ergonomics

This article was downloaded by: [Indian Institute of TechnologyGuwahati]On: 02 March 2015, At: 06:43Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number:1072954 Registered office: Mortimer House, 37-41 Mortimer Street,London W1T 3JH, UK

ErgonomicsPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/terg20

Dutch MusculoskeletalQuestionnaire: descriptionand basic qualitiesV. H. Hildebrandt , P. M. Bongers , F. J. H. vanDijk , H. C. G. Kemper & J. DulPublished online: 09 Nov 2010.

To cite this article: V. H. Hildebrandt , P. M. Bongers , F. J. H. van Dijk , H. C.G. Kemper & J. Dul (2001) Dutch Musculoskeletal Questionnaire: description andbasic qualities, Ergonomics, 44:12, 1038-1055, DOI: 10.1080/00140130110087437

To link to this article: http://dx.doi.org/10.1080/00140130110087437

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of allthe information (the Content) contained in the publications on ourplatform. However, Taylor & Francis, our agents, and our licensorsmake no representations or warranties whatsoever as to the accuracy,completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views ofthe authors, and are not the views of or endorsed by Taylor & Francis.The accuracy of the Content should not be relied upon and should beindependently verified with primary sources of information. Taylor andFrancis shall not be liable for any losses, actions, claims, proceedings,demands, costs, expenses, damages, and other liabilities whatsoeveror howsoever caused arising directly or indirectly in connection with, inrelation to or arising out of the use of the Content.

This article may be used for research, teaching, and private studypurposes. Any substantial or systematic reproduction, redistribution,reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access

and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

Dutch Musculoskeletal Questionnaire: description and basicqualities

V. H. HILDEBRANDT{*, P. M. BONGERS{, F. J. H. VAN DIJK{, H. C. G. KEMPER} andJ. DUL}

{TNO Work and Employment, PO Box 718, 2130 AS Hoofddorp, TheNetherlands

{Coronel Laboratory, University of Ansterdam, Amsterdam, The Netherlands

}Institute for Research in Extramural Medicine (EMGO Institute), VrijeUniversiteit, Amsterdam, The Netherlands

}Erasmus Business Support centre, Rotterdam, The Netherlands

Keywords: Questionnaire; Musculoskeletal workload; Musculoskeletal symp-toms; Validity.

A questionnaire (`Dutch Musculoskeletal Questionnaire, DMQ) for the analysisof musculoskeletal workload and associated potential hazardous workingconditions as well as musculoskeletal symptoms in worker populations isdescribed and its qualities are explored using a database of 1575 workers invarious occupations who completed the questionnaire. The 63 questions onmusculoskeletal workload and associated potentially hazardous working condi-tions can be categorized into seven indices (force, dynamic and static load,repetitive load, climatic factors, vibration and ergonomic environmental factors).Together with four separate questions on standing, sitting, walking anduncomfortable postures, the indices constitute a brief overview of the mainndings on musculoskeletal workload and associated potentially hazardousworking conditions. Homogeneity of the indices is satisfactory. The divergentvalidity of the indices is fair when compared with an index of psychosocialworking conditions and discomfort during exposure to physical loads. Workergroups with contrasting musculoskeletal loads can be diVerentiated on the basisof the indices and other factors. With respect to the concurrent validity, it appearsthat most indices and factors show signicant associations with low back and/orneck shoulder symptoms. This questionnaire can be used as a simple and quickinventory for occupational health services to identify worker groups in which amore thorough ergonomic analysis is indicated.

1. IntroductionIn daily practice, occupational health and safety services and ergonomicconsultancies in companies often have to advise management on interventions toreduce musculoskeletal workload and related disorders. Because such interventionscan have a great impact on the company, a proper analysis is essential to select themost hazardous situations that require ergonomic interventions. Time and resources

*Author for correspondence. e-mail: [email protected]

ERGONOMICS, 2001, VOL. 44, NO. 12, 1038 1055

Ergonomics ISSN 0014-0139 print/ISSN 1366-584 7 online # 2001 Taylor & Francis Ltdhttp://www.tandf.co.uk/journalsDOI: 10.1080/0014013011008743 7

Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

to carry out comprehensive studies are often lacking. Therefore, occupationalphysicians, nurses, hygienists and ergonomists need simple and quick methods toobtain relevant information on work-related factors that contribute to themusculoskeletal workload and related disorders. On the basis of such screening,priorities can be set as to which worker groups or workplaces should be addressed ina more thorough ergonomic analysis.

A detailed measurement of musculoskeletal workload (postures, movements andforce exertions) by direct methods such as observations or inclinometry iscomplicated and time consuming when large worker groups are involved, andskilled analysts are needed for reliable measurements (Buckle 1987, Hagberg 1992,Kilbom 1994, Winkel and Matthiassen 1994). There is, therefore, a need for simplescreening instruments for identifying groups of workers at risk (jobs, departments,tasks, etc.) such as checklists (Keyserling et al. 1992), rating of physical jobrequirements (Buchholz et al. 1996), surveys (Bishu 1989) or periodic surveillance(Weel et al. 2000). Although the quantication of the absolute exposure levels has itslimitations using these methods, the information gathered can be su cient to rankgroups according to their levels of exposure (Burdorf 1999). A subsequent morelaborious detailed ergonomic analysis can be restricted to those workers andworkplaces that are identied as potentially hazardous during the rst screening.

A questionnaire as screening instrument has the great advantage that it yields notonly exposure data, but also information on associated health symptoms and onideas of workers themselves about possibilities for improvements. High symptomrates are important as well as high workload when setting priorities for furtheranalyses and development of solutions. In addition, participation of the workers isensured and thus the use of such a questionnaire ts very well into a participatoryapproach to ergonomic problems (Vink et al. 1992).

TNO (Netherlands Institute for Applied Scientic Research) developed aquestionnaire called the `Dutch Musculoskeletal Questionnaire (DMQ) to measurethe self-reported musculoskeletal workload and other associated hazardous workingconditions as well as related symptoms. This paper addresses the most importantaspects of the validity of this measuring instrument.

. Can the questionnaire constitute a clear-cut description of a particularworker population by a limited number of indices for diVerent types ofworkloads (convergent validity)?

. Do these indices show a relatively low correlation with indices that measure adiVerent adjacent concept, such as psychosocial working conditions and anindex of reported discomfort due to musculoskeletal load (divergentvalidity)?

. Can the questionnaire identify worker groups with relative high workload orother unfavourable working conditions (discriminative power)?

. Do the indices show a signicant association with musculoskeletalsymptoms, indicating that exposure to that load constitutes a risk ofsymptoms for the exposed workers (concurrent validity)?

The criterion-validity of the questionnaire with respect to the measurement ofmusculoskeletal workload and symptoms has been addressed elsewhere (Hildebrandtet al. 2001). This paper is restricted to addressing the convergent, divergent andconcurrent validity of the questionnaire.

1039Dutch Musculoskeletal Questionnaire

Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

2. Methods and materials2.1. DMQThe standard version of the questionnaire consists of nine pages with*25 questionsper page to be lled in by the workers themselves. Completion-time is *30 min.There is also a short version (four pages) and an extended version (14 pages)available. The following sections are distinguished.

. Background variables (e.g. age, gender, education, duration of employment,work history, shift work).

. Tasks (prevalence rates and perceived heaviness of task demands).

. Musculoskeletal workload (postures, forces, movements).

. Work pace and psychosocial working conditions (demands, control andautonomy, work organization and social support, work satisfaction), whichare factors which may play an important role for workers with musculoske-letal disorders (Bongers et al. 1993).

. Health, in particular musculoskeletal symptoms; the phrasing of questions onprevalence is comparable with the `Nordic Questionnaire on MusculoskeletalDisorders (Kuorinka et al. 1987), including the denition of areas of thebody pictorially and, in addition, the extended version contains more detailedquestions on the nature and severity of these symptoms.

. Lifestyle (e.g. sports, smoking) (in the extended version of the questionnaireonly).

. Perceived bottlenecks and ideas for improvements suggested by the workersthemselves (optional).

To enable experts to work with this questionnaire easily, a software package(LOQUEST) has been developed for data entry, data analysis and autoreport of themain results.

The basic concept behind the questionnaire is a simple representation of therelationship between work tasks and musculoskeletal symptoms (Dul et al. 1992,Paul 1993). Work-related musculoskeletal symptoms are explained by a high internalphysical load caused by postures, movements and force-exertions needed in the worktasks. Other factors, such as other working conditions, individual factors (gender,age), psychosocial aspects or lifestyle, can inuence these relationships on diVerentlevels. All these elements are measured in the diVerent parts of the questionnaire.

To ensure an optimal content validity of the questionnaire, the choice ofvariables to be measured was based on available reviews of the epidemiologicalliterature (Hildebrandt 1987, Walsh et al. 1989, Riihima ki 1991, Stock 1991). Thesereviews identied a large number of potentially harmful postures, movements, force-exertions and other potentially hazardous working conditions, which are still valid atthe present time (Bernard 1997, Hoogendoorn et al. 1999, Arie ns et al. 2000).

Musculoskeletal workload (postures, forces, movements) is addressed in 63questions (see table 2 for the phrasing of the questions). These questions can becategorized into the following six types of potentially hazardous workloads andworking conditions.

. Force exertions: lifting, carrying, supporting, pushing, pulling, pinching.

. Dynamic loads: walking, bending and twisting of trunk, neck or wrists,stooping, squatting, reaching.

1040 V. H. Hildebrandt et al.

Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

. Static loads: sitting, standing, prolonged bent or twisted posture of trunk,neck or wrists, working with hands above shoulder level, kneeling orsquatting posture.

. Peak loads: sudden, forceful movements, unexpected movements.

. Repetitive loads.

. Ergonomic environmental conditions: (1) climatic factors, (2) vibration, (3)limited working space and (4) slipping and falling on occasions.

The questions are formulated in such a way that they indicate the presence orabsence of exposure and not the amount of discomfort caused by the exposure,which is addressed in a separate part of the questionnaire. The preciseformulation was based on several eld studies where the preliminary versionsof the questionnaire were used. The exposures addressed in the questions werenot dened, explained or illustrated to limit the size of the questionnaire and thetime needed for completing it. No training was given on the completion of thequestionnaire. Given the goal of the questionnairea quick but comprehensivesurveyit was decided to use mostly dichotomous answering categories (yes/no).This qualitative approach, without attempts to quantify frequency and durationof variables, was also chosen because the validity of quantitative approaches byquestionnaire has been seriously questioned (Kumar 1993, Kilbom 1994, Winkeland Matthiassen 1994, Baty et al. 1986, Rossignol and Baetz 1987, Wiktorin etal. 1993, Viikari-Juntura et al. 1996). The completion of the questions asdescribed above does not generally give any problems, even in less educatedworker groups.

2.2. Study populationA group of 1575 workers in 24 occupations, who completed the questionnaireduring various studies, constituted the population and database for theanalyses. The occupations diVered strongly with respect to musculoskeletalworkload and associated hazardous working conditions, e.g. nurses (n=237),shipyard workers (186), o ce workers (93) and metal workers (69). Table 1shows the main characteristics of this worker population and the subgroupsmentioned.

Table 1. Descriptive data on the total study population and four occupational groups withinthis population.

All(n = 1575)

Nurses(n = 237)

Shipyard(n = 186)

O ce(n = 128)

Metal(n = 69)

Demographic factorsMean age (SD) 35 (9.7) 34 (7.9) 37 (11.2) 37 (9.0) 32 (8.5)Mean education level (1, low; 5, high)3.2 4.0 3.2 3.7 2.4% male gender 61 12 100 34 80Work factors :% Frequent uncomfortable postures 57 52 72 24 28% Frequent sitting at work 33 27 29 76 44% Frequent standing at work 66 63 83 4 78% Frequent walking at work 65 71 57 16 46


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

Table2.

Questionsonworkload,associatedfactorloadingsandexplained

varianceofninefactors(principalcomponentsanalysiswithvarimax

rotation)

asmeasuredin

thetotalstudypopulation(n=1575).Onlyfactorloadings40.39are

given;allcorrelationsare

signicant(P50.05).

Factor

12

34

56

78

9

Eigenvalue

15.3

4.9

3.4

2.2

1.7

1.7

1.5

1.5

1.3

Explained

variance

(%)

23.9

7.7

5.3

3.4

2.7

2.7

2.3

2.3

2.0

Doyouin

work

often

have

to:

1.Liftheavyloads(m

ore

than5kg)?

.76

..

..

..

..

2.Pullorpush

heavyloads(m

ore

than5kg)?

.64

..

..

..

..

3.Carryheavy

loads(m

ore

than5kg)?

.67

..

..

..

..

Doyouin

work

often

have

tolift:

4.In

anaw

kwardposture?

.77

..

..

..

..

5.Withtheload

farfrom

thebody?

.64

..

..

..

..

6.Withtwistedtrunk?

.69

..

..

..

..

7.Withtheload

abovechestheight?

.48

..

..

..

..

8.Withaload

thatishard

tohold?

.60

..

..

..

..

9.Withaveryheavyload(m

ore

than

20kg)?

.67

..

..

..

..

Doyouin

yourwork

often

have

to:

10.Standforaprolongedtime?

..

..

..

..

.54

11.Sitforaprolonged

time?

..

..

..

..

7.64

12.Walk

foraprolonged

time?

..

..

..

..

.61

13.Stoopforaprolongedtime?

..55

..

..

..

.Doyouin

yourwork

often

have

to:

14.Bendslightlywithyourtrunk?

..

..

..

..60

.15.Bendheavilywithyourtrunk?

.46

.42

..

..

..

.16.Twistslightlywithyourtrunk?

..

..

..

..72

.17.Twistheavilywithyourtrunk?

..52

..

..

..

.18.Bendandtwistwithyourtrunk?

..44

..

..

..46

.Doyouin

work

often

have

to:

19.Work

inaslightlybentposture

foraprolonged

time?

..49

..

..

..

.20.Work

inaheavilybentposture

foraprolongedtime?

..70

..

..

..

.21.Work

inaslightlytwistedposture

foraprolongedtime?

..61

..

..

..

.22.Work

inaheavilytwistedposture

foraprolongedtime?

..74

..

..

..

.

continued


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

Table2.

Continued

Factor

12

34

56

78

9

23.Work

inabentandtwistedpostureforaprolongedtime?

..72

..

..

..

.Doyouin

yourwork

often

haveto:

24.Reach

withyourhandsandarm

s?.

..

..

..

..

25.Hold

yourarm

under

yourshoulder-level?

..

..

..

..

.26.Hold

yourarm

atorabove

shoulder-level?

..

..

..47

..

.27.Exertforcewithyourhandsorarm

s?.47

..

..

..

..

28.

Makesm

allmovements

withhands/ngersatahigh

workpace?

..

..44

..

..

.

Doyouin

yourwork

often

haveto:

29.Bendyourneckforwards?

..

..

.62

..

..

30.Bendyourneckbackward?

..

..

..54

..

.31.Twistyourneck?

..

..

.59

..

..

32.Holdyourneckinaforwardbentpostureforaprolonged

time?

..

..

.58

..

..

33.

Hold

yourneck

inabackward

bentposture

fora

prolonged

time?

..

..

..59

..

.

34.Holdyourneckinatwistedpostureforaprolonged

time?

..45

..

.45

..

..

Doyouin

yourwork

often

haveto:

35.Bendyourwrists?

..

..

.51

..

..

36.Twistyourwrists?

..

..

.49

..

..

37.Hold

yourwristbentforaprolonged

time?

..

..

.47

.44

..

.38.Hold

yourwristtwistedforaprolongedtime?

..

..

.44

.45

..

.Doyouin

yourwork

often

haveto:

39.Work

inuncomfortablepostures?

.46

..

..

..

..

40.Work

inthesamepostures?

..

..54

..

..

.Doyouin

yourwork

often

haveto:

41.Alwaysmakethesamemovem

entswithyourtrunk?

..

..77

..

..

.42.Alwaysmakethesamemovem

entswithyourarms?

..

..86

..

..

.43.Always

makethesamemovem

entswithyourwrists?

..

..85

..

..

.

continued


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

Table2.

Continued

Factor

12

34

56

78

9

44.Alwaysmakethesamemovem

entswithyourlegs?

..

..73

..

..

.Doyouin

yourwork

often

haveto:

45.Makesudden,unexpectedmovem

ents?

..

..

.45

..

..

46.Perform

short,butmaximalforce-exertions?

.56

..

..

..

..

47.Exertgreatforceontoolsormachinery?

..

..

..

..

.Doyouin

youwork

often

have:

48.Notenoughroom

aroundyouto

perform

yourwork

properly?

..

..

..

.66

..

49.Notenough

room

aboveyouto

perform

yourwork

withoutbending?

..

..

..

.52

..

Doyouin

yourwork

often

have:

50.Dicultyin

exertingenough

forcebecause

ofincomfor-

tablepostures?

..

..

..

.57

..

51.Toofewfacilities

toleanonduringwork?

..

..

..

.53

..

52.Troublein

reachingthingswithyourtools?

..

..

..

.51

..

53.Doyousometimes

slip

orfallduringyourwork?

..

.46

..

..

..

54.Doyouoften

havetopinch

withyourhandsduringwork?

..

..

..

..

.55.Do

you

inwork

experience

noticeable

vibrationsor

shocks?

..

..

..54

..

.

56.Doyoucarryvibratingtoolsduringyourwork?

..

..

..55

..

.57.Doyoudrivevehiclesduringwork?

.43

..57

..

..

..

58.Isyourwork

physicallyvery

taxing?

..

..

..

..

.59.Doyouin

yourwork

experience

draughts,wind?

..

.74

..

..

..

60.Doyouin

yourwork

experience

cold?

..

.81

..

..

..

61Doyouin

yourwork

experience

warm

th?

..

.43

..

..

..

62.Doyouinyourwork

experience

changesoftemperature?

..

.72

..

..

..

63.Doyouin

work

experience

humid

air?

..

.69

..

..

..


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

2.3. AnalysisThe convergent validity was assessed by a principal component analysis (PCA), usedto construct a limited number of well-dened workload indices for diVerent types ofworkloads, which enables a clear-cut description of a particular worker population.Varimax rotation was applied to ensure minimal correlation between the indices(below). Homogeneity of the indices resulting from the PCA was assessed bycomputing Cronbachs a.

To explore the divergent validity of the indices, rst, the intercorrelation wascomputed between the seven indices and an index of psychosocial workingconditions (sum of 35 questions on demands, control and autonomy, organizationand social support, and work satisfaction). For a good divergent validity, the indicesshould show a relatively low correlation with indices which measure a diVerentadjacent concept, such as psychosocial working conditions. Next, the correlationbetween the indices of workload and an index of reported discomfort due tomusculoskeletal load was computed. The latter was constructed from 10 questionssuch as `Are you experiencing discomfort during sitting at work? These questionshad to be answered regardless of the amount of exposure. The correlation can givean indication of whether the exposure reported by the worker is severely biased bypossible discomfort experienced by the worker during the exposure to this load.

To analyse whether the seven indices could diVerentiate between occupationalgroups with contrasting workload, four specic subgroups (nurses, shipyardworkers, o ce workers and metal production workers) were analysed. For a gooddiscrimination, contrasts between these worker groups should be reproduced bydiVerences in the means of the indices. Means and 95% condence intervals (CI) ofthese indices were computed for each worker group according to the methoddescribed by Brand and Radder (1992), specically developed for indices that consistof dichotomous variables. DiVerences between worker groups were consideredsignicant (p5 0.05) when the computed condence intervals were not overlapping.

The concurrent validity was tested by assessing the relationships of the indices (asindependent variables) with musculoskeletal symptoms (as dependent variables) in amultiple logistic regression analysis on an individual level (see `concurrent validity in`results). For a good concurrent validity, the indices should show a signicantassociation with musculoskeletal symptoms, indicating that exposure to that loadconstitutes a risk of symptoms for the exposed workers. For this analysis, all indiceswere dichotomized into a low- and high-exposure level, with the cut-point at 50% ofthe population analysed. Twelve-month prevalence rates of symptoms (pain,discomfort) of the low back and of the neck shoulder area were taken as themeasure of eVect. These were measured with the same questionnaire (`Have you everhad trouble (ache, pain, discomfort) from your...). All the independent variableswere included simultaneously in the model and were thus adjusted for the others.Age was entered in the model as a possible confounder. Estimated odds ratios (OR)are presented as the measure of association. OR 4 1 indicates that the index isassociated with a higher prevalence rate of symptoms and is considered statisticallysignicant when the 95% CI do not include 1.

3. Results3.1. Construction of indicesTable 2 shows the result of the PCA. Table 3 shows the tentative descriptions of thecontent of these factors. A nine-factor model explained 52% of the total variance.


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

Table3.

Nam

e,content,Cronbachsa ,meanscore

andSD

ofsevenindices

andfourseparatequestions(n=1575).

Nam

eContent

n*

amean**

SD

1Forceexertion

lifting,pushingandpulling,forcefulmovementswitharm

s,highphysical

exertion,liftinginunfavourablepostures,liftingwiththeload

awayfrom

thebody,liftingwithtwistedtrunk,liftingwithloadsabovethechest,

liftingwithbadgrip,liftingwithvery

heavyloads,shortforceexertions,

exertinggreat

forceonhands

13

.90

4.8

3.1

2Dynamicloads

trunk

movem

ents

(bending

and/or

twisting),

movem

ents

ofneck,

shouldersorwrists,reaching,

makingsudden

and/orunexpectedmove-

ments,pinching,workingunder,atoraboveshoulder

level

12

.83

5.9

2.7

3Staticloads

lightlybentandtwistedtrunkposture,heavilybentandtwistedtrunk

posture,bentandtwistedposturesofneckorwrists

11

.87

3.9

2.8

4.

Repetitiveloads

workingin

thesamepostures,makingthesamemovem

entswithtrunk,

arm

s,hands,wristsorlegs,makingsm

allmovem

entswithhandsatahigh

pace

6.85

4.8

3.4

5Ergonomic

environment

availableworkingspace,lack

ofsupport,slipingandfalling,troublewith

reachingthingswithtools,notenough

room

aboveto

perform

work

withoutbending

6.78

3.1

3.0

6Vibration

wholebodyvibration,vibratingtools,driving

3.57

1.8

2.7

7Climate

cold,draught,changesin

temperature,moisture

4.84

4.8

4.0

Uncomfortable

postures

havingoften

todealwithuncomfortableposturesat

work

1-

--

Sitting

sittingoften

atwork

1-

--

Standing

standingoften

atwork

1-

--

Walking

walkingoften

atwork

1-

--

Overallindex

indices

17

55

.95

4.5

2.3

*Numberofquestions.Themaximumscoreequalsthenumberofquestionsintheindex

andcorrespondsto

apositiveanswerto

allquestionsinthe

index.Thehigher

themeanscore,thehigher

theself-reported

exposure.

**Allindices

are

standardized

onamaximum

of10to

enhance

comparability.


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

From tables 2 and 3, it can be concluded that to a great extent the PCA supports thetypes of workload formulated above upon the literature: force exertions (representedmainly by factor 1), dynamic loads (represented mainly by factors 5 and 8), staticloads (represented mainly by factors 2 and 6), repetitive loads (represented by factor4) and ergonomic environmental factors (represented by factors 3 and 7) can bedistinguished. Only peak loads are not represented by a separate factor: they arerepresented by factor 5 (sudden, unexpected movements) as well as by some parts offactor 1 (sudden, forceful movements). Furthermore, dynamic and static loads arediVerentiated for trunk (factors 2 and 8) and neck shoulder arm (factors 5 and 6).Ergonomic environmental factors are diVerentiated into two factors (3 and 7),whereas vibration is not identied as a separate factor, but is included in factor 6.Since walking, standing, sitting and uncomfortable postures are di cult to assign toone of the above-mentioned factors, it seems logical to consider these factors as fourindependent factors.

The PCA thus results in seven `indices of workload and other working conditionsand four separate questions on standing, walking, sitting and uncomfortablepostures. Table 3 shows the description, content and homogeneity (measured withCronbachs a) of the indices and an overall index of musculoskeletal load (as the sumof all seven indices). Six out of seven as are 40.80, which indicates a satisfactoryaverage inter-item correlation.

3.2. Divergent validityTable 4 shows the intercorrelations between the seven indices of workload and otherworking conditions, the four separate factors, the overall index of workload, anindex of psychosocial working conditions (a=0.82), an index of reporteddiscomfort due to musculoskeletal load (a=0.85), and age.The correlation between the indices of workload and the index of psychosocialworking conditions varied between 0.21 and 0.33 and was thus in most cases lowerthan the correlations between the indices of workload themselves, which varied from0.26 to 0.74. Correlation of the workload indices with the index of reporteddiscomfort due to musculoskeletal loads varied between 0.19 and 0.61 and wasrelatively high for the indices force, dynamic load and static load. Correlation withage was low (varying between 0.01 and 0.17).

Table 4 also shows that correlations between the indices force, dynamic load, andstatic load were relatively high (0.59 0.74).

3.3. DiVerentiation of worker groupsFigures 1a and b show the means of all indices and factors for the four selectedworker groups (nurses, shipyard workers, o ce workers and metal productionworkers).

The data show that worker groups can be diVerentiated: each group can bedescribed specically. Shipyard workers show the highest means of exposures to mostindices and o ce workers the lowest (except for sitting, walking and repetitive loads).

3.4. Concurrent validityTables 5a and b show the results of the multiple logistic regression for symptoms ofthe low back and neck shoulder regions.

In particular high force exertion, high static loads, unfavourable ergonomicenvironmental conditions and uncomfortable postures are signicantly associated


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

Table4.

Correlationmatrixofseven

indicesofmusculoskeletalworkloadandassociated

potentialhazardousworkingconditions(17)andfourseparate

factors(811)andoverallindex

(12),psychosocialworkingconditions(13)1,reported

discomfortfrommusculoskeletalworkload(14),andage

(15)

computedforthetotalstudy-population(n=1575).

12

34

56

78

910

11

1213

1415

1Force

2

Dynamicload

.64

3

Staticload

.59

.74

4

Repetitiveload

.35

.52

.59

5

Ergonomicenvironment

.60

.48

.54

.37

6

Vibrations

.42

.26

.30

.33

.42

7

Climate

.44

.32

.40

.34

.47

.48

8

Uncomfortablepostures

.57

.55

.61

.25

.42

.22

.32

9

Sitting

.10

.06

.02

.14

.03*

.12

.01*

.06

10

Standing

.39

.37

.43

.31

.29

.13

.23

.24

.12

11

Walking

.32

.39

.24

.11

.18

.10

.10

.06

.17

.42

12

Overallindex

.82

.83

.87

.68

.71

.48

.58

.61

.03*

.41

.28

13

Psychosocialworking

conditions1

.33

.27

.31

.29

.33

.24

.21

.23

.21

.12

.05

.41

14Reported

discomfort

.51

.53

.61

.39

.45

.19

.30

.48

.02*

.32

.18

.61

.33

15

Age

.02*

.02*

.05

.06

.07

.10

.17

.01*

.08

.03*

.03*

.09

.08

.06

*Notsignicant(P5

0.05).

1Cluster

ofdichotomousquestionsonpsychosocialwork

aspects;ahigher

score

indicates

more

problems.


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

Figure 1a. Means and 95% CI of self-reported exposure summarized in seven indices ofmusculoskeletal workload and potential hazardous working conditions, for fouroccupations (1=nurses; 2=shipyard workers; 3=o ce workers; 4=metal productionworkers). No data were available on the repetitive index for metal production workers.

Figure 1b. Means and 95% CI of self-reported exposure to uncomfortable postures, sitting,standing and walking, for four occupations (1=nurses; 2=shipyard workers; 3=o ceworkers; 4=metal production workers).

dynamicload

staticload

1 2 3 41 2 3 4

climatevibrationsergonomicenviron-ment

repetitiveload

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

10

8

6

4

2

0

a

force

b

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

uncomfortablepostures

sitting standing walking

100

80

60

40

20

0


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

with low back symptoms. High repetitive loads and uncomfortable postures areassociated with neckshoulder symptoms. Vibration and walking are associated withfewer symptoms of the neck shoulder region.

4. Discussion4.1. Convergent validityIn theory, an instrument used to identify risk groups with respect to musculoskeletaldisorders, with the aim of taking eVective preventive measures, should contain onlyitems that show a prospective relation with musculoskeletal symptoms or sick leavedue to musculoskeletal symptoms. Subsequent interventions in the high-risk groupsidentied should be eVective with respect to the reduction of musculoskeletalmorbidity and/or disability. Unfortunately, it appears to be very di cult as yet toidentify the items which show a prospective relation with musculoskeletal disordersor sick leave due to musculoskeletal disorders; recent reviews and epidemiologicalstudies indicate that there are still many questions on the roleand particularly thequantitative importanceof relevant workload factors and intervening variables inthe causation of musculoskeletal symptoms and disability (Kilbom 1994, Feuersteinet al. 1999). They also indicate that only a small proportion of the total variance isexplained (Frank et al. 1995), that there is still little evidence that elimination of

Table 5a. Estimated odds ratios (OR) and 95% condence intervals (CI) in the multiplelogistic regression analysis of seven indices of workload and age on symptoms of low backand neckshoulder (n=1575).

Low back Neck shoulder

OR 95% CI* OR 95% CI*

Force 1.54* 1.172.02 1.09 0.821.43Dynamic load 1.14 0.851.53 1.29 0.971.74Static load 1.33* 1.021.76 1.23 0.941.62Repetitive load 1.13 0.871.45 1.50* 1.161.92Vibrations 0.73* 0.550.96 0.72* 0.550.96Adverse climate 0.89 0.681.18 1.09 0.831.44Ergonomic environment 1.39* 1.061.83 1.17 0.891.54Age 0.79* 0.631.01 1.18 0.931.48

*P5 0.05

Table 5b. Estimated odds ratios (OR) and 95% condence intervals (CI) in the multiplelogistic regression analysis of uncomfortable postures, standing, sitting, walking and ageon symptoms of low back and neckshoulder (n=1575).

Low back Neck shoulder

OR 95% CI* OR 95% CI*

Uncomfortable postures 2.49* 2.003.08 1.95* 1.582.42Standing 1.10 0.861.43 1.15 0.891.48Sitting 1.10 0.871.40 1.22 0.981.52Walking 1.06* 0.841.34 0.75* 0.570.92Age 70.79* 0.630.98 1.23 0.991.53

*P5 0.05


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

ergonomically hazardous work reduces the number of disorders (Bernacki et al.1999) and that our current knowledge of risk factors is largely based on studies withmoderate-to-low quality scores (Viikari-Juntura and Riihima ki 1999). Nevertheless,recent systematic reviews do provide strong evidence for manual materials handling,bending and twisting, and whole-body vibration as risk factors for low back painand moderate evidence for patient handling and heavy physical work as risk factorsfor back pain (Hoogendoorn et al. 1999) as well as some evidence for the duration ofsitting, twisting or bending of the trunk, neck exion, arm force, arm posture, hand arm vibration and workplace design as risk factors for neck pain (Ariens et al. 2000).

Insu cient or invalid exposure measurement may be a major explanation for theremaining gaps in our knowledge (Winkel and Matthiassen 1994). As a consequence,the questionnaire incorporated a large number of potentially harmful postures,movements, force exertions and other potentially hazardous working conditions,which are believed to be important risk factors on the basis of anatomical ,physiological, biomechanical, psychophysiologica l or ergonomic ndings, despitelacking epidemiological evidence. This was also reason for performing anexploratory factor analysis, since it would have been di cult to formulate explicitlya xed number of factors and expected allocation of items. Nevertheless, the factoranalysis conrmed to a large extent the concept that formed the basis for thegeneration of the questions. Force, dynamic and static loads, repetitive movementsand ergonomic environmental factors were identied as separate entities. It shouldbe noted that the correlations between most factors stayed rather high, but this couldbe expected since all factors are based on self-reported data and most workingsituations are characterized by combinations of exposures rather than by a singlehomogeneous exposure. Further aggregation of indices with high intercorrelationswas considered inappropriate since it would merge characteristics of the work whichare really diVerent from an ergonomic point of view.

Since the factor `ergonomic environment contained several quite diVerententities, it was decided to distinguish three factors: poor climate, vibration andergonomic environment sensu stricto, the last factor representing in particular spaceconstraints leading to unfavourable postures. Furthermore, some important factorsthat describe elementary postures or movements (standing, walking, sitting) oruncomfortable postures appeared to be quite independent from the other indices andwere therefore considered as separate factors. `Uncomfortable postures probablymeasures discomfort instead of exposure, which explains its added value with respectto the indices of physical loads.

4.2. Divergent validityAn important question about the usefulness of the DMQ in ergonomic practice iswhether the indices measure actual musculoskeletal workload and not other workdimensions, such as psychosocial work factors or reported discomfort. Thecorrelation of the indices with the index of psychosocial working conditions israther low (*0.30) but signicant and thus shows some degree of association, but atthe same time also a substantial degree of divergence (a fair divergent validity). Thesignicant correlations (between 0.19 and 0.61) of the musculoskeletal workloadindices with the index of reported discomfort indicates an association between thereport of exposure and the presence of discomfort due to the exposure; thisunderlines the importance of diVerentiating as far as possible between self-reportedexposures and self-reported discomfort during exposures. Literature is somewhat


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

conicting on the question of whether self-reported exposures are biased bydiscomfort during these exposures or by the presence of musculoskeletal symptoms.Some studies indicate such a relation (Ryan 1989), while others do not (Riihima ki etal. 1989). Given the quite strong correlation between those two dimensions found inthis study, the conclusion seems justied that the indices can measure exposure tomusculoskeletal workload and associated potentially hazardous working conditionsonly to a certain extent: one has to be aware that the reported exposures may beinuenced by reported discomfort, at least at an individual level.

By using PCA with varimax rotation, the independence of resulting factors wasassured, but this was partly undone by subsequent alterations of the factors to denethe ultimate indices: the resulting intercorrelations between the indices are fairly highin some cases, but they show enough unexplained variance to be considered asseparate dimensions of musculoskeletal workload and associated potentiallyhazardous working conditions (a fair convergent validity).

4.3. Identifying worker groups at riskThe analyses of the four subgroups with contrasting workloads showed that workergroups with contrasting workloads could be identied. This is an essential feature inaccordance with the intended use of the questionnaire: identifying high-risk groups.However, it is obvious that the questionnaire cannot diVerentiate between workergroups with insu cient contrast in workload. In addition, the diVerentiation willalways be `relative (ranking groups relative to each other), since no criteria can beformulated as yet to dene `high and `low exposures on the basis of the qualitativedata of a questionnaire.

It is well established that job title is generally a poor proxy for describingexposures to ergonomic risk factors and that variance can be high within a job title(Burdorf 1992, Hagberg 1992, Li and Buckle 1999). Thus, the associations foundbetween the indices and other measures are probably an underestimation of risks,since the involvement of really homogeneous worker groups would probably resultin a better diVerentiation.

4.4. Concurrent validityAs had been expected on the basis of the literature, most indices showassociations with the symptoms, indicating the relevance and predictive validityof the indices in varying worker groups. In particular, `uncomfortable posturesshowed relatively high ORs both for low back symptoms and for neck shouldersymptoms. Since `discomfort may be regarded as an early manifestation ofsymptoms or disorders, the high ORs could be expected. Nevertheless, inaddition to the independence of this indicator from the other indices, this suggeststhat this indicator might be a very relevant variable for the diVerentiation ofworker groups.

All associations are in agreement with the literature, with the exception of thenegative association between vibration and symptoms for both the low back andneck shoulder, which is di cult to explain, since whole-body vibration isconsidered as a major risk factor for these symptoms (Bovenzi and Hulshof1999). Exposure to vibration is limited to a few specic worker groups (e.g. metalworkers, shipyard workers) with specic exposures to hand-arm vibration andpossibly a healthy worker selection eVect in these groups could explain, at leastpartly, this nding.


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

The strength of the (cross-sectional) associations found is in agreement withother studies (Riihima ki et al. 1989, Hagberg 1992, Tsai et al. 1992) and is wellfounded considering the prevalence measure used and the high prevalence rates ofsymptoms in the unexposed groups.

5. ConclusionsThe DMQ enables a global assessment of musculoskeletal workload and otherpotentially hazardous working conditions by seven homogeneous indices (forces,dynamic loads, static loads, repetitive loads, climatic factors, vibration andergonomic environmental factors) and four separate factors (sitting, standing,walking, uncomfortable postures). With these indices, worker groups withcontrasting musculoskeletal workloads and associated potentially hazardous work-ing conditions can be diVerentiated. Most indices show signicant associations withlow back and/or neck shoulder symptoms. These indices can, therefore, be used asone of the means to identify risk groups and can supply experts in occupationalhealth and safety services and ergonomic consultancies with data for determiningpriorities concerning ergonomic improvements among worker groups.

An English translation of the DMQ can be downloaded from the website of TNOWork and Employment: www.workandhealth.org

ReferencesARIE NS, G. A. M., VAN MECHELEN, W., BONGERS, P. M., BOUTER, L. M. and VAN DER WAL, G.

2000, Physical risk factors for neck pain. Scandinavian Journal of Work andEnvironmental Health, 26, 7 19.

BATY, D., BUCKLE, P. W. and STUBBS, D. A. 1986, Posture recording by direct observation,questionnaire assessment and instrumentation: a comparison based on a recent eldstudy, in E. N. Corlett, I. Manenica and J. R. Wilson (eds), The Ergonomics of WorkingPostures (London: Taylor Francis), 283 292.

BERNARD, B. P. (ed.) 1997,Musculoskeletal Disorders and Workplace Factors: A Critical Reviewof Epidemiologic Evidence for Work Related Musculoskeletal Disorders of the Neck,Upper Extremities and Low Back (Cincinnati: National Institute for OccupationalSafety and Health, US Department of Health and Human Services).

BERNACKI, E. J., GUIDERA, J. A., SCHAEFER, J. A., LAVIN, R. A. and TSAI, S. P. 1999, Anergonomics program designed to reduce the incidence of upper extremity work relatedmusculoskeletal disorder. Journal of Occupational Environmental Health, 41, 1032 1041.

BISHU, R. R. 1989, Risks of back pain. Can a survey help? A discriminant analytic approach.Journal of Occupational Accidents, 11, 51 68.

BONGERS, P. M., DE WINTER, C. R., KOMPIER, M. A. J. and HILDEBRANDT, V. H. 1993,Psychosocial factors at work and musculoskeletal disease. Scandinavian Journal of Workand Environmental Health, 19, 297 312.

BOVENZI, M. and HULSHOF, C. T. J. 1999, An updated review of epidemiologic studies on therelationship between exposure to whole-body vibration and low back pain (1986 1997).International Archives of Occupational and Environmental Health, 6, 351 365.

BRAND, J. P. L. and RADDER, J. 1992, Betrouwbaarheidsintervallen voor somscores vandichotome items in V-prof (Leiden: TNO-PG, Statistiek en Informatica Statistiekreeks92/05).

BUCHHOLZ, B., PAQUET, V., PUNNETT, L., LEE, D. and MOIR, S. 1996, PATH: a work sampling-based approach to ergonomic job analysis for construction and other non-repetitivework. Applied Ergonomics, 27, 177 187.

BUCKLE, P. 1987, Musculoskeletal disorders of the upper extremities: the use ofepidemiological approaches in industrial settings. Journal of Hand Surgery, 12A,885 889.


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

BURDORF, A. 1992, Assessment of postural load on the back in occupational epidemiology.Doctoral thesis, Erasmus University, Rotterdam.

BURDORF, A. 1999, Editorial: In musculoskeletal epidemiology are we asking the unanswerablein questionnaires on physical load? Scandinavian Journal of Work and EnvironmentalHealth, 25, 81 83.

DUL, J., DELLEMAN, N. J. and HILDEBRANDT, V. H. 1992, Posture and movement analysis inergonomics: principles and research, in A. Cappozzo, M. Marchetti and V. Tosi (eds),Biolocomotion: A Century of Research Using Moving Pictures. Proceedings of theSymposium `Biolocomotion: A Century of Research Using Moving Pictures, Formia,Italy, 14 17 April 1989 (Rome: Promograph).

FEUERSTEIN, M., BERKOWITZ, S. M. and HUANG, G. D. 1999, Predictors of occupational lowback disability: implications for secondary prevention. Journal of OccupationalEnvironmental Health, 41, 1024 1031.

FRANK, J. W., PULCINS, I. R., KARR, M. S., SHANNON, H. S. and STANSFELD, S. A. 1995,Occupational back painan unhelpful polemic. Scandinavian Journal of Work andEnvironmental Health, 21, 3 14.

HAGBERG, M. 1992, Exposure variables in ergonomic epidemiology. American Journal ofIndustrial Medicine, 21, 91 100.

HILDEBRANDT, V. H. 1987, A review of epidemiological research on risk factors of low backpain, in P. Buckle (ed.), Musculoskeletal Disorders at Work. Proceedings of aConference held at the University of Surrey, Guildford, 13 15 April (London:Taylor Francis), 9-16.

HILDEBRANDT, V. H. 2001, Prevention of work related musculoskeletal disorders: settingpriorities using the standardized Dutch Musculoskeletal Questionnaire. Doctoral thesis,TNO Work and Employment, Hoofddorp.

HOOGENDOORN, W. E., VAN POPPEL, M. N. M., BONGERS, P. M., KOES, B. W. and BOUTER, L. M.1999, Physical load during work and leisure time as risk factors for back pain.Scandinavian Journal of Work and Environmental Health, 25, 387 403.

KEYSERLING, W. M., BROUWER, M. and SILVERSTEIN, B. A. 1992, A checklist for evaluatingergonomic risk factors resulting from awkward postures of the legs, trunk and neck.International Journal of Industrial Ergonomics, 9, 283 301.

KILBOM, A. 1994, Assessment of physical exposure in relation to work related musculoskeletaldisorderswhat information can be obtained from systematic observations? Scandina-vian Journal of Work and Environmental Health, 20 (suppl.), 30 45.

KUMAR, S. 1993, The accuracy of trunk posture perception among young males subjects, in R.Nielsen and K. Jorgensen (eds), Advances in Industrial Ergonomics and Safety V(London: Taylor Francis), 225 229.

KUORINKA, I., JONSSON, B., KILBOM, A ., VINTERBERG, H., BIERING-SORENSEN, F., ANDERSSON, G.and JORGENSEN, K. 1987, Standardised Nordic questionnaires for the analysis ofmusculoskeletal symptoms. Applied Ergonomics, 18, 233 237.

LI, G. and BUCKLE, P. 1999, Current techniques for assessing physical exposure to work-related musculoskeletal risks, with emphasis on posture-based methods. Ergonomics, 42,674 695.

PAUL, J. A. 1993, Pregnancy and the standing working posture. Doctoral thesis, University ofAmsterdam.

RIIHIMA KI, H. 1991, Low back pain, its origin and risk indicators. Scandinavian Journal ofWork and Environmental Health, 17, 81 90.

RIIHIMA KI, H., TOLA, S., VIDEMAN, T. and HA NNINEN, K. 1989, Low back pain and occupation:a cross-sectional questionnaire study of men in machine operating, dynamic physicalwork and sedentary work. Spine, 14, 204 209.

ROSSIGNOL, M. and BAETZ, J. 1987, Task-related risk factors for spinal injury: validation of aself-administered questionnaire on hospital employees. Ergonomics, 30, 1531 1540.

RYAN, G. A. 1989, The prevalence of musculoskeletal symptoms in supermarket workers.Ergonomics, 32, 359 371.

STOCK, S. R. 1991, Workplace ergonomic factors and the development of musculoskeletaldisorders of the neck and upper limbs: a meta-analysis. American Journal of IndustrialMedicine, 19, 87 107.


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

TSAI, S. P., GILSTRAP, E. L., COWLES, S. R., WADDELL, L. C. and ROSS, C. E. 1992, Personal andjob characteristics of musculoskeletal injuries in an industrial population. Journal ofOccupational Medicine, 34, 606 612.

VILKARI-JUNTURA, E., RAUAS, S., MARTIKAINEN, R., KUOSMA, E., RIIHIMA KI, H., TAKALA, E. P.and SAARENMAA, K. 1996, Validity of self-reported physical work load in epidemiologicstudies on musculoskeletal disorders. Scandinavian Journal of Work and EnvironmentalHealth, 22, 251 259.

VIIKARI-JUNTURA, E. and RIIHIMA KI, H. 1999, New avenues in research on musculoskeletaldisorders. Scandinavian Journal of Work and Environmental Health, 25 (suppl.), 564 568.

VINK, P., LOURIJSEN, E., WORTEL, E. and DUL, J. 1992, Experiences in participatory ergonomics:results of a roundtable session during the 11th IEA Congress, Paris, July 1991.Ergonomics, 35, 123 127.

WALSH, K., VARNES, N., OSMOND, C., STYLES, R. and COGGON, D. 1989, Occupational causes oflow back pain. Scandinavian Journal of Work and Environmental Health, 15, 54 59.

WEEL, A. N. H., BROERSEN, J. P. J. and VAN DIJK, F. J. H. 2000, Questionnaire surveys onhealth and working conditions: development of an instrument for risk assessment incompanies. International Archives of Occupational and Environmental Health, 73, 47 55.

WIKTORIN, C., KARLQVIST, L. and WINKEL, J. 1993, Validity of self-reported exposures to workpostures and manual materials handling. Scandinavian Journal of Work and Environ-mental Health, 19, 208 214.

WINKEL, J. and MATTHIASSEN, S. E. 1994, Assessment of physical work load in epidemiologicstudies: concepts, issues and operational considerations. Ergonomics, 37, 979 988.


Dow

nloa

ded

by [I

ndian

Insti

tute o

f Tec

hnolo

gy G

uwah

ati] a

t 06:4

3 02 M

arch 2

015

ergonomics

Documents

Transcript of ergonomics