GROUP 3
Computer Workstation Ergonomics
There are various health problems associated with the regular use of computers, such
as stress, eyestrain, and injuries to the wrists, neck, and back.
Employers must take steps to protect employees whose work involves the regular use
of computers.
Computer ergonomics is the discipline of matching the task to the worker using the
most appropriate equipment to optimize human well-being and overall performance.
This can be simplified to ―Modify the workplace, not the individual".
Consideration should be given to:
• The accessories required to operate properly
• The layout of equipment on the desk
• The location of furniture in the room
Work Surface Height
Adjust the height of the work surface
and/or the height of the chair so that the
work surface allows your elbows to be bent
at 90 degrees, forearms parallel with the
floor, wrist straight, shoulders relaxed.
Chair
Adjust the seat tilt so that you are
comfortable when you are working on the
keyboard. Usually, this will be close to
horizontal but some people prefer the seat
tilted slightly forwards. Your knees should be
bent at a comfortable angle and greater
than 90 degrees’ flexion. If this places an
uncomfortable strain on the leg muscles or if the feet do not reach the floor, then a
footrest should be used. The footrest height must allow your knees to be bent at
90 degrees. Therefore, the height of the footrest may need to be adjustable. Adjust
the backrest so that it supports the lower back when you are sitting upright.
Keyboard Placement
Place the keyboard in a position that
allows the forearms to be close to the horizontal
and the wrists to be straight. That is, with the
hand in line with the forearm. If this causes the
elbows to be held far out from the side of the body,
then re-check the work surface height. Some
people prefer to have their wrists supported on a
wrist desk or the desk. Be careful not to have the
wrist extended or bent in an up position.
Screen Placement
Set the eye to screen at the distance that permits you to most easily focus on the
screen. Usually, this will be within an arm's length. Set the height of the monitor
so that the top of the screen is below eye level and the bottom of the screen can be
read without a marked inclination of the head. Usually, this means that the center
of the screen will need to be near shoulder height. Eyes must be level with the tool
bar. People who wear bifocal or multi-focal lenses will need to get a balance
between where they see out of their lenses and avoid too much neck flexion.
Document Holder
Place this close to the monitor screen in the position that causes the least twisting
or inclination of the head.
Desk-Top Layout
Place all controls and task materials within a comfortable reach of both hands so
Posture and environment
Change posture at frequent intervals to minimize fatigue. Avoid awkward postures
at the extremes of the joint range, especially the wrists. Take frequent short rest
breaks rather than infrequent longer ones. Avoid sharp increases in work rate.
Changes should be gradual enough to ensure that the workload does not result in
excessive fatigue. After prolonged absences from
work the overall duration of periods of keyboard work should be increased
gradually if conditions permit
Lighting
Place the monitor to the side of the light source/s, not directly underneath. Try to site desks
between rows of lights. If the lighting is fluorescent strip lighting, the sides of the desks should be
parallel with the lights. Try not to put the screen near a window. If it is unavoidable, ensure that
neither the screen nor the operator faces the window. The solution is to increase the refresh rate of
the monitor to at least 75hz. If the monitor is well away from windows, there are no other sources
of bright light and prolonged deskwork is the norm, use a low level of service light of 300 lux. If
there are strongly contrasting light levels, then a moderate level of lighting of 400 - 500 lux may be
desirable.
Glare and Reflection
It is important to detect the presence of glare and reflection. To determine whether there is glare
from overhead lights whilst seated worker should hold an object such as a book above the eyes at
eyebrow level and establish whether the screen image becomes clearer in the absence of overhead
glare. To detect whether there are reflections from the desk surface, the worker should hold the
book above the surface and assess the change in reflected glare from the screen.
Using a Mouse
A well-designed mouse should not cause undue pressure on the wrist and forearm muscles. A large
bulky mouse may keep the wrist continuously bent at an uncomfortable angle. Pressure can be
reduced by releasing the mouse at frequent intervals, by selecting a slim-line, low-profile mouse.
Keep the mouse as close as possible to the keyboard, elbow bent and close to the body.
Posture during Keying
Good posture is essential for all users of computers. It comprises of a natural and
relaxed position, providing opportunity for movement, and from which the operator
can assume a number of alternative positions. It is not a single, rigidly defined
position.
Typing Technique
Typing is a physical activity, and using a keyboard requires skill, hence the need to
learn correct typing technique. Unskilled ('hunt and peck') typists are particularly at
risk of Occupational Overuse Injury because they: often use only one or two fingers
which may overload the finger tendons; are constantly looking from keyboard to
screen to keyboard, which may strain neck muscles; often adopt a tense posture
(wrists bent back and fingers 'poised to strike').
Speed of Keying
The efficiency and speed of modern computers makes it possible for a skilled operator
to type extremely quickly. This capability reinforced by workload pressures means the
potential exists for operators to key at speeds which may cause or contribute to
Occupational Overuse Syndrome. The role of the repetitive movement in injury is not
fully understood but is believed to interfere with the lubrication capacity of tendons,
and the ability of muscles to receive sufficient oxygen supplies. 10,000 - 12,000
keystrokes per hour is considered an acceptable standard.
Length of time on the keyboard
The maintenance of a fixed posture for long periods is tiring and increases the likelihood of muscular
aches and pains. In addition, long periods of repetitive movement and sustained visual attention can also
give rise to fatigue-related complaints. It is recommended that operators avoid spending more than five
hours a day on keyboard duties and no longer than 50 minutes per hour without a postural/stretching
break.
POINTS TO REMEMBER
Computers –Ergonomic Guidelines
• Viewing distance: The monitor should be 2 –2½ feet from the child’s eyes.
• Time at computer: Encourage children to use their physical energy.
• Seat and height posture: The child should sit high enough to have his arms
bent at 90°
• Footrest: Use it prevent dangling feet.
• Mouse: Find one that fits small hands.
• Keyboard: Child-sized keyboards with light pressure keying are recommended.
