Thamar University

College of Medical Sciences

Master of Public Health and Epidemiology

Environmental and Occupational Health

Dr\ Adel Aljawfi

Assistant Professor of Family and Community Health

2024

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 Occupational Health
Work Related Disorders
Outlines:
 Work Related Musculoskeletal Disorders (WRMSDs).

 Ergonomic Hazards.

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 Work Related Musculoskeletal Disorders (WRMSDs)

Introduction:
Musculoskeletal conditions comprise more than 150 diagnoses that affect
the locomotors system; that is, muscles, bones, joints and associated tissues such
as tendons and ligaments, as listed in the International Classification of
Diseases. They range from those that arise suddenly and are short-lived, such as
fractures, sprains and strains, to lifelong conditions associated with ongoing pain
and disability.
Musculoskeletal conditions are typically characterized by pain (often
persistent) and limitations in mobility, dexterity and functional ability, reducing
people’s ability to work and participate in social roles with associated impacts
on mental wellbeing, and at a broader level impacts on the prosperity of
communities. The most common and disabling musculoskeletal conditions are
osteoarthritis, back and neck pain, fractures associated with bone fragility,
injuries and systemic inflammatory conditions such as rheumatoid arthritis.
Definition of Work-related musculoskeletal disorders (WRMSDs)
They are a group of painful disorders of muscles, tendons, and nerves. Carpal
tunnel syndrome, tendonitis, thoracic outlet syndrome, and tension neck
syndrome are examples.
Common Body Parts Prone To Workplace MSDs:
• Lower - Back
• Neck and Upper Back
• Upper Extremities - Arms and Hands
• Lower Extremities - Legs and Feet
Risk factors for WRMSDs:
WMSDs are associated with work patterns that include:
1. Fixed or constrained body positions.
2. Continual repetition of movements.
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3. Force concentrated on small parts of the body, such as the hand or wrist.
4. A pace of work that does not allow sufficient recovery between movements.
Types of injuries of WRMSDs:
 Muscle Injury:
When muscles contract, they use chemical energy from sugars and produce by-
products such as lactic acid which are removed by the blood. A muscle
contraction that lasts a long time reduces the blood flow. Consequently, the
substances produced by the muscles are not removed fast enough, and they
accumulate in the muscles. The accumulation of these substances irritates
muscles and causes pain. The severity of the pain depends on the duration of the
muscle contractions and the amount of time between activities for the muscles to
get rid of those irritating substances.
 Tendon Injury:
Tendons consist of numerous bundles of fibers that attach muscles to bones.
Tendon disorders related to repetitive or frequent work activities and awkward
postures occur in two major categories – tendons with sheaths (Fig. 1), found
mainly in the hand and wrist; and tendons without sheaths (Fig. 2), generally
found around the shoulder, elbow, and forearm.
The tendons of the hand are encased in sheaths through which the tendon slides.

Figure 1: Finger tendons and their sheaths

The inner walls of the sheaths contain cells that produce a slippery fluid to
lubricate the tendon. With repetitive or excessive movement of the hand, the
lubrication system may malfunction. It may not produce enough fluid, or it may

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produce a fluid with poor lubricating qualities. Failure of the lubricating system
creates friction between the tendon and its sheath, causing inflammation and
swelling of the tendon area. Repeated episodes of inflammation cause fibrous
tissue to form. The fibrous tissue thickens the tendon sheath, and hinders tendon
movement. Inflammation of the tendon sheath is known as tenosynovitis.

Figure 2: Tendon, muscle, bone unit.

When inflamed, a tendon sheath may swell up with lubricating fluid and cause a
bump under the skin. This is referred to as a ganglion cyst.
 Nerve Injury:
Nerves carry signals from the brain to control activities of muscles. They also
carry information about temperature, pain and touch from the body to the brain,
and control bodily functions such as sweating and salivation. Nerves are
surrounded by muscles, tendons, and ligaments. With repetitive motions and
awkward postures, the tissues surrounding nerves become swollen, and squeeze
or compress nerves (Fig. 3A, 3B).

Figure 3A: Wrist in natural condition. Figure 3B:Wrist showing symptoms of Carpal Tunnel Syndrome.

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Compression of a nerve causes muscle weakness, sensations of "pins and
needles" and numbness. Dryness of skin, and poor circulation to the extremities,
may also occur.
Signs &Symptoms of WRMSDs:
• Decreased range of motion (ROM).
• Decreased grip and/or pinch strength.
• Swelling
• Fatigue
• Loss of function
• Numbness
• Burning sensation
• Tingling
• Pain
• Cramping
• Stiffness
Stages of WRMSDs :
May progress in stages from mild to severe.
Early stage: Aching and tiredness of the affected limb occur during the work
shift but disappear at night and during days off work. No reduction of work
performance.
Intermediate stage: Aching and tiredness occur early in the work shift and
persist at night. Reduced capacity for repetitive work.
Late stage: Aching, fatigue, and weakness persist at rest. Inability to sleep and
to perform light duties.

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 The most common disorders of the upper body associated with WRMSDs:
Disorders Occupational risk factors Symptoms
Tendonitis/tenosynovitis Repetitive wrist motions Pain, weakness, swelling,
Repetitive shoulder motions burning sensation or dull ache
Sustained hyper extension of arms over affected area
Prolonged load on shoulders
Epicondylitis (elbow Repeated or forceful rotation of Pain, weakness, swelling,
tendonitis) the forearm and bending of the burning sensation or dull ache
wrist at the same time over affected area
Carpal tunnel syndrome Repetitive wrist motions Pain, numbness, tingling,
burning sensations, wasting of
muscles at base of thumb, dry
palm
Thoracic outlet syndrome -Prolonged shoulder flexion Pain, numbness, swelling of
-Extending arms above shoulder the hands
height
-Carrying loads on the shoulder
Tension neck syndrome Prolonged restricted posture Pain

Diagnosis of WRMSDs:
They are confirmed by performing laboratory and electronic tests that
determine nerve or muscle damage. One such test:
- Electroneuromyography (ENMG), encompasses two areas:
electromyography (EMG) and nerve conduction velocity (NCV).
- Magnetic resonance imaging (MRI), an alternative to x-rays, provides
images of tendons, ligaments, and muscles and improves the quality of the
diagnostic information.

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 Treatment of WRMSDs:
There are several approaches including the following:
1. Restriction of Movement:
The first approach to treatment of WMSDs is to avoid the activities causing the
injury. This often requires work restrictions. In some cases, transfer to a
different job should be considered. A splint can also be used to restrict
movements or to immobilize the injured joint. However, the use of splints in
occupational situations requires extreme caution. If used inappropriately, splints
can cause more damage than good.
2. Application of Heat or Cold:
Applying heat or cold seems to relieve pain and may accelerate the repair
process.
- Cold reduces pain and swelling and is recommended for injuries and
inflammations (tissues that are swollen, red, hot and inflamed). The use of
ice it is not recommended in case of muscle pain (spasm) because cold
temperature will contract the muscle even more. Application of ice on
painful muscle is recommended only immediately after an injury
occurred, and only for few days.
- Heat is recommended for muscle pain relief. Heat increases the flow of
blood which facilitates the elimination of lactic acid build up. It is not
recommended for injuries with significant inflammation and swelling.
3. Exercise:
Stretching is beneficial because it promotes circulation and reduces muscle
tension. However, people suffering from WMSDs should consult a physical
therapist before exercising. Stretching or exercise programs can aggravate the
existing condition if not properly designed.
4. Medication and Surgery:
Anti-inflammatory drugs can reduce pain and inflammation. The doctor may try
more elaborate treatments or even surgery if all other approaches fail.

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Prevention of WMSDs
Therefore the main effort to protect workers from WMSDs should focus on
avoiding repetitive patterns of work through job design which may include
mechanization, job rotation, job enlargement and enrichment or teamwork.
A- Job Design:
*Mechanization:
One way to eliminate repetitive tasks is to mechanize the job. Where
mechanization is not feasible or appropriate, other alternatives are available.
*Job Rotation:
Job rotation is one possible approach. It requires workers to move between
different tasks, at fixed or irregular periods of time. But it must be a rotation
where workers do something completely different. Different tasks must engage
different muscle groups in order to allow recovery for those already strained.
However, job rotation alone will not be effective in reducing WMSDs if not
combined with the proper design of workstations. And it will not be effective
while the high pace of work persists.
*Job Enlargement and Enrichment:
Another approach is job enlargement. This increases the variety of tasks built
into the job. It breaks the monotony of the job and avoids overloading one part
of the body. Job enrichment involves more autonomy and control for the worker.
*Team Work:
Team work can provide greater variety and more evenly distributed muscular
work. The whole team is involved in the planning and allocation of the work.
Each team member carries out a set of operations to complete the whole product,
allowing the worker to alternate between tasks, hence, reducing the risk of
WMSDs.
B- Workplace Design
It is to fit the workplace to the worker. Evaluation of the workplace can identify
the source or sources of WMSD. Proper design of the workstation decreases the

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effort required of the worker to maintain a working position. Ideally, the
workstation should be fully adjustable, providing a worker with the options to
work in standing, sitting or sitting-standing positions, as well as fitting the
worker's body size and shape.
*Tools and Equipment Design:
Proper design of tools and equipment significantly decreases the force needed to
complete the task.
Providing the worker with the proper jigs or fixtures for tasks that require
holding elements saves a lot of muscular effort in awkward positions.
Good tools, maintained carefully and where necessary frequently changed, can
also save a lot of muscle strain.
*Work Practices:
A well-designed job, supported by a well-designed workplace and proper tools,
allows the worker to avoid unnecessary motion of the neck, shoulders and upper
limbs. However, the actual performance of the tasks depends on individuals.
Training should be provided for workers who are involved in jobs that include
repetitive tasks. Training should also emphasize the importance of rest periods
and teach how to take advantage of short periods of time between tasks to relax
the muscles, and how to consciously control muscle tension throughout the
whole work shift. Increased communication and support together with an
increased ability of the worker to control his job (where possible) are work
practices that improve worker's satisfaction and have a positive impact on
reducing the risk of WMSDs.

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 Ergonomic Hazards
Definition of Ergonomic:
The applied science and art that seeks to fit the job to the worker through the
evaluation and design of work environment in relation to human characteristics
and interactions in the workplace.
Main Ergonomic principles:
1. Work activities should permit worker to adopt several different healthy
and safe postures.
2. Muscle forces should be done by the largest appropriate muscle groups
available
3. Work activities performed with joints at about mid-point of their ROM (
head, trunk ).
Types of ergonomic
1- Physical Ergonomics:
Physical ergonomics are arguably the most important type of ergonomics, as
most employers prioritize physical comfort when trying to accommodate their
workers. Physical ergonomics focus on the ways in which people’s bodies
interact with the tools they use on a daily basis. Tools include desk chairs,
keyboards and assorted computer equipment. Additionally, the study of physical
ergonomics isn’t limited exclusively to office environments. Biomedical
engineers also study the tools used by people who work in more physically
demanding professions, such as construction and manufacturing.
2- Organizational Ergonomics:
Organizational ergonomics examines ways to optimize entire workplaces. This
entails finding ways to optimize teamwork, improve communications, increase
output and bolster the overall quality of a product.
Dysfunctional workplaces with high rates of job dissatisfaction often provide
biomedical engineers with rich playgrounds in which to work their magic.

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Controlling Ergonomic Hazards:
 Workstation Design—(desks, chairs, space, layout)
 Work Postures (sitting, standing, reaching, lifting)
 Work Organization (Pace, Breaks, Variety)
 Tools, Equipment, and Furniture Design---(body size, height, gender,
promoting neutral postures, reduced vibration, exposure to acceptable
lighting, noise, temperature)
 Manual Materials Handling—(lifting, lowering, pulling, pushing,
carrying and holding materials)
 Work Environment—(ventilation, noise, temperature & humidity,
lighting and vision)
Goals of Ergonomics safety Program:
Reduce work-related musculoskeletal disorders developed by workers when
their jobs involve...
• Awkward postures
• Static positions
• Bending & Lifting
• Force
• Repetition
• Contact stress
• Vibration
• Repetition
The benefits of an ergonomic safety program:
 Decrease injuries, illness & work compensation cost.
 Increase efficiency at work
 Increases physical well being
 Decrease absenteeism & turn over
 Increases in employee morale.

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Ergonomics hazards:
 Painful joints (Shooting or stubbing pains).
 Pain, tingling, numbness in hands, wrists, forearms, shoulders, knees and
feet.
 Swelling or inflammation.
 Fingers or toes turning white.
 Back or neck pain.

Risk Factor of ergonomic hazards

o Static posture
o Forceful exertion
o Repetitive movement
o Extreme range of motion
o Awkward posture
Working in awkward postures / positions
o Prolonged sitting and standing
o Bending, reaching, stretching
o Driving for extended periods of time
o Heavy lifting
o Awkward lifting

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 o Lifting in combination with twisting
o Pushing, pulling, carrying
o Accidents, slips, trips, falls
o Vibration
Static and awkward postures lead to:
 Decreased movement
 Decreased circulation
 Increased stress and fatigue
 Neck pain
Introduction:
Neck pain is one of the most common musculoskeletal disorders worldwide,
ranging from 42 to 67% in young adults and affecting 13% of adults at any one
time and up to 30% males and 50% females in the course of a lifetime. Young
adulthood is a sensitive period of life where development of musculoskeletal
neck pain may be established and impact future health
Definition of neck pain
It is the sensation of discomfort in the neck area, which results from
disorders of any structures in the neck, including the cervical vertebrae and
intervertebral discs, nerves, muscles, blood vessels, esophagus, larynx, trachea,
lymphatic organs, thyroid gland, or parathyroid glands. Neck pain arises from
numerous different conditions
Symptoms of neck pain:
Neck pain is a symptom commonly associated with dull ache. Sometimes it is
worsened with neck movement or turning the head. Other symptoms associated
with neck pain include numbness, tingling, tenderness, sharp shooting pain,
range-of-motion difficulties, fullness, difficulty swallowing, pulsations,
swishing sounds in the head, dizziness or lightheadedness, and lymph node
(gland) swelling.

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 On the other hand neck pain can also be associated with symptoms such
as headache, facial pain, shoulder pain, and arm numbness or tingling (upper
extremity paresthesias). These associated symptoms are often a result of nerves
becoming pinched in the neck. Depending on the condition, sometimes neck
pain is accompanied by upper back and/or lower back pain, as is common in
inflammation of the spine from ankylosing spondylitis.
Causes of neck pain:
 Muscle strains:
Overuse, such as too many hours hunched over your computer or smartphone,
often triggers muscle strains. Even minor things, such as reading in bed or
gritting your teeth, can strain neck muscles.
 Worn joints:
Just like the other joints in your body, neck joints tend to wear down with age.
Osteoarthritis causes the cushions (cartilage) between your bones (vertebrae) to
deteriorate. Body then forms bone spurs that affect joint motion and cause pain.
 Nerve compression:
Herniated disks or bone spurs in the vertebrae of neck can press on the nerves
branching out from the spinal cord.
 Injuries:
Rear-end auto collisions often result in whiplash injury, which occurs when the
head is jerked backward and then forward, straining the soft tissues of the neck.
 Diseases:
Certain diseases, such as rheumatoid arthritis, meningitis or cancer, can cause
neck pain.
Diagnosis of neck pain
 Taking medical history
 Physical examination to check for tenderness, numbness and muscle
weakness, as well as see how far patients can move their head forward,
backward and side to side

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  X-rays can reveal areas in the neck where nerves or spinal cord might be
pinched by bone spurs or other degenerative changes
 Computed tomography scan (CT scan) taken from many different
directions to produce detailed cross-sectional views of the internal
structures of the neck.
 Magnetic resonance imaging (MRI) uses radio waves and a strong
magnetic field to create detailed images of bones and soft tissues,
including the spinal cord and the nerves coming from the spinal cord
 Electromyography (EMG) if doctor suspects that the neck pain might
be related to a pinched nerve, he or she might suggest an EMG.
Prevention of neck pain :
 Use good posture. When standing and sitting, be sure your shoulders
are in a straight line over your hips and your ears are directly over your
shoulders.
 Take frequent breaks. If you travel long distances or work long hours at
your computer, get up, move around and stretch your neck and shoulders.
 Avoid tucking the phone between your ear and shoulder when you talk.
Use a headset or speakerphone instead.
 If you smoke, quit smoking can put you at higher risk of developing neck
pain.
 Avoid carrying heavy bags with straps over your shoulder. The weight
can strain your neck.
 Sleep in a good position. Your head and neck should be aligned with
your body. Use a small pillow under your neck. Try sleeping on your back
with your thighs elevated on pillows, which will flatten your spinal
muscles.
Tips for Working on the Computer
 Head: held straight & squarely over shoulders
 Eyes: top of computer screen should be at or slightly below eye level
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  Shoulders: relaxed, not raised or hunched
 Arms: supported comfortably & close to the body
 Wrists: naturally straight and flat
 Elbows: bent approximately 90 degrees and positioned close to the body
 Back: sufficiently supported to maintain its natural curve
 Hips: bent approximately 90 degrees
 Knees: bent approximately 90 degrees. There should be two to three
finger space between edge of seat and back of knees
 Feet: placed flat on the floor or supported by a footrest

 Back Pain
Definition of Back pain (backache):
It is pain felt in the back. The back is divided into neck pain (cervical),
middle back pain (thoracic), lower back pain (lumbar) or coccydynia
(sacral pain) based on the segment affected. The lumbar area is the most
common area affected.

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Common Back Disorders:
 General joint stiffness
 Acute strains and sprains
 Degenerative disk disease
 Bulging disc
 Herniated disc
 Osteoarthritis
Causes of back pain:
 Poor body posture, working in a stooped position; prolonged
sitting in fixed position
 Lifting and handling heavy loads
 Forceful pushing or pulling
 Bending or twisting
 Psychological stress
 Inadequate rest periods
 Poor fitness level
 Accidents
Prevention of back pain:
A- Neutral postures, using appropriate lifting techniques, alternating
work activities, adequate rest periods.
B- Office Exercises/Stretches
 Stretch regularly throughout day.
 Stretches should be done slowly and smoothly.
 Change your activity. Where possible, every hour, take a few minutes to
alternate your work activities. This will help to relieve muscle aches,
eyestrain and stress.
 If you are under treatment, regarding the exercises, please contact your
physician before doing any of the following suggested exercises.

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Wrist and forearm stretches:
a) Shake your arms
• Drop your arms and hands to your side
• Shake them gently for a few seconds

b) Wrist stretches
• Keep your elbows straight, grasp hand and slowly bend wrist until
you feel a stretch
• Hold stretch for 6-10 seconds.

Shoulder/Arm Stretches:
• Reach with your arm across the chest
• Grasp opposite shoulder with opposite hand
• Gently pull the elbow across your chest towards the body

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 • When the stretch is felt in the shoulder
• hold this position for 6-10 seconds.

Shoulder Shrug:
• Sit in the chair with your back straight against the backrest.
• Let your head relax.
• Squeeze your shoulders up to your ears.
• Follow by stretching shoulders down with fingers pointing to the
floor, draw chin in gently.
• Slowly change from one position to another.

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Executive Stretch:
• Lock your hands behind your head.
• Stretch slowly backwards in your chair.
• Arch your back slightly and gently.
• Hold stretch for 6-10 seconds.
• Repeat 5 times with 5-10 second rest period between stretches.

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