workplace. This instruction was based on the

100


experiment with the 12 subjects mentioned earlier and was provided by the ergon-omist and a

trained employee, that is, an employee of the department who wastrained in ergonomics by the ergonomist.

After 5 months, data for the self-chosen workplace were recorded for eachemployee. The working conditions were observed and a questionnaire was used toevaluate whether improvements were actually implemented. The observed variableswere chair height adjustment, table height adjustment, VDU screen position adjust-ment (both height and position on the table), keyboard position adjustment, theaddition of a document holder, and the addition of an inclined desk. The question-naire contained questions about the positive effects of workplace adjustments onback and neck complaints (Hildebrandt 1992).

8.7 RESULTS OF STUDY 1: THE OLD WORKPLACE (n = 45)

Figure 8.2 presents a typical workplace found before the intervention. From anergonomic point of view, the old workplace was of poor quality. The old workstations in the department consisted of desks with a fixed, flat top 730 mm abovethe floor and swivel desk chairs with height-adjustable seats. The screen was usuallypositioned on the desktop in the right or left corner opposite the subject, and thedocuments were positioned left or right of the keyboard on the desktop. Keyboardswere found in different positions. Extra adjustments such as document holders,screen holders, or desk inclinations were not available.

FIGURE 8.2

Typical work situation found in the old (i.e., preintervention) situation (notethe flexed neck and the VDU screen that is not anterior to the subject).


101

8.8 RESULTS OF STUDY 2: THE ERGONOMIC EXPERIMENT (n = 12)

Study 2 involved the recommended workplace. In order to improve the out-of-datework stations, adjustable furniture was necessary. The department had planned to orderthese new desks and chairs 5 years later, but the steering group advised managementto order the new furniture right away. Management followed this advice. The depart-ment made an additional budget available for extra adjustments (document holders,inclined desks, foot rests, and screen holders). A recommended work station wasestablished for each of the 12 employees (7 men, 5 women), based on ergonomicguidelines. The following improvements, (a) through (f), were chosen because theyhave a favorable effect on the neck, which was perceived to be the largest problem.

a. Optimal seat heightThe optimal seat height was calculated by a procedure described earlierby Verbeek (1991). Using a ruler, the distance from the top of the desk tothe sole of the shoe was measured while the subject sat on the desk withshoes on and fully clothed — the so-called popliteal height (Dainoff andDainoff 1987). The seat height was adjusted to this popliteal height whilethe subject sat on the chair with a compressed seat spring (Fig. 8.3).

b. Optimal desk height While the subject was seated on the desk, the distance from underneaththe maximally flexed elbow to the top of the desk was measured, thisbeing the elbow height. The table height was adjusted to equal the sumof the popliteal height and the elbow height (Verbeek 1991) (Fig. 8.3).

c. Using a document holder A document holder was placed as close to the screen as possible, theviewpoint at the same height as the viewpoint on the screen.

d. Screen height The viewpoint on the screen should be 100 mm below eye height (Delle-man and Berndsen 1992).

FIGURE 8.3

Measurement of seat height (1) and desk height (1 + 2).

2

1

102


e. Position of screen Since the main task for the 12 subjects was VDU work, the screen wasplaced in front of the employee.

f. Position of the keyboard The keyboard was positioned in front of the subject so that the elbowangle was 90 degrees and the wrist was in an approximately neutralposition.

8.8.1 T

HE

S

ELF

-C

HOSEN

W

ORKPLACE

After working for 2 weeks in the recommended workplace, the 12 subjects wereasked to choose the work situation that they preferred. This self-chosen workplaceresembled the recommended workplace, although several employees had changedtheir recommended workplace.

Seat height (a) and desk height (b) were as recommended, except for oneemployee. She was a very small person with a managerial position and, while seatedat the desk, had to talk with colleagues who stood in front of her. Her opinion wasthat extending her neck during the discussions would be uncomfortable and not inkeeping with her status, so she raised the height of her desk and chair. She alsoadded a footrest.

Four employees, who also had to use large-format documents that could not beplaced on a document holder (c), did not always use the document holder.

The middle of the screen was positioned at about 100 to 200 mm below eye height.Most employees occasionally had to look at the keyboard and placed the screen height(d) somewhat lower than the recommended 100 mm to diminish nodding.

The screen and keyboard were placed as recommended (e, f).

8.8.2 C

OMPARING

THE

O

LD

W

ORKPLACE

AND

THE

R

ECOMMENDED

W

ORKPLACE

The position of the subject’s head was significantly different between the old work-place and the recommended workplace. It was closer to the upright position (Table 8.1)in the recommended workplace. This effect was not significant for the trunk position;the local perceived discomfort in the neck region was influenced most (Table 8.2;

TABLE 8.1 Mean Difference in Angle between the Old and the Recommended Situation

Difference SD T-value P-value*

Head positionTrunk position

5.054.10

7.648.55

2,291,66

0.0210.062

* p < 0.05; t-test for paired observations, n = 12.


103

Fig. 8.4). Discomfort in the back also decreased, but this effect did not reachsignificance. The recommended situation had almost no influence on discomfort inthe shoulder, but total discomfort significantly decreased.

8.8.3 C

OMPARING

THE

O

LD

, R

ECOMMENDED

,

AND

S

ELF

-C

HOSEN

S

ITUATIONS

Data from only six employees could be used for comparing the self-chosen condi-tion to the two others. Two subjects were absent but performed the experiment 1week later, after the deadline of the 15th. Their data were not included because thetask they performed a week later differed too much from that in the other twoconditions. The data of three other employees were omitted since it appeared that

TABLE 8.2 Mean Difference in Local Perceived Discomfort between the Old and the Recommended Situation

Difference Z-value P-value*

Neck 3.1* 2.28 0.01Shoulder 0.1 0.47 0.32Back 1.2 1.41 0.08Total 3.2* 2.28 0.01

* significant; p < 0.05; Wilcoxon signed-rank test, n = 12.

FIGURE 8.4.

The LPD in different body regions under both the old and the recommendedworkplace conditions (n = 12). The total is the sum of LPD numbers for all 40 regions,including the three regions mentioned in the figure.

−1

0

1

2

3

4

5

6

7

neck shoulder back total

old

recommended

104


they did not have identical work for half an hour, as a result of too many unexpectedtelephone calls. One employee had a sports injury to the knee and therefore satasymmetrically. The remaining six subjects who were tested in the old, recom-mended, and self-chosen situations showed no significant differences (p < 0.05) inhead posture (Table 8.2).

Despite the small number of subjects, the total postural discomfort in the self-chosen and recommended situations differed significantly from the old situation(Table 8.3). The recommended and self-chosen situations did not differ significantly.

8.9 RESULTS OF STUDY 3: THE FOLLOW-UP STUDY (n = 45)

At this stage it was concluded that the recommended workplace constituted a clearimprovement over the old workplace. Still, this experiment was the basis for severaladjustments that were made at the next stage: instructions to the 45 employees inthe department.

Recommendations (a) seat height, (b) desk height, (c) document holder, and (e)screen in front remained unchanged. Recommendations (d) middle of the screen and(f ) keyboard were adapted. Recommendation (d) was set to 100 to 200 mm beloweye height, but recommendation (f ) unfortunately was not included in the instructionbecause of a technical mistake.

Based on this guideline, the ergonomist discussed the necessary accessories(document holders, inclined desks, screen holders, etc.) with every employee sepa-rately. Adjustable chairs and tables were ordered and a list of accessories to beordered was made. Ordering the chairs, tables, and accessories took a long timebecause the purchasing department was not involved in the participatory ergonomicsprocess and was not immediately convinced of their necessity.

After the accessories were delivered, the ergonomist and the trained employeevisited each employee. The three individuals transferred every employee’s old work-place to their recommended workplace. Before the move, a brochure entitled “Howto Adjust My Workplace,” which contained the instruction mentioned earlier, washanded out.

TABLE 8.3 The Mean Difference in Local Postural Discomfort Summed for All Regions

Difference Z-value P-value*

Old vs. recommended 4.92* 2.2 0.01Old vs. self-chosen 3.75* 1.9 0.02Recommended vs. self-chosen 1.17 0.1 0.46

* significant; p < 0.05; Wilcoxon signed-rank test, n

=

6.


105

8.9.1 C

OMPARING

THE

S

ELF

-C

HOSEN

S

ITUATION

AND

THE

O

LD

S

TUDY

(n = 45)

Five months after the changes in work stations, data for the self-chosen workplace(that is, the workplace as it was at that moment in time) were recorded for everyemployee. Twenty-nine employees completed a questionnaire with respect to theactual implementation and the possible effects on back and neck complaints (foursubjects did not work in the department any more, five were ill, three were on holiday,and four were not able to complete the questionnaire due to work commitments).Almost all (97%) of the twenty-nine employees had changed their work station.Table 8.4 summarizes the adjustments.

Eighteen of the twenty-nine respondents had previous back and neck complaints,whereas eleven others did not. Table 8.4 also shows how many of these eighteenemployees reported positive effects of the workplace adjustments on back and neckcomplaints. Table height, chair height, and VDU screen position were improvedmost often. Keyboard position was changed by only one third of the employees,probably due to the fact that this recommendation was omitted by mistake from the“How to Adjust My Workplace” brochure. Most employees with back and neckcomplaints considered these complaints to be reduced by the adjustments made,especially the adjustments to the chair, table, and VDU screen position.

Figure 8.5 shows the percentages of employees reporting musculoskeletal complaintsduring the 12 months before and after the project. It is clear that the number of muscu-loskeletal complaints was reduced. The reduction in neck, high-back, and shouldercomplaints is significant (t-test for paired observations, p < 0.05). The change in low-back complaints is not significant, nor was sick leave influenced significantly. However,a year after the study the management reported a 1% reduction in sick leave percentage,from 7 to 6%.

8.9.2 C

OMPARING

T

WO

S

UBGROUPS

: T

WELVE

AND

T

HIRTY

-T

HREE

E

MPLOYEES

(n = 45)

Figure 8.6 shows the differences in workplace adjustment between the 12 employeeswho also participated in the previous experiment and the 33 others, who

only

received

TABLE 8.4 Percentage of Employees Who Adjusted the Work (n = 29) and Percentage of Employees with Back or Neck Complaints (n = 18) Who Report a Positive Effect of These Adjustments on Back and Neck Complaints

Workers with adjustments (%)

Workers reporting positive effects (%)

Chair height adjustment 73 67Table height adjustment 83 67VDU screen position adjustment 69 50Keyboard position adjustment 34 11Addition of document holder 14 17Addition of inclined desk 31 11

106


thorough individual instructions and training. Those employees who also participatedin the experiment show the fewest deviations from the recommended workplace.The differences in adjustment between the 12 employees who participated in theergonomic experiment and the other 33 are significant with respect to desk height,

FIGURE 8.5

The percentage of workers reporting complaints during the 12 months beforeand after the project (n = 29).

FIGURE 8.6

Percentage of the employees that adapted the workstation: the 12 employeesthat participated in the ergonomic experiment compared with the other 33.

0

10

20

30

40

50

neck upper back lower back shoulder

beforeafter

0 20 40 60 80 100 120

desk height

chair height

screen position

keyboard position

document holder

inclined desk

12 in test 33 others


107

chair height, screen position, and keyboard position (t-test for paired observations,p < 0.05). From an ergonomic point of view, the 12 appear to work in better workstations. Between the two groups, the difference as to keyboard position adjustmentis striking. It seems to illustrate that the 12 were carefully instructed to adjust theirkeyboard position, whereas the others were not.

Why did the employees deviate from the recommendations? Table 8.5 showsthat there are various reasons why employees deviate from the ergonomic recom-mendations. A major reason for deviating is related to specific task requirements(using A3 format, often rising from the chair, etc.).

8.9.3 A

NSWERS

TO

THE

R

ESEARCH

Q

UESTIONS

Answers to the three questions that were raised earlier can now be summarized asfollows:

• Study 1/Question 1From an ergonomic point of view, the

old

workplace was of poor quality.• Study 2/Question 2

In the ergonomic experiment, clear improvements were demonstrated inthe recommended situation when compared to this original situation, bothwith respect to the head position and with respect to the total perceiveddiscomfort and local perceived discomfort in the neck region. From theergonomic experiment it also appears that when allowed to deviate fromthe recommended workplace, employees may choose individually pre-ferred solutions by reason of specific task demands (e.g., document han-dling, communication) and individual characteristics (e.g., height). Still,from a discomfort point of view, these individual preferences add up toa clearly better workplace than the old workplace.

• Study 3/Question 3From the larger (n = 45) study, the self-preferred workplace appears tobe better than the old workplace in terms of ergonomic standards (97%had changed their work station) and in terms of self-reports and muscu-loskeletal complaints. Most employees with back and neck complaintsconsidered them to be reduced, especially as a result of adjustments tothe chair, desk, and VDU screen position.

From an ergonomic point of view, those 12 employees who also par-ticipated in the ergonomic experiment (Study 2) chose a better self-preferred workplace than their 33 colleagues did. The difference betweenthe group of 12 employees and the other 33 employees suggests that takingpart in an ergonomic experiment in a naturalistic setting performs the roleof an

extra treatment

. It leads to a better ergonomic adjustment comparedto the condition in which employees

only

receive thorough individualinstruction and training.

Thus, close employee participation seems to be very important in reducingphysical discomfort. On the other hand, it does not seem to be necessary to carry

108


out an ergonomic experiment in order to have employees improve their work stations.The work stations of the employees who did not take part in the experiment werealso significantly improved in comparison to the old ones. From the comparisonsbetween the self-chosen and the recommended work situations — questions 2(b) and3(c) — it follows that employees may have good arguments for deviating from

thatwhich is ergonomically best

. In both Studies 2 and 3, employees could very welldescribe their reasons for deliberately changing the recommended layout, and theywere even aware of the fact that it would increase their discomfort (Table 8.5).

8.10 CONCLUSIONS

This study demonstrates that it is possible to reduce discomfort in office work. Ifthe employer provides well-designed office equipment and if, in a participatoryapproach, employees are carefully instructed and trained in its utilization, employeesmay choose a better adjustment of their workplace. However, they may not acceptthe adjustment recommendations in all cases. An important reason for deviatingfrom the ergonomic recommendations is related to specific task requirements. Still,from an ergonomic point of view, the self-chosen situation appears to be a muchbetter condition than the traditional work situation.

Experimental measurements in a naturalistic setting may contribute significantlyto workplace improvements, (1) by presenting adequate and “objective” informationfor workplace improvement and ergonomic redesign, and (2) as a change agent itself,that is, as an “intensified treatment.”

ACKNOWLEDGMENT

The authors want to thank the Dutch Ministry of Home Affairs for their contributions.

TABLE 8.5 Why Employees Choose to Deviate from Ergonomics Recommendations with Respect to a Workplace Adjustment

n Motivation2 Table height is too low for my status.2 A high table does not correspond aesthetically to that of my colleague.2 A high screen hinders communication with my opposite colleague.2 My screen height is higher because I like to think while sitting back and looking

at the screen.3 It takes too much time to use a document holder.3 I can rise faster from a higher chair.5 The screen height feels uncomfortable, so I put it lower.5 A document holder is not easy to use with large documents (e.g., A3).7 We do change the height of the chair dependent on the task.

(Only arguments mentioned twice or more are reported here.)(n = number of employees)

Reducing Discomfort in Office Work 109

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Fogleman, M. and Lewis J.R. (2002) “Factors associated with self-reported musculoskeletaldiscomfort in video display terminal (VDT) users.” International Journal of IndustrialErgonomics, 29(6): 311–318.

Grandjean, E., Hunting, W. and Piderman, M. (1983) “VDT workstation design: Preferredsettings and their effects.” Human Factors, 25: 161–175.

Hildebrandt, V.H. (1992) “Development of a software package questionnaire on musculo-skeletal load and health complaints.” In M. Hagberg and Å. Kilbom, eds., Interna-tional Scientific Conference on Prevention of Work-related Musculoskeletal DisordersPREMUS, Sweden, May 12–14, Book of Abstracts (Arbete och halsa, Solna):123–127.

Hildebrandt, V.H. (1995) “Musculoskeletal symptoms and workload in 12 branches of Dutchagriculture.” Ergonomics, 38: 2576–2587.

Hildebrandt, V.H., Bongers, P.M., Dul, J., Dijk, F.J.H. van and Kemper H.C.G. (1996) “Iden-tification of high-risk groups among maintenance workers in a steel company withrespect to musculoskeletal symptoms and workload.” Ergonomics, 39: 232–242.

Imada, A.S. (1994) “Overcoming cultural barriers within organizations.” In G.E. Bradley andH.W. Hendrick, eds., Human Factors in Organizational Design and Management IV,Amsterdam: Elsevier, 625–630.

Mekhora, K., Listonc, C.B., Nanthavanijd, S. and Coleb, J.H. (2000) “The effect of ergonomicintervention on discomfort in computer users with tension neck syndrome.” Interna-tional Journal of Industrial Ergonomics, 26(3): 367–379.

Noro, K. and Imada, A. (1992) Participatory Ergonomics, London: Taylor & Francis.Ong, C.N., Koh, D., Phoon, W.O. and Low, A. (1988) “Anthropometrics and display station

preferences of VDU-operators.” Ergonomics, 31: 337–347.Verbeek, J. (1991) “The use of adjustable furniture: Evaluation of an instruction programme

for office workers.” Applied Ergonomics, 22: 179–184.Vink, P. and Kompier, M.A.J. (1991) “Participative ergonomics. An intervention strategy for

reducing musculoskeletal injuries.” In Y. Quéinnec and F. Daniellou, eds., Designingfor Everyone: Proceedings of the 11th Congress of the International ErgonomicsAssociation, London: Taylor & Francis, 1699–1671.

Vink, P. and Kompier, M.A.J. 1997 “Improving office work: A participatory ergonomicexperiment in a naturalistic setting.” Ergonomics 40(4): 435–449.

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0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

9

Productivity and Discomfort in Manual Assembly Operations

J.W. van Rhijn, M.P. de Looze, L. Groenesteijn, M.D. Hagedoorn-de Groot, P. Vink, and G.H. Tuinzaad

CONTENTS

9.1 Discomfort in Assembly ..............................................................................1119.2 Market Demands Productivity Increase.......................................................1129.3 Tools to Support Manufacturing..................................................................1129.4 The Faber Case ............................................................................................1179.5 The Original Situation .................................................................................1179.6 The Improvement Process............................................................................1189.7 Unique Possibility ........................................................................................1209.8 The Evaluation .............................................................................................1209.9 Results of the Six Steps ...............................................................................1219.10 Results of the Evaluation .............................................................................1249.11 Discussion ....................................................................................................1269.12 Conclusions ..................................................................................................127Acknowledgment ...................................................................................................127References..............................................................................................................127

Parts of this paper are submitted for publication in the

International Journal ofProduction Research

.

9.1 DISCOMFORT IN ASSEMBLY

Two major issues play a role in manual assembly operations: increasing productivityand increasing health. For a company, it is essential to have efficient operations(Yamada 2002). Handling operations such as searching and walking add only a limited

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value to the product and should be avoided, and the handlings involved in makingthe product should be as short as possible (Yamada 2002). Work should be healthful,and stress and musculoskeletal injuries should be prevented (Yamada 2002).

There is much room for improvement. Chapter 1 reveals that more than onethird of the European working population has musculoskeletal problems developedduring working. Improvement could be achieved by optimal postures and optimalmental loading, as well as by a good variation between static and dynamic activities.If dynamic activities are impossible, the optimum work–rest scheme to achieve goodproductivity and health could be found (Matthiassen et al. 2002; Sauter and Swans-son 1991). Because discomfort is a predictor of musculoskeletal injuries, as notedin Chapter 2, the discomfort factor is often used in experiments to design the optimallayout and work–rest schedules.

9.2 MARKET DEMANDS PRODUCTIVITY INCREASE

Assembly work is under economic pressure (Eijnatten 2002). To survive in worldwidecompetition, companies are forced to produce ever-increasing volumes at the samecosts. Meanwhile, the variety of products increases, shorter delivery times aredemanded, and quality must be kept high as well. This pressure on the companies islikely to increase the pressure on the workers. Under these circumstances, the mainproblems of assembly companies are the logistics of producing the increased volumesper unit of time, the lack of space to run the assembly processes, and getting a healthyand motivated work force. For many companies, the traditional assembly conceptsthat were successful for many years no longer meet the need. These companies arechallenged to find new concepts to solve simultaneously the logistic, spatial, andhuman factor problems.

9.3 TOOLS TO SUPPORT MANUFACTURING

To support innovation in manufacturing, a participatory and integrative approachwas developed by TNO Industrial Technology in cooperation with TNO Work andEmployment. This approach aims at reducing the lead time and the improvement ofthe worker’s job (Rhijn and Tuinzaad 1999; Tuinzaad et al. 2000). Important elementsof the approach are the active participation of the company and the integration oftwo disciplines: assembly engineering and ergonomics. The approach proved to besuccessful in several cases (Tuinzaad el al. 2000). A part of this participative andintegral approach was developed in depth. The ergonomics aspects as well as socio-technical elements and ICT couplings were developed further in a project PSIM.PSIM stands for Participative Simulation environment for Integral Manufacturingenterprise renewal. In PSIM, both a procedure and dedicated software were devel-oped and tested in five companies in Europe (CRFiat, Finland Post, and Volvo),Japan (Yamatake), and the United States (Ford). The PSIM participative simulationprototype supports companies in developing new organizational structures and tech-nology in which humans can perform healthier and better. The companies evaluatedPSIM positively as a breakthrough innovation in the field of business and work (seeFramework PSIM).


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FRAMEWORK PSIM

PSIM (Eijnatten et al. 2002; Vink et al. 2002) is short for Participative Sim-ulation environment for Integral Manufacturing enterprise renewal. The goalof the project is to develop a system that facilitates improvement in production.The system consists of software and a procedure that can be applied byassembly companies. It was developed by TNO (The Netherlands); RWTH(Denmark); Chalmers (Sweden); TU/e (The Netherlands); FIOH (Finland);Baan (The Netherlands); GFI (Italy); and L.A.R. (Germany).

The PSIM prototype that was put to a test consisted of the following siximportant parts:

• Procedure: a stepwise approach to support a company in applyingPSIM

• ergoTool: software including the latest guidelines to evaluate theload on the operator and to test effects or ideas for improvement

• STSD (Socio-Technical Systems Design) tool: software that helpsa group arrive at a socio-technically sound organizational structure

• Navigator: software that supports end users in finding the rightsoftware tool

• Ontology: a language that supports modeling of the enterprise usinginformation and communication technology (ICT) models

• Integrator: software that extracts data from the enterprise resourceplanning (ERP) system to test effects of improvement ideas

These six parts were tested in five companies (Table 1). Not every partwas tested in every company because individual companies had their owninterests and opportunities. The prototype was tested in work sessions. The test

TABLE 1Summary of the Parts of PSIM Tested in the Various Companies

Test site Procedure ergoTool STSD tool Navigator Ontology Integrator

CRFiat ± ± +

Finland Post ± + + ±

Volvo + + + ±

Yamatake ± + ±

Ford ± +

± = partially tested as far as possible or as far as required by the test site+ = complete testEmpty cell = not testedGrey cell = focus of the test

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groups produced an enormous number of ideas for manufacturing improve-ment, part of which were implemented immediately. The others were evalu-ated for later implementation. After the prototype test, a focus group sessionwas organized with the management of the companies and some researchersfrom the PSIM group to discuss the main results and to assess positive andnegative points. The results are presented for each company separately.

RESULTS

CRFIAT

The test proved that efficiency in design could be achieved by applying PSIM.Some ten persons from the company and five PSIM researchers participatedin the test session. Navigator was found to be very useful because it allowsparallel work in the design process. Engineers, managers, and designers cando their work on the same design simultaneously, and proposed changes arenoticed by the other users immediately. However, Navigator should be furtherdeveloped in order to be easier to use. ergoTool was seen as very helpful andcomplete, so this tool will probably replace the existing ergonomic analysissystems in this company.

FINLAND POST

This post-sorting company also developed a large number of ideas for improve-ment that will result in higher productivity and more satisfied employees. Inthe test session, some 35 persons from the company and 12 PSIM researchersparticipated. The most important benefit was the participative test of the tools,especially ergoTool, because it indicated specific improvement opportunitiesbased on numerical data regarding safety, lifting, and pushing and pulling(Fig. 1).

The company found the criteria of the STSD tool also highly usefulbecause they plan to set up self-managing teams in the future and now knowthe effects. A great advantage of the participative character of the PSIM gamewas that more persons were opening up and ready for improvement.

Another benefit mentioned is that more aspects can be evaluated simul-taneously. That is important because sometimes, for example, an improvementfor lifting will conflict with a measure of task rotation. The integral characterof PSIM allows for finding optimal solutions, instead of suboptimizations. Aside effect of the test was that the discussions about Integrator helped thecompany in choosing an appropriate ERP system.

VOLVO CAR SYSTEMS

Applying PSIM generated a large amount of ideas for improvements. Someparts of the ideas were implemented, which resulted in productivity increaseand more satisfied employees. Also, the musculoskeletal loading was reduced.


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In the test session also some 35 persons from the company and 12 PSIMresearchers participated. The companies’ perspective of the PSIM prototypetest was that they had learned a lot because they had to take in all the differentaspects in building a new assembly line. Thanks to the test, more attentionis now being paid to socio-technical issues. The procedure was evaluatedpositively because the operators involved in the tests appreciated the factthat they were being taken away from their normal work and were allowedto think on a higher level and learned more about the topics discussed duringthe tests.

YAMATAKE

Ten people from Yamatake’s printing circuit board department in Japan andthree researchers from Europe’s PSIM were involved in the test. The mostimportant benefit for the company was the participatory procedure that fitextremely well into the company’s culture. Regarding ergoTool, the operatorswere used to working with more qualitative systems, whereas with the PSIMprototype more quantitative analysis is possible. The Japanese company con-sidered this process to be very worthwhile because young employees willfeel the need for more quantitative data in the future as a result of globaliza-tion. Also, Ontology was seen as very valuable for modeling the enterprisein ICT.

FIGURE 1 An example of a software screen used in sessions with workers.

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FORD

Eight people from the U.S. automotive company and three researchers fromEurope’s PSIM were involved. The PSIM participative approach was notnatural for this company, probably because the unions play such an importantrole. For instance, rotating between tasks is difficult because the unions coulddemand more salary. The ergoTool test resulted in a long list of improvementrequests.

GENERAL RESULTS FROM THE END DISCUSSION

In most test sites the PSIM procedure proved to play an essential role inadministering participative simulation. The steps of analyzing the existingsituation and discussing ideas for improvement with groups of engineers,operators, management, and designers were both evaluated positively.

In evaluating the PSIM procedure, companies mentioned that a facili-tator is very much needed along with the software. The Ergonomic andSTSD experts proved to be essential in the process of inviting the users tofollow the procedure and in explaining some background of the PSIM.Also, the visualization support (by use of embedded videos) was evaluatedpositively.

The following similarities and differences were observed among companies:

• Companies that were not used to applying ergonomics evaluatedergoTool more positively then those who already were.

• The application of the mental-workload module, in ergoTool, andthe application of the STSD tool resulted in the largest number ofimprovement ideas. Both tools were evaluated very positively.

• Other parts of the tools were evaluated as being “nice toys,” butwhether they would replace existing checklists, methods, andsoftware that were already in use by the test companies wasquestioned.

• Finally, it was mentioned that the application of the STSD tool wasrather time-consuming.

REFERENCES

Eijnatten, F.M. van, ed., 2002 Intelligent Manufacturing through Participation: AParticipative Simulation Environment for Integral Manufacturing Enter-prise Renewal, TNO Arbeid, Hoofddorp, The Netherlands: The PSIMConsortium.

Vink, P., Eijnatten F.M., van and Rhijn G. van 2002 “Participation: A key for intelligentmanufacturing.” In B. Stanford-Smith, E. Chiozza, and M. Edin, eds., Chal-lenges and Achievements in E-business and E-work, Part 2. Amsterdam: IOS,1328–1335.


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9.4 THE FABER CASE

This chapter gives an example of designing an optimal production layout usingdiscomfort as a parameter to predict health and also using a participative and integralapproach developed by TNO. This participative approach was developed based onTNO experience in several projects, but appeared to be congruent with theories foundin the literature (chapter 4; Looze et al., 2001; Rhijn et al., 2002) and the projectPSIM (see Framework PSIM). Apart from the participative character, knowledge ofthe organizational, logistics, and technical aspects of production engineering was alsoincluded (Tuinzaad et al. 2000).

This approach was applied in Faber Electronics BV, a company producingemergency exit lights (Fig. 9.1). This company experienced an increase in marketdemand, and to cope with these demands the final assembly of the lights had to berenewed. In the final assembly stage, the electronic unit and other components suchas the tube luminescent (TL), the reflector, and the battery are assembled and packed.

9.5 THE ORIGINAL SITUATION

In the original situation the lights were assembled at large tables in batches of 60products (Fig. 9.2). Per batch, two persons are working at two sides of the table.Their work comprises fetching the first components, spreading 60 of them out acrossthe long table and assembling the first components. These activities are repeated forthe second component. This pattern continues until the final component is assembledand the product is packed. This work pattern requires much walking, especially iflarger components are involved, of which only a few can be held in the hand. Theproducts are packed in carton boxes and placed on a pallet, a process that includesmanual lifting.

FIGURE 9.1

One of the products produced at Faber.

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9.6 THE IMPROVEMENT PROCESS

The approach is based on previous experience with the participative and integrativeapproach (Tuinzaad et al., 2000) having elements of the PSIM procedure. (seeFramework PSIM). Six steps are followed to arrive at a higher level of productivityand health in the assembly operations.

1. Preparation (Step 1)The first step is the initialization of a multidisciplinary working groupwithin the company and defining the goal. This small working groupinvolves a mix of participants, including assembly operators (2), middlemanagement (1), process engineers (1), planning and logistics (1), produc-tion management (1), and management (1). Two external specialists guidethe working group: one assembly engineer and one ergonomist. The spe-cialists guide the company through the process and give their expert input.

2. Analysis (Step 2)The second step involves the analysis of the assembly process by settingup an assembly process scheme (MAS); which is drawn on paper duringworking group sessions. It visualizes the sequence of the various processsteps that are required to assemble a certain product. Process steps thatcan occur in parallel are visualized in parallel with the main process flow(Fig. 9.3). The scheme also indicates where in the process these stepsshould end. Estimates of the time required for each process step areindicated, based on available data or estimates by the management andemployees. Based on this scheme, the current layout, with its various workstations, is drawn. Discussions are carried out with the help of the workstations in the scheme. Questions for discussion include: What are theactivities? and How is the transport managed between work stations?Finally, the division of the work among people is described in terms ofwhether individual workers make the whole product or only a part of it.

FIGURE 9.2

The old situation of assembling 60 products batchwise.


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3. Problem definition (Step 3)In this step, the working group makes an inventory of the bottleneckswith regard to the material flow and ergonomics. Bottlenecks could befound regarding factory layout, the delivery of components, the avail-ability of tools and equipment, the time needed to walk and search fortools and components, as well as the physical loads experienced inassembly or transport. In observations at the workplace and interviewswith assembly workers, additional data are gathered. The assembly workand manual transport of materials are recorded by video. On the basisof these recordings the bottlenecks and potential improvements are dis-cussed in the working group.

4. Improvement possibilities (Step 4)Based on the information from Step 3 and from the demands in terms ofproduction volume and product variability, several concepts of the factorylayout and the kind and number of work stations are formulated anddiscussed. The tasks of the workers and the characteristics of the workstations are defined for various options. From these options, the mostproductive and healthful assembly concept is selected.

FIGURE 9.3

Example of an assembly process scheme (MAS) of another case. (© TNOIndustrial Technology.)

Assembleupperframe

Assemblemech. unit A

Assembleelectr. wiring

Preassemblemech. unit B

Preassemblemech. unit C

Preassembleelectr. cabinet

Assemblelowerframe

Mountupperframeon lowerframe

Placement andalignmentframe on final'assy' place

Mountunit Aon frame

Mountunit BCon frame

Integrationcontrolcabinet intofinal product

Finaltest

Packagingfinal product

Mountelectr. unitC on mech.

unit B

Inter-mediate

test unit BC

Intermediatetest electr.

Mountelectr.

plate intocabinet

incl.wiring

Testcontrolcabinet

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5. Test (Step 5)In the fifth step some test work stations are made to simulate the work.The available tools and equipment are used as much as possible. Theworkplace is designed in cooperation with the workers and management,evaluated, and then adapted. The focus is on the location of componentsand tools, the requirements of space, and the proper heights for pickingand placing materials. Based on this experience, the new layout is chosen.

6. Implementation (Step 6)The assembly line and work stations are actually built and implementedin the sixth step.

In this improvement process, Steps 1 through 5 took 3 months, with two sessionsof the working group per week. Step 6 took 6 months to complete, including thetime lost to order and receive the new equipment.

9.7 UNIQUE POSSIBILITY

In this project the new line was built in the same hall as the old line. Both linesoperated simultaneously, which offered the unique possibility of evaluating theeffects of the improvement thoroughly. Subjects could work for 3 months on the oldline and then in the new situation, and their productivity and health could bemeasured and compared.

9.8 THE EVALUATION

After the six steps were completed, a thorough evaluation of effects was carried out.Six workers who were familiar with the traditional and the new concept participatedin this experiment. Their general experience in assembly work ranged from 1.5 to12.5 years. The average age of this subject group was 30.7 years (range, 21 to 41years). In this test, the six subjects worked both in the traditional manner andaccording to the new concept for an entire working day, while various subjectiveand objective measures were recorded. The subjects were asked to perform theirtasks as they usually do (including, for instance, task rotation under the new concept)and at their normal working pace.

Under both sets of conditions productivity was measured in terms of the numberof products per person per day. Furthermore, the order lead time was calculated,that is, the time the product is in the line. The required floor surface was measured,including the workbench, the walking space at the work station, and the materialstorage space at the work station. From video recordings made in both situations,the activities were divided into

added-value

(assembling, mounting) and

non-added-value

(walking, sorting, searching) activities, and the time of added-value activitieswas calculated as a percentage of the total working time.

With respect to the physical load on the workers, the time of occurrence ofhazardous body segment postures was estimated by observation, and the riskinvolved in lifting situations was calculated. Also, the workers’ discomfort andfatigue were recorded.


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The body segment posture estimation was based on video recordings; the liftingsituations were studied using the NIOSH equation (Waters et al. 1994). From thevideo recordings, estimates were made regarding the positions and angles of bodysegments, using a special computer program (Noldus). Local perceived discomfort(LPD) was recorded using a seven-point scale (Grinten and Smitt 1992). Standard-ized questionnaires were used to address the various aspects of the physical workload, the mental work load, the worker’s satisfaction, and the health risks in boththe traditional and the new situation. Paired t-tests or the Wilcoxon test (in case ofranked pairs) were used to determine the significance of differences (p < 0.05)between both situations.

9.9 RESULTS OF THE SIX STEPS

• Step 1In the first step, the different groups were indeed installed as describedin the method. Also, the goal was agreed upon: reducing musculoskeletalloading and reducing throughput times.

• Step 2In the assembly process scheme for the emergency lighting device allsubsequent activities is shown in Fig. 9.3. In the scheme, all subsequentactivities that are required to assemble one device are presented. Thescheme helped indicate the type of added-value activities (assembly) andnon-added-value activities (fetching and spreading out components) thatwere required. A positive effect of developing the assembly processscheme is that all participants became aware of the advantages and dis-advantages of the current assembly system.

• Step 3In the left column of Table 9.1 some bottlenecks in material flow andergonomics are shown.

• Step 4To solve the problems mentioned in Step 3, various production conceptswere studied. For each concept the effects on productivity and health wereestimated. From these studies, two concepts were chosen and furtherspecified. These concepts are presented in Fig. 9.4.

TABLE 9.1Difference between the Old and New Production Line

Old New % Change

Order lead time 155 min 72 min

−

46Time/person/product 5.2 min 3.6 min

−

31Products/person/day 93.3 134.7

+

44Required work space 80.5 m

2

45 m

2

−

44Satisfied with work 17% 83% 66Physical workload: posture acceptable acceptablePhysical workload: lifting unacceptable acceptable

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The first concept shows three parallel, individual workplaces. At eachworkplace one worker assembles a whole product (concept A). The secondconcept is an assembly line of three workplaces in series, where workersassemble parts of the final product and the products are handed over(concept B). The working group evaluated these concepts according tovarious aspects such as flow of materials and logistics, balancing ofactivities, work content per individual, time to learn (for new employees),and the flexibility to cope with volume and product variances.

FIGURE 9.4

Different production concepts that could improve the flow: (

A

) three parallelwork stations; (

B

) three work stations in series; (

C

) two work stations supplying the thirdwork station.

A.

B.

C.


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The advantage of concept A could be that the worker makes a wholeproduct. This is considered advantageous because of less monotony inthe tasks and higher worker satisfaction. In addition, this concept enablesadaptation of the number of operators to the volume demand. A disad-vantage could be longer learning time. A logistic disadvantage of conceptA is that the three workplaces need to be identical, which means that theequipment at the workplaces (tools, aids) and the supply of componentsshould be organized in triplicate.

The advantage of concept B could be that components are supplied atonly one workplace. However, the work content is smaller and there is lessflexibility: three assembly workers are required to keep the line running.

Based on concepts A and B, a new concept was defined by the workinggroup. In this final concept (C), the various advantages of concepts A andB were combined. Concept C is characterized by an assembly line withthree work stations. At two parallel work stations, two operators performnearly all of the assembly steps. The nearly complete products are suppliedfrom both work stations to the third work station, where the products arefinished and packed. The content of the work is balanced, such that theworkers do not have to wait for others. Small buffers between the firsttwo work stations and the final one are established to enable workers towork at an individually preferred pace.

Instead of a conveyor belt, which may stress the workers, a rollerconveyor was chosen to transport products from the first two work stationsto the final one. This roller conveyor was constructed with a certaindeviation from the horizontal so that products would glide from oneworkplace to the other.

Within the new concept, it is agreed that workers will rotate across thethree workplaces every 2 hours. Finally, it was decided that the stock ofmaterials on the work floor should not exceed the amount required forone production day.

• Step 5In assembly concept C the work stations were also designed. All compo-nents are placed within reach by positioning small boxes in a tiltedposition. Several boxes containing components had to be placed in eachwork station, and to reduce reaching distances the sizes of the boxes werekept small. To get smaller quantities of components, agreements withsuppliers had to be changed. Also, the design of some supply boxes hadto be modified to improve reach and supply. For instance, the boxes withTLs were redesigned so that they could be refilled from above while lampscould be easily picked out from the side. Under the new concept, theworkers refilled the boxes themselves.

Where the workers sit at the first two work stations, a fixture was placedon which the product could be rotated and tilted. Furthermore, the lightwas improved, the screwing tool was positioned within reach and weight-lessly balanced, and new and easily adjustable chairs and tables wereimplemented. At most work stations the worker is seated, but the worker

124


stands at the work station where the final assembly takes place. Theproduct could be tilted at this work station also to facilitate the assemblingactivities. Finally, to further facilitate the assembly some modificationsof the product itself were recommended and applied.

• Step 6All proposed improvements were implemented where six people work oneach of two assembly lines.

9.10 RESULTS OF THE EVALUATION

Table 9.1 shows the effects on productivity, throughput time, and physical work load.Throughput time was reduced from 2 hours and 35 minutes to 1 hour and 12 minutes.The time spent per person per product was diminished, and the number of productsper person was almost doubled. All of this could be accomplished in less work spacethan before. The employees were more satisfied with their work in the new situation(Fig. 9.5), but the participatory ergonomics process could also cause this.

Figure 9.6 shows the working postures in percentages of total working time.There were no large differences in scored working postures, except for raising arms.In the new situation we observed that 12% of the time more arms were elevatedwithin 20 to 60

°

.The NIOSH equations for lifting boxes (92 N per box) in both the old and the

new situations showed an improved and safer way of lifting in the new situation.In the traditional situation, the lifting conditions were unacceptable because of thelow placement (vertical factor) of the pallets on the floor (0.3 m) and the reaching

FIGURE 9.5

The new working situation.


125

(horizontal factor) required before placing. In the new situation the boxes wereplaced on a pallet at adjustable height (0.7 to 0.8 m) on a lifting table, so the workersdid not have to reach as far.

No differences were found for locally perceived discomfort in different bodyareas. Workers did experience less overall fatigue in the new situation, compared tothe traditional situation (p = .038) (Fig. 9.7). There were no differences in experienced

FIGURE 9.6

Categorized working postures in the traditional situation and in the new situation(* = significant difference, p < 0.05).

FIGURE 9.7

Experienced fatigue in the traditional situation and in the new situation, scoredon a seven-point scale (1 = [almost] no fatigue; 7 = very much fatigue).

Working postures

80.0

100.0

Neck f

lexion

40-

60

% o

f tot

al w

orki

ng ti

me

traditionalnew

*

*

*

*0.0

20.0

40.0

60.0

Trunk

flexio

n 0-

20

Trunk

flexio

n 20

-60

Trunk

flexio

n >6

0

Neck f

lexion

0-2

0

Neck f

lexion

20-

40

Neck f

lexion

60-

80

Neck f

lexion

>80

Arm ra

ised

0-20

Arm ra

ised

20-6

0

Arm ra

ised

>60

Wris

t dev

iation

No ro

t/lat

Yes ro

t/lat

*

*

*

*

Neutra

l wris

t

Experienced fatigue

0

1

2

3

4

5

6

7

1 3 5

Subjects

Sco

re

traditionalnew

2 4 6

126


workload and mental load. Five of the six subjects felt more satisfied with the newworking concept. They considered their increased productivity, the improved workstation design, and the reduction of lifting tasks to be the reasons.

9.11 DISCUSSION

In this project, a traditional assembly concept in which workers make batches ofproducts from start to finish was replaced by a concept in which workers make onlyone product at a time. This change, which also involved ergonomic workplacemodifications, resulted in some clear effects. The beneficial effects on productionmeasures are beyond dispute. There appeared to be no need for the company toinvest in building a new factory hall, which was the original plan. It appeared to bepossible to produce about twice as much in the same factory area when applyingthe new assembly concept. In addition, we observed a significant decrease in orderlead time (46%). This gain in productivity is partly based on an increase in thepercentage of time that is spent on added-value (assembly) activities. This significantshift toward more added-value assembly work did not lead to a clear increase in thephysical or mental loads on the workers. In our objective and subjective measures,we observed no difference in load (local perceived discomfort, experienced workload, experienced mental load, the occurrence of stressful postures in most bodysegments) and a decreased load in the new situation (less lifting and a lower levelof overall fatigue at the end of the day).

One exception concerns the arm posture: Slightly more frequent

moderate

armelevation is observed in the new situation. The increased arm elevations can beexplained by the fact that part of the time the workers are seated, which requiresmore arm elevation when reaching for components from shelves. Modifying the waythat the components are delivered now eliminates this disadvantage.

Winkel et al. (2002) address the current general tendency in manufacturingtoward work intensification (because of lean production, time-based management,or business process reengineering) and the elevated medically certified sick leaverates that might be associated with these developments (Vahtera et al. 1997). In ourproject the work also became more intense, as more time was spent on assembly.This leads to more products per worker per unit of time within the new concept.However, our results did not point toward elevated health risk, and some caution isrecommended here.

In this study we addressed the hazardous postures, hazardous lifting situations,and subjective experiences of people. We did not really address the important aspectof variation of actions over time. Monotonous work (low variation) in the productionindustry has been associated with increased health problems in the upper extremitiesand elevated sick leave rates in various studies (Johansson and Nonås 1994; Ólafsdóttirand Rafnsson 1998; Parenmark et al. 1993). With regard to task variation, we makethe following observations from our own project.

First, in the traditional situation the periods of assembly work (74% of the totalworking time) are alternated with periods of walking, carrying, lifting, and searchingfor components. One could argue that this alternation is favorable, although theproportion of the non-added-value activities is rather high and some of the activities


127

(the lifting action) themselves might be hazardous. In the new situation, we alsohave the workers alternate assembly work with other work by requiring them tostand up and fetch components at rather fixed intervals of time. Some variation isthereby guaranteed, although the overall duration of other activities is downsized(to 8% of the total working time).

Second, additional variation is introduced within the periods of assembly. In thetraditional batchwise production, the same action is performed on 60 differentproducts prior to proceeding with a new assembly action. By making one productat a time under the new concept, the variation in assembly activities is increased.As the types of these activities are rather diverse, we consider this to be a favorablefeature. Workers themselves also considered this change to be a positive develop-ment, although some caution is needed here. Workers could also be positive becauseof their involvement in the change process.

Finally, alternating sitting and standing is introduced in the new situation,whereas standing was the most observed way to assemble in the former situation.Taking all of the foregoing information into consideration, we see no clear adverseeffects of the new situation due to the changes in activity variation over time.

In conclusion, it appears to be possible to increase production without increasing —rather decreasing — the loads on the workers. This is in line with our experiencesrather projects (Tuinzaad et al. 2000). To obtain this result, it is a prerequisite toreconsider the concept of assembly rather fundamentally and to think about newconcepts of production in discussions with a team of experts (in ergonomics andassembly engineering) and company representatives (including workers).

9.12 CONCLUSIONS

In this project, discomfort measurements are used to optimize the work station. Reduc-ing discomfort in itself is important, but knowing that data on discomfort can preventmusculoskeletal injuries in the future strengthens its importance. The discomfort wasnot at a high level in the old situation and didn’t increase in the new situation, evenwith higher productivity. The comfort increased. This was not measured directly, butfactors related to comfort, such as

satisfied with work

, were improved.

ACKNOWLEDGMENT

The authors want to thank Faber Electronics BV for the nice collaboration.

REFERENCES

Eijnatten, F.M. van, ed. (2002)

Intelligent Manufacturing through Participation: A Participa-tive Simulation Environment for Integral Manufacturing Enterprise Renewal

, Hoofd-dorp: The PSIM Consortium/TNO Arbeid.

Grinten, M.P. van der and Smitt, P. (1992) “Development of a practical method for measuringbody part discomfort.” In S. Kumar, ed.,

Advances in Industrial Ergonomics andSafety IV

, London: Taylor & Francis, 311–318.

128


Johansson, J.Å. and Nonås, K. (1994) “Psychosocial and physical working conditions andassociated musculoskeletal symptoms among operators in five plants using arc weld-ing in robot stations.”

International Journal of Human Factors in Manufacturing

,4(2): 191–204.

Looze, M.P. de, Urlings, I.J.M., Vink, P., Rhijn, G. van, Miedema, M., Bronkhorst, R.E. andGrinten, M.P. van der (2001) “Toward successful physical stress reducing products.An evaluation of seven cases.”

Applied Ergonomics,

32: 525–534.Matthiasen, S.E., Wells, R.P., Winkel, J., Forsman M. and Medbo L. (2002) “Tools for

integrated engineering and ergonomic assessment of time aspects in internationalproduction.” In

Humans in a Complex Environment, Proceedings 34th Annual Con-gress of NES

, Linköping: Linköping University, 579–584.Ólafsdóttir, H. and Rafnsson, V (1998) “Increase in musculoskeletal symptoms of upper limbs

among women after introduction of the flow-line in fish-fillet plants.”

InternationalJournal of Industrial Ergonomics,

21: 69–77.Parenmark, G., Malmkvist, A.K. and Örtengren, R. (1993) “Ergonomic moves in an engi-

neering industry: Effects on sick leave frequency, labor turnover and productivity.”

International Journal of Industrial Ergonomics,

11: 291–300.Rhijn, J.W. van, Looze, M.P. de, Groenesteijn, L., Groot, M.D. de, Vink, P., Tuinzaad, G.H.

(2002) “Efficient flow and human centred assembly. The success of an interactiveapproach.” In

Humans in a Complex Environment. Proceedings 34th Congress ofNES,

Linköping: Linköping University, 805–810.Rhijn, J.W. van, and G.H. Tuinzaad (1999) “Design of effecient assembly flow and human

centered workplaces in Dutch assembly companies.” In

Proceedings of the Interna-tional Conference on TQM and Human Factors

,

Linköping.Sauter, S.L. and Swanson, N.G. (1991)

Increased Rest Breaks Yield Increased Productivityin Repetitive VDT Work

(revision per NIOSH reviewer’s comments). Presented at theannual meeting of the Human Factors Society.

Tuinzaad, G.H., Rhijn, J.W. van, Deursen, J. van and Koningsveld, E.A.P. (2000)

EfficientFlow and Human Centred Assembly: The Success of an Interactive Approach

, Eind-hoven/Hoofddorp: TNO Industrial Technology/TNO Work and Employment.

Vahtera, J., Kivimaki, M. and Pentii, J. (1997) “Effect of organisational downsizing on healthof employees.”

The Lancet

, 350: 1124–1128.Waters, T.R., Putz-Anderson, V., Garg, A. and Fine, L.J. (1993) “Revised NIOSH-equation

for the design and evaluation of manual lifting tasks.”

Ergonomics

, 36: 749–776.Winkel, J., Forsman, M., Kazmierczak, K., Kjellberg, A., Mathiassen, S.E., Neumann, P.W.

and Wells, R.P. (2002) “Ergonomic intervention for occupational musculoskeletalhealth in manufacturing industry — trends, tools and processes.” In

Humans in aComplex Environment, Proceedings 34th Congress of NES

, Linköping: LinköpingUniversity, 833–835.

Yamada, S. (2002) “Challenges in dealing with human factors issues in manufacturingactivities.” In H. Arisawa et al., ed.,

ER 2001 workshops–HUMACS, DASWIS,ECOMO, and DAMA, Yokohama.

Berlin: Springer-Verlag, 10–29.

129

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10

Productivity and Discomfort in Assembly Work: The Effects of an Ergonomic Workplace Adjustment at Philips DAP

M.P. de Looze, J.W. van Rhijn, N. Schoenmaker, M.P. van der Grinten, and J. van Deursen

CONTENTS

10.1 Discomfort and Productivity......................................................................12910.2 Discomfort in Assembly ............................................................................13010.3 Market Demands Productivity Increase.....................................................13010.4 The Philips Case ........................................................................................13110.5 The Test Method ........................................................................................131

10.5.1 Subjects and Task ........................................................................13110.5.2 Productivity ..................................................................................13210.5.3 Discomfort ...................................................................................133

10.6 The Test Effect ...........................................................................................13410.7 Discussion ..................................................................................................13410.8 Conclusions ................................................................................................135Acknowledgment ...................................................................................................135References..............................................................................................................135

10.1 DISCOMFORT AND PRODUCTIVITY

As mentioned in Chapter 9, two major issues play a role in manual assembly opera-tions: reducing discomfort as a precursor to health problems and increasing produc-tivity. In this project the engineering department and the workforce adapted theproduction lines several times. Several tools such as simulation software were used,and at first sight the work stations looked very good at Philips DAP, where the projectwas taking place (Fig. 10.1). Nevertheless, experienced ergonomists who investigatedthe production line assumed that the work stations could be even further improved.This chapter describes the effect of this improvement on productivity and discomfort.

130


10.2 DISCOMFORT IN ASSEMBLY

Musculoskeletal discomfort and pain in the neck and shoulders are serious problemsin many occupations, often leading to sick leave or even disability. The etiology of theseneck and shoulder disorders is multifactorial in nature (Johansson and Rubenowitz1994). Both physical and psychosocial factors are associated with neck and shoulderdisorders (Frederiksson et al. 2001). Among these factors are repetitive work, static andawkward postures, monotonous work, high work pressure, poor social support, and fewopportunities to influence decisions.

In assembly work, many of these risk factors are present. Specifically, frequentelevation of the arms, static neck flexion, and repetitive work are very common inassembly industries. Some assembly lines are also characterized by low personalcontrol, high time pressure, and little variation. Therefore, it is not surprising thatassembly work is mentioned as one of the tasks particularly associated with mus-culoskeletal discomfort and pain in the neck and shoulders (Hagberg and Wegman1987). To keep the workforce optimally motivated, assembly companies shouldaddress these risk factors and minimize employees’ exposure to these risks. At thesame time, however, these companies must meet other challenges, such as increasingthe productivity and flexibility of their production lines.

10.3 MARKET DEMANDS PRODUCTIVITY INCREASE

In today’s worldwide competition, assembly industries are under a lot of pressure(Eijnatten 2002). To survive, companies are forced to increase the numbers ofproducts, decrease delivery times, and minimize the costs. Where products are

FIGURE 10.1

A typical production line work station at Philips DAP.

Productivity and Discomfort in Assembly Work

131

manually assembled, the pressure on the company is likely to reflect the pressureon the individual operator. In this context, an efficient assembly process is definitelyneeded.

Currently, we see several tendencies toward more efficient production in theassembly process. There is a tendency toward more flow production, where productsflow piece-by-piece from one station to the next. This concept is often believed tobe more efficient compared to other concepts such as

batchwise assembly

or

totalassembly at

one station

(Rhijn et al., submitted: Looze et al. 2003). Another tendencyis toward

lean manufacturing

(Docherty et al. 2002), which refers to a process inwhich the numbers of unnecessary steps, waste, and error are kept to a minimum.Lean manufacturing may very well improve efficiency, although others stress itsdetrimental effects on the operators resulting from an intensification of the work(Lansbergis et al. 1999; Vahtera et al. 1997).

In addition to these conceptual considerations, there is a question as to thepotential effect of ergonomic workplace adjustments on productivity at the workstation level. In principle, an ergonomically well-designed work station would reducephysical discomfort, but it might also increase the workers’ productivity because inan optimally designed workplace, one might be able to work at a faster pace.However, this higher work rate might have the effect of increasing discomfort, whichcould neutralize any favorable effects.

In the following case, we studied the effects of an ergonomic workplace adjust-ment in a typical assembly task, both on the productivity rate and on the level ofdiscomfort of workers.

10.4 THE PHILIPS CASE

Philips DAP is a division of the Philips Company (the Netherlands) that produceselectric razors in very large volumes. In this company, an experiment was performedto study the effect of workplace adjustment on the productivity and the discomfortof the workers.

In many work stations at Philips DAP, just as in many other companies, thelocation of supply containers, from which components have to be picked, is far fromoptimal. This is mostly due to the large numbers of different components that needto be at hand simultaneously. This leads to frequent, extended reaching and mucharm elevation. Consequently, risks for shoulder discomfort and pain could increase.We decided for the experiment, therefore, that the workplace adjustment underinvestigation would be the lowering of the picking heights to

comfortable

levels.

10.5 THE TEST METHOD

10.5.1 S

UBJECTS

AND

T

ASK

Fourteen female assembly workers, all working at Philips DAP, participated in theexperiment. At the time of the experiment they had no health complaints. They hada work history at this company division ranging from 1 month to 11 years and wereall able to work at the current standard work pace.

132


We studied these workers when performing the task of assembling the heads ofrazors. The actions consisted of picking the components from small supply containers,assembling the razor heads, and placing the products onto a product carrier. The actionsin one cycle are specified in Table 10.1. All actions were simultaneously performed bythe left and the right hands resulting in two products per cycle. The duration of one cycle(of two products) was roughly 10 to 15 seconds, depending on the overall work pace.

During the performance of the task, each subject was sitting on a chair that wasadjustable in height and depth (distance from the front of the seat to the back rest). Aheight-adjustable footrest was also used. We tested the subject under two conditions.Condition

high

reflected the current situation, where the supply bins and trays and theproduct carrier were located at positions requiring considerably high upper-arm eleva-tions. In condition

low

, these positions were significantly lowered (Fig. 10.2). All 14subjects performed the task in both the

high

and the

low

condition. These performancestook place on two consecutive working days, at the same time of day. The sequence ofexposure to the

low

and

high

conditions was systematically varied across subjects.

10.5.2 P

RODUCTIVITY

During the performance of the tasks a psychophysical protocol was applied in orderto determine the maximum acceptable work pace (MAWP) in each situation. TheMAWP is the work pace considered by workers to be the highest pace that is stillacceptable for an 8-hour working day.

At the start of this 50-minute protocol, the subjects were asked to begin workingat a work pace that they considered productive and comfortable. Over the next30 minutes, changes in the work pace took place every 2 to 3 minutes (after theproduction of 1 or 2 sets of 24 products). The first change involved a decrease in pacefor half of the subjects and an increase for the other half. The next instructions regarding

TABLE 10.1Actions per Cycle and the Division of Actions into Three Action Groups: Picking, Assembling, and Placing

Action Action group

Picking two lockup plates from two supply bins

picking

Positioning these plates onto the product template

assembling

Picking the first set of razor blades from two supply trays

picking

Pressing the first set of razor blades onto the lockup plate

assembling

Picking the second set of razor blades from two supply trays

picking

Pressing the second set of razor blades onto the lockup plate

assembling

Placing two razor heads in a product carrier

placing


133

pace were designed to find out whether even lower (for the first group subjects) andeven higher paces (for the second group) could be applied without becoming “unreal-istic.” The criterion for the remaining work pace changes was the feeling of the subjectsabout the acceptability of the work pace. Thirty minutes appeared to be sufficient tofind the MAWP in both conditions. No further changes were therefore applied after30 minutes. Instead, the workers continued at the same pace for another 20 minutes.

10.5.3 D

ISCOMFORT

Every 5 minutes during the 50-minute protocol, the local musculoskeletal discomfortin various body regions was measured (Grinten and Smitt 1992). This approachapplied a 10-point rating scale, where 0 =

no discomfort

and 10 =

extreme discomfort

.

FIGURE 10.2.

The

high

(upper and lower left) and

low

(upper and lower right) workplaceconditions. In the

low

workplace condition the storage containers for the plates A and bladesB are placed lower and closer to the subject, and the product carrier C is also lowered.

TABLE 10.2 MAWP Expressed in Number of Products per Minute and as the Average across Subjects’ Localized Musculoskeletal Discomfort in the Neck and Shoulders as Measured at the End of the Test (after 50 Minutes)

Condition

Average MAWP (range) Average discomfort (sd)

Workplace

high

9.4 (6.7–13.0) 1.1 (1.0)Workplace

low

10.4 (7.2–14.6) 0.4 (0.6)

A

B C

A

BC

A

B

CC

BB

C

AB

C

A

BC

B

AA

BC

B

AA

B

134


When a subject reported a discomfort level of 3 (moderate discomfort), the exper-imenter intervened in the test protocol by reducing the work pace.

10.6 THE TEST EFFECT

Table 10.2 presents the maximum acceptable work pace and the level of discomfortaveraged across subjects. We observed a significant effect of workplace condition.In the

low

workplace condition, the maximum acceptable work pace was signifi-cantly higher than in the

high

workplace condition. The difference between the

high

and the

low

condition was 1.0 product per minute. This implies a difference in workpace of 10.6%. Furthermore, it appears that the difference between the lowest workpace observation and the highest is defined by a multiplication factor up to 2.0.Further analysis showed that the MAWP had no relation to the level of experience(number of working years at the same factory).

Despite the relatively low measured discomfort levels in general, we were alsoable to find significance for the effect of workplace condition on discomfort. Mus-culoskeletal discomfort in the neck and shoulders was significantly lower in the

low

workplace condition compared to the

high

workplace condition.

10.7 DISCUSSION

Repetitive arm elevation is a well-known risk factor for the development of muscu-loskeletal discomfort and pain in the neck and shoulder region. Therefore, workstations where the number or degree of arm elevations is reduced seem favorablefrom the perspective of health. The lowered picking heights might also lead to ahigher work pace, which might be advantageous from a productivity perspective.However, if the higher work pace would lead to increased levels of fatigue, thebenefits of the lowered picking levels on the worker would still be under debate.

In the present study, we determined the effects of a lowered picking height onboth work pace and discomfort. The lowering of the picking height had a clear effecton the degree of arm elevation. In particular, the upper arm elevation during theactivity of picking components (three times per cycle) was reduced from about 40

°

to about 10

°

(angle of the upper arm with respect to the vertical). The ergonomicadjustment led to a 10% higher work pace under

low

workplace conditions, and thelocal discomfort as perceived by the subjects was no higher. Instead, we evenobserved significantly lower levels of discomfort in the neck and shoulder regionunder

low

workplace conditions.The most important conclusion of the study is that by ergonomic workplace

adjustment it is possible to create a win–win situation in terms of the simultaneousbenefits for the company and the worker. Within the companies, the positive effecton productivity might help to convince production managers and cost engineers ofthe importance of ergonomic workplace adjustment.

Such adjustments also constitute a risk from the human factors point of view.It appears that ergonomic workplace adjustment may well increase the work pace,in which case the work clearly becomes more repetitive and possibly more monot-onous. In our case, this did not lead to more discomfort. However, it is not yet clear


135

for all other cases that the beneficial effect of the ergonomic adjustment on discom-fort would be larger than the potential negative effect of faster and more repetitivework. Moreover, for the specific adjustment of lowering picking heights, it is stillimportant to evaluate whether the positive finding of less discomfort at higherproductivity would also last over longer times (working days and weeks).

To retain the positive effect on production and the worker over a longer term,it is important for the workers to take regular breaks and to rotate across tasks.Another strong recommendation would be to make a proper evaluation of the dis-comfort levels of workers during the working day, especially in all cases whereergonomic interventions would lead to a higher work pace.

10.8 CONCLUSIONS

In high-volume manual assembly operations there is a clear link between workstation design and worker discomfort. In the case discussed here, optimization ofthe work station layout reduced discomfort and increased productivity, which is ofbenefit to both the employees and the company.

ACKNOWLEDGMENT

The authors want to thank Philips DAP for their wonderful support.

REFERENCES

Docherty, P., Forslin, J. and Shani, A.B. (2002)

Creating Sustainable Work Systems

—

EmergingPerspectives and Practice

, London: Routledge.Eijnatten, F.M. van, ed. (2002)

Intelligent Manufacturing through Participation: A Participa-tive Simulation Environment for Integral Manufacturing Enterprise Renewal

, Hoofd-dorp: The PSIM Consortium/TNO Arbeid.

Frederiksson, K., Bildt, C., Hägg, C. and Kilbom, Å. (2001) “The impact on musculoskeletaldisorders of changing physical and psychosocial work environment conditions in theautomobile industry.”


, 28: 31–45.Grinten, M.P. van der and Smitt, P. (1992) “Development of a practical method for measuring

body part discomfort.” In S. Kumar, ed.,

Advances in Industrial Ergonomics andSafety IV

, London: Taylor & Francis, 311–318.Hagberg, M. and Wegman, D.H. (1987) “Prevalence rates and odds ratios of shoulder and

neck diseases in different occupational groups.”

British Journal of Industrial Medi-cine

, 44: 602–610.Johansson, J.Å. and Nonås, K. (1994) “Psychosocial and physical working conditions and

associated musculoskeletal symptoms among operators in five plants using arc weld-ing in robot stations.”

International Journal of Human Factors in Manufacturing

,4(2): 191–204.

Lansbergis, P.A., Schnall, P. and Cahill, J. (1999) “The impact of lean production and relatednew systems of work organisation on worker health.”

Journal of Occupational HealthPsychology

, 42: 108–130.

136


Looze, M.P. de, Rhijn, J.W. van and Tuinzaad, B. (2003) “A participatory and integrativeapproach to improve productivity and ergonomics in assembly.”

Production Planningand Control

, 14: 174–181.Rhijn, J.W. van, Looze, M.P. de, Groenestein, L., Groot, M. de, Tuinzaad, G.H. and Vink, P.

(2003) “The design of a new assembly concept for improved ergonomics and design.”

International Journal of Production Research

(submitted).Vahtera, J. (1997) “Effect of organizational downsizing on health of employees.”

The Lancet

,350: 1124–1128.

137

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

11

Comfort in Furniture at Home

T. Teraoka, R. Mitsuya, and K. Noro

CONTENTS

11.1 Introduction ................................................................................................13711.2 Participatory Design...................................................................................13811.3 Developing Four Sizes ...............................................................................13911.4 The Experiment..........................................................................................14011.5 Results of the Lab Experiment ..................................................................14111.6 Results of the Trade Fair ...........................................................................14211.7 Conclusions ................................................................................................144Acknowledgments..................................................................................................144References..............................................................................................................145

11.1 INTRODUCTION

In designing a piece of furniture for use at home, comfort also plays a role. Oneof the factors to be considered in the design is the human body size. The comfortis affected by the relationship between the product size and the user’s body size.This relationship is often studied in the field of ergonomics (Croney 1981). Work-ing chairs have been the object of study for many years (Chapters 2 and 3). Animportant aspect in this regard is the adjustability of the chair to the body sizeand posture needed for performing the task. However, dining chairs are mostlynot adaptable, probably because they are made of wood. With wood, it is verydifficult to make chairs adjustable as in office chairs. A solution for adapting tothe difference in body size is to design the dining chairs in several sizes, as inshoes and clothing.

Therefore, the Noro Laboratory of Waseda University and the Japan FreelanceInterior Coordinator Association (JAFICA) developed four sizes (XS, S, M, and L) ofchairs for the same model. The chairs were exhibited at IFFT2000 (InternationalFurniture Fair, Tokyo 2000, November 21–24, 2000). Noro Lab led the developmentof the different sizes and the experiment to test the prototypes of the chairs. The elevenprototypes were manufactured by three wooden furniture manufacturers (Karimoku,Kosuga, and Interior Center) (Fig. 11.1). Two chairs were made in four sizes and onein three sizes.

138


11.2 PARTICIPATORY DESIGN

It is possible to base a chair design on anthropometrical data and computer modelsonly. However, as stated earlier, human behavior and the comfort experience arehard to predict. Therefore, ordinary people participated in this academic study.Another reason why they were included is that there could a difference in expe-rience between what academics think is important and what the common under-standing is. The only way to gather useful ideas and information is to involve thereal end users (Noro 1999; Vink 2002).

Especially in the field of ergonomics, where the object is to support the user,the participation of the public is essential. The participatory approach reported inthis chapter is an attempt to build an information loop between the manufacturers,who are suppliers of the product, and the users who are the consumers.

In the Noro Laboratory there is a seating clinic where advice on how to chooseand use chairs is given to the clients. The clinic is the place where researchersprovide information about chairs to users, but at the same time researchers haveopportunities to get information

from

the users. In this example, the seating clinicis a bridge between the public users and the manufacturers (Fig. 11.2). In the sameway, the exhibition at IFFT2000 and the study on the size of chairs could be seenas similar bridges (Fig. 11.3).

FIGURE 11.1

The eleven chairs used in this study.

ManufacturerKarimoku

ModelCT1700UP

ManufacturerKosuga

Model1492-DCH

ManufacturerInterior Center

ModelRuntom

XS S M L


139

11.3 DEVELOPING FOUR SIZES

Based on the demands from users for a better fit, four sizes of prototype chairs weremade. Up to that point, manufacturers had been used to manufacturing one size, butfor the exhibition at the IFFT2000 four sizes were developed. The mass media paidsome attention to this topic. Just before the IFFT, a national newspaper reported thestudy on the size of dining chairs conducted by Noro Lab and JAFICA.

FIGURE 11.2

The gap bridged by the seating clinic.

FIGURE 11.3

The exhibition booth at IFFT2000.

140


The sizes of the chairs were chosen to fit the most people, from small to largeand from young people (except children) to seniors. The current standard chair wasdefined as size M (medium), and three other sizes — XS (extra-small), S (small), andL (large) — were added. The differences in size were chosen to allow for heightdifferences of as little as 0.1 m. The largest difference in sizes was 0.4 m (Fig. 11.4).

The choice of the correct seat height was made on the basis of the lower-leglength. Assuming that the average lower-leg length is approximately one fourth ofthe body height (Molenbroek and Dirken 1987), the chair height difference of 0.1 mwill correspond to approximately 0.025 m of lower-leg length. Therefore, the seatheight of chair size S is 0.025 m lower than that of size M (Table 11.1). To keepthe proper design of the other sizes equivalent to size M, all four sizes were madein the same proportion.

It was expected that more comfort would be experienced in the size that bestfits the subject. This was tested in an experiment.

11.4 THE EXPERIMENT

Two experiments were performed: a lab test with 14 subjects and a test at the IFFTfair with 591 subjects. In the lab test 14 healthy subjects (7 male, 7 female) participated.Their ages were from 20 to 66 and their height ranged from 1.468 m to 1.803 m(Table 11.2). After their body sizes were measured, the subjects were asked to sit oneach of the 11 chairs. As they sat, photographs of the postures were taken and thebody pressure distribution was measured on the seat and the backrest for all 11 chairs.Afterward, the subjects gave their preference. For measuring the pressure distribution,the Force Sensitive Applications by Verg Inc. (Canada) was used.

The experiment at the IFFT consisted of questioning the visitors who tested thechairs. Interest in the exhibition booth was high, and a large number of people sat on

FIGURE 11.4

Assumption of the relationship between chair size and body height.

TABLE 11.1 Seat Heights of the Exhibited Chairs, in Millimeters (mm)

Model XS S M L

CT1700UP (Karimoku) 370 395 420 4451492-DCH (Kosuga) 390 415 440 465Runtom (Interior Center) 410 435 457

140 150

XS S M L

160

Body Height (cm)

170 180 190


141

the exhibited chairs. The visitors who tested the chairs seriously were asked to completea short questionnaire, and 591 people completed it in 4 days. The main questions askedtheir age, sex, body height, and the comfort score on the 11 chairs. Properly answeredquestions from 434 people were collected and used in the results.

11.5 RESULTS OF THE LAB EXPERIMENT

The lab experiment results included a subjective evaluation. In Fig. 11.5 the resultof the subjective preference is shown for the four sizes of chairs. The horizontalaxis is the subject’s height and the vertical axis shows the size of the chair to whichthe subject gave the highest comfort value. However, each chair was valued at grade5 (good) independently (Fig. 11.6), which resulted in more chairs with highestvalues. In that case, we used the average size of the chair. For example, when asubject gave the highest value to sizes S and M, we plotted the middle point betweenS and M. Nobody gave the highest value to size XS.

Regarding seating posture and pressure distribution, Fig. 11.7 shows the seatingposture and the pressure distribution of subject D (height: 1.505 m) sitting on model1492-DCH. In the smallest chair, the pressure is high and localized under thebuttocks. The thighs support relatively little weight. With sizes M and L, the seatheight is too high for the body size, so the soles of the feet do not touch the floor.This causes much pressure under the front of the upper legs. Subjects A, B, and Ddo not touch the floor when sitting in size M of all three models, and the feet ofsubject E (height: 1.468 m) do not touch the floor even in size S of all the threemodels. Contact between the soles of the feet and the floor is preferred in order tohave a good fit with the body, thus preventing reduction in blood flow or nervepressure in the back of the upper leg that may cause swelling and numbness.

TABLE 11.2Height, Age, and Sex of the Subjects

Subject Height (cm) Age Sex

A 146.8 66

Female

B 149.6 22

Female

C 150.3 54

Female

D 150.5 43

Female

E 157.1 45

Female

F 164.4 23

Female

G 166.7 24

Male

H 167.6 20

Male

I 169.0 62

Male

J 171.3 26

Male

K 171.4 20

Female

L 171.7 21

Male

M 173.9 27

Male

N 180.3 24

Male

142


11.6 RESULTS OF THE TRADE FAIR

These results differ somewhat for the different chairs. The results for modelCT1700UP give a good general idea and will be presented here. There were 192people who answered the questions about this chair (Fig. 11.8). Figure 11.9 showsthe percentage of people who preferred a specific size for a category of lengths. Thelengths of the subjects were arranged in groups of 0.05 m, and each group wasnormalized to 100%. Most of the people with a body height shorter than 1.50 mselected chair size XS. Nobody preferred size M. Of the people taller than 1.50 mand shorter than 1.55 m, 61% selected size S. Among the people between 1.55 m and1.60 m in height, the number that selected size S was equal to the number thatselected size M (both 44%).

FIGURE 11.5

The fit of fourteen subjects for the four sizes of chairs (XS, S, M, and L). Theheight of the subject is shown on the

x

-axis. Every dot is the highest comfort score given bythe subject. The line is the regression line.

FIGURE 11.6

The question used to evaluate the chair comfort.


143

FIGURE 11.7

Seating posture and pressure distribution of subject D (height: 1.505 m) sittingon chair model 1492-DCH.

FIGURE 11.8

Body heights of the 192 subjects who completed the questionnaire for chairmodel CT1700UP.

Sea

ting

Pos

ture

Pre

ssur

e D

istr

ibut

ion

XS S M L

Male

Female

Body Height (cm)

140 145 150 155 160 165 170 175 180 185 190

40

30

20

10

0

Num

ber

of P

eopl

e

144


11.7 CONCLUSIONS

As expected, shorter people tend to prefer smaller-sized chairs and taller peopleprefer the larger ones. Also, the feeling of comfort is highest in the chairs that fitbetter because the pressure is better distributed when the chair fits well. This con-clusion is in alignment with the literature (Looze et al. 2003).

At the same time, it is obvious that chair preference differed greatly amongsubjects. As an example, among subjects ranging in height from 1.55 to 1.60 m andfrom 1.60 to 1.65 m, there was a preference expressed for every size. The first reasonfor this is that the subjects had different reasons for their preferences. Second, thesubjects were used to the size M chair (for example) that they used most often indaily life, and they felt a sense of incongruity with the size XS, S, and L chairs.Third, all four sizes are built with the same proportions, but some people just likea cute little chair.

The challenge for the future is to find out whether long-term use would producethe same results and which of the three reasons just mentioned are really important.Also, studying use of the chair in its natural environment (including in relation totable height) could result in other figures.

ACKNOWLEDGMENTS

Special thanks to JAFICA; chair manufacturers Karimoku, Kosuga, and InteriorCenter; and many users for supporting this study.

FIGURE 11.9

Subjects who preferred each size of chair, grouped by height.

Body Height (cm)

145 150 155 160 165 170 175 180 185

100%

90%

80%

70%

60%

50%

40%

30%

20%

10%

0%

L

M

S

XS


145

REFERENCES

Croney, J. (1981)

Anthropometry for Designers

, New York: Van Nostrand Reinhold Co.Looze, M.P. de, Kuijt-Evers, L.F.M. and Dieën, J.H. van (2003) “Sitting comfort and discom-

fort and the relationships with objective measures.”

Ergonomics

, 46: 985–998.Molenbroek, J.F.M. and en Dirken, J.M. (1987) “DINED-tabel.” In M.R. Creemers et al.,

eds.,

Polytechnisch Zakboekje

, Arnhem: PBNA, J3/12–13.Noro, K. (1999) “Participatory ergonomics.” In W. Karwowski and W. S. Marras, eds.,

TheOccupational Ergonomics Handbook

, Boca Raton: CRC Press, 1421–1429.Vink, P. (2002)

Comfort

, Delft: Delft University of Technology (inaugural address).

147

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

12

Discomfort and Dynamics in Office Chairs

M.P. de Looze, P. Vink, and J.H. van Dieën

CONTENTS

12.1 Chair Design Requires More Knowledge..................................................147 12.2 Discomfort and Office Chairs ....................................................................14712.3 Dynamic Chairs..........................................................................................14812.4 This Study ..................................................................................................148 12.5 Subjects and Chairs....................................................................................14912.6 The Experimental Task ..............................................................................14912.7 Measurements.............................................................................................15012.8 Data Analysis .............................................................................................15112.9 Results and Discussion ..............................................................................151Acknowledgment ...................................................................................................153References..............................................................................................................153

12.1 CHAIR DESIGN REQUIRES MORE KNOWLEDGE

Currently, the majority of the work force in the Netherlands is working in offices,as the service industry has grown and much work has been automated (Smulderset al. 2002). This means that many people spend much of their lifetime sitting onoffice chairs. Consequently, the market for office chairs is large; there are manychair manufacturers and many different office chairs. The question is: What is theoptimal chair providing minimal discomfort and no health complaints in the longrun? This question is not easy to answer. The scientific studies on discomfort andhealth effects of office chairs are rather limited. For instance, it is not known whethera dynamic chair is better with regard to discomfort and health than a static seat.

12.2 DISCOMFORT AND OFFICE CHAIRS

Various studies show that prolonged sitting in office chairs leads to elevated levelsof physical discomfort in the low-back region (Looze et al. 2003). This increaseddiscomfort has been assumed to increase the rates of low-back disorders among

148


office personnel. Indeed, back complaints are frequently mentioned among officeworkers (Smulders et al. 2002). Hales and Bernard (1996) demonstrated that pro-longed sitting constitutes a potential risk factor for the development of low-backpain. On the other hand, recent reviews did not find the statistical evidence to supportthis statement (Hoogendoorn 2001). Anyway, it is obvious that chair designers shouldprevent discomfort in sitting as much as possible.

There is much discussion as to whether physical discomfort in sitting can beattributed to the magnitude of the internal load. For many years, it was believedthat sitting leads to higher stress compared to standing (Andersson et al. 1974).This has influenced manufacturers to design backrests that align with the naturalspinal curve in the

standing

posture. More recent measurements on intervertebraldisks, however, point to identical or even lesser stress on the spine while sitting(Wilke et al. 1999).

Currently, there is still much debate on the optimal sitting posture. On the otherhand, there is general support for the assumption that it is the continuous staticcharacter of the load, rather than the magnitude of the load, that leads to discomfortin sitting. According to Graf et al. (1995), a good chair would therefore be a chairthat supports the body in a variety of desirable positions.

12.3 DYNAMIC CHAIRS

A now fairly common characteristic of office chairs is that they have been designedto accommodate a substantial amount of movement. So-called dynamic chairsallow movement of the chair seat and back support, either in a fixed ratio orindependently. Several authors have advocated this principle as a means of pre-venting sitting-related low-back pain (Kroemer 1994; Serber 1994; Suzuki et al.1994). However, to our knowledge no scientific studies have been performed tosupport or refute this claim.

12.4 THIS STUDY

The aim of the present study was to investigate the effects of dynamic office chairson low-back parameters that might potentially affect low-back discomfort and health.We studied three types of office chairs that differed with respect to the dynamicmechanism. The parameters studied were the amount of trunk movement, the activityof the back muscles, the degree of spinal length change during sitting, as well asthe perceived level of discomfort at the low-back level.

The spinal length change was taken as an indicator for low-back load. It haspreviously been suggested that prolonged low compression acting on the discs duringsitting hampers fluid flow into the disc and consequently affects disc nutritionadversely, which could cause back problems. In line with this hypothesis, spinallength change measurements were previously used to assess the effects of differentchairs, for instance, demonstrating the advantage of back supports (Althoff et al.1992; Eklund and Corlett 1987).


149

12.5 SUBJECTS AND CHAIRS

Ten healthy subjects, three females and seven males, participated in the experimentafter signing informed consent. Their mean age was 21 (21 to 24) years, their meanheight was 1.81 (1.71 to 1.90) meters, and their mean body mass was 75 (65 to 87)kilograms. All subjects were experienced users of word processing and computer-aided design (CAD) software.

Three types of chairs were used in the experiment (Fig. 12.1): chair DA, allowingindependent sagittal plane rotation of backrest and seat; chair DB, allowing rotationof the seat in a fixed ratio to backrest rotation (1:2.7); and chair FA, which was chairDA in the mode wherein the backrest and seat pan were fixed (seat horizontal andthe backrest at a 95

°

angle with respect to the seat). The chairs were adjusted foreach subject according to a fixed protocol. A more detailed description of thisexperiment can be found in Dieën et al. (2000).

12.6 THE EXPERIMENTAL TASK

Each subject participated in three sessions (one with each of the three chair types)on separate days, starting at the same time of day. The chairs were used in randomorder. In each session, a standardized 3-hour task was performed. The task con-sisted of three activities: word processing, reading a book, and CAD. The wordprocessing task consisted of reproducing a printed text. The CAD task involvedreproducing a drawing provided on paper, mainly using the mouse as an inputdevice. Word processing and CAD were performed in three blocks of 45 minutes,separated by 15 minutes of reading (Fig. 12.2). During the 3-hour session, thesubject was not allowed to rise from the chair. Prior to the experimental task andthe stature measurements, each subject performed at least two maximum isometrictrunk extension efforts to obtain an estimate of maximum erector spinae muscleactivation.

FIGURE 12.1

Chairs that were used in the test. Chair (

A)

was used in both a dynamicmode (DA) and a fixed mode (FA); chair (

B)

was used in a dynamic mode (DB) only.

150


12.7 MEASUREMENTS

Markers were attached to the subject at the level of the C7 spinous process; at theright hip, knee, and ankle joints; and over the axis of rotation of the seat to measuremovement. Marker positions were recorded on video (sVHS), and the camera waspositioned to provide a sagittal plane image (Fig. 12.3). Video frames were digitizedand marker locations were determined semiautomatically using commercially avail-able WINanalyze software.

The change in length of the spine under the influence of a change in compressiveloading was estimated with a stadiometer (Fig. 12.4) based on previously describedequipment (Dieën et al. 1994; Eklund and Corlett 1984). In short, this instrumentallows for reproducible (within 1 mm) measurements of stature by providing feed-back to the subject as to the accurate reproduction of his or her posture from onemeasurement to another. Twenty measurements of stature were performed just priorto the experimental task, and twenty were performed immediately after the task.Perceived discomfort was measured by the local postural discomfort technique(Chapter 2).

time (min)0

60

120

180

wor

d pr

oces

sing

read

ing

draw

ing

read

ing

wor

d pr

oces

sing

read

ing

FIGURE 12.2

Time schedule for each subject.

FIGURE 12.3

Markers placed on the subject, and the experimental position of the subject.


151

12.8 DATA ANALYSIS

Analysis of the marker data was based on the exposure variance analysis as proposedby Mathiassen and Winkel (1991). Only the C7 marker coordinates were used forfurther analysis because the other markers were found not to provide additionalinformation on trunk kinematics.

The last ten stature measurements taken before and the first ten after the taskwere averaged, and the differences between these were used to estimate spinalshrinkage. The remaining measurements were used to check the reproducibility ofthe measurements and will not be reported here.

Two-way ANOVA for repeated measures was used to test for effects of task(word processing, CAD, and reading) and chair (FA, DA, DB) on kinematic vari-ables. A nonparametric test (Friedman) was used to test for effects of chair type onshrinkage and discomfort.

12.9 RESULTS AND DISCUSSION

The largest effects with regard to movement and muscle activity were not foundamong chairs, but among tasks. More postural and muscle activity changes occurred

FIGURE 12.4

Spinal shrinkage measurement system (stadiometer).

152


in reading compared to the word processing and CAD tasks. The differences inpostural and muscular variations across tasks give support to the often-heard orga-nizational recommendations toward more complete tasks or more task variation(Vink et al. 1998).

We also found differences among the chairs, though to a minor extent. Althoughwe did not find any significant difference in perceived discomfort, or in muscleactivity or the number of movements from one chair to another, the spinal lengthdata were different (Fig. 12.5). It was found that spinal length increased during the3-hour period of sitting on both dynamic chairs, but the spinal length remainedconstant when sitting on the static chair. This result is an indication that the spinewas less loaded on the dynamic chairs than on the static chair.

Similar effects on spinal length change have been reported to occur when usinga chair that imposes cyclic rotator movements on the spine (Deursen et al. 1999).

The beneficial effect on stature change might lead us to the conclusion thatdynamic chairs, such as the ones used in this study, should be advocated. However,it is our experience that in practice, many of the dynamic chairs are not used in theproper way. The use of dynamic chairs in their fixed mode is quite common. Theintroduction of dynamic chairs probably needs to be accompanied by careful instruc-tion, or even training, of the future user. Another option in this respect might beoffered by chairs promoting passive movement, as described by Deursen et al.(1999). Potential health effects of dynamic chairs or chairs providing passive motionneed to be confirmed in field studies.

The aim of the present study was to investigate the effects of dynamic officechairs on the low back, which might potentially affect low-back discomfort andhealth. Two dynamic office chairs were compared to one fixed chair. The resultsshowed the advantage of the dynamic chairs: spinal-length measurements indicated

FIGURE 12.5

The change in spinal length caused by sitting in the three office chairs(* = significantly different from the static chair).

0.6

0

0.1

0.2

0.3

0.4

0.5

A Bfixed

A

*

*

% S

pina

l Len

gth

Cha

nge

dynamicdynamic


153

a beneficial effect. However, a more evident effect was shown by the differences intasks. This indicates that ergonomic measures in the office environment should bemore focused on the design of functions than on the design of the chairs.

ACKNOWLEDGMENT

The authors want to thank ASPA Kantoorinrichting BV, an office furniture company,for their support in this study.

REFERENCES

Althoff, I., Brinckmann, P., Frobin, W., Sandover, J. and Burton, K. (1992) “An improvedmethod of stature measurement for quantitative determination of spinal loading.”

Spine

, 17: 682–693.Andersson, G.B.J., Örtengren, R., Nachemson, A. and Elfström, G. (1974) “Lumbar disc

pressure and myo-electric back muscle activity during sitting.”

Scandinavian Journalof Rehabilitation Medicine

, 6: 101–121.Deursen, D.L. van, Goossens, R.H.M., Evers, J.J.M., Helm, F.C.T. van der and Deursen,

L.L.J.M. van (1999) “Length of the spine while sitting on a new concept for an officechair.”

Applied Ergonomics

, 31: 95–98.Dieën, J.H. van, Creemers, M., Draisma, I., Toussaint, H.M. and Kingma, I. (1994) “Repetitive

lifting and spinal shrinkage: Effects of age and lifting technique.”

Clinical Biome-chanics

, 9: 367–374.Dieën, J.H. van, Looze, M.P. de and Hermans, V. (2001) “The effects of dynamic office chairs

on trunk kinematics, trunk extensor EMG and spinal shrinkage.”

Ergonomics

, 44:739–750.

Eklund, J.A.E. and Corlett, E.N. (1987) “Evaluation of spinal loads and chair design in seatedwork tasks.”

Clinical Biomechanics

, 2: 27–33.Eklund, J.A.E. and Corlett, N. (1984) “Shrinkage as a measure of the effect of load on the

spine.”

Spine

, 9: 189–194.Graf, M., Guggenbuhl, U. and Krueger, H. (1995) “An assessment of seated activity and

postures at five workplaces.”


, 15:81–90.

Hales, T.R. and Bernard, B.P. (1996) “Epidemiology of work-related musculoskeletal disor-ders.”

Orthopedic Clinics of North America

, 27: 679.Hoogendoorn, W.E. (2001)

Work-Related Risk Factors for Low Back Pain

. Amsterdam: VrijeUniversiteit (Ph.D. thesis).

Kroemer, K.H.E. (1994) “Sitting (or standing?) at the computer workplace.” In R. Luederand K. Noro, eds.,

Hard Facts about Soft Machines

, London: Taylor & Francis,181–191.

Looze, M.P. de, Kuijt-Evers, L.F.M. and Dieën, J.H. van (2003) “Sitting comfort and discom-fort and the relationships with objective measures.”

Ergonomics

, 46: 985–998.Mathiassen, S.E. and Winkel, J. (1991) “Quantifying variation in physical load using exposure

vs time data.”

Ergonomics

, 34: 1455–1468.Serber, H. (1994) “The study of lumbar motion in seating.” In R. Lueder and K. Noro, eds.,


, London: Taylor & Francis: 423–431.

154


Smulders, P.G.W., Houtman, I.L.D. and Klein Hesseling, D.J., eds. (2001)

Trends in Work2002

, Alphen a/d Rijn: Kluwer (in Dutch).Suzuki, Y., Sugano, T. and Kato, T. (1994) “An ergonomic study of dynamic sitting.” In

R. Lueder and K. Noro, eds.,


, London: Taylor &Francis, 347–373.

Vink, P., Koningsveld. E.A.P. and Dhondt, S., eds. (1998)

Human Factors in OrganizationalDesign and Management

, IV, Amsterdam: Elsevier.Wilke, H.J., Neef, P., Caimi, M., Hoogland, T. and Claes, L.E. (1999) “New

in vivo

measure-ments of pressures in the intervertebral disc in daily life.”

Spine

, 24: 755–762.

155

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

13

Designing Comfortable Passenger Seats

R.E. Bronkhorst and F. Krause

CONTENTS

13.1 Introduction ............................................................................................... 15513.2 Method: Sitting Behavior...........................................................................15613.3 Method: Benchmark Study ........................................................................15613.4 Modifications..............................................................................................15613.5 Method: Test of the Prototype Seat ...........................................................15613.6 Results: Sitting Behavior ...........................................................................15713.7 Results: Benchmark Study.........................................................................158

13.7.1 Ingress and Egress .......................................................................16013.8 Modifications..............................................................................................16213.9 Redesign Proposals Based on End-User Opinions....................................163

13.9.1 Angle of Seatback and Bottom Cushion.....................................16313.9.2 Armrest Height.............................................................................16413.9.3 Backrest .......................................................................................16413.9.4 Headrest........................................................................................16413.9.5 Back Shell ....................................................................................165

13.10 Results: Test of the Prototype Seat............................................................16513.11 Conclusions ................................................................................................166Acknowledgment ...................................................................................................167References..............................................................................................................167

13.1 INTRODUCTION

To attract more passengers, new seats were developed for new commuter trainsscheduled to run in the United States. Several parties were involved in this study:Long Island Railroad (the commuter train company), Bombardier (the manufacturerof the train), and Multina (the seat manufacturer). TNO was asked to provide designinput concerning the overall comfort experienced by passengers. This chapterdescribes the process that was used to develop a new seat.

156


13.2 METHOD: SITTING BEHAVIOR

After a search on the Web, among colleague institutes, and in the literature, itappeared that there was no knowledge available on how people sit in a commutertrain and what their main activities were. Therefore, the project started with observ-ing the behavior of passengers on the trajectory where the new train will ride.Measurements were taken to monitor the passengers’ activities, posture, size, andmovements. From 1700 observations the 4 most frequent tasks were selected, as wellas the essential anthropometrical characteristics.

13.3 METHOD: BENCHMARK STUDY

It was known by the commuter train company that passengers appreciate one particularseat. This existing seat, hereafter referred to as S1, was chosen to serve as a benchmark.A laboratory study was done to find out why this seat was appreciated. This S1benchmark seat was tested along with the older-type seat (S2) that was used during thefield observations. Eighteen subjects, selected according to the anthropometry found inthe field test, participated in the test, representing the end users. They were asked to sitin specific ways that resembled four postures observed during the tasks in the field test.

Specially designed questionnaires were used to ask test subjects about variousparts of the seat. The following are examples of the detailed questions on the backseat cushion:

• How do you rate the general comfort of the back seat cushion? (5-pointscale)

• How satisfied are you with the back seat angle? (3-point scale)• Does the back seat give you enough support for your lower back? (3-point

scale)• Is the lumbar support in the right position? (3-point scale)• Does the lumbar support have enough volume? (3-point scale)

Subjects were also asked to complete a local postural discomfort (LPD) questionnaire(Fig. 13.1; see also Chapter 2).

13.4 MODIFICATIONS

Modifications were made to S1 based on this questionnaire information. In Phase 3of the study, various modifications to S1 were tested by a group of new test subjectsto confirm or adjust the design input. The manufacturer then built a prototype of thenew seat, referred to as S3.

13.5 METHOD: TEST OF THE PROTOTYPE SEAT

In the next phase, the prototype S3 was tested against the S1 in the lab in a long-duration, paired-comparison test to check the effect of the new seat on comfort. The labtesting consisted of various elements aimed at collecting data on three levels: passengeropinion; expert opinion; and objective data such as seat-pressure distribution quality.


157

13.6 RESULTS: SITTING BEHAVIOR

To characterize the use of the seats and the passengers’ activities and movements,1700 observations were taken. The ways passengers enter and leave the rows ofseats and their actual tasks were studied. The postures in these tasks were recordedand described in terms of the angles of body segments.

Because of the variety in anthropometrics among the population using the train,data on posture and size were collected during the field test. Results of the field testshowed that about two thirds of the passengers sit in the straight position seen inthe ergonomic manikins. Others use the seat in a different way, for example, withstretched legs, with folded legs, or for sleeping. For the new S3 seat it was consideredimportant to facilitate all major postures that were observed (Table 13.1).

FIGURE 13.1

LPD map of the body showing the separate regions to be given a discomfortscore on a 0–10 scale.

TABLE 13.1 Characteristics of Sitting Postures in a Commuter Train (Percentage of Total Time Observed)

Sitting postures Men (%) Women (%)

Leaning against backrest 63 73Leaning forward 4 4Slumped in seat 20 10Leaning toward to the right or the left 13 13Legs parallel, feet on floor 24 52Legs wide 41 10Legs stretched out 7 5Legs crossed 14 22Feet on heater 8 4Legs propped against seat in front or on other chairs 6 5

158


Sleeping or napping, reading (newspaper or books), and relaxing (listening to music,talking, or staring out the window) are the three most frequently observed activities.These activities divided the passenger population into almost equal thirds (Table 13.2).

There were slightly more male than female commuters. The majority of thepopulation measured average in both height and weight. Only 4% of the passengerschose to sit in the middle seat, 50% preferred the aisle, and 46% chose the windowseat. The number of times an activity was observed and the percentage of times itwas observed are listed in Table 13.2.

13.7 RESULTS: BENCHMARK STUDY

The lab tests were carried out at the Ergolab in the Netherlands. A test site was builtas shown in Fig. 13.2.

TABLE 13.2 Activities Observed in a Commuter Train (Percentage of Total Time Observed)

Activities n %

Sleeping/napping 423 29Listening to music/talking/staring 530 36Reading a newspaper 268 18Reading a book or magazine 192 13Writing and typing 64 4

n = number of subjects observed doing the activity.

FIGURE 13.2

The test setup in the Ergolab.


159

A seat that is comfortable in the short term (often referred to as

showroomcomfort

) may not necessarily be comfortable after a long period of sitting. Feelingsof discomfort may arise only after a period of prolonged sitting, which requires atest of prolonged sitting duration. Discomfort is regularly avoided by changing one’sposture (Chapter 3). It is therefore necessary to have subjects maintain a specificposture in order to collect precise data on discomfort.

As mentioned earlier, the lab tests consisted of various elements. All tests weredone under controlled conditions. To facilitate discussion of the results with thedesigners and with the management of Long Island Railroad, Bombardier, andMultina, the seats were color-coded light green, green, white, red, and dark red,represented with plus and minus signs as shown in Table 13.3.

Eighteen subjects were asked to sit for 1 hour on seat S1 or S2, during whichtime specific postures had to be maintained that resembled postures observed inthe field test. Nine subjects started on S1 and nine on S2. After a short break thesubjects were asked to change seats, at which time ingress and egress tests wereperformed and the sitting test was continued on the other seat. Results are shownin Tables 13.4 and 13.5.

Neither the S1 (benchmark) nor the other seat (S2) had a comfortable seat cushion.The test subjects had comments on various aspects. The total score for the benchmark

TABLE 13.3 Five Levels of Seat Element Ratings

% “(very)comfortable/good” Rating

>75 ++60–75 +40–59 +/

−

25–39

−

<25

−

−

TABLE 13.4 The Evaluation of Two Seats, S1 and S2, by End Users

Seat cushion criterion S1 S2

Comfortable +/

− −

−

Height to floor + +Width ++ ++Depth +/

−

+/

−

Angle backward + +Hardness of cushion +/

−

+/

−

Support for legs and buttocks +/

−

+/

−

Cushion cover

−

+Postural constraints of row in front

−

−

+/

−

160


seat was neutral, whereas the old seat was evaluated as very uncomfortable. Also,neither backrest cushion was evaluated as comfortable (Table 13.5), so the variousitems on which S1 (the best of the two) could be optimized were localized.

13.7.1 I

NGRESS

AND

E

GRESS

In between sitting tests, subjects carried out an ingress–egress task (Fig. 13.3) inwhich they were required to move to the window seat (i.e., the seat farthest away),sit down for a few seconds, and then leave the seat again. This was performed withand without carrying a small piece of hand luggage, as was observed in the fieldtest. The purpose of this test was to collect data on ease of ingress and egress andthe proper form and positioning of grips on the seats.

In both tests data were collected by using video cameras and questionnaires.Questionnaires were used to obtain user information on the specific aspects of theseat that involved comfort. By interviewing the test subjects and using the LPDmethod, all subjects could indicate where discomfort or pressure points were experi-enced and how cushions should be changed.

Objective data were collected by measuring seat characteristics and by submit-ting the seat cushions to special laboratory tests regarding their pressure-distributionquality (Fig. 13.4).

All data were analyzed and discussed by experts in meetings where ideas toimprove the benchmark S1 were generated. During those meetings the experts inter-preted information from the test subjects that led to seat improvement ideas. One idea,for example, was to improve the sleeping possibilities by pivoting the seat around theaxis to the front edge of the seat. This was suggested in combination with shifting theheadrest to the front.

TABLE 13.5 Backrest and Entire Seat Evaluation Results of the Two Seats

Criterion S1 S2Backrest

Comfortable +/

− −

−

Width ++ ++Angle backwards +/

−

+Hardness cushion +/

−

+/

−

Lumbar support +/

−

+/

−

Lumbar height +/

−

+/

−

Lumbar swell +/

−

+/

−

Upper back support

−

− −

−

Head support

−

− −

−

Entire seat

Comfortable +/

− −

−


161

FIGURE 13.3

Examples of ingress (

A)

and egress (

B)

used in the lab tests.

FIGURE 13.4

The system used in this project to measure pressure distribution objectivelyin different seats.

162


13.8 MODIFICATIONS

At this stage, two S1 seats were changed in order to evaluate the suggestedmodifications. Modifications were made to the lumbar support, the backrest angle,and the headrest. Eighteen subjects then compared the two modified versions ofthe S1 to the original S1. One version of the modified S1 was pivoted 5

°

backward(Fig. 13.5). The other version was not pivoted and had changes only to the lumbarsupport and headrest.

The test consisted of three parts: upright sitting in a fixed position, ingress–egress,and free-posture sitting. Results from the test of upright sitting in a prescribedposition showed that the pivoted version of S1 improved backrest cushion comfort(Table 13.6). The other test parts confirmed that the pivoted version of the improvedS1 had the best results.

FIGURE 13.5

The S1 seat, upright and tilted 5

°

backward.

TABLE 13.6 Backrest Cushion Evaluation, Sitting Upright (Two Improved Seats Compared to the Benchmark (Original S1)

Backrest cushion criterionImproved S1 (

−

5

°

)Improved S1 (0

°

)Original

S1

Comfortable + +/

−

+/

−

Angle backward ++ +/

−

+/

−

Hardness of cushion ++ + +/

−

Lumbar support + +/

−

+/

−

Lumbar height ++ + +/

−

Lumbar swell + +/

−

+/

−

Upper back support +/

−

+/

− −

−

Head support +/

− − −

−


163

13.9 REDESIGN PROPOSALS BASED ON END-USER OPINIONS

All of the tests and the analysis and interpretation of the data resulted in a finalredesign proposal for the new S3 seat. The proposal focused on the following aspects:

• Seatback angle and bottom cushion angle• Bottom cushion height from floor• Seat depth• Armrest (height, width, length, position, padding on surface, corners)• Back shell including recessed area with respect to hip-to-knee space; shin

space; and padding/form to protect knees and shin• Horizontal spacing for occupants• Bottom cushion contours• Back cushion contours (horizontal and vertical, including lumbar support)• Stiffness of back and bottom cushions• Chamfer on the front part of the bottom seat• Headrest dimensions• Headrest wings• Styling

The majority of the proposed changes to S1 were used to design the prototypeS3. The most important redesign features of the S3 are highlighted below.

13.9.1 A

NGLE

OF

S

EATBACK

AND

B

OTTOM

C

USHION

The internal angle between seat and back was not changed. The entire seat was tiltedbackward 5

°

. The pivot axis was the top front edge of the seat cushion (Figure 13.6).By increasing the seatback and bottom cushion angle by 5

°

, the sleeping andresting quality of the seat should improve, based on data gathered from the usertests. In addition, more upper-body weight is transferred to the backrest, and there-fore the amount of pressure on the buttocks is reduced. The reduction in hip-to-kneespace and ingress–egress width could be a problem now, but this is counteracted bysome of the alterations that follow.

FIGURE 13.6

Pivoting the seat around an axis at the front of the seat.

S1S3

5° tilt

164


13.9.2 A

RMREST

H

EIGHT

Because the S1 armrest was generally evaluated as too low, the S3 has an armrestthat is 0.03 m higher. This recommendation was based on an extra experiment with26 new subjects. The experiment also showed that preferred armrest height does notappear to correlate to length, which is in accordance with the literature (Molenbroek1994). It did show, however, a tendency toward a median preferred height.

13.9.3 B

ACKREST

The lab tests showed that the S1 lumbar support was too high and too thick. Thelumbar support was therefore flattened and lowered, and the literature supports thisidea. Reynolds (1993) states that highly contoured seat backs will not fit many people.Some will find such a lumbar support very good, others very bad, and only fewconsider it perfect. With flatter lumbar supports more people will appreciate thesupport without being extremely positive or negative about it.

This was also found in the S1 testing and may be explained by the followingthought. If passengers have the opportunity they will sit in a slightly slumped (relaxed)way (Han et al. 1998; Zhao and Tang 1994). This reduces or even flattens the lumbarcurvature. Therefore, it is necessary to design the seat profile to fit a slumped sittingposture while still providing enough lower-back support to prevent long-term spinalstress (Zhao and Tang 1994). An extra benefit from flattening the lumbar support isthat the seat cushion moves rearward, thus improving the ingress–egress width.

13.9.4 H

EADREST

The folding line between headrest and backrest was lowered by 0.07 m, but that didnot change the relative angle. Lowering the folding line translates the headresthorizontally to the front (Figure 13.7), resulting in more space for ingress and egressactivities. This horizontal translation meets the requirements of 55% of the peoplewho rated the original headrest as too far rearward. People sleep with their mouthopen because of a headrest that is too far to the rear. By moving the headrest forwardthere is more space gained for ingress and egress.

FIGURE 13.7

Change in the headrest folding line. The 7 cm longer line to the right is thenew one.

7 cm

approx. 2 cm

foldingline


165

13.9.5 B

ACK

S

HELL

The overall back shell and back construction are reduced to a minimum to gainhip-to-knee space. By extending the recess in the back shell to the top, enoughhip-to-knee space is created to counteract the reduction caused by the seat pivot.The hip-to-knee space fits the 97.5 percentile male to 2.5 percentile female segmentsof the target population. The recess area is constructed to give more shin space andthus facilitates leg stretching (Fig. 13.8). The ideal leg-stretching space was checkedin the Ergomix, where passengers were mixed into a drawing of a seat and stretchedtheir legs (Chapter 4, Figure 4.4). In this way, the ideal space under the seat in frontof the passenger could be designed.

13.10 RESULTS: TEST OF THE PROTOTYPE SEAT

The prototype S3 was tested against the benchmark seat S1 using the same methodsand long-duration tests as used earlier, but with 20 new subjects who did not knowthe new seat from the benchmark seat. This test was performed to see if the S3 seatdesign succeeded in scoring at least as comfortable as the S1 baseline seat. The S3was made almost 0.05 m narrower than the benchmark S1 in order to place five S3seats in one row. Both types of seat looked brand new.

The experiments showed that the S3 seat was generally regarded as more com-fortable than the S1. The average score given to the S3 seat on a scale from 1 (verypoor) to 10 (perfect) was 7.3. The S1 received an average score of 6.2. This differencewas statistically significant (p = 0.012, t-test for paired comparison).

After 1 hour in the constrained upright testing position, 61% rated the S3“comfortable” to “very comfortable,” compared to 22% for the S1. Similar resultswere found in the ratings of both seats for their suitability for sleeping and readingin the constrained upright testing position. The S3 seat was rated as “very comfort-able” for reading by 61% of the subjects, whereas only 39% rated the S1 seat as“very comfortable.” In regard to sleeping, 28% of the subjects rated the S3 seat as“very comfortable,” but only 6% rated the S1 seat as “very comfortable” for sleeping.Given the choice of riding in either seat during 1 or 2 hours while commuting, 83%chose the S3. Table 13.7 shows the results of all questions in which the subjectswere asked to choose between seats.

FIGURE 13.8

Design of the high recess and optimal shin space of the new S3.

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In 2003, the first trains were on the track and the actual passengers wereinterviewed on television. One of the first things mentioned by the passengers wasthat the seats were much more comfortable than in the old trains.

13.11 CONCLUSIONS

Taking an existing seat as a starting point for the design of a new commuter trainseat and applying end-user opinion research led to good end results. The scientificend-user test methods used to test the seats provided valuable data for the redesign.

TABLE 13.7 Ratings for Prototype (S3) and Benchmark (S1) Seats by 20 Subjects Sitting for 1 Hour

CriterionS1

(benchmark)S3

(new)Entire seat

Report mark 6.2 7.3*General preference 16.7% 83.3%

Forced choice

General comfort 16.7% 83.3%Preferred for sleeping 27.8% 72.2%

* significant, p = 0.012.

FIGURE 13.9

An impression of the new interior with the new seats.


167

The data from end users, with the added interpretation of experts, played a key rolein the experiments, and the design of the new seat was primarily based on theiropinions. An impression of the end results is shown in Fig. 13.9.

ACKNOWLEDGMENT

The authors want to thank Long Island Railroad, Bombardier, and Multina for theirwonderful support.

REFERENCES

Han, S.H., Jung, E.S., Jung, M., Kwahk J. and Park, S. (1998) “Psychophysical methods andpassenger preferences of interior designs.” Applied Ergonomics, 29(6): 499–506.

Molenbroek, J.F.M. (2001) Human Scales for the Design and Evaluation of User Goods,Delft: Delftse Universitaire Pers (in Dutch).

Reynolds, H.M. (1993) “Automotive seat design for sitting comfort.” In B. Peacock andW. Karwowski, eds., Automotive Ergonomics, London: Taylor & Francis.

Zhao, J. and Tang, L. (1994) “An evaluation of comfort of a bus seat.” Applied Ergonomics,25(6): 386–392.

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14

Comfort through an Emotion-Aware Office Chair

C.J. Overbeeke, M.P. de Looze, P. Vink, andF.K. Cheung

CONTENTS

14.1 Emotions in Sales.......................................................................................16914.2 Emotional Reaction to an Office Chair .....................................................17014.3 Results and Conclusion..............................................................................17114.4 Controls and Office Chairs.........................................................................17214.5 Emotions during Seating............................................................................17314.6 Design and Emotion...................................................................................17314.7 The Design Steps.........................................................................................173

14.7.1 Step 1: The Measurements...........................................................17414.7.1.2 Step 1 Results ...................................................................174

14.7.2 Step 2: Emotional Aspects..........................................................17514.7.3 Step 3: Pros and Cons..................................................................17714.7.4 Step 4: Final Design.....................................................................178

14.8 Conclusions.................................................................................................179References..............................................................................................................180

14.1 EMOTIONS IN SALES

Many industries have started to launch their products as emotion carriers, containers, orgenerators. They have realized that mere functionality does not sell any longer. Not onlyare customers not interested in the 54th new function, so many products have reached alevel of technical perfection that it has become difficult to discriminate on that basis.

(Overbeeke and Hekkert 1999, p. 5)

When two office chairs basically have the same functionality, we prefer the one thatgives us a pleasant, desirable, or inspired feeling. The challenge is to design theappearance that evokes the emotions that are wanted by the chair’s users. Theseemotions are important because they primarily and strongly influence the decision

170


to purchase the chair (Holbrook 1985). Chairs that do not look good at first sightare not even tried in the showroom (Chapter 2). In the long run, the emotionsexperienced at first sight are likely to increase the pleasure of owning and using thechair after the purchase (Desmet et al. 2001). For designers, it is important toanticipate human emotions. One manufacturer even call its chair

Emotion

(Fig. 14.1).However, it is difficult to understand precisely how these emotions influence thepurchase of a chair.

14.2 EMOTIONAL REACTION TO AN OFFICE CHAIR

As described in Chapter 1, Desmet et al. (2001) developed emocards to help studythe role of emotions (Fig. 14.2). Sixteen cards show faces with different emotions,and a subject chooses the card that illustrates his or her emotion on seeing theproduct.

This method was applied to a study of 15 office chairs (Looze et al. 2003).Seventy-nine subjects (28 male, 51 female) participated in the study. Fifty-ninesubjects were office workers. Twenty were considered to be chair experts, because

FIGURE 14.1

The

Emotion

, an office chair made by Sitag. (Photo courtesy of Sitag.)


171

they were professionally involved in the evaluation or purchase of office chairs.Fifteen office chairs with wheeled undercarriage, armrests, and back and seat uphol-stered in black were evaluated. The chairs were different with respect to form,dimensions, and materials.

The sequence of the 15 evaluations varied randomly across subjects. To measurethe emotional responses at first sight (i.e., prior to sitting in the chair), the nonverbalself-report method using emocards was applied. The subjects had a few minutes tolook at the chairs, but were not allowed to touch them. Then, each subject selectedthe emocard that best represented his or her actual emotional response to each chair.This process was repeated for each chair. Before the experiment, subjects also wereasked to choose the emocard representing the response they wanted to experience(preferred response.) For each chair, the deviation of the actual emotional responsefrom the preferred response within the circumplex was computed. The results foreach chair were statistically compared (paired t-test, p < 0.05) with the averageresults across chairs.

14.3 RESULTS AND CONCLUSION

Because the results for the office workers were not significantly different from thoseof the expert group, the results are grouped together. Figure 14.3 shows the emotionalresponse (the deviation from the preferred) of the subjects. Five chairs show anemotional response that deviates significantly from the average emotional response(across all chairs). This shows that the method discriminates, even with chairs that

FIGURE 14.2

The 16 emocards developed by Desmet (2000) that help determine emotionalreactions to products.

−1

−1

0

1

10

pleasantness

arou

sal

7

8

65

4

3

2

1

172


are all black. Therefore, for designers of office chairs trying to improve the emotionalattractiveness of office chairs, this method can be useful.

14.4 CONTROLS AND OFFICE CHAIRS

The emotion at first sight, based on the appearance of the chair, is believed to affectthe comfort experienced while sitting in the chair (Helander and Zhang 1997).Obviously, other factors such as the physical seating qualities will also influence thefeeling of comfort.

Another influential factor is the chair’s adjustability to individual needs. Toenable adjustments, office chairs have many controls. Fully adjustable office chairsshould, in principle, heighten comfort when working, but people use often thesecontrols wrongly, or rarely. It is well known from ergonomic studies (Ong et al.1988; Grandjean et al. 1983; Vink and Kompier 1997) that employees do notautomatically adopt well-designed office furniture, such as adjustable chairs anddesks. Even with an instruction program, results with respect to adjustment areusually limited to adjustments such as desk inclinations and document holders(Verbeek 1991). The end user is probably not aware of the need for another positionof the chair, or may feel that actually changing the posture by adjusting the chair istoo big a bother.

Certain handles change different dimensions of the chair (Fig. 14.4). There areoffice chairs with controls for pneumatic seat height adjustment, tilt tension, tilt lock(eliminates tilt function when the chair is in an upright position), seat front–backwardadaptation, backrest height and front–backward position, and so forth. Most peopleare not experienced enough in handling different dimensions separately (Djajadin-ingrat et al. 1996). An adjustable chair requires them to construct a mental modelwith many degrees of freedom, that is, to decompose a movement into its Cartesiancomponents.

FIGURE 14.3

The deviation from the preferred emotional reaction for chairs A through O.Black bars indicate significantly

better

ratings than average; white bars indicate significantly

worse

ratings than average (p

<

0.05). All vertical axes run from the minimum to themaximum values.

A0

B C D E F G H I J K L M N O

emot

ion:

devi

atio

n fr

om p

refe

rred


173

14.5 EMOTIONS DURING SEATING

Perhaps it is better to let the chair do all the work. Technology has reached the pointwhere sensors in the chair can feel when a person is tired, and the chair cansubsequently adapt its posture. The questions are what the chair should feel, whatit should know, and what it should do with this information. These are the threebasic questions discussed in an explorative study reported in the rest of this chapter.

14.6 DESIGN AND EMOTION

Having said that emotions play an important role at first sight, as well as whenusing a product, the design process that anticipates emotions is more difficult. Thischapter describes a design process with a focus on emotions. It is the first pilotstudy on the subject.

14.7 THE DESIGN STEPS

People express their feelings by actions. If you ever met a really angry person, youknow what is meant. The philosophy of the human–product interaction research anddesign of the work in this chapter thus concentrates on what people can do, know,and feel (Overbeeke et al. 2003; Wensveen et al. 2000).

As a first step, an experiment was performed to analyze the current office worksituation, testing whether the emotional state during office work was correlated with

FIGURE 14.4

Some controls of a simple office chair.

174


the sitting behavior. To this end, we measured the macromovements of the sittingsubjects, as well as their emotional state using emocards (Step 1). The relevantemotional aspects were described, followed by a series of concept designs (Step 2).The pros and cons of the different designs were discussed with end users, ergono-mists, and emotional design experts (Step 3). These comments became input for theend product: a conceptual chair that moves between states of emotion, according tothe state the sitter is in and the task at hand (Step 4).

14.7.1 S

TEP

1: T

HE

M

EASUREMENTS

An experimental setup was arranged in the laboratory of the faculty of MovementSciences of the Amsterdam Free University. Four subjects sat at a table with a computerin three types of office chairs, respectively. The table and chair were ergonomicallycorrectly adjusted for each subject (Fig. 8.3, Chapter 8). The three types of chairs were

1. A fixed chair that could not be moved in any way by the subject2. A synchro-chair — the seat and the back could be moved, but only simul-

taneously because they were in a fixed ratio to each other3. A multidynamic chair whose seat and back could be moved independently

Three types of recordings were made: general observations, specific recordingsof macromovements, and changes in emotional reactions, using the emocards. Twocameras recorded the subjects’ movements during the whole experiment. The view-ing angles were chosen so that the each subject was wholly in view all of the time.

The four subjects (two male and two female students) did three sessions (onefor each chair, randomized) that lasted 3 hours each, on three separate days. Theirtasks were 45 minutes of typing a given text, 15 minutes of relaxed reading,45 minutes of AutoCad drawing, 15 minutes of relaxed reading, 45 minutes of typinga given text, and 15 minutes of relaxed reading.

The recordings were made three times. At the start, the subjects were askedabout their first impression of the chair and how comfortable it seemed to them.emocards were used for each task after 15, 45, and 60 minutes. To finish, they wereasked what their general impression of the chair was after each session.

14.7.1.2 Step 1 Results

Because the results are based on four subjects only, they should be seen as indicativeof a general trend only. When looking at the videos, we noticed that the subjects’legs were usually moving. We defined four positions of the legs: outstretched, straightdown, slightly backward, and fully backward. We counted every transition betweenthose positions as a macromovement. The results for the three types of chairs andthe six consecutive tasks, summed over subjects, are shown in Table 14.1. Thenumbers are per 15-minute periods (because the reading took 15 minutes and theother tasks 45 minutes).

For the fixed chair and the synchro-chair the data are as expected. After sometime, the subjects grew tired and made more movements. With the fixed chair the


175

movements increased from 20 in 15 minutes to 80 in 15 minutes. The subjects movedmore when reading (54 movements in 15 minutes) than in the other tasks (typing33, CAD 12), probably because the reading task is less constraining. The dynamicchair invites more movement than the static chair.

The emotional reactions did not differ much over time. Probably the test methodis not suitable to this type of research or the number of subjects was too low.

14.7.2 S

TEP

2: E

MOTIONAL

A

SPECTS

Step 1 showed that the frequency of macromovements changes over time and is relatedto the type of chair and to the task being executed. The question is, however, howshould the chair get to know what it should adapt to? In other words, the chair shouldbe aware of the office environment, on the one hand, and of the person sitting in it andhis or her current task, on the other hand.

The office environment and the required tasks were explored in several scenarios.This led to interesting themes. The chair could be an integrating factor within theoffice. It could also be the user’s guardian angel, and it could have different charactersplaying this role, from dominant to caring. Furthermore, the chair could be expressivein communicating the emotional state of the user to the rest of the office. Severalof these themes were translated into design concepts and discussed with users andexperts. Figures 14.5 through 14.9 show some concept drawings.

TABLE 14.1 Number of Macromovements

Fixed chair

Synchro-chair

Dynamic chair

t r c r t r t r c r t r t r c r t r20 38 22 34 46 80 23 61 24 52 37 72 37 61 27 39 36 53

t = typing; r = reading; c = CAD

FIGURE 14.5

Concept

bar

. This chair adapts to the emotions: relaxed (left), concentratedwork (middle), and short sitting work (right).

176


FIGURE 14.6

Concept

cylinder protector

. This chair adapts to the level of concentrationneeded in the work. The right-hand position is for more concentrated work.

FIGURE 14.7

Concept

spring

. This chair could be a kind of stool (left), and then changeinto a fixed office chair (middle) or an easy-up chair (right).

FIGURE 14.8

Concept

starfish

chair. This chair invites you to sit, and it has the ability toclose for concentrated work and open for more communication.


177

14.7.3 S

TEP

3: P

ROS

AND

C

ONS

Based on the pros and cons mentioned by end users and experts, it was not yet clearwhat the requirements were for the design. For the time being, we chose two levelsof communication to the environment (open or closed) and two levels of personal state(relaxed or concentrated) because these were seen in almost all situations. Furthermore,we wanted the chair to be caring and to be dominant only to prevent WMSD(work-related musculoskeletal disorders), for example, by stimulating movement.

The chair should than have the technical capability to measure four resultingsituations:

1. Concentrated and closed, for example when writing this text or duringimportant telephone conversations. The user is sitting up straight andrelatively still. The task is done individually and under high pressure.

2. Concentrated and open, for example when cleaning the desk or consultingcolleagues. The user uses the chair infrequently and more as a leaningsupport, often rushing around. The high-priority task is done in collabo-ration with others under time pressure.

3. Relaxed and closed, for example, when surfing the Internet, checking e-mail,or reading. The user sits relatively still, straight, or shoved under the table.

4. Relaxed and open, for example, when taking a coffee break, or talking tocolleagues in a Friday-afternoon atmosphere. The user moves a lot, isopen to others, and generally leans back in the chair.

In these four situations the chair should at least be able to measure (1) leaningforward; (2) leaning backward and its intensity; (3) the absence of macromovements;(4) nobody on the chair; (5) orientation toward the desk; and (6) distance to thedesk. All of these measurements are technically feasible.

FIGURE 14.9

Concept

tilt

. This chair can be used from different positions: for average work(left), for work where you can easily stand up (middle), and for more relaxed work (right).

178


14.7.4 S

TEP

4: F

INAL

D

ESIGN

Once the four situations have been described, a new concept was designed for a chairthat reacts to the user and adapts itself to facilitate the four work situations. The finaldesign is shown in Fig. 14.10. It adapts to the four work situations as follows:

1. Concentrated and closed: The chair gives a stable seat, whereby arm restsand back support are given. The chair shields users from the environmentso as to heighten their concentration and to let their colleagues know theyare not to be disturbed.

2. Concentrated and open: The chair supports standing and leaning. The seatis at an angle inclined to the front and fixed.

3. Relaxed and closed: The chair is wobbly and can be changed from straightup to inclining backward. It shields the user from the surroundings.

4. Relaxed and open: The chair is wobbly and can turn. The user can get inand out of the chair easily, and it offers great freedom of use.

As indicated earlier, we decided to give the chair a

caring

character. This means,for example, that when a user pushes backward for a while, the chair will changeits current position to the desired position. But caring also means being dominantsometimes. To prevent WMSD the chair will become dynamic (loosen the seat andbecome wobbly) and will thus stimulate the user to move when he or she has beensitting still too long. But caring also means obedient. When the chair wants to changeits position, it can always be overruled by simply giving it a jerk.

Figure 14.10 shows how such a chair could look. Along with the usual officechair possibilities, this conceptual design offers more. Of course the chair already

FIGURE 14.10

The conceptual chair. (Design by Kin Fai Cheung, TU Delft.)

The arm rests canpivot and rotate

Thewheels havea collective

brake system

The screen offersprivacy or openness

The seat can beadjusted in height

and topple


179

knows things (and might even be equipped with learning capacities), but it also hasnew capacities. The armrest can be retracted or turned down to serve as a legrest.A screen can shield the user from the environment. The chair itself is mounted ona spring so that it can wobble or, when the spring is deactivated, the chair is static.

Figure 14.11 shows the different states of the chair for the different situations. Thechair moves from one state to another, according to the situation at hand. In theconcentrated and open situation, for example, the chair is high like a stool and doesnot support the arms or shield the head. When the situation is relaxed and open, thechair is low, turns away from the desk, and affords sitting in unconventional ways.

14.8 CONCLUSIONS

The emotional reactions of end users to office chairs can be found by using emocards.Differences are shown even between office chairs that are all black. The conclusionfrom the exploratory study is that there are possibilities for letting the chair react tothe user’s emotional state. This feature could be used to reduce WMSDs. Forexample, a chair may monitor the user’s state of well-being and convince the userto change his posture or to change to a different task to counter WMSD-relatedproblems.

Another application would be to have the chair act as an input device forcommunication devices such as a telephone or ICQ. The chair could detect a stateof stress or concentration and communicate that to the telephone or computer system,which would enables these systems to filter incoming messages and limit them tothe urgent or important.

Finally, an interactive chair could support the user’s current state by changingconfiguration. When the user is highly concentrated, the chair could support thatmode of working by shielding the user from his colleagues.

This study is of an explorative nature, and it can aid further study of therelationship between the user’s state of emotion and chair adaptation to it. Furtherresearch is needed with respect to the way macromovements are related to comfortand state of emotion, and a better insight is needed into whether the four chosenoptions are the most functional in regard to tasks to be done at the office.

FIGURE 14.11

The chair changes to different positions according to the sitter’s state andtask at hand.

Concentrated and Private Relaxed and PrivateConcentrated and Open Relaxed and Open

180


REFERENCES

Desmet, P.M.A., Overbeeke, C.J. and Tax, S.J.E.T. (2001) “Designing products with addedemotional value: Development and application of an approach for research throughdesign.”

The Design Journal

, 4(1): 32–47.Djajadiningrat, J.P., Overbeeke, C.J. and Smets, G.J.F. (1996) “The importance of simulta-

neous accessible degrees of freedom.”

Human Behaviour and Information Technology

,16(6): 337–347.

Grandjean, E., Hunting, W. and Piderman, M. (1983) “VDT workstation design: Preferredsettings and their effects.”

Human Factors

, 25: 161–175.Helander, M.G. and Zhang, L. (1997) “Field studies of comfort and discomfort in sitting.”

Ergonomics

, 40: 895–915.Holbrook, M.B. (1985) “Emotion in the consumption experience: Toward a new model of the

human consumer.” In R.A. Peterson, W.D. Hoyer and W.R. Wilson, eds.,

The Roleof Affect in Consumer Behavior: Emerging Theories and Applications

, Lexington,MA: Heath, 17–52.

Looze, M.P. de, Krause, F., Reijneveld, K., Desmet, P. and Vink, P. (2003) “Seat appearanceand sitting comfort.” In

Proceedings of the 15th Triennial Congress of the Interna-tional Ergonomics Association and the 7th Joint Conference of the ErgonomicsSociety of Korea/Japan Ergonomics Society

,

Vol. 3: Product Design

,

Seoul: TheErgonomics Society of Korea, 632–635.

Ong, C. N., Koh, D., Phoon, W. O. and Low, A. (1988) “Anthropometrics and display stationpreferences of VDU-operators.”

Ergonomics

, 31: 337–347.Overbeeke, K., Djajadiningrat, T., Hummels, C., Wensveen, S. and Frens, J. (2003) “Let’s

make things engaging.” In M.A. Blythe, A.F. Monk, K. Overbeeke and P.C. Wright,eds.,

Funology: From Usability to Enjoyment

, Dordrecht: Kluwer: 7–17.Overbeeke, C.J. and Hekkert, P., eds. (1999)

Proceedings of the 1st International ConferenceDesign and Emotion

, Delft: University of Technology.Verbeek, J. (1991) “The use of adjustable furniture: Evaluation of an instruction programme

for office workers.”

Applied Ergonomics

, 22: 179–184.Vink, P. and Kompier, M.A.J. (1997) “Improving office work: A participatory ergonomic


Ergonomics

, 40(4): 435–449.Wensveen, S.A.G., Overbeeke, C.J. and Djajadiningrat, J.P. (2000) “Touch me, hit me and I

know how you feel. A design approach to emotionally rich interaction.”

Proceedingsof DIS’00, Designing Interactive Systems

, New York: ACM, 48–53.

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0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

15

Toward a Comfortable Paint Scraper

S.M. Eikhout, R.E. Bronkhorst, P. Vink, and M.P. van der Grinten

CONTENTS

15.1 The Problem...............................................................................................18115.2 The First Ideas for Redesign .....................................................................18215.3 Bahco Ergotools .........................................................................................18415.4 The User Test Method.................................................................................185

15.4.1 Setup ............................................................................................18515.4.2 Physical Load...............................................................................18515.4.3 Goniometry ..................................................................................18515.4.4 Trial of Strength...........................................................................18615.4.5 User Friendliness .........................................................................186

15.5 Results.........................................................................................................18715.5.1 Posture and Movement.................................................................18715.5.2 Forces and Torque on the Wrist...................................................18715.5.3 User Friendliness: Subjects’ Opinions..........................................18715.5.4 Discomfort and Comfort..............................................................18815.5.5 Qualitative Evaluation..................................................................188

15.6 Discussion...................................................................................................189Acknowledgment ...................................................................................................190References..............................................................................................................190

15.1 THE PROBLEM

Painters are a high-risk group for health problems. According to European and Dutchdata of the building industry, painters suffer from more complaints of the upperextremities than the control group in the construction industry (Arbouw 1997).Construction workers already show more health impairment than the general workingpopulation (Blatter and Bongers 1999). A study at the University of Iowa (Cooket al. 1996) also found a greater incidence of health complaints involving the upperlimbs of painters, compared to construction workers.

182


Frequent use of tools can lead to health complaints from the following riskfactors: unfavorable postures and movements of wrists and shoulders, high torques,high repetition of movements or effort, excessive localized friction or pressure inthe contact hand grip, vibrations, and high precision (Grinten 1999). According toFeggeler et al. (1992), a significant number of the complaints can be prevented bythe ergonomic shape of tools.

At present, all Dutch painters use the traditional triangular scraper (Fig. 15.1).However, the design of this tool could be improved and better adapted to the painter’stask and to the possibilities and limitations of the human body. Rhijn and Eikhout(1998) found hazardous forces and torque affecting the wrist during work with thetriangular scraper.

15.2 THE FIRST IDEAS FOR REDESIGN

Ideas for redesign were generated in a session with designers, human movementspecialists, painters, and a person representing the Dutch sector organization forpainters. Before this session, observations and measurements were made of thephysical load and user friendliness of the traditional paint scraper. Professionalpainters were involved in these measurements. The main problems in working withthe traditional triangular paint scraper were (Rhijn and Eikhout 1998): (1) frequentextreme wrist postures; (2) high forces of the arm, also due to the large momentarm; and (3) awkward postures in the back, shoulder, neck, and elbow.

Several ideas were generated during the session on redesign ideas, and threewere explored further (Figs. 15.2, 15.3, and 15.4). One idea was to use two handsto grip the paint scraper. Another concept was to reduce the distance between thescraping area and the hand. This reduces the moment arm, and thereby reducesthe forces on the hand. The third idea was to change the angle between the gripand the scraper, which improves the position of the hand, wrist, elbow, andshoulder.

FIGURE 15.1

The traditional paint scraper that is now frequently used.


183

FIGURE 15.2

An idea for improving the paint scraper: Lower forces are needed in eachhand when two hands are used.

FIGURE 15.3

Reducing the distance between the scraping area and the hand reduces themoment arm, and thus the forces on the hand.

FIGURE 15.4

Changing the angle between the grip and the scraper can improve the positionof the hand, wrist, elbow, and shoulder.

184


15.3 BAHCO ERGOTOOLS

These redesign ideas led to collaboration with Bahco Tools of Sweden. Bahcoproduces the so-called

ergotool

line, in which much attention is paid to ergonomicsto arrive at comfortable hand tools. The ergotools have been developed in closecollaboration with end users, following a scientific 11-point program (Bobjer andJansson 1997).

Essentially, the development program requires that operators are intensivelyinvolved. This 11-step program can be summarized as follows: After preliminaryspecifications are determined by interviewing and observing users (step 1), a marketanalysis (step 2) is performed. In step 3, background information is collected frompapers, textbooks, and reports, followed by the design of a first prototype (step 4).Then professionals are exposed to the experimental prototypes (step 5) and improve-ments are defined in interviews based on research (step 6). A user test (step 7) isthen completed by a wider selection of users in several countries. In step 8, the finaldesign recommendations are made, followed by product specification (step 9).Another user test is performed in step 10 to prove that the tools work, and the productis launched. In step 11, more field tests are performed to gather data for furtherproduct improvement.

The new scraper (Fig. 15.5) that is developed in the 11-step process has a bladeof hard sintered metal, so that blade grinding is no longer needed. The shape of thehandle is also different. The triangular scraper has the largest handle diameter closeto the blade, whereas the new scraper’s handle is thickest close to the body. Thisreduces slip between hand and tool. The form of the handle is also better adaptedto its use in the scraping task by improving the grip.

This sounds wonderful: an ideal participatory design process and applause fora good, comfortable product! However, the effects of use and the end users’ opinionsare unknown. Therefore, an extensive user test was conducted and will be describedin the next paragraphs.

FIGURE 15.5

The new paint scraper developed in the 11-step program.


185

15.4 THE USER TEST METHOD

15.4.1 S

ETUP

Twenty Dutch professional painters from seven different painting businesses volun-teered to participate in this field study. The selection criteria required painters tohave a large number of scrape activities during the test period and to have no historyof health complaints. All subjects were males with 14 ± 11 years of paintingexperience; age 33 ± 12 years; height 1.82 ± 0.07 m; and weight 81 ± 11 kg. Afteran introduction, the painters used the new scrapers in their normal work for two tothree weeks. After one week the subjects were visited for guidance, and the testperiod ended with a test day.

15.4.2 P

HYSICAL

L

OAD

Physical load was measured by recording posture, movements, effort, and torqueduring scraping. Posture and movements were recorded by goniometry. Forces andtorques were recorded by a trial of strength.

15.4.3 G

ONIOMETRY

Using goniometry (Biometrics, 1999), the exact position of the hand in relation tothe lower arm is measured (Fig. 15.6). The registration of the wrist angle in degreestook place during a task that continued in time with a frequency of 20 Hz.

This study measured flexion, extension, radial deviation, and ulnar deviation.Rotation of the lower arm hardly seems to occur and is therefore not dealt with

FIGURE 15.6

Measuring the position of the hand by goniometry.

186


in this research. In the field, goniometry took place during the performance of astandard task. It is assumed that the extreme wrist angle is reached at 75% of thesubject’s range of motion of the wrist (maximum active wrist movement). Thisindividual marginal value was determined for each subject. With this value thesubject’s results were assessed so that the percentage of time in this posture wascalculated and the difference tested within the group of subjects, using a pairedt-test.

15.4.4 T

RIAL

OF

S

TRENGTH

The strength to scrape was measured in two directions: horizontally (the push force)and vertically (the pull force). A special test surface was constructed (Fig. 15.7) toenable force measurement during a scrape task. The scrape motion was measuredunder multiple conditions, and the different torques were calculated. The torque wastested on significant differences using the paired t-test.

15.4.5 U

SER

F

RIENDLINESS

A questionnaire was used to record the opinion of the subjects. It consisted ofquestions on subjects’ descriptions, their opinions on comfort and discomfort, andtheir experiences in working with the traditional triangular scraper and the newscraper. The subjects completed the questionnaire under supervision of theresearcher, and the results are presented in percentages or numbers of subjects. Thepaired t-test was used for statistical testing of differences. Finally, a qualitativeevaluation was conducted to compare the handle of the new scraper with that ofthe of the triangular scraper. This evaluation is based on hand tool guidelines ofGrinten (1999).

FIGURE 15.7

Trial of strength measurement setup.


187

15.5 RESULTS

15.5.1 P

OSTURE

AND

M

OVEMENT

Nine gonio-measurements were analyzed. Percentages of the time in extreme pos-tures are presented in Fig. 15.8. The differences were not significant.

15.5.2 F

ORCES

AND

T

ORQUE

ON

THE

W

RIST

Seventeen subjects participated in the test under “dry” paint conditions. Elevensubjects participated under “burner” conditions in which the paint was first burned,which normally reduces the duration or force of paint scraping activities. The resultsare presented in Fig. 15.9. The mean forces under burner conditions were 17% loweron the new scraper than on the triangle.

Without burner, the mean torque of the new scraper (n = 17) was 13.2 ± 7.1Nm, and for the triangular scraper it was 14.7 ± 7.2 Nm. With burner (n = 11),the mean torque of the new scraper was 11.2 ± 4.5 Nm, and for the triangle itwas 14.2 ± 5.8 Nm. These differences were significant. The torque of the newscraper, measured with burner, decreased 21% compared to the torque of thetriangle with burner. Without burner, 10% torque reduction was found.

15.5.3 U

SER

F

RIENDLINESS

: S

UBJECTS

’ O

PINIONS

Twenty painters completed the questionnaire. The new handle was evaluated as “verywell manageable” under separate conditions of dust, grease, and moisture by 74%,71%, and 72% of the painters, respectively. The new scraper was considered to be

FIGURE 15.8

Percentage of the time in extreme wrist position while working around dif-ferent angles (n = 9) with the new scraper and the traditional scraper.

0

1

2

3

4

5

6

7

extensionflexion

mea

n tim

e pe

rcen

tage

ulnar deviationradial deviation

traditional triangular scrapernew scraper

188


very comfortable in use by all subjects. Significantly less discomfort was experiencedin the upper arm and in the joints of the fingers with the new scraper. Fewer blisters,less strength required for use, and a better hold were reported for the new scraper.The blades of the new scraper do not need to be ground, which is seen as anadvantage, because grinding the old triangular scraper blades took much time. Thesharpness of the new blades was very satisfying to 95% of the subjects. Accordingto the painters, less damage to the surface had occurred while working with the newscraper. They even reported a higher productivity, which was confirmed by obser-vations in which fewer scrape motions were recorded, and 74% stated that the qualityof their work had improved. The painters evaluated the new scraper as safer thanthe triangle.

15.5.4 D

ISCOMFORT

AND

C

OMFORT

Perceived discomfort was reduced (Fig. 15.10) in working with the new scrapercompared to the old scraper. In the upper arm and fingers a significant improvementin comfort was shown. Probably more importantly, 70% evaluated the new paintscraper as “very comfortable.”

Regarding the handle, more than 90% of the painters gave a positive evaluation(Table 15.1). In the final evaluation, the new scraper was given 8.5 and the triangle7.0 on a scale of 1 to 10. This difference was significant.

15.5.5 Q

UALITATIVE

E

VALUATION

Experts evaluated the handles of both scrapers on the following aspects: formenclosed force-transfer, material, “stick-slip,” form, and contact surface. Except interms of the form, these factors were evaluated in favor of the new scraper. Theshapes of both scrapers were evaluated equally.

FIGURE 15.9

Mean pull and push forces (n = 17): “dry” and after treating the paint with aburner.

0

10

20

30

40

50

60

70

pull force“dry”

push force“dry”

pull forceburner

push forceburner

Newton “dry”

new scrapertraditional triangle


189

15.6 DISCUSSION

Scraping results in unfavorable motions and high torques that cause a great deal ofstrain on the wrist (Rhijn and Eikhout 1998). The new scraper results in lower torqueson the wrist, but improvement is still possible because it does not meet all the healthlimits of a daily load (Eikhout et al. 2001). The measured decrease in movement ofthe new scraper compared to the triangular scraper is mainly due to the decrease inpull and push forces. The distance from the grip to the contact surface is almostequal on the two scrapers. By decreasing this distance, the torque can be reduced

TABLE 15.1 Evaluation of the New Scraper Handle by Percentages of Subjects Approving (n = 20)

Approval

Length of handle 90%Diameter/circumference for hand 95%Squarely section 100%Hold on material 100%Smooth finish 100%Fit in hand 93%Thickening of end of handle 100%Distance of hand to handle 90%Does not rub against wood/surface during scraping 84%

FIGURE 15.10

Local perceived discomfort (as percentage of the maximal discomfort of 20painters) working with the traditional triangular paint scraper and the new scraper (

*

= significant,paired t-test, p < 0.05).

0 20 30 40fin

gers

*

wrist

uppe

r arm

*shou

lder/n

eck

%

new scrapertriangular

10

190


f

urther. However, it is uncertain whether this reduction will yield an optimum result,since there has to be room for the burner, the position of the fingers, and so on. Itis also uncertain what the effect of this decrease will be on the limit forces.

Both the traditional triangular scraper and the new scraper position the gripperpendicular to the blade, and in both scrapers the tool is held with a fist grip. Theblade of the new scraper is convex-ground. The painter’s posture is mainly deter-mined by the surface (i.e., inside or outside of a frame). Therefore, the painter hasto adapt his posture to reach all spots. This might be an explanation for the smalldifference in wrist motion and posture when using the two scrapers. Working withextreme wrist angles carries a very high risk for health complaints and needs to beprevented as much as possible (Arbouw 1996). However, extreme wrist posturesduring scraping are probably inevitable because of dependence on the nature of thesurface and the anthropometrical limitations of the human body. It might be possibleto decrease the duration of extreme poses by modifying the shape of the grip andthe position of the grip relative to the blade (Figs. 15.2, 15.3, 15.4).

In the user test method applied, not all possible body postures during scrapingare included. Some risks have possibly been excluded. In a given situation, the resultsmay be positive for both scrapers in regard to the forces measured as well as thegoniometry. This project evaluated only the short-term effects; it did not considerthe long-term effects on the painters’ health. That would have to be done in alongitudinal study in order to reduce the risk of musculoskeletal injuries amongpainters and to benefit their health. Scraping places a high physical load on thepainter. The new scraper makes his job easier and reduces physical load, comparedto the triangular scraper. This is shown by results with the new scraper that demon-strate a 21% reduction in wrist moments, a 17% reduction in pull force, and someimprovement of the wrist posture and wrist movement.

Finally, taking into account the very positive evaluations by the end users andthe positive qualitative evaluation with the health guidelines, the usability of the newscraper compared to the traditional one is a substantial improvement. Sales of theBahco paint scraper continued to be very good after the project.

ACKNOWLEDGMENT

The authors wish to thank Bahco Tools BV for providing the scrapers and the Boardfor Painters and Decorators for funding this research project.

REFERENCES

Arbouw (1996)

Arbouw-richtlijnen voor fysieke belasting in de bouwnijverheid

, Amsterdam:Stichting Arbouw.

Arbouw (1997)

Bedrijfstakatlas. Arbeid en gezondheid bouwnijverheid

, Amsterdam: StichtingArbouw.

Biometrics (1999)

Operating Manual

, Cwmfelinfach, Gwent, UK.


191

Blatter, B.M. and Bongers, P.M. (1999)

Work Related Neck and Upper Limb Symptoms (RSI):High Risk Occupations and Risk Factors in the Dutch Working Population

. Hoofd-dorp: TNO Arbeid.

Bobjer, O. and Jansson, C. (1997) “A research approach to the design of ergonomic handtools. The 11-point programme.” In P. Seppälä, T. Luopajärvi, C.H. Nygård, and M.Mattila, eds.,

From Experience to Innovation. Proceedings of the 13th TriennialCongress of the International Ergonomics Association

, Helsinki: Finnish Institute ofOccupational Health, Vol. 2, 193–195.

Cook, T.M., Rosecrance, J.C., and Zimmermann, C.L. (1996)

The University of Iowa Con-struction Survey

. Iowa City, Iowa: University of Iowa.Eikhout, S.M., Bronkhorst, R.E., and Grinten, M.P. van der (2001) “Evaluation of a New

Scraper.”

Proceedings of the 45th HFES Congress 2001

, Minneapolis: HFES,722–726 (on CD-ROM).

Feggeler, A., Yoo, J.W., and Hornung, V. (1992)

Ergonomische Gestaltung von handgeführtenelektromotorischen Arbeitsmitteln

. Dortmund: Bundesanstalt für Arbeitsschutz. For-schungsbericht Fb 668.

Grinten, M.P. van der (1999)

Arbouw-richtlijnen voor fysieke belasting bij gebruik vanhandgereedschap en hanteren van verpakkingen in de bouwnijverheid

. Hoofddorp:TNO Arbeid.

Hall, Ch. (1995)

Hand Function with Special Regard to Work with Tools

. Stockholm: NationalInstitute of Occupational Health. Arbete och hälsa 1995:4.

prEN 1005-3 (1998)

Safety of Machinery — Human Physical Performance Part 3: Recom-mended Force Limits for Machinery Operation

. Brussels: CEN/TC 122. Draft March,1998E.

Rhijn, J.W. van and Eikhout, S.M. (1998)

Ergonomische beoordeling van handgereedschapmet aanzet tot herontwerp

. Hoofddorp: NIA TNO.

193

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

16

Development ofa Handheld Steel-Fixing Tool

J. Visser, T. König, I. Ruiter, and P. Vink

CONTENTS

16.1 Introduction.................................................................................................19316.2 TyTecker and the Market.............................................................................19416.3 Problem Definition .....................................................................................19416.4 Approach.....................................................................................................19516.5 Analysis ......................................................................................................19616.6 Results of the Observations.........................................................................19616.7 Results of the Interviews ...........................................................................19616.8 Literature Results Concerning Static and Dynamic Loading ...................197

16.8.1 Working Posture...........................................................................19716.8.2 Repetitive Movements .................................................................19816.8.3 Ergonomics Guidelines: Wrist and Hand....................................199

16.9 Synthesis and Evaluation ...........................................................................20116.9.1 Posture, Configuration, and Balance.............................................201

16.10 Design Proposal..........................................................................................20316.11 Detailed Model...........................................................................................204

16.11.1 Usability Tests with the Model ...................................................20416.12 Conclusions and Recommendations............................................................205References..............................................................................................................205

16.1 INTRODUCTION

One of the construction activities where working conditions certainly can beimproved is rebar tying. In particular, the forward-bent working posture, the repet-itive movements, and the cyclic character of the work increase the chance of dis-comfort and musculoskeletal injuries in the long run. The Dutch rate of sick leavein this profession is 7.9%, compared to 6.2% in the Dutch construction industryoverall (CBS 2002).

194


An innovative rebar tying system developed by the Dutch company TyTeckerpotentially solves several of these problems. However, the first and current designof the tying tool introduces several new issues concerning ergonomics and usability.A redesign was therefore initiated at TyTecker by the first author as a graduationassignment. The redesign process is described in this chapter.

16.2 TYTECKER AND THE MARKET

TyTecker, founded in 2000, is a relatively new player in the rebar tying market. Thecompany has already developed an innovative and patented clip to fasten the rebarties. The clip is the main source of income for TyTecker, with the tying tool beinga necessary, but secondary, product — much like the business model of telecommu-nication providers. As a result, the tying tool itself can be sold nearly at cost, leavingroom for optimization of ergonomics and usability.

The tying solution that TyTecker developed is not the only one on the market.However, existing alternatives to the common tying tool have not succeeded inacquiring substantial market share and thus do not significantly improve workingconditions. The perceived cost increase and less-than-optimal usability and reliabilityhave limited the acceptance of these products by end users and tying companies.

16.3 PROBLEM DEFINITION

The large number of publications concerned with occupational health on constructionsites (see

From Experience to Innovation, Proceedings of the 13th Triennial

Congressof the International Ergonomics Association

, 1997) illustrates the need for improve-ment. Several studies (Broersen et al. 1991; Cook 1996; Smallwood 1997; Wakulaet al. 1997; Ploeger 2000; Koningsveld 2002) show that working postures andrepetitive movements are key problems in rebar tying, resulting in back injuries andmusculoskeletal disorders of the upper extremities. Working postures are especiallyawkward when tying at floor level because this work requires prolonged extremebending of the lower back (Fig. 16.1)

FIGURE 16.1

Bending forward during rebar tying is frequently observed.

Development of a Handheld Steel-Fixing Tool

195

TyTecker’s tying tool — currently in the prototype phase — allows for animproved posture during floor rebar tying. However, floor tying represents only partof the tying work. Rebar tiers also tie in the vertical plane (walls, columns) andunder special conditions (for instance, in tilted rebar planes and prefab tying). Forthese cases, the current tool is not the best solution.

TyTecker recognized the opportunity to develop a compact, flexible, hand-held toolfor various situations. The target was to develop a compact, hand-held rebar tying toolfor use in walls, ceilings, and other situations. Key aspects of the new product are usability(operating and refilling the tool) and function integration (one design incorporating allcomponents). Apart from the occupational ergonomics challenge, there’s a second,equally important aspect to the development of this new steel-fixing tool: the acceptanceof the tool by the workers. Over the past years, several new tools claiming ergonomicaloperation have been introduced, but these still have a negligible market share and thusdo not significantly contribute to better conditions in the trade (Fig. 16.2).

According to the thesis of Jong (2002) and Chapter 4, reliability of operationand communication with target groups are key aspects in market acceptance of aproduct. Consequently, communication with workers during the development stageis an important source of design criteria for new tools and solutions to achievesuccessful implementation.

16.4 APPROACH

The design approach used is based on the design theory developed at the Facultyof Industrial Design Engineering (Roozenburg and Eekels 1991; Marinissen 1993)and consists of an analysis phase followed by several iterations of synthesis andevaluation. In the analysis phase, both literature and field research were carried out.During the synthesis and evaluation iterations, the design was developed from spatialconfigurations, through concepts, to a detailed final proposal. Following the iterativeand creative nature of the design process, further research was conducted whennecessary during the development of the design.

FIGURE 16.2

An old model of the TyTecker machine, which was improved in this project.One of the problems was that the old model was too heavy, and it took too much time torefill the tool with a new cartridge.

196


16.5 ANALYSIS

Ergonomics literature on design guidelines was studied, ranging from whole bodypostural advice and anthropometrical data to overall suggestions on product safetyor left- and right-hand use (Dreyfuss 1960; Buurman 1996; Fransson and Kilbom1991; Garner 1992; Kapandji 1980; Radwin and Haney 1996; Woodson 1981).Where possible, different sources of data were compared to make a sound decisionon a particular ergonomic design criterion.

In addition to the literature research, field experts were interviewed. The inter-views yielded insight into the factors that determine the success of a new productintroduction. The major factor in the highly conservative construction industry isworkers’ opinion on the tool. In addition to this insight, an article in

HarvardBusiness Review

showed the importance of actual on-site research to the success ofnew product development (Leonard and Rayport 1997). Therefore, the actual needs,opinions and working habits of the steelfixer, as well as the currently used tools,were investigated during two on-site observation sessions.

16.6 RESULTS OF THE OBSERVATIONS

The observations showed the working posture to be a major concern (bending thelower back and lifting heavy loads), but repetitive movements of the wrist are aproblem as well. The video material obtained during the two observations revealedseveral remarkable issues:

• Steelfixers leave their equipment in odd places, and every worker has hisown tying tool. When the tool is not in use, they store it in a variety oflocations: on the boarding, on a solid floor, in the back pocket of theirwork clothing, or suspended from a do-it-yourself ring.

• The tool is used for other tasks than just tying rebar. During the observa-tions, the steelfixers regularly used the tool as a hammer, banging againstrebars that were not correctly in place.

• The steelfixers need a free hand to manipulate the work. Just before a tieis made, steelfixers sometimes need to adjust a rebar or to support a barin order to be able to make the connection. In these cases they need onehand to manipulate the rebars, holding the tying tool in the other one.

These observations are important signals for the tool that is being developed:The worker should be able to suspend it from a belt or otherwise put it away, thetool must be operable with one hand, and it must withstand rough treatment(reliability).

16.7 RESULTS OF THE INTERVIEWS

The interviews revealed useful user experiences with — and opinions on — the othertying solutions. From the interviews, several conclusions could be drawn with respectto TyTecker’s tying tool:


197

• The tool should be compact.Because rebar tiers use one hand for materials manipulation, it is importantthat the tool can be operated with just the other hand. Tiers also preferreda small-sized tool so they could suspend it (e.g., from a belt) when it is notin use.

• The tool should be lightweight.This requirement seems straightforward, but it is of vital importance. Becausethe rebar tier uses the tool for long periods of time,

tool mass

is a key usabilityaspect.

• Reliability is important.At one of the observed construction sites, a competing brand of tying tool(Drillfix

®

) was present. The six available tools were not in use, however,because several of them malfunctioned. The defects caused the rebar tiersto abandon those competing tools. Because it has a major influence onuser acceptance, reliability is a major concern for the new TyTecker tool.

• The tool should be easy to operate.Key manipulations with the tool should be easy to understand and perform.Refilling the tool should require the minimum number of steps. Adequategrip size and other design aspects allow the rebar tier to have a comfortablegrasp of the tool.

• Good after-sales service should be provided.This conclusion has no direct relation to the tool design, but it seems tobe just as important as instance reliability in terms of user acceptance. Afast, attentive, and effective repair service and after-sales department haveestablished a positive image of the TyTecker brand within the trade.

16.8 LITERATURE RESULTS CONCERNING STATIC AND DYNAMIC LOADING

The two main factors determining the on-site working conditions of rebar tiers areworking posture and the repetitive movements of the wrist and arm.

16.8.1 W

ORKING

P

OSTURE

The main physical loads affecting a steelfixer are of a static nature. Rebar tyingrequires significant bending of the lower back, reaching out in awkward positions,and (to a lesser extent) kneeling. Steelfixers are exposed to long periods of workingin one position (Fig. 16.1).

Several sources in the literature provide guidelines for the maximum allowablebending of the lower back. Generally, such extreme postures should be avoided (Duland Weerdmeester 2001). If bending is necessary, only slight bending of the backresults in significantly less risk of lower-back pain (Bongers et al. 2000). If workershave to bend their lower back for more than 5% of the working time (half an hourper day), they have a 50% higher risk of developing lower-back injuries (Bongerset al. 2000). Vink et al. (1994) suggest that a 20

°

flexion of the back should be allowedfor 20-minute periods at most. Flexions between 20 and 60

°

are acceptable only for

198


periods shorter than four minutes. It is clear from these sources that a working posturethat requires bending of the lower back should be avoided as much as possible. Ifnecessary, the flexion should be minimized, both in angle and duration. Even thoughthese results apply mainly to floor rebar tying, they are also of interest for cases oftying in the vertical plane, or on tilted rebar planes.

Apart from bending the lower back, steelfixers regularly have to stretch out tohard-to-reach tying spots, or kneel when the tying takes place closer to floor level.Twenty inches (0.5 m) is suggested by Dul and Weerdmeester (2001) as the radiusof the reach envelope in which the majority of manipulations take place. The Dutchlabor inspection authority emphasizes the individual nature of reach envelopes andadvises workers to perform tasks

close to the body

when forces must be exerted.No further specification on

close

is given, but the 0.5 m suggested by Dul andWeerdmeester can be taken as a reference.

Furthermore, dexterity is important when reach envelopes are concerned (thehuman lateral reach exceeds the medial reach).

16.8.2 R

EPETITIVE

M

OVEMENTS

A second problem in the steelfixing profession is posed by the repetitive movementsof arm and wrist necessary to make a tie. Rebar tying requires a combination of precisionand force exertion. It is, therefore, a job with a high risk of repetitive strain injuries(RSI). From the field observations, the average time needed to make one connectionwas 3.8 seconds (Table 16.1). This is a repetitive movement, especially considering thefact that ten or more consecutive ties are made regularly. Because the time needed tomake one connection is mainly determined by outside pressure (deadlines and super-visors), an improvement is not likely to relieve the

repetitiveness

of the work.The second factor, posture during the tying movement, certainly offers room for

improvement. The competing tying tool

Max Rebar Tier

replaces the combination ofpinching and twisting that is inherent in the current working method with positioningthe tool and pulling a trigger. These actions do not require a combination of force andprecision, nor do they rely on twisting the arm and wrist. TyTecker’s tool should followthis direction, because it ideally combines low-precision positioning with little forceexertion, plus a simple actuator, to make a rebar connection with the clip.

TABLE 16.1 Estimated Time Needed to Make a Tie

Number of ties Elapsed time (s) Time per tie

Observation 1 8 27Observation 2 5 27Observation 3 3 11Observation 4 6 23Observation 5 22 71Observation 6 13 55Total 57 214 3.8


199

16.8.3 E

RGONOMICS

G

UIDELINES

: W

RIST

AND

H

AND

Whereas the field observations yielded important real-life information, a number ofpublications in the human factors and design literature provided useful anthropo-metrical data for tools in general, and specifically for the TyTecker product. Theresults are described below.

• Balance, mass, and forcesTo ensure easy manipulation of the tool, it should be well balanced. Bal-ance here has two components: center of gravity and the working linesof forces. The center of gravity should be as close as possible to the cen-ter of the grasping hand. Ideally, the center of gravity also lies on theneutral axis of the lower arm (Radwin and Haney 1996; Woodson 1981).The mass of power tools is experienced as “just right” when it is in arange from 0.9 to 1.75 kg (9–17.5 N) (Radwin and Haney 1996). Themass should not exceed two kg, as benchmarked against competingproducts. Even though Eikhout and Koningsveld (2002) suggest four kgas the maximum weight of a power tool, this seems rather heavy com-pared to the mass of common battery-powered tools (average 2 kg). Theforces that act through the tool upon the hand and arm of the steelfixerwould ideally coincide with the working axis of the arm (Radwin andHaney 1996). If this is not possible, the force axis should be parallel tothe working axis of the forearm. Because of the low forces involved inTyTecker’s system, this is an acceptable alternative.

• Grip designSeveral guidelines concerning grip design have been found, covering thegrip’s angle, shape, and geometry. For the steelfixer to be able to holdthe tool with a neutral wrist position, the grip should be angled at 15

°

(Fig. 16.3).For a power grip Bullinger and Solf (1979) suggest a hexagonal or four-

sided design, with a cross-section that slightly increases toward the middleof the grip. These basic shapes suggest a preferred orientation for holdingthe tool and thus increase ease of operation. The corners of the grip shapeshould be rounded. The straight sides of the grip should follow the fingerdigits of a bent hand (Bullinger and Solf 1979). To make a sound decision

FIGURE 16.3

The grip angle for neutral wrist position between the underarm and the axisthrough the hand (Dreyfuss 1960).

200


on the target values for the length and cross-section of the grip, severalsources of anthropometrical data were compared (Table 16.2).

• Comfortable wrist anglesBecause of the various steelfixing situations, the worker will in some caseshave to operate the tool with an angled wrist. To determine which deviationsand angles are acceptable during product use, six sources were comparedand evaluated (Table 16.3).

TABLE 16.2 Anthropometrical Data for the Grip Derived from Five Sources

Grip length

Dreyfuss

Molenbroek & Dirken

Garner

p2.5 p50 p97.5 p5 p50 p95 p5 p50 p95

width of hand (+ thumb) 94 104.1 114.3 102.8 111 119.3width of hand (

−

thumb) 91.3 88.9 96.5 80 90 95…bent 92.7 101.4 110

Grip diameter

Dreyfuss

Bullinger & Solf

Fraser

p2.5 p50 p97.5 p5 p50 p95

Diameter 40.6 45.7 53.3 40–50*at the end 18 22 28in the middle 28 32 38

Switch

Molenbroek & Dirken

p5 p50 p95

pointing finger width 17.4 19 20.7

p = percentile; lengths in mm*diameter 50 mm, 5% less forceDerived from Bullinger and Solf (1979); Fraser (1980); Dreyfuss (1960); Garner (1992); and Molen-broek and Dirken (1986).

TABLE 16.3 Six Sources Used to Derive Comfortable Wrist Angles for the Tool Design

Ulnar deviation Radial deviation

Kapandji (1980) Maximum angles 15 45Dreyfuss (1982) p2.5/p50/p97.5 15/27/40 15/66/70Houy (1983) p5/p50/p95 22/30/40 14/22/30Landstra (2000) Estimates 20 30Lange* Maximum angles 20 30Lange* Comfortable angles 0 0 Drawn steelfixer tool angles 10 20

*Both mentioned in Buurman (1996).


201

• Left-hand and right-hand useThe design of the tool should facilitate both left-handed and right-handedworkers, because a significant portion of the target workforce is left-handed.To achieve this versatility, the tool can be designed to be symmetrical in thevertical plane (Bauer and Schmauder 1995). This way, balance, workingaxis, and operation are identical for left- and right-handers.

• Product switchesTo determine the minimum size of the switches to be used in the tool, thewidth of the index finger (as suggested by the Dutch DINED tables) is tak-en and increased to accommodate for gloves (Molenbroek and Dirken1986). The exact values are presented in the last row of Table 16.2. On topof the previously mentioned aspects of the tool’s design, several other in-fluences that were mentioned in the literature should be taken into account:product noise and vibration, dust, weather, and temperature.

16.9 SYNTHESIS AND EVALUATION

Results from the observations, the interviews, and the literature were the input forthe design process. In a systematic series of idea generations and evaluation, thefixing tool evolved from spatial configuration to a product design, including detailson materials, color, and mechanical components. This iterative process can bedescribed along with the resulting design, using photographs of the detailed modelto discuss the features of the tool. An evaluation of the design, including an on-siteusability test, concludes this section.

16.9.1 P

OSTURE

, C

ONFIGURATION

,

AND

B

ALANCE

The process can be divided into four main stages, in which the three essential designaspects — working posture, spatial configuration, and tool balance — were covered.The first stage identified the functional components, which together form the actualtying tool. Using mock-ups of these components, many configurations were gener-ated and finally clustered into four typological categories.

These four basic configurations (Fig. 16.4) were then evaluated using a subsetof the ergonomic guidelines, which resulted in two promising basic configurations:a

pistol

grip

type and a

grip-on-top

type (parts (A) and (B) of Fig. 16.4, respectively).These configurations were taken as the starting point for an analysis of the centerof gravity with respect to the grasping hand. This product aspect is highly important,because it determines the ease of manipulation of the tool. Using mass measurementsof the components of similar products, resulting torques exerted on the graspinghand center were calculated for several solutions. The solution with optimum balancewas selected for both basic configurations.

With the layout for both configurations clearly determined, focus shifted to theease-of-use of the tool during the third stage of the development. Special attentionwas paid to the process of (re)filling the tool with tying clips, a key aspect in theusability of the tool and thus essential for its success. The design of the battery packand the controls, and the overall styling, were also explored. The resulting two draft

202


designs were evaluated on the criteria from the program of specifications and werestudied in computer simulation.

The working postures during operation were evaluated using the AnthropometricDesign Assessment Program System (ADAPS) (Fig. 16.5), a mannequin-based

FIGURE 16.4

Mock-ups of four typological categories composing the basic parts of the tool:the grip, the engine, the battery, and the refill compartment. The refill compartment is thetube, the grip is in (

D

) shown between the refill compartment and the battery.

FIGURE 16.5

Two sample images of working postures with the new tool, made with ADAPS.


203

computer simulation tool developed by the Faculty of Industrial Design Engineer-ing (Ruiter 1996). The evaluation and posture analysis showed the

pistol grip

concept to be a better alternative than the

grip-on-top

concept. Postures with thepistol grip configuration were more in keeping with the ergonomic guidelinesreferred to earlier.

16.10 DESIGN PROPOSAL

In Fig. 16.6 the final proposal is presented. The main characteristics of the designare discussed below (the numbers correspond with those in Fig. 16.6).

1. Adjustable tying headThe head of the tool can be adjusted (in two positions) to suit tying workfrom ground level to above eye-level.

2. Main body shellsThe main part of the tool consists of two injection-molded polymer shellsthat hold all other parts. The grip is designed according to the ergonomicguidelines described earlier.

3. Sliding refill doorFor easy access to refill the tying tool, the upper (silver) part of the tool slidesback, revealing the internal clip holder where new clips can be inserted.

4. Reversible battery packThe battery pack can be mounted on the tool in two orientations: facingforward or facing backward. This way, the tool can be adapted to specificsituations (e.g., confined spaces).

FIGURE 16.6

Photographs of the model of the design (see text for an explanation of thenumbers in the left photograph). Right a backward-side ward view, left a front-side view ofthe steel-fixing tool showing the tying head.

204


5. Operating switchThe switch used is a dedicated design, based on a standard off-the-shelfmodel. To accommodate the drive system, the switch has to be smaller insize than the standard model.

6. Wrist or security cordTo allow the steelfixer to suspend the tool when not in use, a cord is provid-ed. Apart from this function, the cord also communicates the brand image.

16.11 DETAILED MODEL

As shown in Fig. 16.6, a detailed, true-to-scale model was made. Using the proto-typing facilities at the Faculty of Industrial Design Engineering, the model was hand-built in a six-week period with wood, metals, polystyrene sheet, and several otherplastics. The model has a functional tying head and sliding door, because the aimwas to test the usability of these two main aspects.

16.11.1 U

SABILITY

T

ESTS

WITH

THE

M

ODEL

The model was tested by professionals in rebar tying during a small-scale usabilitysession. Because the test took place on an actual construction site, time and accom-modations were limited. The modest setting, unobtrusive video equipment, andmainly open-ended questions made a more natural setting. Seven rebar tiers partic-ipated, and five of these steelfixers were specifically interviewed on the refillingprocess. Three workers performed common tasks, such as positioning or adjustingthe head. The results of the test are summarized in Table 16.4.

Although the user test was simple, some very useful insights were achieved:

• Positioning is easy.None of the steelfixers had a real problem with the positioning of the toolon a rebar. Two positioned the head correctly without any help. One sub-ject discovered later how the positioning can be improved, after a closerlook at the tying head. Another subject discovered the purpose of the in-dentation on the battery pack without specific clarification.

• It is not clear how to adjust the tying head. No worker understands immediately the way the adjustable head works. Theicons designed to clarify the position of the head only seem to increase con-fusion. Clearly, this part needs additional development and design.

TABLE 16.4 Results of the Usability Test in Tabular Foam

Task n 1 attempt >1 attempts Result

Positioning 3 2 1 +Adjusting head 3 0 0

−

Refilling sliding open 5 5 n/a ++Refilling filling clips 3 0 2 +/

−


205

• Refilling: Opening the sliding door is easy. The first step in refilling the tool poses no problem to the tiers. They all rec-ognize the way the door opens and act accordingly.

• Refilling: Placing the clips is more difficult. The second step appears to be less easy to understand, but after a while, oneof the rebar tiers gets the idea and starts to explain it to the others. The clipsrequire a specific orientation when refilling the tool, which is not obvious. Itis necessary to clarify the orientation in the design of the clip holder.

16.12 CONCLUSIONS AND RECOMMENDATIONS

This is a good example of how it is possible to design a comfortable hand tool. Theattention to comfort has many consequences for the process. Apart from the stronguser orientation and user tests, ergonomics knowledge is used in connection withweight, balance, whole-body postures, grip requirements, and anthropometrics. Also,emphasis on how the tool should be used (refilling, view of the work, the disadvan-tages of older models) is taken into account.

REFERENCES

Bauer, W. and Schmauder, M. (1995) “Lefthanders and product design.” In

Proceedings ofthe IEA World Conference 1995

, Rio de Janeiro: Associação Brasileira e Ergonomia,536–539.

Bongers, P.M., Hoogendoorn, L. and Heuvel, S. van den (2000)

Risk Factors for Lower BackInjuries: Results of a Longitudinal Study

, Den Haag: Elsevier bedrijfsinformatie (inDutch).

Broersen, J.P.J., Weel, A.N.H. and Dijk, F.J.H. van (1991)

Reference Guide to OccupationalHealth, Presented per Profession

,

part 2, Amsterdam: NIA (in Dutch).Bullinger, H.-J. and Solf, J.J. (1979)

Ergonomische Arbeitsmittelgestaltung I — Systematik

,Dortmund: Bundesanstalt für Arbeitsschutz und Unfallforschung.

Buurman, R. den (1996)

Design Ergonomics

, Delft: Delft University of Technology (in Dutch).CBS Statline, sector data in construction industry (SBI ’93:45a) and rebar tying (SBI ’93:

94–99), www.cbs.nl May 2002.Cook, T. et al. (1996)

Characteristics of Injuries and Illnesses Resulting in Absences fromWork, 1994

, Washington, D.C.: Bureau of Labor Statistics, U.S. Department of Labor.Dreyfuss, H. (1960)

The Measure of Man

, New York: Whitney.Dul, J. and Weerdmeester, B.A. (2001)

Ergonomics for Beginners

, London: Taylor & Francis.Eikhout, S.M. and Koningsveld, E.A.P (2002) “Designing hand tools.” In P. Voskamp, P.A.M.

van Scheijndel and K.J. Peereboom, eds.,

Handboek Ergonomie 2002

, Alphen aanden Rijn: Kluwer, 337–345.

Fransson, C. and Kilbom, Å. (1991) “Tools and hand function: The sensitivity of the hand toexternal surface pressure.” In Y. Quéinnec and F. Daniellou, eds.,

Designing forEveryone: Proceedings of the 11th Congress of the International Ergonomics Asso-ciation

,

London: Taylor & Francis, 188–190.Fraser, T.M. (1980) “Ergonomic principles in the design of hand tools.”

Occupational Safetyand Health Series No. 44

. Geneva: International Labour Office.Garner, S. (1992)

Design Topics: Human Factors

, Oxford: Oxford University Press.

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Houy, D.R. (1983) “Range of joint motion in college males.”

Proceedings of the Conferenceof the Human Factors Society ’83

, 1: 374–378.Jong, A.M. de (2002)

Improvement of Working Conditions at the Construction Site

, Delft:University of Technology (Ph.D. thesis, in Dutch).

Kapandji, I.A. (1980)

Biomechanics of the Human Body

:

Part I, The Upper Extremities

,Utrecht: Bohn, Scheltema & Holkema (in Dutch).

Koningsveld, E.A.P. (2002)

Rebar Tying, Ergonomic Aspects

, Hoofddorp: TNO Work andEmployment (confidential).

Landstra, R. (2000)

Operator Comfort in Forklift Truck Design

, Delft: Delft University ofTechnology.

Leopard, D. and Rayport, J.F. (1997) “Spark innovation through empathic design.”

HarvardBusiness Review

, Nov./Dec.: 102–113.Marinissen, A.H. (1993) “Information on product use in the design process.” In

Ergonomicsin a Changing World: Proceedings of the 29th Annual Conference of the ErgonomicsSociety of Australia

, Canberra: Ergonomics Society of Australia, 78–85.Molenbroek, J.F.M. and Dirken, J.M. (1986)

Dutch Body Measurements for Design, DINED-table

(3rd version), Delft: University of Technology, Faculty of Industrial DesignEngineering (in Dutch).

Ploeger, A. (2000)

Work Related Disabilities in the Construction Industry

, Amsterdam: EIB(in Dutch).

Radwin, R.G. and Haney, J.T. (1996)

An Ergonomics Guide to Hand Tools

, Fairfax: AmericanIndustrial Hygiene Association.

Roozenburg, N.F.M. and Eekels, J. (1991)

Product Development: Structure and Methodology

,Utrecht: Lemma (in Dutch).

Ruiter, I.A. and Vaart, A.J.M. van der (1996) “Use of the ADAPS computer man-model byexpert and novice users—A pilot study.” In S.A. Robertson, ed.,

ContemporaryErgonomics 1996. Proceedings of the Annual Conference of the Ergonomics Society,

London: Taylor & Francis, 136–141.Smallwood, J.J. (1997) “Ergonomics in construction.” In

Proceedings of the 13th TriennialCongress of the IEA

,

Tampere, Finland: 184–187.Vink, P. and Dul, J., eds. (1994)

Physical Strain during Labor. Legislation and Solutions

.(Lichamelijke belasting tijdens arbeid. Wetgeving en oplossingen), Zeist: TNO/Uitgeverij Kerckebosch, 161.

Wakula, J., Wimmel, F., Linke-Kaiser, G., Hoffmann, G. and Kaiser, R. (1997) “Ergonomicanalysis of load on the back in concrete work.”

Proceedings of the 13th TriennialCongress of the IEA

, Tampere, Finland: 191–193.Woodson, W.E. (1981) Human Factors Design Handbook, New York: McGraw-Hill.

207

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

17

Comfort Effects of Participatory Design of Screwdrivers

S.M. Eikhout, P. Vink, and M.P. van der Grinten

CONTENTS

17.1 Introduction ................................................................................................20717.2 Method........................................................................................................209

17.2.1 Health and Discomfort Measurements........................................21117.2.2 Productivity Measurements .........................................................21217.2.3 End-User Opinion........................................................................21217.2.4 Statistics .......................................................................................212

17.3 Results ........................................................................................................21217.3.1 Health and Discomfort ................................................................21317.3.2 Productivity ..................................................................................21317.3.3 End-User Opinion........................................................................213

17.4 Discussion ..................................................................................................21317.4.1 Health ...........................................................................................21417.4.2 Productivity ..................................................................................21517.4.3 Comfort ........................................................................................21517.4.4 General Observations...................................................................215

17.5 Conclusions ................................................................................................216Acknowledgment ...................................................................................................216References..............................................................................................................216

17.1 INTRODUCTION

The requirements put on companies that make hand tools have increased consider-ably. Nowadays, products should have a specific added value, should be focused onindividual needs, should be safe and user friendly, and should even have a wow!effect. One way to develop unique products is to have them be highly comfortablein use. Ergonomics especially could be of great value in tuning products to the needsof users (Vink and Koningsveld 2000).

For companies making hand tools, user discomfort and the need for ergonomicallydesigned hand tools present an opportunity. The use of hand tools (such as screwdrivers)

208


could cause discomfort during work. These feelings of discomfort can reduce theefficiency and job satisfaction of workers (Fellows and Freivalds 1991). Accordingto Chao, et al. (2000), the use of hand tools can also cause musculoskeletal disorders.In industries such as poultry processing and automobile upholstering, where handtools are used extensively, upper-extremity disorders are much greater than theaverage (McGorry 2001).

There is a need, therefore, for better hand tools that reduce discomfort. Interviewsamong 16 successful small- and medium-sized enterprises making professionalproducts (products used in work) that were nominated for the 1997 European DesignPrize (Thackara 1997) showed that these enterprises invest in ergonomics (Table 17.1).Approximately 16% of their total R&D budget was dedicated to ergonomics.

However, there is a question as to whether these kinds of investments pay offand contribute to health, productivity, and comfort improvement. The hypothesis ofthis study is that investment in ergonomics has no effect on health, productivity, andcomfort when using a hand tool.

TABLE 17.1 Attention to Ergonomics in the R&D Budget for the Product Design Process of 16 EU Companies Developing and Producing Products

Main productNumber of employees Country

% R&D for ergonomics Ergonomics research

Headphones 450 Austria 10 Acoustics, anthropometrics of the ear

Prostheses 300 UK 10 Microprocessor tests, shape measurement of the human body

Demolition equipment 45 Sweden 30 User tests, control logisticsKitchen furniture 480 Germany 5 Anthropometrics, user testsGardening tools 4000 Finland 15 Balance, user testsCommunication for control rooms

350 Austria 2 User interface tests

Welding helmets 150 Sweden 10 Airco, visibility, anthropometrics

Hand tools 200 Sweden 50 Contact, user testsWheel loaders 3000 UK 10 Cabin ergonomics, entry testsBackpacks 1300 France 50 Wearing testsBrain scan helmets 25 Finland 2 Head anthropometrics,

usability testsPalmtop computers >1000 UK 10 Hardware and interface testsAccess control systems 300 Austria 6 Keyboard design, user testsSeats 230 Norway 35 Seat and design researchSpectators 445 Austria 5 Balance, handle, user testsElectronic payment systems

220 Ireland 10 Keyboard design, information logistics

From Polling (1999).


209

To test this hypothesis, an ergonomically designed product (a Bahco screwdriverset) was compared with another screwdriver set that is also well known in theprofessional market, has a comparable price, and was not ergonomically designed.In this case,

ergonomically designed

means that an 11-step program (Bobjer andJansson 1997) was followed. In this program it is essential that operators are inten-sively involved. The 11-step program may be summarized as follows:

After a preliminary specification is made by interviewing and observing users(step 1), a market analysis (step 2) is conducted. In step 3, background informationis collected from papers, textbooks, and reports, followed by the design of a firstprototype (step 4). Then professionals are exposed to the experimental prototypes(step 5) and improvements are defined in interviews based on research (step 6).Another user test (step 7) is undertaken by a wider selection of users in severalcountries. In step 8, the final design recommendations are made, followed by productspecification (step 9). In step 10 another user test is performed to prove that the toolworks, and the product is launched. In step 11, more scientific tests are performedto gather data for further improvement of the product.

The

control

set of screwdrivers did not follow this 11-step program. There are someimportant differences between the ergonomical screwdriver and the control. Forinstance, the ergonomical screwdriver grip is made of a special material that immedi-ately matches the temperature of the user’s hand, and it has a high friction coefficientrelative to other screwdrivers. The diameter is larger at the handle end to support forcefuluse, but in the area close to the metal it has a smaller diameter to enable precision tasks(Fig. 17.1). The ergonomical set is also color-coded. Every type of screwdriver in theset (Phillips-head, slotted-head, etc.) has a different color (Fig. 17.2).

17.2 METHOD

As discussed by Arisz and Kanis (1999), under strict conditions and for comparisonwithin a subject it is better to study fewer subjects thoroughly than a large numberunder varying conditions. To test the hypothesis, eight subjects used both sets ofscrewdrivers (the ergonomical set and the control set) on a standardized task. Sub-jects were not familiar with either screwdriver set and were not informed about thebackground. The subjects (average age 20 years) were students in their last year ofautomotive maintenance study. Manually operated (nonpowered) screwdrivers arestill often seen in this sector. All subjects had at least 3 years of experience workingintensively with hand tools, including nonpowered screwdrivers.

FIGURE 17.1

One of the ergonomically designed screwdrivers. In the area close to the metalit has a smaller diameter to enable precision tasks.

210


Health and discomfort, productivity, and end-user opinion were evaluated duringand after a standardized task (Fig. 17.3) and compared within one subject. Thestandard task was screwing 24 screws into a wooden object. The screws were ofdifferent types and sizes (Phillips-head screws of 3.5 mm and 4.5 mm and slot-ted-head screws of 4.0 mm and 5.0 mm) and had to be fastened into drilled holes(2.5 mm diameter, 30 mm deep) in a wooden object. This object had exactly thesame dimensions in all situations. Twelve screws had to be screwed in forward(screw horizontal) and twelve downward (screw vertical), all in front of the body atelbow height, while the subjects were seated in a prescribed way on a fixed seat.The screwdrivers were positioned in a box on a low table to the left of the subject.The subjects had to replace the screwdrivers in the box after using each screwdriver.Four subjects started with the set of four ergonomical screwdrivers and used thecontrol set of four screwdrivers later. The other four subjects began with the controlset, followed by the ergonomical set.

FIGURE 17.2

The ergonomically designed screwdriver set.

FIGURE 17.3

A picture of the situation during the test.


211

17.2.1 H

EALTH

AND

D

ISCOMFORT

M

EASUREMENTS

For every subject the test started by experiencing the local perceived discomfort(LPD) scale. Subjects were asked to rate their postural discomfort in one of theregions (Fig. 17.4) shown on a diagram of the rear view of the arm, using a scaleranging from 1 (no discomfort) to 5 (extreme discomfort) modified after Corlett andBishop (1976) and Borg (1982).

First, the subjects learned the LPD scale. For every region they had to rate theirexperienced discomfort every 30 seconds by holding a 5 kg weight with armshorizontal anterior to the body until they were unable to hold the weight.

After a rest period the test started, but before each test an LPD form wascompleted (pretest). The form was also completed four times during the test. Thesubjects were asked to fasten six screws as fast as possible, followed by completionof the LPD form and a break of 1 minute. The pretest value was subtracted fromthe other four measurement values and the result was taken as the LPD value. Thesame procedure was performed using the other screwdriver after a break of45 minutes.

In addition to LPD, postures were recorded by making lateral photographs witha camera from a fixed location. After the test, the subjects’ hands were evaluatedfor redness and blisters, and questions were asked about experienced friction, pres-sure points, and feelings of cramp.

Before all tests the moment was measured by a special device. Subjects had toput the screwdrivers into the device and were asked to exert maximum force on a

FIGURE 17.4

The drawing used to evaluate local postural discomfort. Four times during thetest the subjects had to report their discomfort in the different regions A through P, using ascale from 0 to 5 (0 = no problems at all; 1 = very little discomfort; 2 = some discomfort; 3 =much discomfort; 4 = a lot of discomfort; 5 = maximal discomfort).

212


placebo screw

mounted on a force measurement device. The same measurement wasrepeated for the other set of screwdrivers.

17.2.2 P

RODUCTIVITY

M

EASUREMENTS

Productivity was recorded by measuring the time it took to fasten the 24 screws.Quality was measured by counting the number of incompletely fastened screws orscrews that were not screwed straight into the drilled hole.

17.2.3 E

ND-

U

SER

O

PINION

After all experiments were done, the subjects completed a questionnaire on health,perceived productivity, quality, and the characteristics of the screwdriver sets.

17.2.4 S

TATISTICS

When possible, all of the differences previously discussed were tested with the t-test for paired comparison (p < 0.05).

17.3 RESULTS

An overview of the differences between the two sets of screwdrivers is shown inTable 17.2.

TABLE 17.2 Results on Differences between Both Screwdrivers

Ergonomical set Control

LPD in % of the maximal difference between last measurement and pretest, averaged over 8 subjects

• total• hand• lower arm

Productivity• average duration of the task (sec.)• number of wrong screws

Maximal force in % of the reference (averaged over 8 subjects)

Experience of users:• experienced comfort• yes, I would choose this screwdriver• average score (1 = worse, 10 = superb)

55% (sd = 23)30% (sd = 16)

*

31% (sd = 22)

829 (sd = 88)

*

6

140% (sd = 11)

*

8 yes

*

7 yes

*

7.6 (sd = 1.0)

*

61%(sd = 25)45%(sd = 21)18%(sd = 22)

983 (sd = 177)33

reference

0 yes1 yes

6.3 (sd = 1.2)

*

significant difference (t-test for paired comparison, p < 0.05).


213

17.3.1 H

EALTH

AND

D

ISCOMFORT

The differences in discomfort appeared to be very small. The differences were shownbest by subtracting the first of the four LPD measurements from the last LPDmeasurement. The total score (the sum of all regions) was lower for the ergonomicalscrewdrivers, but not significant. Also, in the lower-arm region the differences werenot significant. In the hand, the local experienced discomfort was significantly lowerworking with the ergonomical set.

Inspection of the hands showed differences between both sets. After workingwith the control set, three subjects were found to have blisters that were not observedafter working with the ergonomical set. Four subjects reported that they expectedto have blisters after working with the control set.

All subjects had problems with the high level of friction during the test, bothfor the ergonomical as well as for the control set. Four subjects complained aboutpressure on the ball of the thumb while working with the control set, and two subjectscomplained about this pressure with both sets. Working with the control set, twosubjects experienced feelings of cramp, whereas no one experienced this workingwith the ergonomical set. Also, two subjects experienced irritating friction with thecontrol set, but no one experienced this with the ergonomical set.

The average maximum force with the ergonomical screwdrivers was 40% higherthan the force that was measured with the control screwdriver. This could be causedby the fact that the diameter averaged over the four grips was 1.18 times larger withthe ergonomical screwdriver compared to the control. However, if we correct forthis difference in diameter the average maximum force is still 34% higher.

17.3.2 P

RODUCTIVITY

The average screw time was significantly lower with the ergonomical set than withthe control set. The reduction in screwing time was 16%, and the number of errorswas also lower. Working with the control set resulted in thirty-three sloping screwsor partly fixed screws, whereas using the ergonomical set resulted in only six errors(Table 17.2).

17.3.3 E

ND-

U

SER

O

PINION

The users’ preferences are presented in Table 17.3. Most of the users prefer theergonomical set in regard to faster work, force exertion, balance, and grip on thehandle and screw. The experienced comfort rating is better for the ergonomical set,as well as the average score (Table 17.2). After this research, one subject chose thecontrol. His motivation was that the same brand of hand tool is used often in his sector.

17.4 DISCUSSION

If we assume that the parameters of this study are good indicators for health,productivity, and comfort, the hypothesis that investment in ergonomics has no effecton health, productivity, and comfort in using a hand tool is falsified. In this section

214


the effects on health, productivity, and comfort are discussed per subject, followedby general remarks.

17.4.1 H

EALTH

The indicators for health are local experienced discomfort and blisters. Previousstudies (Grinten 1991) demonstrated that the variables constructed provide reliableresults for comparison of conditions, such as in this study. Furthermore, for groupsof subjects, reasonably linear relationships were found between load in the bodyand discomfort in a body region (Boussena et al. 1982), as well as between discom-fort and holding time (Manenica 1986). Also, increased heart rates are observedwith high discomfort values (Bystrom 1991).

This strengthens our assumption that LPD is related to health. The LPD in thehand is lower with the ergonomical set, which could therefore be more healthful touse. The combination of pressure and local friction, which stretches the skin threeto seven milimeters and also chafes the skin (Hall 1995; Bullinger and Solf 1979),is hazardous for the skin because it could result in blisters. The ergonomical setprobably has lower values for pressure, friction, and chafing, which reduces thechance of blisters. The force level needed to insert the screw is lower with theergonomical set, partly because of the diameter of the handle, partly because of abetter fit in the hand, and partly because of the material used to make the screwdriver.This is in alignment with the fact that the chance of blisters is lower with theergonomical set.

However, some care should be taken regarding the conclusion that the ergonom-ical set is more healthful. First, for both screwdriver sets the experienced friction ishigh; second, a reduction in discomfort is shown in the hand region, but there is noreduction seen in total discomfort. Also, the test situation was tougher than actualworking situations in order to increase the chance of showing differences. It couldtake a long time for these differences to be found in a real work environment, alsoin part because pneumatic or electric tools could be used for some screwdrivingtasks. Furthermore, only short-term health effects are studied in this experiment,although long-term effects should be studied as well.

Generalizing the results should also be done with care, because only eight youngmale subjects accustomed to screwdriving were studied. The effects on older persons

TABLE 17.3 Preferences Given after the Test by the Eight End Users, Regarding the Topics Described in the Left Column

Preference for Ergonomical set No difference Control

• faster working• force exertion• good grip on handle• good grip on the screw• good grip with oil on the grip

66755

22133

00000


215

or persons not used to screwdriving could be larger. Nevertheless, objective as wellas subjective data indicate all trend in the same direction, which allows a conclusion(as this study indicates) that the ergonomical set is better from a health point of view.

17.4.2 P

RODUCTIVITY

Objective as well as subjective data indicate a productivity increase with the newergonomical set. In other words, the time needed to complete a specific screwingtask is reduced using the ergonomical set. Also, the users found that the ergonomicalset works faster. Not only is the task performed faster, but the quality is also better(fewer errors), which means that less repair time is required. It is to be expectedthat under real working conditions this productivity increase of 16% would also befound. That value will probably be lower because the intensive screwdriving per-formed in the test will rarely be found during real work, but in reality errors shouldbe repaired quickly as well.

17.4.3 C

OMFORT

According to Helander and Zhang (1997),

discomfort

and

comfort

are differententities. Discomfort is more related to physical exposures, and comfort is moreinfluenced by other factors such history and emotions. Comfort is very subjective,and the best way to measure comfort is by questioning.

Parameters influencing comfort positively — such as faster work, lower forceexertion, and a better grip on the handle and screw — are evaluated positively. Basedon these data, it could be assumed that all subjects would buy the ergonomical set,after the test one subject still favors the control set. This shows how many factorsinfluence a person’s preference.

17.4.4 G

ENERAL

O

BSERVATIONS

As discussed earlier, extrapolation of these results to real working situations isdifficult, because the test conditions were extreme and the subjects were a selectgroup. However, standardizing the test conditions and increasing the loading on thehuman body was needed in order to ensure that differences were found. It is plausiblethat in the long run some of the effects found in this study would still be seen underreal working conditions.

Of course this study could not demonstrate that the specific 11-step ergonomicaldesign program mentioned in Section 17.1 caused the better performance of theergonomical set. The important parts of the development process cannot be showneither. Therefore, this study only indicates that finding some way to emphasize ergo-nomics and the participation of end users is important to improve health, productivity,and comfort of workers using the end product. Ergonomics is important because thisdiscipline focuses on adapting products to the behavior of humans using them. Userparticipation is needed in product development because users are the only ones whocan evaluate comfort during normal use of a product. To anticipate on that user parti-cipation is the only possibility.

216


17.5 CONCLUSIONS

Investments in ergonomics and user participation in product design can result inmore healthful, productive, and comfortable products. In this chapter the effects canbe shown objectively using an ergonomically designed screwdriver in a specific testsituation, with specific subjects. However, health and comfort are very difficult tostudy objectively. In this study, only the effects on specific aspects of health (dis-comfort in the hand and blisters) could be shown. Long-term health effects shouldbe studied further.

The effects on several aspects influencing increase in comfort are also shown,but the comfort aspects studied are probably not strong enough to affect sales of theproduct. The importance of gaining more knowledge regarding comfort and handtools is emphasized.

ACKNOWLEDGMENT

The authors would like to thank Bahco Tools BV for providing the hand tools usedin this study.

REFERENCES

Arisz, H. and Kanis, H. (1999) “Towards concurrent monitoring of the number of subjectsin user trials.” In M.A. Hanson, E.J. Lovesey and S.A. Robertson, eds.,

ContemporaryErgonomics,

50th Annual Conference of the Ergonomics Society

, London: Taylor &Francis, 417–421.

Bobjer, O. and Jansson, C. (1997) “A research approach to the design of ergonomic hand tools.The 11-point programme.” P. Seppälä, T. Luopajärvi, C.H. Nygård and M. Mattila, eds.,

From Experience to Innovation. Proceedings of the 13th Triennial Congress

of theInternational Ergonomics Association

, Helsinki: Finnish Institute of OccupationalHealth, Vol. 2, 193–195.

Borg, G. (1982) “Psychophysical bases of perceived exertion.”

Medicine and Science in Sportsand Exercise

, 14(5): 377–381.Boussena, M., Corlett, E.N. and Pheasant, S.T. (1982). “The relation between discomfort and

postural loading at the joints.”

Ergonomics,

25: 315–322.Bullinger, H.J. and Solf, J.J. (1997)

Ergonomische Arbeitsgestaltung II Hand gefurthewerkzeuge Fallstudien

, Dortmund: BAU (Forschungsbericht nr 197).Byström, S. (1991)

Physiological Response and Acceptability of Isometric Handgrip

Con-tractions

, Solna: Arbetsmiljöinstitutet (Arbete och Hälsa).Chao, A., Kumar, A.J., Emery, C.T.N.D., Nagarajarao, K. and You, H. (2000) “An ergonomic

evaluation of cleco pliers.” In

Proceedings of the 14th Triennial Congress of

theInternational Ergonomics Association

, San Diego: 4-601 (on CD-ROM).Corlett, E.N. and Bishop, R.N. (1976) “A technique for assessing postural discomfort.”

Ergonomics

, 19: 175–182.Fellows, G.L. and Freivalds, A. (1991) “Ergonomics evaluation of a foam rubber grip for tool

handles.”

Applied Ergonomics

, 22(4): 225–230.Grinten, M.P. van der (1991) “Test-retest reliability of a practical method for measuring body

part discomfort.” In S. Kumar, ed.,

Advances in Industrial Ergonomics and Safety

IV: 311–318.


217

Hall, C. (1995)

Hand Function with Special Regard to Work with Tools

, Stockholm: NIOH(Arbete Och Hälsa 4).

Helander, M.G. and Zhang, L. (1997) “Field studies of comfort and discomfort in sitting.”

Ergonomics

, 40: 895–915.Manenica, I. (1986) “A technique for postural load assessment.” In E.N. Corlett, I. Mananica,

and J.R. Wilson, eds.,

The Ergonomics of Working Postures

, London: Taylor & Francis,270–277.

McGorry, M. (2001) “A system for the measurement of grip forces and applied momentsduring hand tool use.”

Applied Ergonomics

, 32: 271–279.Mital, A. (1991) “Hand tools: Injuries, illness, design and usage.” In A. Mital and W. Karwowski,

eds.,

Workspace, Equipment and Tool Design

, Amsterdam: Elsevier, 219–256.Polling, D. (1999)

Ergonomics in the Product Design Process

, Hoofddorp: TNO (in Dutch).Thackara, J. (1997)

Winners! How Today’s Successful Companies Innovate by

Design

,Amsterdam: BIS.

Vink, P. and Koningsveld, E.A.P. (2000) “Impressions of the IEA2000 congress.”

NederlandTijdschrift voor Ergonomie

, 25(50): 146–148 (in Dutch).

219

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18

Comfortable Manual Bag Sealing

M.D. Hagedoorn-de Groot, T. Bosch, S.M. Eikhout, and P. Vink

CONTENTS

18.1 Manual Bag Sealing...................................................................................21918.2 Development...............................................................................................22018.3 User Research.............................................................................................22018.4 Methods ......................................................................................................22018.5 Results ........................................................................................................223

18.5.1 Sealing by Shop Assistants..........................................................22318.5.2 Opening by Consumers ...............................................................22318.5.3 Safety ...........................................................................................22518.5.4 Overall Score ...............................................................................225


18.1 MANUAL BAG SEALING

Customers continually expect faster, more efficient, and more thorough service atsupermarkets (Carrasco et al. 1995), but also in other shops where bags are sealed.Manual bag sealing is often used in shops where products are sold that have to beprotected for hygienic reasons (meat or bread) or to bundle several smaller products(candy). A variety of seals are used to close these bags. Shop assistants use seals mainlyto close the plastic bags which the consumer opens at home and often seals again.

For shop assistants, sealing the bags is a repetitive, physically demanding actionthat takes some time and could cause discomfort because of the physical load incombination with the time pressure. Several studies show the negative effects of highlyfrequent movements in combination with force exerted in poor working postures(Bongers, 2003; Macfarlane et al. 2000). Opening and closing the bags again can causesome discomfort or annoyance for consumers also, in the event they cannot open thebag or when the seal is not closing the bag well enough. This activity can create asafety hazard as well because children could swallow the sealing devices.

220


18.2 DEVELOPMENT

Several systems are available for sealing plastic bags, but both consumers and shopassistants mention that most of them have disadvantages. Some could be hazardous,for example, if children swallow the bag sealing devices. Some are made withadhesive tape, which could be difficult to open, and some take a lot of time to wraparound the plastic bag.

Knowing these potential shortcomings, Twin Seal developed a new system ofsealing. Various ideas and prototypes resulted in a system with an adhesive tape thathas a piece of paper at each end to keep them from sticking together. The idea isthat shop assistants could save time, because a special machine fastens the seals.Consumers could experience more comfort in easily opening the bag, and it shouldbe safer because it is more difficult for children to swallow it.

18.3 USER RESEARCH

An evaluation was set up to study whether the assumed improvements are alsoexperienced by end users. A comparative test of the discomfort, safety, and effi-ciency of four different types of plastic bag seals was performed. This test wasperformed by both shop assistants (for sealing) and consumers (for opening andsealing again). The tested seals are a) a paper- or plastic-covered iron wire; b) ametal clip; c) standard adhesive tape; and d) the new adhesive tape with a piece ofpaper at each end (Fig. 18.1). Systems (c) and (d) are always used in combinationwith a tape machine (Fig. 18.2), so, these two sealing devices are tested using thetape machines.

The research questions are

1. Which system do shop assistants prefer?2. Which system do consumers prefer?3. How do the different kinds of systems score on safety?4. What is the final evaluation?

18.4 METHODS

Twenty shop assistants (age 16 to 50 years old, average age 31.5 years), twenty-four consumers (age 8 to 85 years old, average age 40.3 years) and five experts onergonomics and safety participated in the study. The shop assistants evaluated thesealing of the bags, the consumers evaluated the opening and sealing, and theexperts evaluated the safety and also the user friendliness and physical load. Theshop assistants are employees of the bread and meat products department who haveto seal many bags daily.

Three groups of consumers were selected: eight youngsters (age 8 to 19 years,average age 13 years), eight adults (age 26 to 51 years, average 34.4 years) and eightseniors (age 57 to 85 years, average age 73.4 years). Every participant evaluated


221

the four sealing systems. To answer the four research questions, the study consistedof four activities:

1. During the sealing done by the shop assistants the sealing time wasmeasured while sealing five bags, one after the other. The time started themoment the first bag was picked up and ended when the fifth bag waslaid down. The average time for every seal was measured and tested witha t-test for paired comparison (p

<

0.05). Video recordings were made,and the experts evaluated these recordings. After using all systems, every

FIGURE 18.1

The four different seals compared in this test: (

A

) a paper- or plastic- covered iron wire; (

B

) a metal clip; (

C

) adhesive tape; and (

D

) the new adhesive tape with a piece of paper at the ends.

222


participant was asked to complete a questionnaire with questions aboutefficiency, safety, and the experienced comfort and discomfort.

2. The opening of the bags was tested by twenty-four consumers. The con-sumers were selected at sports fields (youngsters), among families andfriends (middle age), and in a residence for the elderly (seniors). Thesubjects were informed that TNO, an independent research organization,would like to know which of the four sealing systems is preferable. Afteropening five bags with each type of sealing system, every participant wasinterviewed with questions regarding discomfort, physical load, and userfriendliness. Some subjects were also recorded on tape, the recordings tobe used in the expert session.

The video recordings were used in the expert session for further analysis.The experts also sealed bags using the four systems. Their opinions on safety,physical load, and productivity were based on the video and their own expe-rience. The expert panel consisted of five members (two industrial designers,a movement scientist, an ergonomics expert, and a product safety expert).

3. The issue of safety was studied based on the observations and videorecordings, as well as in discussions by the expert panel. Also, additionalinformation was gathered by mind-mapping on what and who could befound in the neighborhood of the bag sealing products. In the question-naires for the consumers and shop assistants, the subjects had to give asafety rating for each system.

4. For the food industry, a total evaluation could help to show which systemis best. Therefore, all consumers and shop assistants were asked whichelement is most important: safety, user friendliness, quality, or work pace.The expert panel made a total judgement over all systems, having all thedata available. All separate evaluations and a total expert judgment were

FIGURE 18.2

Example of a tape machine often used to seal bags with adhesive tape.


223

combined in a table (see Table 18.1 in Section 18.5.4) rating the systemsas very good, good, neutral, bad, or very bad.

18.5 RESULTS

18.5.1 S

EALING

BY

S

HOP

A

SSISTANTS

Regarding comfort, the average score of the shop assistants was higher for the usualadhesive tape and the adhesive tape with paper than for the other two systems. Themajority of the shop assistants called the ordinary adhesive tape and the adhesivetape with paper very easy to use, whereas the plastic-covered wire and the clip wererated difficult or very difficult to use (Fig. 18.3).

The physical workload estimated by the experts based on the video recordingis lowest for the tape-and-paper system and the traditional tape system. The tradi-tional tape system is somewhat better, because less force is needed to push the bagdownward. Both other systems (wire and clip) have a higher physical load, becausevarious repetitive handlings are needed.

The recorded sealing times for the adhesive tape and the adhesive tape withpaper were significantly lower (Fig. 18.4; t-test paired comparison, p

<

0.05) thanfor the other two systems.

18.5.2 O

PENING

BY

C

ONSUMERS

Fair

and

good

ratings in regard to opening the fastener were given for the paper- orplastic-covered iron wire and for the metal clip by all ages of consumers (Fig. 18.5).

FIGURE 18.3

Percentage of the twenty shop assistants rating the comfort and use of the fourbag-sealing systems

fair

or

good

, using a five-item scale (bad, moderate, neutral, fair, good).

0%

20%

40%

60%

80%

100%

plastic metal tape tape+paper

fair/good comfort fair/good use

224


The youngsters and middle-aged consumers also rate the adhesive tape with a pieceof paper in between

fair

or

good

. Not all groups appreciate the use of the adhesivetape system in opening bags.

Regarding comfort, a comparable result was found (Fig. 18.5).

Fair

and

good

comfort ratings for opening were recorded by all ages for the paper- or plastic-covered

FIGURE 18.4

The recorded sealing time for the four types of sealing systems, averaged overtwenty shop assistants, each sealing five bags (100 recordings per tape).

FIGURE 18.5

The opinion of consumers on the opening of plastic bags sealed with the foursystems, given as the percentage of consumers (youngsters, middle-aged, elderly) rating eachof the four systems

fair

or

good

.

sealing time (s)

0

2

4

6

8

10

plastic metal tape tape + paper

0

20

40

60

80

100


fair

/go

od

use

(%

)

youngsters

middle aged

elderly


225

iron wire and for the metal clip. The youngsters and middle-aged consumers alsorated the adhesive tape with a piece of paper in between

fair

or

good

. The comfortrating by all groups for the adhesive tape system was

low

or

neutral

when openingbags. The seniors rated the comfort level relatively low for all systems.

When we asked the preferences of the groups, the seniors preferred the metalclip (56%) (although the seniors did not experience any seal as comfortable). Theadults did appreciate the adhesive tape with paper (50%), and the youngsters pre-ferred the adhesive tape with paper as well (46%). The seniors mentioned problemswith opening the adhesive tape with paper, because this action requires musclestrength and fine coordination.

18.5.3 S

AFETY

The experts’ opinion is that safety is an important item, and they mentioned therisks of using the different seals. One of these risks is that a loose plastic-coverediron wire, or a clip, could fall or slide into an area where children could find it. Achild could put it into the mouth and swallow it. The experts also mentioned thedanger that a small part of the clip might break off and could also be swallowed.For both the ordinary adhesive tape and the adhesive tape with paper, the swallowingrisk is smaller.

Other risks that were mentioned by the experts are that one could possibly bepricked or cut by the sharp edges of the plastic-covered wire, or the clip. Shopassistants can hurt their hands at the sides of the machines that apply the adhesivetape seal. This is confirmed by shop assistants, who say that they sometimes cuttheir fingers on the metal clip or are pricked by the plastic-covered wire. Six outof nine shop assistants who regularly worked with the metal clip mentioned cuttinginjuries to the fingers, and two mentioned the hand. Two out the thirteen shopassistants who worked regularly with tape mentioned hand injuries, and one men-tioned finger injuries.

Both the expert panel and the consumers mentioned the possibility of gettinginjured by the use of a knife, fork, or scissors to open both kinds of adhesive tapeseals. This risk is higher when using the adhesive tape without paper, because thechance that a consumer will use a scissor or knife to open that type of seal is higher.Figure 18.6 presents the total safety score for the four seals that was given by theshop assistants and the consumers.

The adhesive tape seal with paper was evaluated as the safest by the expertpanel. This rating is somewhat different from that given by users. Figure 18.6 showsthe total score for safety of the four seal systems given by the shop assistants andconsumers. In fact, all systems are evaluated safe enough. Figure 18.8 shows shotsof the video recordings that were used in the expert session.

18.5.4 O

VERALL

S

CORE

Most of the shop assistants (59.3%) prefer adhesive tape with paper (Fig. 18.7).Looking at the consumers’ results, the preference is less evident. Their preferencesdiffer and show an equal division. Approximately 30% prefer the plastic-covered

226


iron wire, the clip, or the adhesive tape with paper (34.6%, 30.8%, and 30.8%,respectively). If a division is made between the three ages, it is clear that the elderlyprefer the metal clip and the young and middle-aged groups prefer the tape withpaper, followed by the plastic-covered iron wire.

FIGURE 18.6

Ratings given by the twenty-four consumers and twenty shop assistants regard-ing the safety of the different systems (0 = unsafe, 10 = extremely safe).

FIGURE 18.7

Percentage of the consumers and shop assistants who preferred one or anotherof the sealing systems. The total is higher than 100%, because almost half of the subjectsmentioned two preferences.

0

1

2

3

4

5

6

7

8

9

10

plasti

cm

etal

tape

tape

+pap

er

rati

ng

consumers

shop assistants

0

10

20

30

40

50

60

70


% t

hat

ch

oo

ses

the

syst

em

shop assistants

young cons.

middle cons.

old cons.


227

Table 18.1 summarizes the judgments of the shop assistants, the consumers, and theexpert panel. The table with the total score has some arbitrary elements, but theexpert panel agreed on the scores. Because of positive ratings for safety, physicalload, comfort in use, and the high speed mentioned by shop assistants, thetape-and-paper system was evaluated as the best, which means that the developmentof this system was successful.

FIGURE 18.8

Screen shots from the video recordings used by the expert panel: (

A

) plastic-covered iron wire is used to seal a bag; (

B

) an older woman is reclosing the bag with plasticcovered iron; (

C

) middle aged man is opening a bag with adhesive tape.

TABLE 18.1 Summary of the Scores for the Four Sealing Systems

Shop assistant

Consumer

Expert Totalscore Speed Safety Comfort

and use Speed Comfort

and usePhysical

loadSafety

Plastic-covered wire

−

+/

− −

+ +

− − − −

Metal clip

− − −

+ +

− − −

Tape ++ ++ +

− − − −

++

−

+/

−

Tape with paper ++ ++ + +/

−

+/

−

+ + ++

++ (very good); + (good); = (neutral);

−

(bad);

− −

(very bad)

228


18.6 CONCLUSIONS

Improvement of a simple activity such as sealing a bag could play a role in theprevention of musculoskeletal injuries or some other type of hazardous situation. Thenew system was developed and rated positive in regard to comfort by most of the endusers, and it can certainly be seen as an improvement. This new system should bepromoted, but further instruction to end users is needed regarding safety. If possible,innovations should be found to make unsealing easy for everyone, including the elderly.

The following conclusions can be drawn from this study:

• For sealing plastic bags, the adhesive tape with paper is the best of thefour systems, closely followed by the plain adhesive tape. Both seals scorewell as far as speed and safety are concerned. These two seals are alsothe best in regard to comfort. Consumers prefer the system of the adhesivetape with paper and it is evaluated safer by the experts. The physical loadinvolved in sealing with adhesive tape is evaluated more positively thanin sealing with adhesive tape with paper.

• Consumers think that the plastic-covered iron wire and the clip openfastest, and they think these are the easiest ones to use. The consumersprefer the plastic-covered iron wire, clip, and adhesive tape with paper tothe plain adhesive tape.

• The young and middle-aged prefer the adhesive tape with paper. For seniors,there is no seal available that is easy and comfortable to use, in their opinion.Safety is rated higher in sealing with adhesive tape with paper.

• According to the shop assistants, sealing bags with both systems using adhe-sive tape is the easiest and fastest. However, the consumers mention that theseal without paper is the most difficult to open. They also mention the diffi-culty of resealing bags that have been opened. In short, there is still no sealthat is experienced to be comfortable by all shop assistants and all consumers.

• If we had to recommend a seal it would be the seal using adhesive tapewith paper, because sealing plastic bags is a daily recurring, intensiveactivity for shop assistants.

ACKNOWLEDGMENT

The authors want to thank Twin Seal for their support in this research.

REFERENCES

Bongers, P.M. (2003)

Make Work to Prevent RSI

, Amsterdam: Vrije Universiteit (inauguraladdress).

Carrasco, C., Coleman, N. and Healey, S. (1995) “Packing products for customers.”

AppliedErgonomics

, 26(2): 101–109.Macfarlane, G.J., Hunt, I.M. and Silman, A.J. (2000) “Role of mechanical and psychosocial

factors in the onset of forearm pain: Prospective population base study.”

BritishMedical Journal

, 321: 676–679.

229

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

19

Comfortable View in an Earth-Moving Machine of 2015

L. Vormer, M.C. Dekker, A.A. Visser, F. Krause, and P. Vink

CONTENTS

19.1 Introduction ..................................................................................................22919.2 Current Situation ..........................................................................................23019.3 Improvement Possibilities for View.............................................................23019.4 Demands from the Literature.......................................................................230

19.4.1 Direct View.......................................................................................23119.4.2 Indirect View ....................................................................................232

19.5 Information from Operators and Manufacturers .........................................23219.6 The Design Approach ..................................................................................23419.7 The Three Concepts .....................................................................................23519.8 The Future Machine.................................................................................... 23619.9 Conclusions ..................................................................................................237References..............................................................................................................237

19.1 INTRODUCTION

The operator’s comfort is increasingly recognized as a factor of importance in sellingearth-moving machines (Krause et al. 2003). From 2001 to 2003 a Eurocabin projectwas carried out for three medium-sized earth-moving machine manufacturers: PausGmbH (Germany), coordinator of the project; ETEC (the Netherlands), and Kaiser(Liechtenstein). A part of this project, which describes the design of the excavatorof the future, concerns improvement of the operator’s view. The highlights of thisstudy are presented in this chapter.

230


19.2 CURRENT SITUATION

Operator comfort in earth-moving machines has improved drastically the last fouryears (Chapter 2). An old excavator cab, such as the one shown in Fig. 19.1, isseldom seen nowadays. However, improvement possibilities can still be found inthe new machines. The most frequently mentioned improvement possibilities innew machines (less then 4 years old) involve the seat and vibration. In excavators,22% of the drivers also mention the need for improvement of the operator’s view(Kuijt-Evers et al. 2003). This chapter is concerned with that view, an aspect ofinterest to both manufacturers and operators. View is not only related to comfort, butalso — perhaps even more importantly — to quality and productivity. A good operator’sview of the direct working area reduces the chance of extra corrections or mistakes.

19.3 IMPROVEMENT POSSIBILITIES FOR VIEW

In this project, a study of the operators’ existing view was carried out. Literaturewas studied; operators, manufacturers, and experts were interviewed; and the viewfrom existing excavator cabins was analyzed.

19.4 DEMANDS FROM THE LITERATURE

Reviewing the literature, a paper by Roetting (2003) that presents an overview ofthe subject of view appeared to be important. Roetting divides the concept into twoparts:

direct view

and

indirect view

.

FIGURE 19.1

Example of an old excavator cab.


231

19.4.1 D

IRECT

V

IEW

Different methods are in use and/or proposed to identify blind spots in the field ofview of an operator (Giguère and Lame 1996). Most of them calculate the visibilityfor an average person (e.g., 50th percentile male) and assume only a static posturefor the operator. Although this makes it easier to compare different vehicles or toquantify changes made to a vehicle, it is a gross simplification. Operators of varyingheights will operate a wheel loader, and they can (and will) change their head andbody positions dynamically. See Land and Horwood (1996) for a study of the relationof head and eye movements to driving).

Demands for a direct view from a wheel loader cabin can be summarized asfollows:

• The windows should allow viewing of as much of the surrounding envi-ronment as possible. Table 19.1 gives an indication of the relative impor-tance of the different areas to different tasks. The windows should be aslow as possible to allow viewing of the immediate surroundings.

• The number of occlusions (e.g., parts of the cabin frame, the bucket, thebucket arm, mirrors, and displays and other elements within the cabin)should be minimized. If occlusions cannot be prevented, their size shouldbe minimized.

• All windows that are essential to the outside view should be equippedwith windshield washers and wipers. The wipers’ field of coverage shouldbe maximized.

• Reflections from inside the cabin should be minimized.• Blinding by the sun should be prevented by a blind or a window coating.

Fogging of the windows should be prevented by heated windows andadequate ventilation; distortions due to curvatures of the windows shouldbe minimized.

TABLE 19.1Weight Factors for Different Aspects of the Outside View

Front viewWork area

view Rear view

Transport 0.8 0.2Transport with loading/unloading 0.6 0.2 0.2Loading/unloading with transport 0.4 0.4 0.2Loading/unloading with transport moving forward and backward

0.3 0.4 0.3

Loading/unloading or handling/processing without transport

0.2 0.7 0.1

From Roetting (2003) after Vedder (1997).

232


19.4.2 I

NDIRECT

V

IEW

Indirect vision systems serve two purposes. They reduce the time needed to viewareas behind the vehicle, for example, by moving parts of the rear view into thefront view field (Flannagan and Sivak 1993). They also give access to informationnecessary for safe task execution in areas that are not directly viewable, the so-calledblind spots. Indirect view can be achieved by means of mirrors or cameras or byother (technical) means (e.g., collision avoidance systems). There is always atrade-off between the area made visible by the indirect view system and the occlusionof information in the forward visual field. Demands for indirect viewing by wheelloader operators can be summarized as follows:

• Provide indirect view systems to minimize the number of blind spots.• Do not occlude important areas of information with indirect view systems.• All indirect view systems should be easily adjustable to different operators

and different operating conditions (e.g., servo-adjustable mirrors).• All indirect view systems should be provided with means to ensure their

function even during adverse environmental conditions (e.g., heated mir-rors to prevent fogging).

• Indirect view systems should be evaluated under working conditions (e.g.,vibrations can reduce the usefulness of indirect view systems).

19.5 INFORMATION FROM OPERATORS AND MANUFACTURERS

The interviews with operators and manufacturers also generated some valuable infor-mation. It appeared that the operator’s view of the direct working area could be restrictedby the cabin frame, dashboard, or the undercarriage (Fig. 19.2). The hydraulic armcould restrict the view (Fig. 19.3), and visibility around the machine is restricted bythe machine itself. There is little visibility to the vehicle’s right and rear, but this viewcould be important in maneuvering backward and rotating the upper carriage.

Other problems that came out of the interviews related to the view are sunlight,dust, window damaging and deformation of visibility:

1. Sunlight. A solution increasing the view could be to increase the windowsurface. However, a larger screen surface means more sunlight, which canbe troublesome, especially on summer days. Currently, sunlight is alreadyseen as a problem.

2. Dust. Dust reduces visibility, so a larger window surface implies that alarger area has to be cleared of dust.

3. Damage. More window area means more possibilities for vandalism andfalling objects to damage the window. In the interviews, subjects men-tioned that vandals sometimes damage vehicle windows.

4. Deformation. Sometimes curved windows are used to enlarge the viewingarea. From a styling point of view, this also offers also interesting formpossibilities (Figure 19.4). According to the operators, however, lookingthrough curved windows deforms the image and could even result in


233

FIGURE 19.2

The work area that can be seen by the operator (gray = areas with restrictedvisibility).

FIGURE 19.3

The hydraulic arm could restrict the view.

234


headache or tired eyes. It is best to look through window glass that isperpendicular to the viewing axis.

These are only a few of the problems related to view that make finding a solutionvery difficult.

19.6 THE DESIGN APPROACH

Based on the defined problems, including the related problems mentioned above,improvements were developed by a design team. It started with ideas that wereformulated based on discussions with operators and manufacturers. The ideaswere again shown to operators and the discussions led to three concepts that were

FIGURE 19.4

An O&K machine with very nice styling made possible by curved glass. (

A

) isa closeup of the cab; (

B

) is an overview of the complete machine. (Photo courtesy of O&K.)


235

developed further. The three concepts were presented and discussed with operators,manufacturers and experts in the field of comfort and design. All of this was inputfor the final design of the Machine of 2015.

19.7 THE THREE CONCEPTS

In this chapter the three designed concepts are called

longneck

,

rocking chair

, and

solist

. A characteristic of the

longneck

concept (Fig. 19.5) is that the operator alwayslooks through a flat window and the work area is seen without deformation. Themoving cabin allows repositioning in order to achieve the best position for a goodview. The

rocking chair

concept (Fig. 19.6) has a saddle seat, which enables the

FIGURE 19.5

Concept

longneck.

FIGURE 19.6

Concept

rocking chair

. (

A

) shows the in- and egress situation; (

B

) showsdifferent positions of the chair that increase view and variation in posture.

236


operator to sit like a motorcyclist and look downward. A window in the floor iscovered by a plate that can be opened so the operator can look downward. A slidingdoor makes it possible to increase the view to the left and also improves theventilation possibilities, because now the door can be opened and fixed in differentpositions. The

solist

concept (Fig. 19.7) has a movable cabin that can be separatedfrom the machine, and the machine can be operated by remote control. The operatorcan then choose the ideal position for looking at the working area.

19.8 THE FUTURE MACHINE

In evaluating the three design concepts, both disadvantages and advantages werementioned by the operators, manufacturers, experts, and designers. These were alllisted and became the input for the final design of an excavator for 2015. This finaldesign (Fig. 19.8) has a moving cabin that can be elevated to look over obstaclesor the hydraulic arm. It can also be tilted forward and backward to optimize theview through the flat window.

A sliding floor panel can be uncovered to reveal a window underneath, enabling adirect downward view. Almost all grey areas in Fig. 19.2 now become white, which isa significant (almost 100%) improvement of the view. When working overhead thecabin can be elevated (Fig. 19.8A), and in working under the machine the cabin can

FIGURE 19.7

Concept

solist

. (

A

) is working with the remote control enabling optimal view;(

B

) is driving to the ideal position to see the working area.


237

be positioned forward and the sliding floor panel can be opened (Fig. 19.8B). A touchscreen in the cabin allows the operator to view the area around the machine via cameras.Sensors warn of obstacles while the machine is moving.

The windows are made of a special material that is almost unbreakable, with aspecial coating that cleans itself in rain, as many office building windows now do.Each part of the window can be made darker (to reflect sunshine) by changing anelectrical current, and the operator can make this change himself.

19.9 CONCLUSIONS

Innovations are still possible to increase the view, and thereby the comfort, of theearth-moving machine operator. There is a question as to whether this machinewill be operating in 2015. However, the study has generated a large number ofideas that could be helpful in designing new machines in the short term, as well.Some of these ideas are implemented in today’s new machines, and a few ideashave been mentioned in this chapter to show that there are more possibilities forimproving the operator’s view. A better view is important because it is a salesargument. A machine that enables more accurate work, increases productivity, andis safer and more comfortable is interesting to operators, management, and man-ufacturers alike.

REFERENCES

Flannagan, M. and Sivak, M. “Indirect vision systems.” In B. Peacock and W. Karwowski,eds.,

Automotive Ergonomics

, London: Taylor & Francis, 205–217.Giguère, D. and Larue, C. “The visibility audit: A conceptual framework for the assessment

of visibility around trucks and industrial vehicles.” In A.G. Gale, I.D. Brown, C.M.Haslegrave and S.P. Taylor, eds.,

Vision in Vehicles V

, Amsterdam: Elsevier, 371–378.

FIGURE 19.8

The excavator of 2015, featuring a better view with the hydraulic arm raised(

A

) and lowered (

B

).

238


Krause, F., Bronkhorst, R.E. and Looze, M.P. de, eds. (2003)

Comfortable Earth-MovingMachinery

, Hoofddorp: TNO.Kuijt-Evers, L.F.M., Krause F. and Vink P. (2003) Aspects to improve cabin comfort of wheel

loaders and excavators according to operators.”

Applied Ergonomics

, 34(3): 265–272.Land, M. and Horwood J. “The relations between head and eye movements during driving.”

In A.G. Gale, I.D. Brown, C.M. Haslegrave and S.P. Taylor, eds.,

Vision in

VehiclesV

, Amsterdam: Elsevier, 153–160.Roetting, M. (2003) “View.” In F. Krause, R.E. Bronkhorst and M.P. de Looze, eds.,

Com-fortable Earth-Moving Machinery

, Hoofddorp: TNO, 21–30.Vedder, J. (1997)

Systematische Bewertung der ergonomischen Gestaltung

ausgewahlterNutzfahrzeuge

, Düsseldorf: VDI-Verlag.Vink, P. and Hark. T. ter. (2003) “Future demands on comfort in construction vehicles’ interiors

according to manufacturers.” In F. Krause, R.E. Bronkhorst and M.P. de Looze, eds.,

Comfortable Earth-Moving Machinery

, Hoofddorp: TNO: 99–105.

239

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20

Tram Drivers’ Comfort

D.S.C. Osinga, P. Vink, and J.C. Becker

CONTENTS

20.1 Tram Interior Requirements.......................................................................23920.2 Requirements to Optimize Driver Performance ........................................24020.3 The Design Process....................................................................................240

20.3.1 A Stepwise Participatory Approach ............................................24020.3.1.1 Step 1: Test the First Design .....................................24120.3.1.2 Step 2: Test the First Mock-Up .................................24120.3.1.3 Step 3: Test the Improved Mock-Up

and Emergency Handle ..............................................24220.3.1.4 Step 4: Dynamic Test of Seats ..................................24320.3.1.5 Step 5: Final Evaluation ............................................244

20.4 Results ........................................................................................................244References..............................................................................................................245

20.1 TRAM INTERIOR REQUIREMENTS

The requirements placed on trams in regard to comfort, safety, and capacity arehigh-level and numerous at the same time. Trams should be comfortable and safefor passengers and should allow them to get in and out of the tram fast. Also, capacityshould be enlarged due to the increasing number of passengers. Apart from the needsof passengers, the driver’s cab should meet the driver’s needs. The cab should becomfortable for small, tall, slender, and corpulent drivers, and should stimulate safedriving as well as good visibility and clearance.

The public transport enterprise of Rotterdam RET (Rotterdamse ElektrischeTram) is confronted with these changing demands and therefore pays much attentionto the process of designing new trams. First, the requirements for a new tram aredefined, and after an invitation for European bidders, the company is chosen thatwill deliver the new trams.

The supplier was Alstom (France). Their tram was chosen because it best fit therequirements, but also because adaptations were still possible. An important advantagewas the high capacity. The Alstom is a relatively wide tram and has a low floor, whichincreases capacity and passenger comfort in getting in and out of the tram. Based on the

240


existing Alstom concept the RET specified the outside appearance and many technicalfeatures. Also, the interior was specified in cooperation with specialists in vehicle interiordesign from TNO. The process of the driver’s cab specification is the focus of this chapter.

20.2 REQUIREMENTS TO OPTIMIZE DRIVER PERFORMANCE

It is essential to adapt a driver’s cab to the principles of human behavior in orderto enable optimal human performance. Nowadays, many software packages areavailable to support an ergonomical design. An ergonomical design is needed bothto let drivers fit in the vehicle and to check sight lines and reach envelopes. Thesesoftware packages are especially useful in the early stages of development. However,it is impossible to predict both human behavior and the feeling of comfort. Therefore,in a later stage of design the participation of various drivers will always be neededto test the cab’s handling, view, and comfort.

This is essential because all drivers should have a good view of the traffic infront and to the left and right of the tram. An example of a RET requirement isthat the driver should be able to see an object one meter high located at a distanceof one meter from the tram. Also, real users should test the controls and displays,because they know the driver’s work best.

Comfort is also an essential element for other reasons. First, comfort promotesa healthful environment so that drivers become less ill and are sooner able to workagain. Another reason is that comfort can keep the driver more alert during the shiftwithout being diverted or tired by discomfort. Finally, drivers are used to the highcomfort standards in their cars or at home, and they expect that in the work station, too.

20.3 THE DESIGN PROCESS

20.3.1 A S

TEPWISE

P

ARTICIPATORY

A

PPROACH

Ultimately, the driver’s cab should be a workplace that enables optimal performanceby the driver. Therefore, in the process of developing the new tram the driver playedan important role. In this project a stepwise approach used in a train interior designprocess was used (Bronkhorst, et al. 2002). Explicit attention was given to thecommunication in the process between designers of Alstom, drivers of the RET andresearchers of TNO (see also Chapter 4). We tried to make the drivers and designersowners of the solutions (Wilson 1995).

The three groups met in each step of five successive steps. A project groupguided this process. The project group consisted of a “manager tram” of the RET,a representative of the RET union, a number of drivers, an instructor from the drivers’training department, and a specialist in work research. This project group guidedthe process of the optimal cab design through the five crucial steps.

At a few points in the process the project group had to report their progress toa steering group, which arranged coordination with other project groups in regardto technology, exploitation, and the passenger interior of the new tram. During theprocess Alstom delivered a number of mock-ups to evaluate the design and to


241

communicate about possible changes. TNO added an expert opinion and analyzedthe tests done by the drivers, and then converted these data into redesign proposals.

20.3.1.1 Step 1: Test the First Design

In the first step designers of Alstom made drawings of the cab interior based on therequirements. These designs were discussed at the end of this step, and discussionof these drawings resulted in some changes. Climate control was hardly possible inthe proposed interior because of the large dashboard. The dashboard was a largehorizontal plane extending from close to the driver to the coachwork, makingventilation nearly impossible because the air flow is hindered. Also, and probablymore important, sight lines drawn in the design showed that the driver’s sight wasreduced because of the large dashboard. Smaller drivers were not able to have agood view of the traffic. The position of displays and controls could also be improved.

20.3.1.2 Step 2: Test the First Mock-Up

Based on the results of step 1 the project group decided to make a new design basedon other designs that were available for this tram. The new design included modifiedcontrols and displays and a more rounded dashboard surface to enable a better viewof traffic. Another adaptation was the addition of height-adjustable pedals (Fig. 20.1)next to the height-adjustable seats.

Height-adjustable pedals are relatively new in trams. To enable good traffic sightfor drivers of different heights, height-adjustable seats are often found in trams, andsometimes even height-adjustable dashboards. Height-adjustable pedals are not oftenfound, but their advantage is that the driver’s sight lines relative to the dashboard andthe coach-work can remain fixed, regardless of the anthropometrics of the individualdrivers. This design was shown in a mock-up (Fig. 20.2) that was evaluated by eight

FIGURE 20.1

Height-adjustable pedals.

242


drivers in four sessions, using a protocol set up by TNO. Drivers with extreme bodycharacteristics were used to test the adjustability. Tall and short drivers, as well as bothslender and corpulent drivers, participated in the test. Three seats that were chosenbased on previous tests (two new seats and one used in the current tram) were testedin the mock-up. The height adjustability of both seats and pedals were evaluatedpositively. Traffic close to the tram could be observed adequately during a simulation.

All three seats were evaluated positively. Drivers mentioned during the test thata dynamic test is needed to choose a seat, because the vertical vibration is not alwaysdampened effectively by the seat. It was decided to do a dynamic test in a comparabletram. New problems were also discovered during this test, for example, the problemof knee space. The knee space provided was theoretically (and in the software)adequate, but for real drivers the test showed that the knee space was too small.Based on the discussion of the test results it was decided to make the dashboardmore U-shaped to create additional space in front of the driver. Another problemwas the fact that for precision handling and steering a more adequate armrest waspreferred. It was decided to add an adjustable arm support for the right arm and afixed wrist support for the left hand (Fig. 20.3).

20.3.1.3 Step 3: Test the Improved Mock-Up and Emergency Handle

In the third step six drivers evaluated the U-shaped mock-up, and it was decidedto choose this design. At this point further refinements were made, such as thepositioning of the controls and displays, the instructor’s seat for the instructor tram,and a sun-blind.

In this step the emergency brake was also tested. Alstom was able to delivera new emergency brake integrated into the drive-stop handle (Fig. 20.4). In existingRET trams drivers have to press a pedal continuously, and taking the foot off thispedal causes an immediate stop. In the new tram the integrated handle requires

FIGURE 20.2

The mock-up used in the test.


243

that the driver’s hand cannot leave the handle, because doing so causes the emer-gency stop. Drivers tested the new system in an existing tram. Based on this test,the old system was preferred by drivers as well as by the experts, because of thearmload required by the new system. Therefore, the old system will be built intothe new tram.

20.3.1.4 Step 4: Dynamic Test of Seats

The next step was the dynamic evaluation of three seats in an existing comparabletram. All three seats were tested by drivers according to a fixed protocol, and

FIGURE 20.3

The armrests supporting precise handling.

FIGURE 20.4

The emergency stop feature integrated into the drive-stop handle.

244


objective tests were done regarding vibration and pressure distribution. Analysis ofthese tests showed that one of the seats was not appropriate for the tram in theRotterdam area. This seat did not provide enough support in the lateral directionand did not dampen the vibration enough. One seat was rated best, but improvementswere needed, such as adjustment of the armrests to give more support, a flatter frontof the seat, and better pressure distribution characteristics.

Other recommendations concerned technical aspects to improve stability andmaintenance. The supplier was satisfied with the specific research-based commentsand was willing to adapt the seat.

20.3.1.5 Step 5: Final Evaluation

In the last step a complete mock-up was evaluated, consisting of a part of the passengercabin. Also, the chosen colors, light, and pictograms of displays were tested sepa-rately. The first prototype was again checked by drivers and management (Fig. 20.5).Some details were modified, but the total was evaluated positively.

20.4 RESULTS

The active involvement of several drivers and the use of the research-based redesignapproach ensure that all knowledge available in designers, drivers, and experts is used.

New knowledge also became available in the course of doing the tests. It isexpected that Alstom’s final tram interior will be optimally adapted to the needs ofthe drivers, because the designers of Alstom were aware of the needs and werecreative enough to adapt their design to the new demands.

FIGURE 20.5

The prototype for examining all parts of the interior and exterior design.


245

Of course the expectation is that the tram drivers will experience a comfortablecab and — of greater importance — that the cab will be safer, because drivers havea good view of the traffic. The first impression driving with the tram, was that ithad no surprises anymore (Fig. 20.6). RET designed their subway cab in a compa-rable way, and this resulted also in a comfortable and safe workplace for the driversand other participants in the traffic environment.

REFERENCES

Bronkhorst, R.E. and Krause, F. (2002) “End-users help design mass transport seats.” In

Human Factors in Seating and Automotive Telematics

(SP-1670). SAE World Con-gress, Detroit, March 4–7. SAE Technical Paper Series 2002-01-0780, 1–6. Warren-dale, PA: SAE.

Wilson, J.R. (1995) “Solution ownership in participative work design: The case of a cranecontrol room.”


, 15: 329–344.

FIGURE 20.6

Reality has no surprises anymore.

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0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

21

Redesign of Earth-Moving Machines:It’s Also in the Details

F. Krause, M.P. van der Grinten,K. Reijneveld, and R.E. Bronkhorst

CONTENTS

21.1 Introduction ................................................................................................24821.2 Method........................................................................................................24821.3 Results ........................................................................................................24921.4 End-User Opinion on Improvements in the Paus Machine ......................249

21.4.1 Subjects ........................................................................................24921.4.2 Ingress and Egress .......................................................................25021.4.3 Seat...............................................................................................25021.4.4 Steering Column ..........................................................................25121.4.5 Dashboard ....................................................................................25221.4.6 Controls........................................................................................25221.4.7 Climate .........................................................................................25321.4.8 Mirrors .........................................................................................25421.4.9 Noise ............................................................................................254

21.5 End-User Opinion on the Kaiser Machine Improvements........................25521.5.1 Seat...............................................................................................25521.5.2 Ingress and Egress .......................................................................25621.5.3 Pedals ...........................................................................................25621.5.4 Joysticks .......................................................................................25721.5.5 Front Window ..............................................................................25721.5.6 Heat Regulation ...........................................................................25821.5.7 Noise ............................................................................................25821.5.8 Retest Results for ETEC .............................................................259


248


This work is reproduced with permission of TNO, Copyright 2004.

21.1 INTRODUCTION

Chapter 19 describes the development of a new machine for 2015. However, increas-ing comfort does not always require a very expensive and impressive improvement.In this chapter, minor changes in vehicles are introduced to reduce discomfort andimprove comfort.

To keep up with large competitors, small- and medium-sized companies have theadvantage that they are closer to clients and can adapt faster to their needs. Furtherinnovation in this field could make the difference in being able to sell competitivewheel loaders in the future. With this in mind, Maschinenfabrik Paus GmbH (Germany),Van Vliet BV, manufacturing ETEC machines (the Netherlands), and Kaiser AG(Liechtenstein) formed a consortium. These are European medium-sized (<250employees) manufacturers of earth-moving machinery. Together with TNO theyfounded the Eurocabin project, which was partly funded by the European Union.

The goal of this project was to further innovate and optimize the cabins of theirmachines. Because musculoskeletal injuries (Oliver, et al. 2000) are a major problemamong earth-moving machinery drivers, special attention was paid to comfort andthe prevention of work-related musculoskeletal injuries.

21.2 METHOD

Based on previous studies (Vink and Kompier 1997; Noro and Imada 1991) (Chapter 4),several steps were defined to result in the production of better machines:

1. Step 1: Kick-off and project definitionIn this step the project was structured, appointments were made, and tasksdivided.

2. Step 2: OrientationIn this step, existing knowledge was studied in the literature and discus-sions were held with experts. An overview of trends in comfort and designin the automotive industry was conducted to identify issues relevant toearth-moving machines. The aspects to be studied were also defined.

3. Step 3: End-user opinionMore than 300 operators were questioned regarding comfort aspects ofearth-moving machines (Kuijt-Evers, et al. 2003). For the specificmachines of Paus, Etec, and Kaiser, additional interviews were held withtheir end users (see Fig. 21.1).

4. Step 4: Expert opinionA group of experts examined the machines, sometimes with specificevaluation methods to study the fit (with ergomix), or to study vibrationand noise.

5. Step 5: Adaptation proposalsBased on the end-user opinion and expert evaluations, the main problemson the specific machines were described and improvement proposals weredefined.

Redesign of Earth-Moving Machines: It’s Also in the Details

249

6. Step 6: First redesigned machinesBased on the advice generated in Step 5, some machines were redesignedand were tested by end users again.

7. Step 7: Implementation in the new production processIn this step the companies decided which changes would be standard inthe new machines, which ones could be bought as an additional feature,and which ones would not be implemented.

21.3 RESULTS

The process followed the steps as described in the method. In this section mostattention is paid to the results of Step 6, which shows the specific changes. Theprocesses of change have been described extensively in previous chapters (see alsoKrause et al. 2003) and will not be repeated here. The results will be described forthe Paus and Kaiser machines, but because the ETEC machine had similar changes,only a table with ETEC results will be presented.

In general, the elements that were found to need improvement in Chapter 2 are alsotaken up in this study: seat comfort, vibration and damping, dashboard and displays,climate control, what the machine looks like, cab dimensions, interior space, getting inand out, noise reduction, view, adjustability of seat and controls, and reliability.

21.4 END-USER OPINION ON IMPROVEMENTSIN THE PAUS MACHINE

21.4.1 S

UBJECTS

Three operators with experience in the old machine (Fig. 21.2) were asked to givetheir opinion about the new machine during a test.

FIGURE 21.1

Discussions with end users.

250


21.4.2 I

NGRESS

AND

E

GRESS

From the previous steps it was known that ingress and egress often take placebetween 20 and 50 times a day. Each time, the height difference between the groundand the cabin (approximately 1.2 m) has to be mastered, so improving ingress andegress was considered to be important, with respect to both ease and safety.

As an improvement, the climbing aid's grip diameter was increased to 25mmand the hand clearance between the climbing aid and cabin was increased to 65mm,thus improving the feel of the grip and the ease with which it can be grabbed, evenwhile wearing gloves. The steps were also modified to make all step heights moreor less equal, and a strip was added to each step that increased the step depth toimprove stability for the foot (Fig. 21.3).

Operators were mostly satisfied with the ingress-egress improvements (steps andgrips). All operators find the new grips more comfortable, but all state that they stillrequire the same amount of strength for ingress and egress. This can be explainedby the fact that the height from ground and cabin is still the same. Operators findthe new steps more comfortable and safe, although the new step heights requiregetting used to.

21.4.3 S

EAT

The seat height adjustment range was lowered 30 mm to improve seating, especiallyfor smaller persons. This was achieved by modifying the seat pedestal, and additionalelevation of the seat can be effected by means of spacer blocks if necessary. Thelowered seat height was mostly appreciated, but one small operator, surprisingly,was not pleased with the new height. He liked to use the seat in the highest positionto be able to have a good view of the ground and the shovel, because otherwise hehad less of a “feel” for the machine. This problem can be explained by the fact thatmore than one driver often uses this type of machine, generally for short periods of

FIGURE 21.2

The Paus machine used in this study.


251

time. For these short-term drivers it is harder to acquire the same feel for the machinethat an experienced driver has.

21.4.4 S

TEERING

C

OLUMN

A steering column that could be adjusted for height and inclination was installed(Fig. 21.4A). At the same time, changes were made to the dashboard support, the

FIGURE 21.3

The step modification (

A

, old situation;

B

, new situation).

FIGURE 21.4

The new adjustable steering column (

A

) and related modifications (

B

).

252


support structure in the cabin floor, and the cabin matting (Fig. 21.4B). This wasdone to reduce rattle, an annoying feature of the older cabin.

The new adjustable steering column is very much appreciated. All operatorsfound that it enabled them to improve their seating position in the cab. Additionally,operators all agreed that ease of ingress and egress was improved because the steeringwheel folds away with one easy lever movement, increasing the space for bodymovements.

21.4.5 D

ASHBOARD

The instrument board was changed completely according to TNO’s design sugges-tions (Fig. 21.5). This required constructing a new casing; regrouping gauges, controllamps, and switches; changing electric wiring; and building a new steel support forthe casing. In the redesign process and in the manufacturing, careful attention waspaid to avoid rattles and squeaks in the new dashboard. Other aspects considered inthe design were avoiding reflections and making the machine easy to maintain. Thelatter was important because eastern Europe is a target market where owners mostlydo their own servicing.

Operators evaluate the new dashboard as equal to the former model. They donot notice the improved layout of gauges and switches, most likely because theamount of time spent looking at the dashboard is very small. Furthermore, the qualityand speed of their work is not affected by the way the dashboard is laid out. Theydo find the new dashboard more appealing to the eye than the previous model.

21.4.6 C

ONTROLS

The possibilities for adjusting the joystick relative to the driver are now limited, dueto the design of the control console. Adjusting the seat for optimal viewing andoperation of pedals could result in a suboptimal joystick position. Therefore, additionaladjustment of the joystick or control console was proposed. Grammer, a large man-ufacturer of operator seats, cooperated in the project and came up with a new andimportant prototype seat that has a multiadjustable armrest to which the joysticks canbe attached. Such a system is preferred because a seat adjustment will not lead to achanged position relative to the joystick. Furthermore, the adjustability of the joystick

FIGURE 21.5

Dashboard improvements.


253

relative to the driver is increased and the seat offers good arm support. Unfortunately,this improvement could not be built in time to be included in the test machine, andtherefore it was not tested in this study.

21.4.7 C

LIMATE

In the Paus machine, as in the other tested machines, climate was a point oftenmentioned by operators. Due to the large glass surfaces, heat buildup can easily takeplace on sunny days. Therefore, many operators would appreciate having air-con-ditioning in their cab. Installing air-conditioning is not necessarily a solution to theproblem, however, because operators prefer to work with the door or window opento improve the outside view, communications, and sense of space. The desire forair-conditioning is also likely to be connected to the fact that the operators’ ownluxury cars often have air-conditioning as a standard feature. In most earth-movingmachines, air-conditioning is already optional.

Installing air-conditioning as a standard feature was economically not feasible.A simple and feasible measure to at least reduce blinding by the sun was attachinggreen sun-protection foil to the upper part of the windows.

Another problem the operators reported was insufficient defrosting of the windows.New air routing systems to improve defrosting and defogging were built into themachine. The defrosting unit was changed to create more vents and lifted to be moreeffective. Two additional vents were especially needed to defrost the side panels ofthe front window (Fig. 21.6).

FIGURE 21.6

(A

) The old defogging unit was most effective in window areas unused byoperators. (

B

) The improved defogging unit is lifted and has additional vents for betterdefogging of front window side panels.

B.

254


21.4.8 M

IRRORS

The mirror suspension was a problem in the old machine. The inflexible part of thesuspension protruded too far from the cab and the flexible part was too small(Fig. 21.7A). Mirrors and the mirror suspension were often damaged. The improve-ment is shown in Fig. 21.7B, and operators all consider it to be better than the oldersystem. The risk of damaging cab structures when the mirrors collide with a tree orsimilar protruding object has significantly decreased. The view seen in the mirrorsremained the same.

21.4.9 N

OISE

The following measures have been taken to reduce interior noise:

• The flexible sealing used to connect the three windows that form the frontand rear windows was replaced by a stiffer glue to reduce resonance whenthe engine is idling.

• The steering column and instrument casing were designed and mountedto avoid rattle and squeak.

• Insulating material under the cabin’s bottom made it thicker (from 15 to30 mm).

• Openings around the engine were closed and measures were taken todampen the engine air intake and engine cooling. Careful attention waspaid not to disturb the engine’s heat balance.

The measures that were taken to reduce interior noise in the cabin have had apositive effect, according to the operators. They all find that the sound level is lowerand more pleasant in the new machines.

FIGURE 21.7

Mirror suspension (

A

, old inflexible situation;

B

, new flexible situation).


255

21.5 END-USER OPINION ON THE KAISER MACHINE IMPROVEMENTS

Four subjects experienced in operating the original Kaiser machine (Fig. 21.8) testedthe new machine.

21.5.1 S

EAT

The choice of seat supplier is limited. There are only a few major players in themarket. From questioning the operators it became clear that operators in generalrated the seat itself as fairly comfortable. Improvements were desired with respectto the following aspects:

• Armrests. They were considered to be very important. The seat offeredsub-standard armrest adjustability and comfort. Some seats come withoutarmrests in which cases armrests are often fitted onto the joystick console(Fig. 21.9). Operators often complain about the width, hardness, andimproper height of armrests.

• Adjustability. Adjustment levers are often not easy to reach and requiretoo much pressure to be operated. Also, it is often unclear what the lever’sfunction is. The weight adjustment of seats with mechanical springs isdifficult. As a result, the adjustment is often not done.

• Suspension. Seat suspension can still be improved. Several operatorscomplain about the seat bottoming out, which leads to peak forces on thelower back. Also, the damping characteristics of air-suspended seatschange with the chosen seat height.

Obtaining these improvements was not possible within the parameters of theproject. Buying a more expensive seat from the seat supplier would not necessarily

FIGURE 21.8

The Kaiser excavator used in this study.

256


solve the problems, and the market being as competitive as it is, constructioncompanies are not willing to pay for many extras.

One improvement could be made, however. The seat’s adjustment range waslarger than needed, and by restricting the range extra storage space was created inthe very confined space of the excavator cab.

21.5.2 I

NGRESS

AND

E

GRESS

The climbing aid grips were also improved in the Kaiser machine. This was expectedto be an improvement because operators step in and out of the machine 20 to 50times a day. The grips were extended downward so operators could catch them whilestanding on the ground or climbing up one of the legs in steep terrain. In general,the extended grip was appreciated by all but one of the test operators. That operatorfound the grip to be no better than the older type.

Surprisingly, the questionnaires show no increase in safety experienced by oper-ators using the new grip. This may be caused by the fact that the prototype wasscarcely tested in very steep terrain, where the new grip would best show itsadvantages. The retest further revealed a new operator wish that was not recognizedin the first testing. The test operators also wanted to have a grip on the left insidesurface of the door opening. This modification is being further investigated.

21.5.3 P

EDALS

This type of excavator is designed to work in very difficult terrain (Fig. 21.8).Footrests were added to improve operator support possibilities while working withthe machine in a tilted position. Also, the outer pedals were turned 10

°

to enable amore neutral position of the leg and foot (Fig. 21.10). A foot switch that requiredfrequent pushing and 90

°

turning was removed, and its function was allocated to a

FIGURE 21.9

A console mounted armrest has poor adjustment qualities (here mounted in awheel loader).


257

joystick switch. Though they corresponded to a more natural foot position, operatorsdid not find the changed position of the pedals better than the parallel position. Onthe other hand, they did not find them to be worse.

Operators appreciated the fact that they no longer had to operate a switch with thefoot, but they had varying opinions about the new footrest to the right. Some said it wasnot needed. However, because it hardly obstructs the operator’s view they agreed that itshould be left in place. The new footrests in front of the tilted foot rests are appreciatedby the shorter operators, although the new rests should be extended a bit toward theoperator. One operator stated that he likes the seat up high so the air suspension in theseat works properly. With the new footrests, it is easier to reach the floor.

21.5.4 J

OYSTICKS

In the old situation there was a thumb-operated switch on the joystick that neededfrequent depressing during longer periods of time. This was replaced by a switchoperated by the index finger (see Fig. 21.11A and B) thus improving its position.By doing so the foot switch mentioned earlier could be replaced by a joystick switchto improve handling and reduce leg load. This switch had approximately the sameposition as the first mentioned thumb-operated switch, only higher up on the joystickto improve thumb position (see Fig. 21.11C).

In a meeting, the opinion of six experienced operators was asked, and theiranswers checked by an expert, as to whether different hand sizes could operate theswitches safely. With respect to joysticks, operator preferences vary greatly. Aconsensus was reached that the new joystick would definitely need getting used to,but it was better than the existing one. The switches have a better position and thejoystick is lighter, so the operating force can be reduced and it fits more hands thanthe older type.

21.5.5 F

RONT

W

INDOW

The window opening mechanism was improved, thus significantly reducing the loadon the operator’s shoulders and back. The standard pane was replaced by special

FIGURE 21.10

The position of the pedals (

A

, old configuration;

B

, new configuration).

258


heat-reflecting glass that reduced radiant heat buildup in the cab. Half of the testoperators found the changed window-sliding system easier to operate, but the otherhalf found it equal to the older type. One operator who found it easier said he alsobelieves that an operator has less control over the closing of the window when thecab is tilted forward. The effect of the heat-reflecting glass could not be evaluatedat the time.

21.5.6 H

EAT

R

EGULATION

The position and design of the air vent near the feet was changed in order to preventinadvertently closing the vent with the foot. Also, heat regulation in the cab wasdifficult because of a hard-to-control regulation switch. The regulation switch wasreplaced by a better one, and all operators find the new position of the air vent tobe better. They also found that the new regulation switch enabled them to adjust thetemperature better than before.

21.5.7 N

OISE

Several measures were taken to reduce noise in the cab (Fig.21.12). Though mea-surements revealed that the interior sound level decreased by 5 dB inside the cab,most operators had not noticed this due to the fact that they mostly work with either

FIGURE 21.11

The frequently used thumb-operated switch on the joystick (

A

) was replacedby an index finger operated switch (

B

). The foot switch was replaced by a joystick switch(

C

: lower middle switch).

B. C.

A.


259

the front window or the door open. Measurements had been made with both doorand window closed. Surprisingly, the retest brought another fact to light that hadnot been noticed previously. One operator experienced an increase in cab noise whileworking with an opened front window rather than a closed window. The noiseincrease observed may well have been caused by the reflection of cab noise fromthe window. When it is open, the window covers the padded ceiling of the cab. Thisnoise phenomenon certainly deserves attention in the future.

21.5.8 R

ETEST

R

ESULTS

FOR

ETEC

The changes to the ETEC machine will not be explained here, because they aresimilar to changes made in the Paus and Kaiser machines. Six subjects experiencedin operating the original ETEC machine tested the new ETEC machine. Table 21.1gives an overview of the results. Improvements in grip, view, and noise reductionwere evaluated as especially positive.

21.6 CONCLUSIONS

The improvements discussed in this chapter are, in fact, details. However, thesedetails solved problems mentioned by end users, and in the retest the end usersmentioned that most details had a positive effect on comfort, and even on workoutput. The retests showed that, as a whole, the improved prototypes provide bettercab comfort than their predecessors, due to the various small improvements in theseat, controls, climate, view, and noise level.

An important step in work-related musculoskeletal risk reduction in the armwas taken in collaboration with seat manufacturer Grammer, who designed amultiadjustable armrest on their seat to which a joystick can be mounted. This wasthe first seat-control system for earth-moving machinery in which armrests andjoysticks are adjusted together. Both are thus easier to adjust by the operator andoffer better positioning of the controls relative to the operator.

FIGURE 21.12

The padding of the cab’s outside floor (

A

) and side (

B

) panels with soundinsulating material around the engine.

260

Co

mfo

rt and

Design

: Princip

les and

Go

od

Practice

TABLE 21.1Overview of the Opinion of Six Operators in the Retest

ETEC retest results # of answersop. 1 op. 2 op. 3 op. 4 op. 5 op. 6 better equal

ingress–egress general 2 1 2 2 1 1 3 3grips techn construction 1 1 1 1 2 1 5 1

ingress-egress comfort 2 1 2 2 1 1 3 3muscle load 1 2 2 2 2 2 1 5

view: window sill techn construction 1 1 1 1 2 1 5 1view on work 1 1 1 1 1 1 6 0

front window: opening techn construction 1 2 2 2 2 2 1 5position of grips 1 1 2 1 1 1 5 1muscle load 1 2 1 1 1 2 5 1

view: rooftop window techn construction 1 1 1 1 1 1 6 (good) 0view through window 1 1 1 1 1 1 6 (good) 0usability 1 1 1 1 1 1 6 (good) 0

noise next to the machine 1 1 1 1 1 1 6 0in cabin with door closed 1 1 1 1 1 1 6 0sound comfort 1 1 2 1 1 1 5 1

improvements effect on work output 1 1 1 1 1 1 6 0

op.

=

Operator1

=

better, 2

=

equal, 3

=

worse, 4

=

no opinionquestion rooftop window. 1

=

good, 2

=

reasonable


261

In the final meeting of this project the companies mentioned that they consideredthe retest to be a very important part of the project. Information from the retest madethe effects of improvements explicitly known to the manufacturers. Although theimprovements were based on problems mentioned by end users, they did create achanged cab. Only retesting by the end users could reveal whether the right adjust-ments to the cab were made. With this information, manufacturers are better ableto make plans for their future products, which is very important considering thecompetition in this market sector.

ACKNOWLEDGMENT

The authors wish to thank the EU (Mr. Katalagarianakis), Paus GmbH, Kaiser AG,and ETEC (Van Vliet) for their support and collaboration.

REFERENCES

Krause, F., Bronkhorst, R.E. and Looze, M.P. de, eds. (2003)

Comfortable Earth-MovingMachinery

, Hoofddorp: TNO.Kuijt-Evers, L.F.M., Krause, F. and Vink, P. (2003) “Aspects to improve cabin comfort of

wheel loaders and excavators according to operators.”

Applied Ergonomics

, 34(3):265–272.

Noro, K. and Imada, A. (1991)


, London: Taylor & Francis.Oliver, M., Richards, J. and Biden, E. (2000) “Off-road machine controls: Investigating the

risk of carpal tunnel syndrome.”

Ergonomics

, 43(11): 1887–1903.Vink, P. and Kompier, M.A.J. (1997) “Improving office work: A participatory ergonomic


Ergonomics

, 40(4): 435–449.

263

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

22

Concept of a Future Nissan Car Interior

B.J.A. van Haperen, P. Vink, C.J. Overbeeke, J.P. Djajadiningrat, and S.H. Lee

CONTENTS

22.1 Introduction ................................................................................................26322.2 Experiential Design....................................................................................26422.3 Influencing Experience...............................................................................26522.4 People .........................................................................................................26522.5 The Car.......................................................................................................26622.6 The Environment........................................................................................26822.7 Time............................................................................................................26822.8 Summary of People–Car–Environment–Time...........................................26922.9 The Idea Phase ...........................................................................................26922.10 Three Elaborated Concepts ........................................................................26922.11 Toward the Final Design............................................................................27122.12 Final Concept .............................................................................................271

22.12.1 Collecting Information on theEnvironment...............................................................................272

22.12.2 Select and Watch .......................................................................27422.12.3 Ending the Experience ..............................................................27822.12.4 The Exterior...............................................................................278

22.13 Conclusions and Discussion ......................................................................278Acknowledgment ...................................................................................................280References..............................................................................................................280

22.1 INTRODUCTION

The previous chapter demonstrated the effects of small changes on the experienceof comfort. Of course this is important to achieve short term effects, but to stayahead of competitors long term developments are needed as well. This chapterdescribes the process of designing a more future-oriented car interior.

Car manufacturers have to be very competitive to keep, and preferably expand,their market share; new products are a must. To find out which new products will

264


be successful, concept cars are often shared with future buyers. In this study, thedevelopment of a concept for a new car interior is described. The project is acollaboration between Nissan, Creative Box Inc., and the industrial design fac-ulties of the Delft University of Technology and the Eindhoven University ofTechnology. Creative Box Inc. is perhaps not so well-known and may need someintroduction.

Car Styling

magazine sharply described Creative Box as NissanDesign’s “think-tank.” Most of the work of Creative Box, mainly the design ofnew concept cars for various motor shows throughout the year, is commissionedby Nissan.

In this project, Creative Box was interested in the design of a new conceptinterior for young people living in Tokyo. The approach that was used in this projectis the

experiential design

approach (Overbeeke et al. 2003). As discussed in Chapter 2,discomfort is more related to physical characteristics, whereas comfort is morerelated to experience, emotion, unexpected features, and luxury. The experientialdesign approach is particularly interesting in regard to comfort, and is therefore alsodescribed in this book.

This chapter first presents a short description of experiential design, followedby an orientation to the possibilities for innovation in the car interior. Based on thisknowledge, new ideas were generated that led to a final design concept.

22.2 EXPERIENTIAL DESIGN

The experience of a person is the basis for the design in the experiential designapproach. In this case, the experience of the car interior is the central issue. A carride is more than just getting from point A to point B. It is a total experience. Intraditional design methods the designer often provides a package of functions (thecar) that is presented to the user, with the main objective being to let the userunderstand the functions (Fig. 22.1). Experiential design focuses on the quality ofthe user’s experience during the whole period of engagement with the product(Fig. 22.2).

In order to experientially design a product, first, the (desired) experience mustfirst be clear to the designer. But what exactly

is

an experience? The dictionary(www.dictionary.com) is very clear on this subject: Experience is the apprehension

FIGURE 22.1

Traditional design.

SystemImage

(product)

User'sModel

DesignModel


265

of an object, thought, or emotion through the senses or the mind. Although onemight argue about the exact wording of this definition, the keywords are obvious:

object,

emotion,

senses,

and

mind

. Everybody has the same sensorial apprehensionof an object, but our experiences are different because for each person differentemotions are elicited.

22.3 INFLUENCING EXPERIENCE

The car is not the only factor that has an influence on the experience of the ride. Inthe definition of

experience

it was already mentioned that an experience differsstrongly between individuals. However, the total experience of sitting in the car isalso different from being outside of it. The environment that is passed by while drivingalso influences the experience. Finally, the experience changes over time as well.An

enhanced car ride

should link these factors — people, car, and environment —through the whole period of the car’s use. One might say that a

bond

between thefactors should be elicited. In the next paragraphs, these factors and their influenceon the experience are described in more detail.

22.4 PEOPLE

Most designers are aware of the difference between people and their wishes. Thisstudy focuses on young people living in Tokyo, because this is the target group forthe new interior. Based on observations and on interviews with people familiar withthe area, the group can be given the following description.

The Tokyo districts Shibuya, Shinjuku, and Harajuku especially are inhabitedby some of the most fashionable people in the world. Night and day, people between20 and 30 years old dominate the streets. These are the trend makers, or

earlyadapters

. They spend a lot of time with friends (family is less important), and theyare always looking for a good time in life. Contact with others is very important,and seeing and being seen is crucial!

These attitudes are also important in terms of the products they use and buy.Whether the products are for daily use or for a special occasion, both personalpleasure and expressing a desired image to others are extremely important.

FIGURE 22.2

Experiential design.

SystemImage

(product)

User'sModel

DesignModel

266


22.5 THE CAR

The enhanced car ride is not a new concept to manufacturers. Several designs alreadyemphasize this approach. Next to the popular small cars, there is a trend toward(bigger) interiors with a secondary function that is not so closely related to driving(Figs. 22.3 and 22.4).

These interiors are made both for recreational purposes and for professional use.An example is the Ford Galaxy, which has power outlets and seats that can bechanged into worktables. Technical developments also support the interior designer.Smaller engines — maybe even integrated into the floor panel (Fig. 22.5) — andsmart construction with more use of plastics, for example, offer greater volume andadditional possibilities for the interior. Also, the more

organic

interiors that arewithin reach because of these new production techniques have drawn the interest ofthe designers (Fig. 22.6).

One of the best-known current examples of a car that tries to adapt with ouremotions is the Toyota POD (Fig. 22.7). In this concept car, activity within the carand the driving style are used to capture or display emotion. For example, the lights

FIGURE 22.3

Isuzu Funkybox: a mobile recreation room. (Courtesy of Isuzu.)

FIGURE 22.4

Renault Ellypse: a very plausible solution for relaxing in a car. (Courtesy ofRenault.)


267

FIGURE 22.5

General Motors’AUTOnomy: fuel-cells, engines, and steering combined intoone. (Courtesy of

Car Design News

: www.cardesignnews.com)

FIGURE 22.6

BMW CS1: A more organic use of materials. (Courtesy of

Car Design News

:www.cardesignnews.com)

FIGURE 22.7

Toyota’s POD is one of the first examples of a new implementation of elec-tronics. (Courtesy of Toyota.)

268


on the exterior of the car change color according to the driver’s behavior. Still, thisconcept focuses mainly on measuring and displaying emotions—not on influencingemotions or interacting with the passengers or driver.

Finally, the application of electronics continues to grow in many cars. Mostcurrently used techniques have been available for ten years, but they have becomereally affordable only in the last few years. The use of the electronics still has roomfor improvement, because it is not always optimally adapted to the user’s needs andwishes. When a person needs to press the same button eight times to change fromradio to CD player, or to adjust the air conditioner, there is an obvious gap betweenwhat really works and what is useful.

22.6 THE ENVIRONMENT

The cars belonging to people who live in large cities usually are not just for drivingwithin the city. Public transport is often more convenient and faster. However, whenpeople take a trip with others to a location outside the city, for example, the flexibilityof the car is preferable. It is therefore likely that a car bought by young people ina city will mostly be used for that purpose. During those car rides, there is a greatdifference between the part in the city, and the part on the (open) highway. The rideusually starts in the city, where it is very crowded, and many things can happen.The city is an interesting place to drive through, but the high buildings, traffic lights,neon signs, and crowds sometimes generate too many impressions. Contact withpeople outside the car is brief, but close.

All this is in contrast with the highway, which may be relatively empty. Theroads are straight, and the sound shields at the sides of the road often create a boringview. Contact with people in other cars may last for a longer time, but at a greaterdistance. On this highway portion of the ride the interior of the car, and the travelersinside it, become more important. The focus shifts from outside to inside.

22.7 TIME

Time in relation to a car can be divided into short-term and long-term contact. Long-term contact can be defined as the relationship, or bond, that a person has with thecar. The bond is created because the long-term contact consists of all of the momentsof short-term contact. In this study, we take

one car ride

as the definition of short-term contact.

First the person approaches the car, opens the door, takes a seat, and preparesto ride. Next, the trip begins by starting the car and driving through differentenvironments, adjusting controls in the car, picking up friends, and communicatingwith others. This communicating and sharing of experiences is seen as very importantto the target group of this study.

Finally, the destination is reached, people get out and the car is locked. This isthe actual end of the experience. Realizing this it is obvious that a car ride is morethan just driving. The ride can be divided into three phases: initiate, travel, and end.It is clear that the experience needs to be enhanced throughout the whole process,not just during the travel phase.


269

22.8 SUMMARY OFPEOPLE–CAR–ENVIRONMENT–TIME

The previous paragraphs explained that in order to fully influence the experienceof a car ride, four important factors need to be taken into regard: people, product,environment, and time. The future users live in a world where it is important thatproducts provide both pleasure and the possibility to express a desired image.For young people this means a rapidly changing style and interest. Currenttechnology provides more freedom for designers to meet these wishes. Electronicsare more frequently seen, and spacious interiors with more flexibility have beenintroduced.

When the car is used, two main environments are encountered: The crowdedcity with many impressions and the boring, less interesting highway. Especially inthis last area the car can provide a more exciting experience. Regarding the aspectof time it is important to realize the complete car-user interaction must be considered:from approaching the car to stepping away from it after the ride.

With this knowledge the basis for new ideas to enhance the experience of thecar ride was formed. How these ideas were elaborated is described in the next section.

22.9 THE IDEA PHASE

In this phase, several uncompromising new ideas were created for enhancing the carexperience. To begin with, sketches were created with one car ride as a startingpoint. In this car ride, contact with the car was conducted as if the car were a humanfriend. This resulted in the insight that such contact should be about two-way

interacting

, not just an action-reaction event. To achieve this interaction, a conceptualway of designing was used that resulted in somewhat wild, but inspiring, ideas. Forinstance, instead of a person having to put on a safety belt, the car actually

hugs

theperson, creating a warm and welcoming feeling.

These different ideas were shown to potential users and other designers. Basedon their comments and reactions, a second and more realistic range of ideas wascreated. This resulted in seven main concept directions. Of these, three illustrativeconcepts are described in the following section.

22.10 THREE ELABORATED CONCEPTS

1. Direct contact with people (Fig. 22.8)This idea focuses on enhancing communication between persons. In cur-rent cars communication between the front seat and the rear is not com-fortable. To enhance communication the interior of existing cars can be

transformed

, but this transformation needs to take place before the ridestarts. Communication within a group is often not a planned action,according to a predefined pattern. By giving the user the opportunity toflexibly adjust the interior while driving, optimal communication condi-tions can be realized at any time.

270


2. Personal settings vs. group controls (Fig. 22.9)Communication with the car and with other passengers can also be influencedby controls. Personal settings can be made real personal by placing themclose to, or actually

on

the body. In a practical situation these personal controlscould be built into the safety belt. Not only do others keep their hands off

your

controls, but also the bond with the vehicle is genuinely improved. And,as an advantage the user has an extra reason to wear the safety belt.

In contrast to personal controls are group controls. By sharing functionssuch as the car’s audio system, the interaction between people in the car isimproved. In both ideas controlling the car has an influence on the way

FIGURE 22.8

A flexible interior for better communication and a spacious feeling.

FIGURE 22.9

Adjust the setting in an interesting, social way.


271

people interact. Next to the location of the controls, the way these controlsare operated can also be improved. Making digital controls more physicalcreates controls that are easier to understand, and more fun to use. Forinstance, one can actually place the next song into the radio system or turna speaker to open it and get more volume.

3. Direct contact with the environment (Fig. 22.10)A bigger window surface, or even an open body, can improve the directcontact with the environment. It is not only easier to look outside, but itis also easier for people outside to see the people inside the car.

22.11 TOWARD THE FINAL DESIGN

Seven ideas, including the three mentioned above, were shown to Japanese andDutch designers and students — all young people living in an urban area. Thediscussions that followed led to the understanding that almost all ideas have potential,although some of them are just a support to the bigger picture. The flexible carinterior, for instance, provides the necessary freedom to have more contact, but itwas not seen as a really exciting new concept. However, the freedom does help toget an enhanced experience up to a certain level. In fact, the designers and studentspointed to using multiple ideas into one concept.

Therefore, many ideas were combined to create one design in which enhancedcontact with the environment is the main concept. How this enhancement is con-trolled, and how it influences the social behavior inside the car is based on the ideasdescribed in the previous paragraph. The final design constrains the styling of thecar as little as possible. Different cars can have the same elements, but with differentstyling. A

style-free

concept shows that the design ideas can be applicable to manycars. This notion is further clarified in the following section.

22.12 FINAL CONCEPT

The final concept is presented with the future in mind, a future where cars can driveautomatically. Nowadays, experiments are conducted in which cars can click togetherinto

trains

on the highway and drive with a fixed distance between them. Such

FIGURE 22.10

An open car for direct contact with the environment.

272


systems will become more and more advanced in the future, which means thateveryone in the car will have the freedom to communicate or to do other thingswithout risk. A flexible interior will help them to turn the seats and face each other,or to have a better look outside.

The car windows and roof in this final concept are big displays. Future organiclight-emitting diode (OLED) technology will be able to create a display on a simplepiece of car window glass (Fig. 22.11). When the driver walks toward the car, thisdisplay becomes transparent, as if the car is welcoming the driver with an invitationto come inside (Fig. 22.12).

The most important aspects of the final concept are: how the information iscollected, how the user handles the data, the way the ride ends and how the exteriorwill look to others. All these were designed with the user experience as a basis.

22.12.1 C

OLLECTING

I

NFORMATION

ON

THE

E

NVIRONMENT

As described earlier, the city provides an overflow of information to the drivingexperience, whereas the highway is much quieter. In order to create a better balance,the overflow of information can be taken from the city to the highway. When the

FIGURE 22.11

OLED, a display on glass.

FIGURE 22.12

The car

opens

as you approach.


273

car drives through the city it passes many sources of information that are surroundedby

location-based surfaces

(Fig. 22.13). Whenever the car drives through such asurface, an internet-like connection is opened and a small image (thumbnail) isprojected onto the roof. These images create a riverlike flow of information fromthe front of the car to the rear (Fig. 22.14). By adjusting the width of this river, theamount of received information is controlled.

FIGURE 22.13

A location-based surface (LBS).

FIGURE 22.14

Information flows from front to rear, over the roof.

274


In making such an adjustment, the combination between physical controls andthe digital world is very important. When the information river is turned off, thesliders (Fig. 22.15) are locked together, but a small part of the display remains turnedon. Because of the physical groove and the visibility of the display, the user easilyunderstands that the sliders can move, and that they can control something on thedisplay. This provides the necessary feed-forward and inherent feedback of infor-mation (Djajadiningrat et al. 2002).

Figure 22.16 shows the many information sources in the city. The size ofthe location-based surfaces around these sources depends on the width of thesliders (left and middle). The figure also shows the amount of sources differsfrom the city to the highway (right). In order to keep getting information the LBS’sare bigger. People in cars still receive information while on the highway, only less.The information is very diverse. It has to be provided by a variety of differentsources, and just one source can provide different kinds of information (Fig. 22.17).Sources can be movie theaters, stadiums, libraries, stores, and museums, amongmany other things.

22.12.2 S

ELECT

AND

W

ATCH

Now that the information is on the roof, it can be browsed through. Simple, easy-to-detect hand movements can shuttle the information flow back and forth, as inFig. 22.18. A thermal CCD, which is a sensor that creates a digital image from aheat pattern, detects the hand movements.

FIGURE 22.15

Widening the info-zone with physical controls.

FIGURE 22.16

LBS locations in the city (left and middle) and on the highway (right).


275

In case an interesting piece of information appears, it can be pulled to the sidewindow for a closer look. At the sides of the preview area on the roof, there areopenings for scrolling the information (again providing necessary feed-forward).To transport the information from the roof to the side window, the roof pillar barriermust be crossed by using a so-called

transporter

.

FIGURE 22.17

Information is place- and time-dependent. A stadium (left) will providedifferent information than a movie theater. The information from the stadium will also differfrom time to time. Examples of the information that can be provided are: (top) views younever get from the car, (middle) yesterday’s concert fragments, and (bottom) player information.

FIGURE 22.18

Browsing through content.

276


The transporter is a physical object that has a number of functions. First,images can be viewed in sequence and can be locked onto the window likewallpaper. The procedure is very simple: Just turn the transporter, and thus removethe path.

Second, the transporter (Fig. 22.19) can store an image, clip, or sound. This isdone simply by sliding information into one of the side pockets (Fig. 22.20). Whena clip is stored, the transporter can be taken off the pillar and given to somebodyelse in the car for viewing (Figs. 22.21 and 22.22). This physical interaction isnatural, is easy to understand, and improves the social contact in the car.

When a piece of information is watched, it can also be rated

good

or

bad

. Thisis done by pressing the thumbs-up or thumbs-down images that appear when ahand moves close to the side window. The car then filters new information thatenters the car according to the user profile that is built from these ratings. It is asif the location-based surfaces all have a different size for each car (Fig. 22.23).Some sources will be missed when the car isn’t close enough, but interesting sourcescan be farther away and the information can still be received. Note that the userprofile is bound to the car, not to the individual users. Since the owner uses the carmost often, the profile will be closest to his or her wishes — although there maystill be some surprises!

FIGURE 22.19

The transporter.

FIGURE 22.20

Putting content into the transporter.


277

FIGURE 22.21

Exchanging transporters.

FIGURE 22.22

Pushing information out.

FIGURE 22.23

Rating information to create a user profile.

278


22.12.3 E

NDING

THE

E

XPERIENCE

At the end of the car ride, the experience also comes to an end. This means thatthere is no need for further information, and it can just disappear. Of course, theinformation stored in the transporters can be saved, but the rest is gone forever. Theinformation doesn’t just disappear right away when the car comes to a stop. Some-times one needs to stop for gas, or to buy a snack and stretch the legs, or to have acup of coffee. Thirty minutes is normally more than enough time to do these thingsand start the car again with no information lost. If the car is stopped for a longertime, the information fades away (Fig. 22.24).

22.12.4 T

HE

E

XTERIOR

The information flow is interesting not only for the people

inside

the car. When thecar passes by, it will also draw the attention of people on the sidewalk. This meansthat the people inside get the attention they want and the people on the sidewalk getan interesting view. But it would be a waste just to use this big display when the caris being driven. When the car is standing still, the display can be used for otherpurposes. A company can place advertisement on it, people can play the newest videogames, or Nissan can use it to show their latest new models (Fig. 22.25). But whywould one give away this display space? What’s the advantage to the owner? Obvi-ously, advertisers are interested in crowded places, and parking fees are high there.An advertiser can pay this fee for the car owner, to the advantage of both parties! (Formore movies and more information on this subject see www.bartvanhaperen.com)

22.13 CONCLUSIONS AND DISCUSSION

The goal of this study was to create a new car concept for young people living inTokyo. These youngsters and their experiences were analyzed. Using many sketches,an enhanced experience was researched and discussed with the youngsters anddesigners. Based on this process, a final concept was developed. This final concept

FIGURE 22.24

Information fades away.


279

enhances the car ride and the experience young people have in their car, but in factit might be applied to any car for any group of people.

The new car concept provides many advantages for the user. It shows that usingelectronics can help people enjoy themselves more, and thus enhance their experi-ence. But it has to be implemented in a subtle way. The TVs, DVD players, or evencomplete computer systems we see nowadays are not coupled to the driving process,and in that sense are not enhancing the experience. Next to that, the question iswhether these items lead to an improved experience of comfort, or a better experiencein general. Or is the experience of traveling traded for the experience of watchinga TV? Taking information from the environment creates many new opportunitiesand possibilities for great improvement.

Another improvement is in how the information is handled. Many interfacedesigners still try to create a format that burdens the user with functionality. Tech-nology allows for all these functions, but that doesn’t mean people want them, andmost people hate to control screens with just one button. Separating functions andcombining physical controls with the digital world not only creates an interface thatis more fun, but one that is easier to understand as well.

Of course, some unsolved questions still remain. Who should prevent so-calledpirates from sending out viruses or, with less destructive results, spam? Who keepstrack of the quality of the information? And why do people want to send out infor-mation in the first place? To these questions we have no clear answer. There will

FIGURE 22.25

Extra options while parking.

280


always be vandals, but since the information is location-based, tracing the source andshutting it down will be much easier. Also, by rating the information received theoverall quality of the information will rise. Sources want people to look at theirinformation, so they need to make it interesting.

Finally, next to noncommercial sources that simply want attention, companiescan learn very fast whether a new product, such as a movie, is popular or not — agood reason to create an information source.

The concept discussed in this chapter might still seem far-fetched to some people,but the technology is closer than we think. Big OLED displays can be expectedwithin ten years, and the CCD hand tracing is in its test phase already. What iscertain, however, is that product design should take the lead in opening up thesenew technologies for the user. That is essentially what this chapter is about.

ACKNOWLEDGMENT

Special thanks are extended to Creative Box Inc., and all their employees. Theyoffered the opportunity to conduct this project at their offices, and without their helpthis chapter would not exist. Many thanks are offered also to all who helped in anyway to finish this project.

REFERENCES

Djajadiningrat, J.P., Overbeeke, C.J. and Wensveen, S.A.G. (2002) “But how, Donald, tell ushow?” In

Proceedings of DIS2002

, London: 285–291.Overbeeke, C.J. and Tax, S.J.E.T. (2001) “Designing products with added emotional value:

Development and application of an approach for research through design.”

The DesignJournal

, 4(1): 32–47.Overbeeke, C.J., Djajadiningrat, J.P., Hummels, C., Wensveen, S.A.G. and Frens, J. (2003)

“Let’s make things engaging.” In Mark A. Blythe, Andrew F. Monk, Kees Overbeekeand Peter C. Wright, eds.

Funology: From Usability to Enjoyment

, Dordrecht: Kluwer.

281

0-8493-2830-6/05/$0.00+$1.50© 2005 by CRC Press LLC

23

Costs and Benefits of Comfort Products for Professional Use

E.A.P. Koningsveld

CONTENTS

23.1 Introduction ................................................................................................28123.2 Method........................................................................................................28123.3 Case 1: Glaziers .........................................................................................28323.4 Case 2: Cleaners in Home Care ................................................................28523.5 Conclusions ................................................................................................287References..............................................................................................................287

23.1 INTRODUCTION

In the previous chapters, design processes and evaluations of products related tocomfort and discomfort are described. This chapter focuses on the costs and benefitsof these products. The general perception is that the implementation of improvementsis hampered by a lack of consciousness of costs and benefits and by a deficiency ofdata (Jong 2002). Several models are available to study cost and benefits (Stantonand Baber 2003; Beune 2001; Koningsveld and Thé 2000; Koningsveld 2003; Kon-ingsveld et al. 2002). In our research and consultancy projects our clients needed arather simple model, which will be described in this chapter.

First a general model is described, based on experiences in projects and theliterature (Reyneveld 2001; Koningsveld 2003), followed by two examples in whichcosts and benefits are calculated. One example concerns a work situation in whichdiscomfort by physical loads are evident. The second example concerns proposalsto improve the work of cleaners in the home care industry.

23.2 METHOD

The word

costs

indicates the actual costs in terms of money, as well as other efforts,that cannot be represented in quantitative terms but can be indicated by qualitativemeasures, such as attractiveness, increased health, or reduced discomfort.

Benefits

282


can be productivity gains, lower costs, and higher quality, as well as nonquantitativeadvantages.

There may be

negative

costs, for instance if a grant is received or if certainmeasures do not have to be taken when an improvement is implemented. Forexample, if a rolling carpet is chosen as the floor of a loading space in a van inorder to decrease the discomfort of people who deliver parcels, the wooden floorthat is usually ordered in a new van does not have to be bought.

Benefits can also be gained by reducing costs. Negative benefits are possible aswell, for instance in a case where the output of a work station is reduced by theimplemented safety improvements.

The aspects to consider in regard to the cost/benefit issue are

• Investments (consultancy, selection of solutions, purchase, installation,training, grants)

• Operating costs (maintenance, space, energy, interest, and personnel costs)• Health (health complaints, lost working days, disability, insurance, and

occupational rehabilitation)• Safety (safety behavior, accidents, and near-accidents)• Performance (productivity, output, time to market, lead time, service level,

quality, flexibility, personnel turnover, and recruitment power)• Liability (costs of processes, lawyers, penalties, and claims)• Values, standards (image: “We pay serious attention to health and safety!”)

There are no general rules on how to value a parameter. For instance: what arethe costs of a lost working day? Possible answers to that question include thefollowing:

• The absent worker’s wages for that lost day.• The production that was planned but not realized.• The costs of a temporary worker. In addition, the differences in output

quantity and quality between the regular and the temporary worker maybe considered, as well as the costs involved in losing a client as a resultof the mistakes made that day.

It is clear that in each individual case it is necessary to determine the real costsfor all aspects, as well as the real benefits.

Depending on the goal of a costs and benefits evaluation, the appropriate methodcan be chosen. A quick scan is adequate for a relatively small investment, in orderto improve the work of one person or a small group. For long-lasting improvementswith a wide scope, a more thorough assessment of factors and parameters is moreappropriate. In general, if estimations have to be made, it is advisable to make themin close collaboration with the responsible management. They have easy access todata and are familiar with the business indices. Management involvement preventsthe consultant from having to prove the data. Because management has taken partin validating the data, the outcomes are traceable and acceptable.


283

23.3 CASE 1: GLAZIERS

The work of glaziers is physically straining (see Chapter 6); it results in discomfortand in an unacceptable level of health hazard. In particular, the double panes thatnowadays have become common are heavy.

Over the past years several new tools and methods of transport have beenintroduced. These tools and methods were developed in a participatory ergonomicsproject (Urlings 1998). Despite a lot of promotional activities, the implementationof these improvements on the work floor goes slowly. Employers are reluctant,because they doubt their investments will be repaid.

In a costs and benefits evaluation a set of tools was considered: 1) a simple cranemounted on the glaziers’ van to help hoist the glass on and off; 2) two carts, eachof which has a specific application depending on the transport circumstances; 3) analuminium hoisting unit ten meters tall for lifting panes vertically to the windowframe; and 4) a new electric hand tool that eliminates the strain of manually cuttingglass putty. All of these devices are always available in the van, so the workersthemselves can choose which aids to use in a certain situation (Fig. 23.1).

The investment leads to annual depreciation costs of

€

640 (Table 23.1). Thetime required to learn to work with the new methods is short and can be depreciatedover many years. Therefore, the annual costs will be very small and are not takeninto account (these are stated as

pro memoria

). The annual exploitation costs consistof an inspection of the crane and some maintenance for

€

200, so the total annualexpenses amount to a total of 840 (Table 23.1).

For the benefits, we look at the performance of the workforce. According to law,the maximum lifting weight is 25 kg per person. To handle and lift glass panes of

FIGURE 23.1

A simple cart for the transport of windowpanes by glaziers.

284


more than 50 kg the regular team of two glaziers will need a third man, which indeedis the practice when necessary. Together with management it was estimated that thethird man spends a total of 15% of his working time to get to and help a team oftwo glaziers. That represents 15% of his wages (

€

26,000/year). With the new toolsand lifting devices no third man is needed, so the reduction of costs annually is 15%of

€

26,000, or

€

3900. The costs of travel to the jobsite for that third man are includedin the calculation.

Analysis of work has shown that the net productivity hardly differs when theglaziers use the improved methods, but the time spent for rests was reduced by about10%. Presumably this is the result of a reduction of the musculoskeletal workload. Itmay be expected that part of that time formerly spent resting will be used to performmore work. Since a working day consists of many different tasks, including travel,management and consultants estimate that an increase in productivity of 3% is likely.This is equivalent to 3% of the margin between the turnover of two men, minus theirwages. The team’s annual turnover is 1670 man-hours times two men times

€

35/hour,a total of

€

116,900. Their annual wages together are twice

€

26,000, or

€

52,000. Sothe margin of their work is

€

64,900. Therefore, the new working methods produce again in productivity of 3% of

€

64,900, or

€

1947 per year.The increased productivity does not mean that the workload and the discomfort

will not decrease. Peak loads on the back, arms, and shoulders in particular are reduced.As a result, the related health complaints are expected to decrease, and so will thenumber of lost working days. The absenteeism rate in this branch of industry is 7%.From previous projects (Koningsveld and Thé 1999), we know that 45% of the absen-teeism among glaziers is caused by musculoskeletal disorders, and 50% of these casesoriginate mostly or completely in the work. That means that 7% of 45% of 50%, or1.58% of the work force is lost by absenteeism as a result of manual handling problems.

When the workers do use the improved tools and methods frequently, the mostphysically straining work is eliminated, though not all of it. Therefore, it is likelythat only part of the work-related absenteeism caused by musculoskeletal disorderswould decrease. Ergonomists have estimated a decrease of 40%. So the decrease inabsenteeism would be 40% of 1.58%, or 0.63%, with a value of

€

328 per year(0.63%

×

2 men

×

€

26,000 wages).

TABLE 23.1 Investment, Depreciation, and Operating Costs of New Equipment for Glaziers

Equipment Costs Depreciation time Annual costs

Crane mounted on the van

€

1250 5 years

€

250Cart 1

€

150 5 years

€

30Cart 2

€

250 5 years

€

50Electric glass putty cutter

€

300 5 years

€

60Aluminium hoisting unit

€

1250 5 years

€

250Annual inspection, maintenance

€

200 —

€

200

Total annual costs

€

840


285

The benefits generated by productivity gains and reduced absenteeism add upto an annual total of

€

6175. When these benefits are compared to the annual costsof

€

840, we can conclude that the financial ratio is very positive.In addition, several nonfinancial benefits can be seen. Work-related discomfort

is decreased and the health of the glaziers will be better over the long term, soit is more likely that they can stay active in their work. These points are importantfor employers, because the recruitment of new young workers is a big problem.If the workload is lighter, more people can perform the work, and recruitmentcan be directed at a larger target group. The risk of damage to the panes, to theframes, and to parts of the building is reduced because the carts and hoists allowbetter control over the handling process. The risk of cutting and falling accidentsis also reduced.

Table 23.2 presents the usual information given in a cash flow table. The benefitsare given as negative amounts and the costs as positive amounts.

23.4 CASE 2: CLEANERS IN HOME CARE

Those who work as cleaners in home care organizations encounter several problemsin their work. First, the work is not appreciated as important. Second, the cleanershave to work with the equipment and methods that happen to be available in theclient’s home. The home care organizations suffer from high absenteeism rates, ahigh personnel turnover, low customer satisfaction, and an even lower worker sat-isfaction. The employers’ organizations and the employee unions decided to collab-orate with the aim of improving the work.

One of their proposed interventions is the development of a new set of tools andprocedures for cleaning. The system is based on microfiber technology. Cloths forcleaning surfaces can be used without chemical additives and only a little water.The cleaning is done with only minor physical effort, because the cloths don’t needto be wrung out. The whole cleaning set is based on this kind of material, so mopsand even feather dusters are newly designed. A specially developed bag contains all

TABLE 23.2 Financial Costs and Benefits of New Equipment for Glaziers

Cash flow

Per yearInvestments

• Depreciation costs

€

640• Training in new working methods p.m.

Operating costs

• Inspection, maintenance

€

200• Reduction of lost working days

−

€

328

Performance:

• No 3rd man needed

−

€

3,900• Increased productivity

−

€

1,947

Total cash flow

−

€

5,335

286


or most of the materials and shows that the cleaner is a professional using profes-sional methods. All of this improves the comfort aspects of the work.

Like some other important factors, the costs/benefits ratio is of major concernto the management of home care companies. The initial investment in cleaning setsis high, and the benefits cannot always be been seen easily.

In close collaboration with a major supplier, management from home careorganizations, ergonomists, and a costs/benefits expert, a computer model is con-structed in MS Excel in order to calculate three options:

• The whole set of tools and cleaning cloths stays with the client.• Part of the set stays with the client, but the cleaner owns a personal set

of cloths and takes care of the cleaning process.• The whole set belongs personally to the cleaner, who takes it to and from

the client’s location. The set can be carried as a bag on the shoulder, orit can be hung on the bicycle.

Cost categories to be considered are the initial investment; replacement ofcloths and tools after a specific term; training; information to workers and toclients; and costs of absenteeism. Turnover of personnel and of clients is alsotaken into account, and each individual home care organization can fill in its ownspecific data (Fig. 23.2).

Benefits are calculated by reduction of the costs to replace absent workers. Thecompany chooses out of four solutions to help solve the problems created by lostworking days:

• Temporary workers• Overtime work• Larger work force (same % as the absenteeism rate)• No service to the home if a cleaner is ill

FIGURE 23.2

The input data for the costs and benefits calculation for home care cleaning.


287

In addition to reducing the cost of lost working days, a 15% higher productivityrate can be reached by using the new set of cleaning tools. However, most cleanerswork only a couple of hours a day and visit only two or three clients, so that productivityincrease would not lead to more clients per day. Instead of a reducing the extent ofthe cleaners’ contracts, most home care organizations prefer to allow their cleaners touse the extra time for providing social care and attention to the client. It is proven thatthis helps to improve both the quality of work and the quality of service.

Returning to the cleaning set options discussed earlier, results show that in mostcases, option A (the whole cleaning set remains at client’s place) is too expensive.This option yields a positive ratio only if a relatively large number of hours are spentper client per week. With option B, the ratio depends mostly on the extent of thecleaner’s contractual working hours per week: Above ten hours per week the benefitsexceed the costs. Option C is beneficial in almost all cases.

Of course the choice of how to solve the absenteeism problem is important.Temporary workers are a costly solution, although they offer maximum flexibility.A larger workforce is cheapest, but basically not very flexible.

With the computer model developed for this study, a home care company canget insight into the financial consequences of all options when considering changingthe cleaning tools and procedures. The most comfortable solution for the workersis relatively costly, and it is likely to be a solution that does not completely repaythe investment. Nevertheless, some companies choose that option in the belief thatgood working conditions are always a good investment.

23.5 CONCLUSIONS

Investing in products that increase comfort or reduce discomfort can pay off. Thischapter describes a method for managing professional products that is successfulwhen applied on a variety of products. It is difficult to have the payback completelyfinanced by sick leave reduction, and combinations with productivity increases areoften more interesting (see also Chapters 5 and 7).

REFERENCES

Beune, H.A.Th. (2001) “The approach of physical load in Dutch homecare.” In C.H. Nygaard,T. Luopajärvi, S. Lusa and M. Lappänen, eds.,

Proceedings of NES 2001: Promotionof Health through Ergonomic Working and Living Conditions

(Tampere, Finland)University of Tampere, School of Public Health: 402–406.

Jong, A.M. de (2002)

Improving Working Condition at the Construction Site

, Delft: Universityof Technology (Ph.D. thesis, in Dutch).

Koningsveld, E.A.P. and Thé, K. (2000) “Ergonomics and economics: Dilemmas andchances.”

Proceedings of the 14th Triennial Congress of the International ErgonomicsAssociation

, San Diego (on CD-ROM).Koningsveld, E.A.P. (2003) “Indicators that convince management, workers, and supporting

departments.” In H. Luczak and K.J. Zink, eds.,

Human Factors in OrganizationalDesign and Management

,

VII

. Re-Designing Work and Macroergonomics—FuturePerspectives and Challenges,

Santa Monica: International Ergonomics Association,753–756.

288


Koningsveld, E.A.P., Dul, J,. Rhijn, J.W. van and Vink, P. (2003) “Enhancing the impact ofergonomic interventions.” In

Ergonomics in the Digital Age. Proceedings of the 15thTriennial Congress of the International Ergonomics Association

, Seoul (onCD-ROM).

Koningsveld, E.A.P. (2003) “Costs related to working conditions in the construction industry.”In H. Strasser, K. Kluth, H. Rausch and H. Bubb, eds.,

Quality of Work and Productsin Enterprises of the Future,

Stuttgart: Ergonomia Verlag, 208–212.Koningsveld, E.A.P. and Thé, K. (1999)

Macro Costs of Poor Working Conditions in theDutch Construction Industry

, Amsterdam: Elsevier (in Dutch).Koningsveld, E.A.P., Bronkhorst, R.E. and Schoenmaker, N. (2002

) A Pilot Study into theCosts and Benefits of Solutions in the Field of Design for All and Disability Man-agement

,

Hoofddorp: TNO Arbeid (in Dutch).Koningsveld, E.A.P., Overbosch, H. and Bronkhorst, R.E. (2003) “Costs and benefits of design

for all.” In

Ergonomics in the Digital Age. Proceedings of the 15th Triennial Congressof the International Ergonomics Association

, Seoul (on CD-ROM).Reyneveld, K., Koningsveld, E.A.P. and Rhijn, J.W. van (2001)

Costs and Benefits of ErgonomicInterventions in the Assembly Industry

, Hoofddorp: TNO Work and Employment (inDutch).

Stanton, N.A., Baber, C.(2003) “Editorial: On the cost-effectiveness of ergonomics.”

AppliedErgonomics

, 34: 407–411.Urlings, I.J.M., Bronkhorst, R.E. and Grinten, M.P. van der (1998) “A participatory ergonom-

ics approach to redesign working methods and tools of glaziers.” In P. Vink, E.A.P.Koningsveld and S. Dhondt, eds.,

Human Factors in Organizational Design andManagement

,

IV, Amsterdam: Elsevier, 597–602.

289

Index

A

ADAPS, 202Adjustable chair, 101Adjustable table, 101Airplane comfort, 4Alstom, 239Althoff, 148Andersson, 148Arbouw, 73Arisz, 209Armrest, 23, 164, 243, 256Armstrong, 21ASPA, 153Assembly, 111, 130Assembly Process Scheme, 119Attebrant, 27

B

Back shell, 165Backrest, 23, 149, 164Bag sealing, 219Bahco Tools, 184, 190, 216 Batchwise, 128, 131Bauer, 201Becker, 239Bernoux, 83Beune, 281Biometrics, 185Blatter, 181Bobjer, 184, 207Body height, 143Bombardier, 155Bongers, 19, 197, 219Borg, 211Bosch, 219Boussena, 214Brambilla, 27Bricklayers, 56Bricklayers’ assistant, 66Bricks raised, 59Broersen, 194Bronkhorst, 14, 155, 181, 240, 247Bullinger, 199, 214 Buttock and body pressure, 34

Buurman, 196Byström, 214

C

CAD, 149Carrasco, 219Chaffin, 61Chair, 35, 101, 137, 148, 170, 235Chair elements, 23Chair size, 142Chao, 24, 208 Cheung, 169Cleaning, 285Climate, 253Comfort and emotion, 9Comfort in literature, 5Comfort model, 15Concept car, 264Conflict, 47Construction, 193Controls, 173, 240, 252, 270 Cook, 181, 194Corlett, 211Cost/benefit, 91, 92, 281Costs, 42Cotton, 46Creative Box Inc., 264CRFiat, 114Croney, 137

D

Dainoff, 101Dashboard, 252Davies, 41Definition of comfort, 14Definition of ergonomics, 8Definition of participatory ergonomics, 43Dekker, 229Delleman, 101Design process, 51, 138Desmet, 1, 170 Details, 247Deursen, 129, 152

290

Index

Dieën, 147Diffusion, 75Discomfort at work, 19Discomfort in literature, 7Djajadiningrat, 172, 263 Docherty, 131Dreyfuss, 196Driver, 230, 272Driver performance, 240Drivers’ comfort, 239Dul, 8, 197 Dynamic chair, 148Dynamics in sitting, 147

E

Earth-moving machines, 17, 24, 229, 247Easy-roll, 90Ebe, 33Egress, 160, 250Ehn, 49Eijnatten, 112, 130Eikhout, 181, 199, 207Eklund, 148Elderly, 224Elements of the comfort model, 16Eleven-step program, 209Emergency lights, 117Emocard, 10, 171Emotion, 9, 169, 264End-user opinion, 27Envisioning tools, 50Ergomix, 51, 248Ergonomical design, 240Ergonomical set, 210Ergonomics, 8Ergoseating, 33ergoTool, 113, 184 ETEC, 229, 259European Foundation for the Improvement

of Living and Working Conditions, 42Excavator, 28, 230, 256Experiental design, 264

F

Faber Electronics BV, 117Feelings, 173, 269Feggeler, 182Fellows, 24, 208Finland Post, 114FIOH, 113Fixed chair, 174

Flannagan, 232Flexed back, 90Flexible interior, 270Fogleman, 96Ford, 115FOSAG, 76Fransson, 196Fraser, 200Frederiksson, 130Fujimaki, 33Furniture, 137Future car, 263Future machine, 236

G

Garner, 196Giguère, 231Glass cart, 78Glass hoist, 77Glass sledge, 78Glaziers, 73, 283 Goniometry, 181Goossens, 19Graf, 148Grammer, 252Grandjean, 96, 172 Grinten, 129, 181, 207, 247 Groenesteijn, 111

H

Hagberg, 130Hagedoorn-de Groot, 111, 219 Haines, 51Hales, 148Han, 164Hand, 24, 182, 199, 207, 225Hand tool comfort, 24, 181, 207Handle, 184, 242Haperen, 263Headrest, 164Heat regulation, 258Height adjustable pedals, 241Height adjustable seats, 241Helander, 8, 22, 172, 215Herzberg, 20Hildebrandt, 97History, 16Holbrook, 170Home care, 285Home furniture, 137Hoogendoorn, 148

Index

291

Hornyánszky, 49Houy, 200Hsiao, 70Humidity, 18

I

Imada, 96Implementation, 47Importance of comfort, 1Inalfa Roof Systems, 51Indirect view, 232Ingress, 160, 250Installation work, 85Interior, 17, 241, 263Interior Centre, 137Ishihara, 9ISO/CD 11226, 62

J

JAFICA, 137Jäger, 65Jensen, 24Jianghong, 24Johansson, 126, 130Jong, 55, 73, 85, 195, 281Jørgensen, 66joysticks, 257

K

Kaiser AG, 229, 255Kamijo, 33Kansei, 9Kapandji, 196Karimoku, 137Keyboard, 96Kilbom, 62Kishi, 33Kittusamy, 26Kneeling, 90Kogi, 48Kompier, 95König, 193Koningsveld, 55, 83, 194, 281Kosuga, 137Krause, 155, 229, 247Kroemer, 148Kuijt-Evers, 7, 13, 230, 248Kuorinka, 43

L

Land, 231Landstra, 200Lansbergis, 131Lean manufacturing, 131Lee, 263Lifting, 61, 75, 90, 114Local perceived discomfort, 189Local postural discomfort, 99, 157, 211Long Island Railroad, 167Longneck, 235Looze, 13, 33, 85, 111, 129, 147Lugt, 17Luttman, 65

M

Macfarlane, 219Macromovements, 175Manenica, 214Manual bag sealing, 219Manufacturing, 112Marinissen, 195Markers, 150Marras, 20MAS, 119Mathiassen, 112, 151 MAWP, 132McGorry, 208Meijer, 66Mekhora, 96Merllié, 2Metal clip, 221Miedema, 56Mirror, 254Mital, 62Mitsuya, 137Mock-up, 51, 202, 241Modification, 156Molen, 61, 73 Molenbroek, 140, 164, 200Mortar raised, 59Movement, 19Multina, 167Musculoskeletal problems, 2

N

Nagamachi, 9Nakada, 27NF X 35–106, 62Nichols, 41

292

Index

NIOSH, 62Nissan, 263Noise, 18, 254, 259Noro, 33, 44, 96, 137, 248

O

Office work, 96Ólafsdóttir, 126Oliver, 248Ong, 96, 172 Operator, 118, 232 Opinion of experts, 44Osinga, 239Östman, 49Overbeeke, 1, 169, 263

P

Paint scraper, 181Painters, 181Palacios, 42Parenmark, 126Park, 33Participants, 45, 118 Participating groups, 45Participation, 42Participatory design, 51, 207 Participatory ergonomics, 8, 41 Passenger seat, 155Patry, 46Paus GmbH, 229, 249Pedals, 241, 256 Pelvis angle, 36Philips DAP, 131Picking, 132Placing, 132Ploeger, 194Polling, 208Posture, 19prEmo, 10prEN 1005-4, 62Pressure, 19, 33 Pressure distribution, 37, 143 Preventing discomfort, 19Problem identification, 46Production concept, 122Production line, 130Productivity, 112, 132, 215, 285Proper, 2, 19 Prototype, 165, 244 PSIM, 113

R

Radwin, 196Rebar tying, 194Reflection, 231Reijneveld, 247, 181 RET, 239Reynolds, 164Rhijn, 111, 129, 182Richards, 14Ridder, 79Roetting, 230Rogers, 82, 92Roozenburg, 195Ruiter, 193Russell, 10

S

Safety, 225Salary records, 96Sauter, 112Schifferstein , 19Schoenmaker, 129Schön, 49Screwdriver, 207Seat, 155, 235, 243, 250Seat comfort, 20, 33 Seat pan, 23Seating clinic, 139Sector, 75Self-chosen, 102Serber, 148Shop assistants, 223Sick leave, 70Sitting behavior, 157Slater, 14Smallwood, 194Smell, 18Smets, 9Smulders, 147Solution choice, 46Sonneveld, 19Spinal shrinkage, 151Stadiometer, 150Stakeholders, 42Stanton, 281State, 17Static chair, 152Steelcase, 42Steel-fixing tool, 193Steering column, 251Stoeckli, 48Street car, 239Suzuki, 148

Index

293

T

Table height, 106Tape, 221Temperature, 18Tereoka, 137Thackara, 208Theimer, 18Theory on comfort, 14Tola, 27Tool, 184, 196 Touch, 19Train seat, 155Tram, 239Tram driver, 239Transporter, 276Transporting bricks, 66Tuinzaad, 51, 111Twin Seal, 220Tying tool, 195TyTecker, 194

U

Urlings, 75, 87, 283

V

Vahtera, 126, 131VDU screen, 98Vedder, 231Vehicle interior comfort, 24Vents, 253Verbeek, 101, 172 Vergare, 24Vibration, 26, 230, 242, 248 View, 231, 240

Virtual reality, 49Visibility, 233Visser, 193, 229 Visual input, 17Volvo Car Corperation, 114Vormer, 229

W

Wakula, 194Waters, 62, 121 Wensveen, 173Wheel barrow, 68Wheel loader, 28Wilder, 24Wilke, 148Wilson, 43, 83, 240Window, 231, 257, 272Winkel, 21, 126 Woodson, 196Word processing, 149Workplace design, 133Workbench, 88

Y

Yamada, 111Yamatake, 115

Z

Zhang, 7, 21Zhao, 164Zimmerman, 27

COMFORT and DESIGN Principles and Good Practice

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