LECTURE 18: WORK-RELATED MUSCULOSKELETAL DISORDERS

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Musculoskeletal: Skeletal muscle + Bone structure

+ Soft Tissues

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Musculoskeletal

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1. Skeletal muscle

2. Bone structure

3. Joint

4. Ligament

5. Tendon

6. Bursa

7. Related blood vessels

8. Nerve

Functions

Muscle contract and stretch

Force on bone and joints

Movement/

Posture/

Physical exertion

TASK

Functions…

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1. Body movement and posture:

Integration between - Muscle-joint-bone

2. Voluntary process through nerve innervations

and electrical stimulation

Muscles capability

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Mental LIMITED:

• Strength/Power

• Duration

• Frequency

Physiology requirements for action

Basic elements

• Energy: glucose, protein, fat and

oxygen.

• Bloos supply.

• Minerals: Calsium (Ca), Sodium (Na)

and Potassium (K)

• Nerve supply

Mechanical

• Contraction: dynamic or static.

• Contraction strength:

– Number of activated motor

unit;

– cross section; and

– length (limited).

• Tetanus

METABOLIC

• Temperature

• Lactic acid

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Contraction-Stretch mechanism Characteristics Static (Isometric) Dynamic

(Isotonic)

1. Contraction Continuous Repetitive

2. Length Not change Change

3. Tension Not change Change

4. Blood supply Less Increase

5. Oxygen consumption Less Increase

6. Metabolic product Lactic acid CO2 + H2O

7. Duration of activity Short Long

8. Example Holding Walking

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Work Related Musculoskeletal Disorder (WRMSDs)

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Structures involved:

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1. Skeletal muscle

2. Bone structure

3. Joint

4. Ligament

5. Tendon

6. Bursa

7. Related blood vessels

8. Nerve

General Symptoms and Signs

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LEVEL 1: Early stage

Pain

Aching

Discomfort

Numbness LEVEL 2: Intermediate

Prolong symptoms in level 1.

Inflammation

Disturb movement: weakness/stiffness

LEVEL 3: Disabilities

Prolong level 1 and 2;

Difficult to recover

Permanent disabilities

HAZARD

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RISK

S EX

PO

SUR

E YusofOmar - 2010

WORKSTATION

HUMAN AT WORK

WR

MSD

s

Ph

ysical Force

Chronic Tissue Inflammatory and

Degeneration

Acute Injury

Human susceptibility

Source of Hazards (Ergonomic Components)

Physical Environment

Workstation

Tools/

Machine

Task

Human

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WORK ORGANIZATION

Contributing factors

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Contributing factors

1. Awkward postures

2. Repetitive motions

3. Forceful exertions

4. Pressure points (e.g., local contact stress)

5. Vibration

6. Environent: High/cold temperature

Workplace designs are mismatched to the human capabilities, limitation and other characteristics

1. Awkward postures

Repeated or prolonged: • Reaching • Twisting • Bending • Working overhead • Kneeling • Squatting • Holding of fixed positions • Pinch grips

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Adverse effects

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Increasing the exertion on smaller muscle groups

Impairs blood flow and

Increases the rate of fatigue and weakness

2. Repetitive Motions

• the same types of movements are performed over and over again using the same muscles, tendons, or joints.

• Examples of jobs - machine-controlled pace include working on assembly, packaging, or quality-control lines.

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3. Forceful Exertions

• Exerting large amounts of force can result in fatigue and physical damage to the body.

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The amount of force depends on a combination of factors:

1. Load shape, weight, dimensions, and bulkiness

2. Grip type, position, and friction characteristics

3. Amount of effort required to start and stop the load when moving it

4. Length of time continuous force is applied by the muscles

5. Number of frequencies the load is handled per hour or work shift

6. Amount of associated vibration

7. Body posture used

8. Resistance associated with moving the load.

9. Duration of the task over the work shift

10. Environmental temperature

11. Amount of rotational force

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4. Pressure Points (local contact stress)

• Pressure points - the body pressing against hard or sharp surfaces.

• Certain areas of the body - susceptible because nerves, tendons, and blood vessels are close to the skin and underlying bones include the sides of the fingers, palms, wrists and forearms, elbows, and the knees.

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5. Vibration

• Part or whole body expose to continuous or of very high intensity of frequency.

• Example:

Hand-arm vibration - such as sanders, grinders, chippers, routers, impact guns, drills, chain saws, and circular saws.

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Adverse effects

• fatigue,

• pain,

• numbness,

• tingling,

• increased sensitivity to cold, and

• decreased sensitivity to touch in the fingers, hands, and arm.

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6. Environment

• High/cold temperature of workstation.

• Poor lighting/vision.

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Risk Impact

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WRMSDs

WMSDisorders

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Common Diseases: 1. Ligament/tendon injuries. 2. Backbone(vertebrae): Acute/Chronic

backache. 3. Wrist and hand: Carpal Tunnel Syndrome. 4. Tendon: Tendinitis/Tenosynovitis. 5. Bursa: Bursitis 6. De Quervain’s. 7. Thoracic Outlet Syndrome. 8. White hand syndrome.

1. Ligament/tendon injuries

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Healthy tendon

Damaged tendon

Rani Lueder, CPE. Humanics ErgoSystems, Inc.

2. PID

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3.. Carpal Tunnel

Carpal Tunnel Syndrome

When lining around tendons is inflamed, there is less space for the nerve and it becomes compressed.

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4. Tendonitis

• Tendonitis or tenosynovitis

– is an inflammation of the tendon or tendon sheath

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5. Bursitis • Bursitis

– bursa becomes inflamed due to excessive friction or rubbing. • A bursa is a sac

like cavity filled with slippery fluid found between tendons and bony prominence-reduces friction

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Other related diseases

1. Varicose vein or ulcer dilatation of vein.

2. Osteoarthritis – joint damage.

3. Peripheral arteritis.

4. Neuropathy.

5. Etc.

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Implications

• Individual:

Sickness absenteeism;

Disabilities;

Loss of job.

• Organization:

Image;

Productivity: loss competent person, retraining;

High cost for long term treatment such as

rehabilitation.

• Government:

SOCSO reclamations.

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Thank you

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