Section 5
Ergonomics
Blitz Personnel - Ergonomics
Definition: The study of fitting the task to the human.
Goal: To prevent musculoskeletal disorders by taking preventative steps, relying on employee input, and addressing problems early.
This section will cover the following:
•
Musculoskeletal Disorders (MSDs).
•
Recognizing signs and symptoms of MSDs and how to report it.
•
Common causes of MSDs.
•
Computer Ergonomics.
•
Safe Lifting Principles.
Musculoskeletal Disorders are caused by the overuse or repetition involving:
•
Muscles
•
Nerves
•
Tendons
•
Ligaments
•
Joints
•
Spinal disks
•
Cartilage
The following symptoms should be reported to your supervisor early:
•
Muscle fatigue
•
Aching
•
Burning
•
Numbness
•
Stiffness
•
Tingling
The following signs should be reported to your supervisor immediately:
•
Decreased range of motion
•
Decreased grip strength
•
Loss of function
•
Loss of balance
•
Deformity
•
Swelling
•
Cramping
•
Redness
•
Color loss
Common causes of MSDs
•
Lifting – continuously lifting and/or moving
•
Repetitive motion – angle alignment, force, length of time without break – ex. assembly line.
•
Contact stress – ex. Hammering
•
Extreme force – ex. Tightening objects
•
Vibration – ex. Drilling
•
Awkward postures – pulling carts
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Section 5
Ergonomics
Goal: To configure your workstation properly, in order to minimize the demands placed on your body while working. To maintain
posture at the wrist, elbow, and neck. Support your back, legs and feet. Maintain an optimal line of sight.
Muscles, Ligaments, and Tendons
We have three different types of muscles in our body:
•
Cardiac
•
Visceral
•
Skeletal
Skeletal muscles are most important when considering the arrangement of your workstation in the
office.
Skeletal muscles are attached to your skeleton and are termed voluntary muscles because we can
move then on command. These muscles are responsible for moving our joints when they contract.
For example, contracting our bicep muscle will flex our elbow joint.
Muscles, Ligaments and Tendons
Ligaments connect bone to bone. Tendons connect muscle to bone.
In our hands and wrists we have many ligaments and tendons.
The forearm muscles are connected to the bones in our fingers via tendons. The muscles and
tendons work to move our fingers and hands.
These tendons, along with nerves and blood vessels, pass through the “Carpal Tunnel” at our wrist.
This is a high risk area for injury for computer based office tasks, because if the tendons in this
tunnel are irritated, they may swell and pinch the blood vessels and nerves, creating pain and
numbness in the hand and fingers.
The Spine
Our spine is made up of vertebrae (bones) that are stacked on top of each other.
Between each vertebra are discs, which act as shock absorbers to help decrease any stress in our
spine.
There are three natural curves in our back:
•
Cervical
•
Thoracic
•
Lumbar
Our back is in its neutral position when all three curves are present. The lower lumbar curve requires
support from our chair to keep its shape and to decrease the effort required by our back to maintain
its neutral position.
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Section 5
Ergonomics
Ergonomic analysis involves applying three main principles:
•
Force
•
Repetition
•
Posture
Each of these factors alone poses a risk of injury. However, it is the interaction between all three
factors that poses the greatest risk of injury.
Therefore, by optimizing posture, controlling repetition rate, and minimizing force for most tasks, you
can minimize the risk of injury and enhance your task performance.
When we apply high forces to our body, we stress our muscles, tendons and ligaments. The level of
force that our body can tolerate is relative to the strength and condition of the muscles and joints we
are using.
It is important that the keys on the keyboard can be pressed easily and with little force. High finger
forces combined with high repetition rate increases the risk of injury.
When lifting, whether at home or at the office, it is important to keep your back straight and to use
your arms and legs to lift.
Repetition
Each time a muscle contracts, we are placing stress on that muscle, its tendons, and nearby ligaments. Therefore, if we control the
amount and duration of repetitive tasks, we can give our muscles, tendons, and ligaments a break and ensure they are not injured.
For office tasks, especially typing, it is recommended that a break be taken after one hour of continuous typing or data entry.
A break can simply mean performing a different task, such as filing or reviewing a document.
Posture
Our body functions best when each body segment is
in its neutral posture.
The neutral posture for any body segment:
•
•
•
Provides the greatest strength and stability
Places the least stress on muscles and
tendons
Results in the lowest risk of repetitive strain
injury
The illustrations below show correct neutral postures
for the lumbar spine, the neck, the elbow and the
wrist. These are the primary focus of office
ergonomics.
Seated posture
The first area to consider is how you are sitting on your chair.
The goal is to have your knee between a 90-110-degree angle while seated, with your feet fully supported
(whether on the floor or on a footrest). There should be a 90-degree angle between the calf and the sole of
the foot.
Your seat pan (the part of the chair you sit on) should give a slightly rounded and padded front edge and
should not be pressing into the back of your knee. If it does, you probably need a smaller chair.
A
B
A. Adjust your chair so that your knee is at a 90-110-degree angle when your
feet are resting flat on the floor.
B. Adjust your chair so that your knee is at a 90-110-degree angle when your
feet are resting on a footrest.
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Section 5
Ergonomics
Back Support
One of the most important principals in office ergonomics is to keep your back in its neutral position.
In order to maintain the lumbar curve, it is important that the chair’s lumbar support be positioned in the
correct part of your back.
The goal is to align the curve on that chair back with the curve in your back.
A.
Adjust your chair back up and down to position the lumbar support to the
correct height.
B.
Adjust your chair forward and backward (if possible) to get the lumbar
support pressed against your back. This may be required if your current
natural seated position does not allow your back to touch the backrest.
A
B
Typing posture
The best typing posture keeps the elbow and the wrist in a neutral position.
The optimum typing posture has the following characteristics:
•
90-110-degree elbow angle
•
Neutral wrist posture (in line with the horizontal forearm). Do not rest wrists on desk or wrist rest
while typing. This can reduce blood flow to the hands/wrists, creating symptoms of tingling,
numbness and/or pain.
•
No interference with chair arm rests. Arm rests should fit comfortably underneath the desk work
surface.
A.
Raise your chair to the correct typing height and use a footrest if
maintain support to your feet.
necessary to
B.
Use an adjustable keyboard tray to set your correct typing height
correct seated posture.
while keeping a
A
B
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Section 5
Ergonomics
Monitor Height
The monitor is at the correct height when your neck is in its neutral posture. Our relaxed line of sight is
about 10-15 degrees below horizontal.
To optimize monitor height, the goal is to place the top of the viewable area of the screen in line with
your eyes when looking straight ahead.
•
For bifocal wearers, the top of the viewable area of the screen should be placed 5-10 cm
below eye level.
A.
If your monitor is too low, place something under it to raise it.
You can use an old phonebook, a slab type monitor support
or a monitor arm.
B.
If your computer is too high because is situated on top of
your hard drive (CPU), use a CPU stand and place your
monitor on the desk (use a monitor rise if required.)
C.
If your monitor is simply too high, remove the base of the
monitor.
A
B
Viewing Distance
The monitor should be placed 45-61 cm from your eyes.
Move the monitor forward and backward as necessary to achieve the correct viewing distance.
Reach Zones
Frequently accessed items should be placed close to the body, in
Zone A in the diagram below.
Less frequently accessed items and emergency items should be
placed further out from the body, in Zone B in the diagram.
Very infrequently used items should be located on the periphery of
the work surface, in Zone C.
The keyboard and mouse should be located at the same height within
Zone A.
Monitors should be located straight in front, at the Zone A/B border.
If you use the phone frequently, it should be located in Zone A, or on the closer side of Zone B. If you frequently cradle the phone
between your ear and your shoulder, consider using a headset.
Less frequently used items should be placed at the back of the work surface.
If you refer to papers regularly while typing they should be placed in Zone A. This may require the use of a keyboard tray to position
your keyboard and mouse off of your desk. If you use a document holder, it should be placed at the same viewing distance and as
close to the computer monitor as possible. The document holder may eliminate the need to change focus when viewing documents
while typing.
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Section 5
Ergonomics
Material handling, lifting, and back safety
There are safe ways to complete all types of manual material handling. One of the most important things you must do is take an active
role in preparing yourself properly for the task. In general, if you follow these principals you will be able to safely handle any load.
Manual material handling can be broken down into:
•
Lifting
•
Pushing/pulling
•
Carrying/holding
Safe Lifting Tips
You are practicing safe lifting if:
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The lift is performed between knuckle and elbow height.
•
There is a minimal horizontal distance between the load and the body.
•
You avoid twisting when lifting or lowering a load.
•
You alternate lifting tasks with lighter work to give your body a chance to recover.
•
You bend at your hips, not your back, if you have to bend.
•
You use handles.
•
You do not lift a load alone if it is too heavy or awkward.
Remember to:
•
Test the weight of the load and make sure your path is clear.
•
Rotate your hips (keep curve in low back).
•
Bend your knees
•
Get close to the load
•
Contract your stomach muscles
•
Position you feet in a “V” instead of twisting.
•
Lift with both hands.
Safe Pushing / Pulling Tips
Remember to:
•
Grasp handles or items slightly below your elbow height.
•
Maintain a minimum horizontal distance from the item.
•
Avoid twisting
•
Try to push rather than pull
•
Find good foot traction
•
Stagger your feet for a stable base.
•
Use your body weight as force – lean in to it.
Remember to:
•
Keep a minimal horizontal distance between the load and your body
•
Avoid twisting when lifting or lowering a load
•
Use handles
•
Try to push or pull rather than carry the load
•
Use both hands
•
Use handles if they are there
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Section 5
Ergonomics
It is recommended that you complete stretches 2 to 3 times a day. It important to read the instructions carefully and only stretch to the
point when you feel pressure – not pain. If you have an injury, you should see your doctor before completing stretches of the affected
area.
Reach above your head, grasp your hands
together, turn your elbows in and press up.
Hold for 5 seconds and repeat 3-5 times.
Roll your shoulders up and back. Hold for 5
seconds and repeat 3-5 times.
Reach one hand behind your head (toward
the other shoulder blade) and use your other
hand to increase the stretch. Hold for 5
seconds and repeat 3-5 time.
Sitting in a chair, lean forward and reach for
the floor. Hold for 5 seconds and then
slowly sit up. Repeat 3-5 times.
Bring knee up towards your chest, while
keeping your back against the backrest of the
chair. Hold for 5 seconds and repeat 3-5
times.
Place your hands on the small of your back
(just above your buttocks) and bend
backwards. Keep you knees straight. Hold for
5 seconds and repeat 3-5 times.
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Section 5
Ergonomics
Stand facing the wall (close enough to lean on it) with
toes pointed straight forward. Move one leg forward
and bend your knee as in picture. While leaning on wall
and keeping back heel on floor, press hips forward to
get stretch in back calf muscle. Hold for 5 seconds and
repeat 3-5 times.
Place your palms on the wall, at shoulder
height, straddling the corner. S lowly step
into the corner and stretch chest muscles by
moving shoulder blades together. Hold for 5
seconds and repeat 3-5 times.
Raise your shoulders up towards your ears.
Hold for 5 seconds and repeat 3-5 times.
Look straight ahead; tilt your head moving your chin
towards your chest. Hold for 5 seconds and repeat 3-5
times.
Look straight ahead; tilt your head, moving
your chin towards your chest. Hold for 5
seconds and repeat 3-5 times.
Bring arm across your body and use other
hand to increase the stretch. Hold for 5
seconds and repeat 3-5 times.
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