ERGONOMICS

Recognition of Work-Related Musculoskeletal, Nerve

Disease

What is Ergonomics?

• Ergonomics is the science of fitting the job to the worker.

• Ergonomics refers to a work environment designed to maximize safety and increase productivity.

What is Ergonomics Gone Bad?

• When there is a mismatch between the physical requirements of the job and the physical capacity of the worker, work-related musculoskeletal disorders (MSD) may result.

• Repetitive motion injury• Cumulative trauma disorder• Musculoskeletal disorder (MSD)• Repetitive stress injury• Sprains, strains, tears

Ergonomic Disease

Musculoskeletal Disorders

• Injuries or disorders of:– muscles– tendons– ligaments– nerves (compression or entrapment)– spinal discs– joints and cartilage

• Muscle pain• Joint pain• Swelling• Numbness• Restricted motion• Low back pain

Signs and Symptoms

Musculoskeletal Disorders

• Upper Extremities

• Upper Back

• Lower Back

• Feet and Legs

• Hands• Arms• Shoulder• Neck

Benefits of Good Ergonomics

• Decreased injury risk

• Increased productivity

• Decreased mistakes/rework

• Decreased lost work days

• Decreased turnover• Improved moral

Risk Factors for Ergonomic Hazards

Repetitive Motion/Cycle

• Same repetitive task

• Use of same muscle groups

• Short cycle (~<2/min)

Awkward Posture

Overhead Reach

Twisting

Force• Heavy lifting

• Forceful exertions, pulling, pushing, twisting

Contact Stress

• Using the hand or knee as a “hammer”

Vibration

• Whole body vibration– e.g.., Crane operators, truck drivers

• Segmental vibration– Pneumatic tools, grinders

Risk Factors Also Depend On:

• Duration of stress

• Amount of recovery time

• Temperature– Decrease blood flow to muscles

(cold)

And a Higher Risk Occurs When:

• Risk factors are multiple

Controlling Ergonomic Hazards

Control Hierarchy 1) Engineering controls• Physical changes

2) Administrative controls• Employee rotation• Change of pace• Job enlargement

3) Work practice controls• Utilization of better procedures, posture

4) Personal Protective equipment

Manual Material Handling and Back Protection

• Acute: – Where the injury arises from a single identifiable

event - when transient loads exceed internal tolerances.

• Chronic:– Where repeated trauma (albeit incapable of injury

in isolation), after sufficient duration, reduces internal capacity resulting in eventual injury.

– Microtrauma

Acute vs. Chronic Stressors

Back Injury

• Muscle

• Ligament

• Vertebrae

• Discs

Ergonomic Risk Factors for Backs

• Awkward posture

• Sitting

• Static, bent postures

• Fatigue/aging

• Whole body vibration

Ergonomic Risk Factors for Backs

• Handling excessive weight/force

• Load size

• Frequency of lifting

• Grip consideration

• Poor physical condition

Kinds of Back Injuries

• Back strains-When weak or tense muscles are stretched beyond their limit

• Back sprains-A partial or complete tear of a back ligament

• Herniated discs-Resulting when stress, strain or gradual deterioration on a disc causes it to stick out between the vertebrae

• Ruptured discs-When the wall of a disc breaks open.

Upper Extremities Work-Related MSDs

Effects

• Pain

• Inflammation

• Swelling

• Numbness

• Decrease in range of motion

• Loss of function

• Cycle of injury

UECTD Risk Factors Awkward Wrist Postures

Tendon Disorders

• Tendonitis:– Fibers can become inflamed, fray or tear

apart, tendons can thicken, become bumpy and irregular and without sufficient recovery time become permanently weakened

Tendon Disorders• Epicondylitis

• Lateral epicondylitis - tennis elbow (inflammation of tendon fibers - outside of elbow)

Source: American Society for Surgery of the Hand

• Medial epicondylitis or golfers elbow (inside)

Tendon Disorders

Rotator cuff tendonitis

Source:NIH, Medline Plus

• Repetitive overhead work• Elevated elbows

Tendons

• Stenosing Tenosynovitis (progressive restriction of the synovial sheath)

• De Quervain’s disease (thumb tendons)

TendonsTenosynovitis (injury of the synovial sheath)

Source: Cleveland Clinic

• Ganglionic cyst (swelling

of the synovial fluid)

• Trigger finger (stenosing tenosynovitis crepitans)

Nerve Disorders• Injuries or disorders of the median nerve:

– Carpal tunnel syndrome (compression of he median nerve as it passes through the carpal tunnel)

– Pronator syndrome (compression of median nerve as it passes between the two heads of the pronator teres muscle)

Cubital Tunnel Pain/Numbness

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Bursitis

• Shoulder Bursitis- Bursa irritated and

thickens with overuse

Neurovascular Disorders

• Thoracic outlet syndrome- Caused by compression of the neurovascular bundle from repetitive activities overhead or with the arm pulled down towards the back

Neck Disorders• Tension or ache in the neck (local

muscle tightness/spasm)

• Numbness in the arms or hands (nerve impingement)

Lower Extremities Work-Related MSDs

Knee Disorders

• Chondromalacia: degeneration (softening) of the cartilage on the posterior aspect of the kneecap

• Bursitis of the knee

Lower leg disorders• Shin splints: involve damage to

one of two groups of muscles along the shin bone (caused by standing for a long time or repetitive stress to the lower leg)

Foot Disorders

• Plantar fasciitis (inflammation of the plantar fascia--the tissue that forms the arch of the foot)

• Tarsal tunnel syndrome (entrapment of the tibial nerve)

• Reduce forces

Work Tool Design

• Use power grip

Work Tool Design

• Use optimal grasp span

Work Tool Design

Work Environmental Concerns

(Heat Stress,Energy Expenditure and Vibration)

Heat Disorders

• Heat stroke

• Heat exhaustion

• Heat cramp

• Heat collapse

• Heat rash

• Heat fatigue

• Iron and steel foundries

• Nonferrous foundries

• Brickfiring and ceramic plants

• Glass product facilities

• Rubber product factories

Heat Stress Operations

Factors Affecting Susceptibility to Heat

• Age

• Weight

• Degree of physical fitness and acclimatization

• Metabolism

Environmental Factors

• Air movement

• Humidity

• Conduction

• Radiant heat exchange

Engineering Controls

• Ventilation

• Air cooling

• Fans

• Shielding

• Insulation

Types of Vibration

• Whole Body

• Hand-Arm (HAVS)

Summary• When there is a mismatch between the physical

requirements of the job and the physical capacity of the worker, work-related musculoskeletal disorders (MSD) may result.

• Risk Factors for ergonomic hazards:– Repetitive motion cycle– Awkward posture– Force– Contact stress– Vibration

• Upper extremities work-related MSD’s• Lower extremities work-related MSD’s