International Module W506

Ergonomic Essentials

Day 3

MUSCULOSKELETAL DISORDERS(MSDs)

Outline

• MSDs– Definition– Parts of body at risk– Impact of MSDs on industry– Risk factors– Low back disorders– Risk management

• WRULD– Definition– Risk Factors– Injury mechanisms– Risk management

Nature & Causes of Manual Handling Disorders

• 4 key physical risk factors:– Repetition– Force– Posture– Vibration– Combination of factors

• Cumulative damage

Low Back Disorders

• The spine– Function

• Facilitates movement

• Protects spinal cord

• Protects vital body organs

Low Back Disorders

• Structures of the spine– Muscles, tendons and

ligaments– Vertebrae– Discs

McPhee

Low Back Disorders

• Injury Mechanisms of the Spine– Lifting/forceful movement– Awkward postures– Heavy physical work– Whole body vibration– Personal variables

(strength, age, gender, abdominal girth

HOW?

Risk Identification

• Indicators for risk in manual handling tasks:– Weight & load (force)– Frequency of lift (repetition)– Distances moved (force, posture)– Workplace layout (posture, vibration)– Personal variables (abdominal girth, age, gender,

strength and mobility)

Risk Assessment Strategies

• Review work tasks to identify ‘risky’ tasks/personnel– Physical demands– Psychological demands– Individual risk factors

• Undertake formal manual task risk assessment– Legislative requirement to

use specific tool?• MAC (UK)

• COP Risk Assessment Tool (Australia)

• OCRA (EU standard)

Detailed Ergonomics Methods

• Biomechanical– ‘risk’ at max. compression force of 3.4 kN at L4/L5 or

L5/S1 joints

• Physiological– ‘risk’ at max. energy expenditure of 2.2 – 4.7 kcal/min

• Psychophysical– ‘risk’ at max. acceptable weight (75% female & ~ 90%

male workers)

• Combination Approach

Examples of these ergonomics methods (1)

• Biomechanical– 2D & 3D static strength models– Lumbar Motion Monitor

Source: http://www.nexgenergo.com/ergonomics/lumbarmm.html

Examples of these ergonomics methods (2)

• Physiological– HR monitoring– Borg rating of perceived

exertion scale (RPE)

• 6 No exertion at all

• 7 Extremely light

• 8

• 9 Very light

• 10

• 11 Light

• 12

• 13 Somewhat hard

• 14

• 15 Hard

• 16

• 17 Very hard

• 18

• 19 Extremely hard

• 20 Maximal exertion

Borg’s RPE (15 level scale)

Examples of these ergonomics methods (3)

• Psychophysical Methods– Snook Tables

• Designing manual tasks for more than 75% female work population reduces risk of injury

• Tables provide information on object weight, distances load is lifted from and to, and frequency of lift.

• Useful for running ‘what if’ scenarios.

• Useful web link: http://libertymmhtables.libertymutual.com/CM_LMTablesWeb/pdf/LibertyMutualTables.pdf

Examples of these ergonomics methods (4)

• Combination Approach– NIOSH equation

• Biomechanical, physiological, psychological criteria to determine lifting limits

• 3 indices: – lifting index

» Ratio of load to recommended weight limit

– Job severity index» Measurement of job demands

– Lifting strength rating» Strength requirements

Other Ergonomics Methods (1)• Epidemiological

– Nordic Questionnaire

Other Ergonomics Methods (2)

• Postural methods– OWAS– RULA– RULA– REBA

• Combination postural methods– QEC– ManTRA

UOW

Risk Control

1. Eliminate manual handling activity

2. Redesign to eliminate risk

3. Reduce the risk1. Redesign load

2. Redesign work area

3. Use mechanical aids &/or equipment

4. Training in risk assessment and ergonomic principles

Example of Workplace Modification

• This workplace washes hospital linen.

• Linen bags are suspended on a conveyor system and delivered to worker who unties the bottom of the bag and directs washing into chute, eliminating need to manually handle the bag.

UOW

Use of mechanical aids

• Use of bin lifter to assist with emptying large and or heavy bins.

Backwatch collections WorkCover NSW

Principles of manual handling

• Commit to risk management approach (eliminate manual handling risk!)

• When lifting & handling a load– Plan the lift/handling activity– Keep the load close to waist (centre of gravity)– Keep stable position– Ensure good grip– ‘good posture’ (head up, keep the curves0– Avoid twisting/sideways bending– Move smoothly– Know your capacity– Adjust the load position AFTER putting it down – e.g. sliding

General Guidance for Lifting & Handling

Source: HSE: Getting to Grips with Manual Handling

Lifting & Lowering Mass Guidance

Source: HSE: Getting to Grips with Manual Handling

WORK-RELATED UPPER LIMB DISORDERS (WRULDs)

• CTD• RSI• OCD• OOS• WRULD!

BP

WORK-RELATED UPPER LIMB DISORDERS (WRULDs)

• Increasing occurrence of WRULDs• Risk Factors:

Physical Risk Factors

Psychosocial Risk Factors Individual Risk Factors

Repetition Job demands Age

Force Job control Gender

Posture Social relations at work Socioeconomic status

Vibration Pre-existing musculoskeletal disorders

The Upper Limb (1)

• Shoulder• Upper arm• Forearm• Wrist• Hand

BP

The Upper Limb (2)

• Function of the arm and hand– Mechanical power (large

muscles)– Manipulation (small

muscles of hand)

BP

Types of grip

• Pinch/Precision • Power/Palmar

McPhee

McPhee

UL: Injury Mechanisms (1)

• Shoulder– High moments at shoulder– Static load on shoulder– Awkward shoulder posture– No time for tissue recovery

BP

UL: Injury Mechanisms (2)

• Hand & Forearm– High forces + repetitive work– High forces required by task– Non-optimal postures– Static loads– Use of power tools

• High vibration• High/poor torques

– High levels of precision placement in task

• Increases time• Increases static loading• Increases force requirements

WRULD: Risk Identification

• Risk Identification– Force (weight and load)– Repetition (frequency of activity)– Posture (workplace layout: distances, forces)– Duration– Psychosocial factors– Work organisational factors (e.g. shift work)– Personal variables (e.g. age, gender)

WRULD: Risk Assessment

• Risk Assessment Techniques– Simple

• e.g. HSE risk Assessment Worksheet

– Complex• e.g. RULA, OWAS, OCRA (ISO 11228-3:2007)

WRULD: Risk Control (1)

• Risk Control– Structural modifications

• Use of ‘ergonomic’ work tools– Bend tool handles to 5o-10o

– Avoid extreme ulnar/radial deviation– Use low forces when rotating or flexing wrist– Minimise forces for finger pinch movements

(<10N (20% of weakest operator max. pinch strength))

ASCC 2007

Stevenson

WRULD: Risk Control (2)

• Risk Control– Structural modifications

(cont.)• Appropriate workstation

layout & equipment

– Facilitates optimal postures

• Reduce excessive force, awkward postures and any compression of tissues while working

– Use large muscle groups, not small

Stevenson

WRULD: Risk Control (3)

• Organisational modifications– ‘Ergonomically’ designed job (pace, variation, etc)

• Rotate between high and low repetition jobs• Use machinery for repetitive jobs and workers for variable tasks• Allow self pacing• Utilise ergonomic criteria in planning work systems and

purchasing equipment– Reduce duration of frequent & repetitive movements

• Design out repetitive tasks/jobs (esp. < 30 second cycle time)– Ensure adequate recovery time

• Eliminate unnecessary overtime• Avoid repetitive work in extreme tempts.• Pauses in work cycles

• Training & Retraining

Summary

• MSDs– Definition– Parts of body at risk– Impact of MSDs on industry– Risk factors– Low back disorders– Risk management

• WRULD– Definition– Risk Factors– Injury mechanisms– Risk management