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Awkward postures
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Awkward postures means working with various parts of the body in bent, extended
or flexed positions rather than in a straight or neutral position. Working in
awkward postures increases the exertion and muscle force that
employees must apply
to complete a task and compresses tendons, nerves and blood vessels. In general,
the more extreme the posture the more force is needed to complete the task.
Examples of awkward postures include
any task that may:
- pull the elbows away
from the torso such as performing overhead
work or reaching in
front, to the side, or
in behind the
body;
- bending the elbow past
about 90 degrees for
prolonged periods of
time;
- bending or
twisting the torso to lift an
object from low or
distant locations;
- extending, flexing, or
bending a wrist to the
side while using tools or
performing connection
tasks;
- bending the neck
backward or forward for
prolonged periods while
working overhead or on
low surfaces; and
- bending the knee or
ankle to work in a
squatting or kneeling
position.
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Bending the elbow
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 Repetitive elbow bending can irritate nerves and tendons in the forearms, and
even lead to epicondylitis, or "tennis elbow".
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Bent wrist
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 Working with wrists in a bent rather than straight position
increases the risk of injury especially where the task also involves high hand force.
Working with bent wrists puts stress on the tendons and tendon sheaths in the
hands and wrists. When the wrists are bent the tendons and sheaths rub against
hard bones and ligaments. If this happens repeatedly, the tendons and sheaths
can become irritated and inflamed, resulting in injuries such as tendonitis. The
inflamed tendons and sheaths can also press against the nerves that run through
the wrist to the hand, resulting in carpal tunnel syndrome.
General controls to reduce awkward wrist postures:
- Tool handles may
be bent or modified
depending on the
task to allow the
user to maintain a
straight, neutral
wrist.
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Contact stress |
 Contact stress results from
prolonged or repeated contact between hard or sharp objects/surfaces and sensitive body tissue, such
as soft tissues of the fingers, palms, thighs and feet. This contact creates
localized pressure for a small area of the body, which can inhibit blood
flow, nerve
function, movement of tendons and muscles
and create localized
irritation.
Some contact stress problems include:
-
Use of tools with short
handles which can press
into the palm of the
hand.
-
Standing for long periods of time
on hard and small areas
such as ladder rungs
which may create
pressure on the arch of
the foot.
-
Carrying hard or sharp
items such as ladders or
conduit on the shoulder
where muscles and
tendons can be
irritated.
General controls to reduce contact stress:
-
Use electric or power
tools to minimize
repeated hand
activations.
-
Purchasing tools with
appropriately-designed handles
(should have a span of
about 2 inches, a
diameter of about 1.5
inches, should be long
enough to extend across
the palm, and may be
bent to minimize wrist
bending).
-
Wrap or coat tool handles and grips with cushioning material.
-
Use
gloves with palm pads.
Use shoes with thick or cushioned soles
to spread the force over
a wider area.
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Crouching and kneeling |
 Electrical employees will frequently need to bend or crouch to reach the work
space. This kind of activity can contribute to poor circulation of blood, and
may injure the knees where they come in contact with the floor. |
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Lifting heavy loads |
 Many tasks require employees to lift, push, pull and carry heavy loads. Heavy
lifting can result in overexertion and injury to the lower back.
How much weight an employee can safely lift depends on a number of factors. When the factors are such that the
employee can assume an "ideal" body posture during the lift, the
employee is able to lift greater loads. However, when the body posture is not ideal (e.g., back is bent or arms are outstretched), then the amount of weight the
employee can safely lift is reduced. Factors affecting how much weight an
employee can safely lift include:
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Lifting factors
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More weight can be safely lifted when:
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The amount of weight that can safely be lifted is reduced when:
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How far from the body the load is held (horizontal distance).
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The load is close to the body and not too large/bulky, which allows the
arms and elbows to be close to the torso during the lift.
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The load is farther away from the body or is large/bulky, forcing the arms
and elbows away from the torso during the lift.
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How high or low is the lift (vertical distance).
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The lift is at waist height.
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The lift must be made from below the knees or above the shoulder.
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How much the employee must twist to lift and move the load.
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The lift is performed in front of the body.
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The employee must twist the torso to lift and move the load.
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How often the lift is repeated.
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The lift is performed only occasionally.
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The lift is performed repeatedly (several times a minute).
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How far the load is carried.
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The lift does not involve carrying.
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The load must be carried a distance (more than 3 feet).
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How the load is gripped.
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The load has handles.
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The load does not have handles or is slippery.
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General controls to reduce lifting hazards:
- Use lift assists such as hand trucks, carts, and forklifts.
- Reduce size of product boxes to lighten load.
- Arrange work space so employees can move closer to loads and perform lifts
with arms close to the body.
- Use pallets that can rotate.
- Put objects to be lifted at waist level.
- Arrange workstation so lifting is done in front, without twisting.
- Put handles or grips on boxes.
- Use gloves that aid in holding slippery objects.
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Reaching |
 A number of tasks require employees to work with their hands above their
head or shoulders, their arms extended to arm's length, or their elbows raised
out from their body. These kinds of tasks place stress on the
shoulders, elbows and back, and can result in an ergonomic injury.
Elevated reaches - Examples of jobs and tasks that require employees to repeatedly reach or work with their hands above their head or their elbows above their shoulders include:
- Installing ceiling fixtures
- Pulling wire in a plenum space
Extended reaches - Employees also have to perform extended reaches when there is not adequate access to the work area, extending the elbows away from the body. Examples include:
- Lifting a bulky, large load
- Providing improper hand tools may force
employees to raise their elbows away
from the torso in order to prevent wrist deviation.
- Using in-line tools on horizontal surfaces can force shorter employees to
lift their elbows as high as shoulder height in order to keep their wrists
straight.
General controls to reduce reaching hazards:
- Ladders and lifts to reduce reaching.
- Bent handled tools that allow straight wrists and elbows
close to the body.
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Repetitive motion |
Some tasks involve repeating the same actions with little
variation. When motions are repeated frequently for prolonged
periods, such as several hours without any break or over an entire work shift,
there may be inadequate time for muscles and tendons to recover. If the
repetitive tasks also involve other ergonomic risk factors, muscles and tendons
become extremely strained or fatigued more quickly.
Highly repetitive tasks often involve the use of only a few muscles or body
parts while the rest of the body is unaffected. To reduce the strain that
repetitive tasks pose to those body parts, use these solutions:
-
Rotate employees into several different jobs during the course of a work shift
is a way to distribute work so that each employee spends less time performing
the same repetitive tasks. In order for job rotation to reduce muscle/tendon
strain and provide adequate recovery time, the different jobs into which
employees rotate need to involve the use of different muscles or body parts.
-
Design jobs so they include a wider variety of tasks
(longer motion pattern) is another way to reduce the frequency and duration of
repetitive motions.
-
Build short micro pauses between motions or tasks is another way to give
muscles and tendons recovery time.
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Static postures |
Maintaining the same posture for an extended period of time can cause problems
including pooling of blood and fatigue in muscles. Long periods of standing can
cause pain and contact
stress to the feet. |
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Temperature |
Extreme temperatures can cause problems for
employees. Cold temperatures make the
muscles less flexible, resulting in muscle strain and pulls. Hot temperatures
lead to dehydration and muscle fatigue. |
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Twisted torso |
 The
back is designed to operate
efficiently with both hands
lifting loads directly in
front of the body. In this
manner muscles work
symmetrically in tandem
across a balanced spine.
Twisting the torso creates
an asymmetry which stretches
some sets of muscles while
compressing others forcing
smaller, isolated groups of
muscles to provide the
needed force for the task.
Twisting the spine creates
non-symmetrical forces on
the fibers of the disc which
weakens the structure making
it more susceptible to
bulging and rupture from the
compressive force created
during lifting.
Supporting a load with the
torso bent forward greatly
increases both the muscle
force which must be exerted
and the compressive force on
the spine. When significant
force exertion is combined
with the structural
instability created from
twisting, the opportunity
for injury is greatly
increased. |
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Vibration |
 Although using powered hand tools may help reduce employee exposure to ergonomic risk factors such as repetition and force, they can expose employees to vibration. Vibration restricts the blood supply to the hands and fingers, which, depending on the vibration level and duration of exposure, can contribute to an ergonomic injury. Signs and symptoms of vibration-induced injury, such as Reynaud's phenomenon, start with occasional numbness or loss of color in the fingertips. They progress to more frequent and persistent symptoms affecting a larger area of the fingers and resulting in reduction in feeling and manual dexterity.
Factors that increase the amount of employee exposure to vibration include:
- Bad power tool design - Even new tools can expose employees to excessive vibration if they are not designed with devices that dampen or shield employees from vibration.
- Poor power tool maintenance.
- Old power tools.
General controls to reduce vibration:
- Use low vibration tools.
- Use vibration dampeners or shields to isolate source of vibration from
employee.
- Inspect and maintain power tools regularly.
- Limit the duration of tasks that involve vibration, and rotate tasks.
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