Transcript Slide 1

International Module W506
Ergonomic Essentials
Day 3
MUSCULOSKELETAL DISORDERS
(MSDs)
Outline
• MSDs
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Definition
Parts of body at risk
Impact of MSDs on industry
Risk factors
Low back disorders
Risk management
• WRULD
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Definition
Risk Factors
Injury mechanisms
Risk management
Nature & Causes of Manual Handling
Disorders
• 4 key physical risk factors:
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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
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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:
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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)
Borg’s RPE (15 level scale)
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No exertion at all
Extremely light
Very light
Light
Somewhat hard
Hard
Very hard
Extremely hard
Maximal exertion
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.
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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
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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 risk
1. 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
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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)
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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)
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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
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High moments at shoulder
Static load on shoulder
Awkward shoulder posture
No time for tissue recovery
BP
UL: Injury Mechanisms (2)
• Hand & Forearm
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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
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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))
Stevenson
ASCC 2007
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)
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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
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Definition
Parts of body at risk
Impact of MSDs on industry
Risk factors
Low back disorders
Risk management
• WRULD
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Definition
Risk Factors
Injury mechanisms
Risk management