Natale Battevi: Occupational Physician

Variable Lifting Index for Manual-Lifting Risk Assessment:

A Validation Study

NIOSH 1997 National Institute for Occupational Safety and Health(National Accademy 2001)

Risk Factors Strong

Evidence (+++)

Evidence (++)

Insuff. Evidence

(+/0)

Lifting +++

Awkward posture ++

Heavy physical work ++

Whole Body Vibration +++

Fixed posture +/0

Causal relationship between lumbar spine injury

and risk factors

EPIDEMIOLOGICAL DATA

The World Health Organization announced in

2009 that “37% of back pain is related to

occupational risk factors” and it is the “main

cause of absence from work, generating

economic losses” (Driscoll et al., 2014)

https://www.eurofound.europa.eu/data/european-working-conditions-survey

41 %

Does your work involve carrying or lifting heavy objects at

least ¼ of the time?

6th EUROPEAN SURVEY (2015)

Estimation of exposed

workers in

Turkey-

10.000.000 workers

Exposed to MMH by sectors in Turkey

0% 20% 40% 60%

Finance & Other services

Commerce & Hospitality

0% 10% 20% 30% 40% 50% 60% 70%

Finance & Other services

Commerce & Hospitality

Public Administration, education & Health

Construction &Transport

Agriculture & Industry

Does your work involve carrying or lifting heavy objects at least ¼ of the time ?

0,0%

5,0%

10,0%

15,0%

20,0%

25,0%

30,0%

35,0%

40,0%

1991 1995 2000 2005 2010

YEARS

Does your work involve carrying or lifting heavy objects at least ¼ of the

time?

EPIDEMIOLOGICAL DATA (whole Europe)

5th EUROPEAN SURVEY - 2010

Men

Women

History of Niosh Lifting Equation

• 1981 - “Work Practices Guide for Manual

Lifting” (for monotask)

• 1991 - Scientific Support Documentation for

the Revised 1991 NIOSH Lifting Equation, PB91-226274 May 8, 1991, National Technical Information Service, Springfield, Virginia

• 1994 - Applications manual for the revised NIOSH lifting

equation. Waters, TR. et al. Cincinnati, Ohio: NIOSH; 1994 (for monotask and composite tasks)

Why Variable Lifting Index ?

• Composite Lifting Index can be applied only to 10-12 monotasks maximum

• We cannot apply CLI when different weights and geometries are present (common situation in almost all working places)

• For instance, we have to simplify risk assessment while improving productivity and find solutions at the same time.

The birth of VLI• A group of experts met in Spain to discuss how to

find a new method

• After one year this group presented VLI for the first time at IEA congress in Beijin (China-2012)

• In 2015 Thomas Water died and in 2016 a monograph on NIOSH Lifting Index was published in his memory

• This monograph includes the theory of VLI and my presentation on the first validation study

Vol. 58, No. 5, August

2016, pp. 695–711

Recommended Weight Limit is the Maximum Weight that can be lifted under ideal conditions

reduced due to other risk factors

Comparison between

WEIGHT LIFTED

RECOMMENDED WEIGHT LIMITLI=

NIOSH Method

VERTICAL MULTIPLIER

Reference Mass

DISTANCE MULTIPLIER

HORIZONTAL MULTIPLIER

ASYMMETRIC MULTIPLIER

FREQUENCY MULTIPLIER

COUPLING MULTIPLIER

Maximum recommended mass under optimal lifting conditions Distance of the hands from the floor at the

start or end of lifting

Vertical distance of the load between the

beginning and the end of lifting

Maximum distance between the load and the body during lifting Angular measure of displacement of the load from the sagittal plane Frequency of lifts per minute and duration Assessment of the object grip

X

= RECOMMENDED LIMIT WEIGHT(RWL)

X

X

X

X

X

CALCULATION OF THE RECOMMENDED LIMIT WEIGHT

NIOSH Method

Variable Lifting Index for Manual-

Lifting Risk Assessment and its

relationship with acute low back pain

PLAN OF THE STUDY • Exposure index calculated with the same method

(systematic organizational analysis approach” Waters 2016) and verified with numerous inspections in the company

• Clearly identified exposed subjects

• Standard method for damage evaluation

performed by occupational physicians

• Damage and exposure index evaluation had to be

carried out in a short time range

DAMAGE VARIABLEDefinition : EPISODE OF ACUTE LOW BACK PAIN

“ presence of lumbar pain with or without irradiation

obliging the patient to remain immobile, for at least

two days, or one day if medication was taken”

WHY ? Because there is A DIRECT RELATIONSHIP

BETWEEN BIOMECHANICAL OVERLOAD AND

PAINFUL LUMBAR SPINE STIMULATION

(MARRAS, RADWIN, YASSI, EPM)

Selection criteria for exposed subjects

• Having performed daily lifting activities for at

least 167 days in the past year;

• Having spent more than 12 months on the current job;

• Pulling, pushing, and carrying activities had to

be residual tasks of the whole work shift;

• No exposure to whole-body vibration;

• No exposure to handling activities for more than

8 hour in a work shift.

Selection criteria for Unexposed subjects

• Be employed in the same company as the

exposed subjects;

• Perform mainly clerical jobs or use a visual display unit;

• Make autonomous decisions for what concerns breaks and have the possibility to switch between sitting and standing position.

Sample characterisics

• 2374 Exposed to MMH risk• 1029 Not exposed to MMH risk (working in the same companies)

• 16 Companies• 298 different job, of which:

37 in critical conditions (exceeding NIOSH limits) for horizontal distance and 22 for vertical location

3357 subjects exposed to MMH risk 1409 subjects unexposed

Eligible

Sample Characteristics:VLI_EU (with referent mass for RWL set at 25, 20 and 15 kg)

Type of statistical analysis

• Linear logistic

• Use of ODDS (exposed/unexposed cases)

• ODDS Ratio (OR) - reference: ODDS of unexposed subjects =1

• Raw analysis first, then adjusted for potential confounding factors (BMI, gender, age)

Results of Logistic analysis (raw): VLI_EU

Results (OR)

Association between VLI – EU and acute low back pain

Reflections and limits

• BMI is the only significant confounding factor

• Risk is significant for VLI values higher than 1

• The study of association is related to a symptom, not a disease

• Being a cross-sectional study, it needs validation

• Adjusting one-handed lifting and team lifting (simultaneous lifting by two operators) does not seem to affect the results

• Psychosocial aspects which proved to be significant for low-level exposure in a previous study by Water have not been considered (Marras 2008)

• Wide range of cumulative mass values across all VLI risk classes

Reflections and limits

Cumulative Mass for VLI Risk Classes

VLI_EU

Cumulative Mass (Kg)

N° Mean Median 10 th Pct 25 th Pct 75 th Pct 90 th Pact

0 < VLI ≤ 1 329 1205 900 104 159 1886 2625

1 < VLI ≤ 2 626 1913 730 202 211 2609 4620

2 < VLI ≤ 3 963 2064 448 198 299 3070 6793

VLI > 3 459 4183 1519 386 717 4014 13987

Dikkat etmeniz için teşekkürler

Dr. Natale BatteviE-mail:battevi.ergonomia@gmail.com