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Usually,
the alignment between the user and the computer components and
accessory devices is not proper. This makes it difficult for the user
to maintain good postures, such as straight wrists, elbows close to the
body, and head straight and in -line with the torso. Let’s see a few
instances that we face in our everyday life to which causes such
misalignment:
- When
your monitor is positioned too high, you tend to tilt your head back,
which fatigues the neck and shoulder muscles.
- If
your keyboard tray is too small, you tend to move the mouse to a
position of the desk that requires you to reach to perform mouse tasks.
This pulls the elbow away from the body and can cause you to support
your arm in an elevated position for prolonged hours leading to
discomfort and fatigue.
- If
your keyboard is too low, you tend to bend your wrists at extreme
angles, which can cause the finger tendons and tendon sheaths to bend
around the bones of the wrist. Sitting in such awkward postures
irritate or strain the bone-tendon-muscle connections.
4.
Muscles when stretched or compressed become inefficient resulting in
possible fatigue and overexertion.
- Postures
that are not neutral ones can pull and stretch tendons, blood vessels,
and nerves over ligaments or bone thus increasing their chances of
becoming pinched and restricted.
- Tendons
and their sheaths can rub on bone and ligaments leading to irritation
and fraying. This in turn leads to swelling within confined areas such
as the carpal tunnel, which then restricts nerves and blood vessels.
- The
user may also suffer from tingling and numbness of the fingers and
hands as well as pain from tendonitis and tenosynovitis (inflammation
of a tendon sheath). If the workstation is properly adjusted, it can
help the users to minimize awkward postures. It is ideal to place the
monitor in front of you at a height where you can look straight ahead
and not tilt your head forward or backward. You can keep the items that
you access frequently such as keyboards and pointing devices very near
to you so that you don’t have to strain yourself while reaching out for
them every time.
- You
need to adjust and position keyboard trays and chairs so that you don’t
have to bend your wrists up, down, or to the side. Adjust the chair so
as to give good support to your feet and back. If you maintain proper
neutral postures, you can work with minimal stress on the
musculoskeletal system.
Contact Stress
There
are two types of contact stress - internal and external. When a tendon,
nerve, or blood vessel is stretched or bent around a bone or tendon,
you suffer from internal contact stress. When a part of your body rubs
against a component or device in the workstation, like chair seat pan
or the desk edge, you are said to be suffering from external contact
stress. This may lead to irritation of the nerves or contraction of the
blood vessels.
- The
users experience contact stress to their forearms when they rest them
on the leading edges of worktables or, if the nerves in the forearm are
affected, their fingers and hands may tingle and feel numb, similar to
the feeling when they hit their "funny bone".
- If
blood circulation is cut off by contact with the leading edge of a
chair, the users are sure to experience pain and numbness in their
legs.
- The forearms and wrists can be affected if the edges of the wrist rests are sharp and hard leading edges.
- If
the wrist is kept bent throughout the jobs like typing which is a
repetitive finger motion task, the tendons are sure to get damaged.
You
can solve such problems by carefully selecting wrist rests, chairs, and
desk surfaces as well as by taking frequent rest and stretch breaks to
minimize the amount of contact stress that you may experience. Your
workstation should be adjusted in such a way as to maintain neutral
wrist postures.
Force
Usually, when we talk about force, it is thought of as a strenuous
physical exertion, such as when lifting a heavy weight or pushing a
heavy load. In computer parlance, force is totally different from the
usual definition. Computer work seldom requires this type of laborious
exertion, but there are tasks that require concentrated force that can
affect smaller, localized muscle groups.
For instance.
- Pretend
you are using a pointing device that is too sensitive that you find it
so difficult to control. There are all chances that your finger and
forearm muscles become sore because the muscles of hand and arm must
work hard continually to keep the device steady.
- Pretend
your mouse is placed very far from you that you have difficulty
reaching for it every time. This time what really happens is that your
shoulder and neck muscles become strained as they are continually being
used to lift the arm away from your body.
- Pretend
your monitor is kept very high from the recommended height. You tend to
tilt your head back to get a clear view of the monitor. This time the
muscles of your back can become strained due to continued use.
Normally, when injuries happen, the first point of pain is the muscle.
But, the tendon, which attaches the muscle to bone, can also be
affected. Localized pain, stiffness, and tenderness are some of the
symptoms showing that the muscle or tendon has been exerted beyond its
capacity. If you arrange the computer and associated components in your
workstation properly and appropriately, so as to maintain neutral
postures, you can avoid such problems to a large extend. Select
adjustable furniture so that you can minimize the amount of time spent
in one posture.
General Controls
Keep in mind the following body postures when you arrange your work components and purchase new equipments:
- Do not bent or twist your head and neck. Keep them vertical and in-line with the spine.
- Maintain a straight torso. It should not be twisted, especially when lifting or bending.
- Whether in standing or sitting postures, keep your torso vertical or within 20 to 30 degrees of vertical.
- Avoid
reaching your elbows frequently to your side, in front, or above your
head. Keep them close to your body.
- Your forearms should be placed approximately parallel to the floor.
- Do
not rotate your forearm repeatedly, especially when your wrist is bent.
Try to maintain a neutral forearm posture whenever possible.
- Your wrists should be kept straight and in-line with your forearms. Do not bent them up or down or to either side.
8.
Your thighs should be placed approximately parallel to the floor and
your hips slightly higher than your knees.
- Your feet should be placed firmly on the floor and your legs approximately perpendicular to the floor.
- Your keyboard and mouse should be placed close together at about the same height to minimize reaching.
- If
you use a fully adjustable chair, it supports your body fully so that
you can change your body postures frequently.
- Your
work surface should be height adjustable so that multiple users can sit
with their feet firmly on the floor. Do use an adjustable footrest if
the work surface is not fully adjustable.
13.
All frequently used components such as monitor, keyboard, and mouse
should be placed in front of you so that you don’t have to turn your
head from side to side every time you reach them.
Learn more about Healthy Computing habits.
- Your
monitor needs to be placed low enough so its top is not above your
horizontal line of sight. This will minimize the need for you to tilt
your head backward to see the screen.
- It
is important to provide auxiliary, full-sized, keyboards and monitors
if you are using laptops as primary work computers where intensive
keyboard use is necessary.
Repetition
Most of the jobs that we do on the computer are highly repetitive in
nature. We may perform the same motions repeatedly at a fast pace and
with little variation. The recovery time for the muscles and tendons
become insufficient when your motions are isolated and repeated
frequently for prolonged periods. The risk of injury is more if you
combine repetitive tasks with factors such as awkward postures and
force.
- Computers
require little task variation. Old typing activities, such as adding
paper or mechanically advancing pages, have been reduced or eliminated.
Now, users can stay in their chairs and type/perform mouse work for
prolonged hours. A proficient typist can easily perform more than
18,000 keystrokes per hour in such conditions. Such kind of repetitive
motions can cause tendon and tendon sheath injuries, especially if the
wrist is bent during the activity.
- The
same is the case while using a pointing device such as a mouse. Here,
the risk is greater because the concentration is only on a few fingers
of a single hand.
3.
Most of the computer operators usually remain in essentially the same
posture for an entire shift. This forces a few isolated muscles to
repeatedly activate to accomplish a task such as holding the head up or
focusing on a computer screen.
- A
poorly designed workstation may force the user to repeatedly reach to
use a mouse or answer the phone. This can fatigue the muscles of the
shoulder and irritate the tendons.
By properly arranging the workstation and its components, you can
reduce repetition. Ideally, a mouse that is placed close to the
keyboard should minimize repetitive reaching. However, for jobs like
data entry operation, even the best-designed workstation cannot
eliminate all highly repetitive motions.
Hence, it is extremely important to maintain good posture by providing
adequate adjustability at the workstation. All hand jobs should be
performed with the wrist in a straight, neutral posture to allow the
tendons to slide easily without interference. The following work
process suggestions may also help reduce repetition.
- Task
Rotation or Job Enlargement - Doing the same job for prolonged hours in
front of the computer is monotonous as well as tiring. If your job
involves a variety of other tasks too along with the computer job,
manage your time and mix the tasks so that you don’t have to strain
yourself from doing the same job for long time. Other non-computer
tasks such as photocopying, phone work, filing papers, cleaning up,
etc. can be done taking short breaks.
2.
Micro Breaks or Rest Pauses. You need to make it a habit to take short
rest pauses while doing computer tasks. It is recommended to take short
breaks frequently to avoid any kind of stress or strain. You can look
at a farther distance, stretch your arms and feet, get up from your
chair, or walk for sometime every hour taking a five-minute break. By
taking such brief rest pauses, you are giving ample time for your
muscles and tendons to recover.
Note: While every care is taken
to provide medically accurate and up to date information in this web
site, it is to be noted that this advice is not intended to replace the
advice of your physician. Before undertaking the advice contained in
this web site, you should consult a medical professional.
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Other pages on healthy computing:
chairs Cts Desk Exercises Eyestrain
Keyboard Lighting Monitors Mouse Msd
Other Computer Hazards Telephones Ventilation
Work Station Setup
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