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Keyboards
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Keyboard
Quick Tips |
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- Put the keyboard directly
in front of you.
- Your shoulders should be
relaxed and your elbows close
to your body.
- Your wrists should be straight
and in-line with your forearms.
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Proper selection and arrangement
of the computer keyboard helps reduce exposure to awkward
postures, repetition,
and contact
stress.
Consider the following factors when evaluating your computer
workstation.
You should choose a keyboard and
consider its placement in conjunction with other components
of the computer workstation, including the pointer/mouse
and wrist/palm
rests.
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Potential
Hazard
- Keyboards, pointing
devices, or
working
surfaces that are too high or too low can
lead to awkward wrist, arm, and shoulder postures.
For example, when keyboards are too low you
may type with your wrists bent up, and when
keyboards are too high, you may need to raise
your shoulders to elevate your arms. Performing
keying tasks in
awkward
postures such as these can result in hand,
wrist, and shoulder discomfort.
Figure 1.
Keyboard tray
Figure 2.
Side view illustration showing the recommended
range for keyboard placement
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Possible
Solutions
- Adjust the chair height and work surface height
to maintain a
neutral
body posture. Elbows should be about the
same height as the keyboard and hang comfortably
to the side of the body. Shoulders should be
relaxed, and wrists should not bend up or down
or to either side during keyboard use.
- Remove central pencil drawers from traditional
desks if you can't raise your chair high enough
because of contact between the drawer and the
top of the thighs. The work surface should generally
be no more than 2 inches thick.
- A keyboard tray (Figure
1) may be needed if the work surface or chair
cannot be properly adjusted. The keyboard tray
should
- Be adjustable in height and tilt,
- Provide adequate leg and foot clearance,
and
- Have adequate space for multiple input devices
(for example, a keyboard and
pointer/mouse).
- The keyboard's vertical position should be
maintained within the recommended range shown
in Figure 2. The tilt of the keyboard may need
to be raised or lowered using the keyboard feet
to maintain straight, neutral wrist postures
while accommodating changes in arm angles.
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Potential
Hazard
- A keyboard or
pointer/mouse
that is too close or too far away may cause
you to assume awkward postures such as reaching
with the arms, leaning forward with the torso
(Figure 3), and extreme elbow angles (Figure
4). These awkward postures may lead to musculoskeletal
disorders of the elbows, shoulders, hands, and
wrists.
Figure 3.
Keyboard that is too far away
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Figure 4.
Keyboard that is too close
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Possible
Solutions
- Place the keyboard directly in front of you
at a distance that allows your elbows to stay
close to your body with your forearms approximately
parallel with the floor.
- A keyboard tray may be useful if you have
limited desk space or if your chair has armrests
that interfere with adequate positioning.
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Potential Hazard
- A traditional keyboard may cause you to bend
your wrists sideways (Figure 5) to reach all the
keys. Keyboard tilt, caused by extending the
legs on the back of the keyboard or by a steep
design angle, may cause the wrist to bend upward
(Figure 6). Smaller keyboards, such as those
found on laptops, may also contribute to
stressful postures. These awkward wrist postures
can create
contact stress to the tendon sheath and
tendons that must move within the wrist during
repetitive keying.
Possible Solutions
- Reduce awkward wrist angles by lowering or
raising the keyboard or chair to achieve a
neutral wrist posture.
- Elevate the back or front of keyboards to
achieve a neutral wrist posture. For example, if
the operator sits lower in relation to the
keyboard, slightly elevating the back of the
keyboard may help maintain a neutral
wrist. Similarly, raising the front of the
keyboard may help maintain neutral wrist
postures for users who type with the keyboard in
a lower position. Do not use keyboard feet if
they increase bending of the wrist.
- Consider
alternative keyboards (Figures 8 and 9) to
promote neutral wrist postures. Alternative
keyboards may be provided on a case-by-case
basis. Users may need time to become
accustomed to these devices.
Note: alternative keyboards help
maintain neutral wrist postures, but available
research does not provide conclusive evidence
that using these keyboards prevents discomfort
and injury.
- Keyboards should be of appropriate
size and key-spacing to accommodate most
users. Generally, the horizontal spacing
between the centers of two keys should be
0.71-0.75 inches (18-19 mm) and the
vertical spacing should be between
0.71-0.82 inches (18-21 mm) (Figure 7).
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Figure 7.
Keyboard with 18-19 mm horizontal spacing and 18-21 mm vertical spacing between keys |
Figure 8.
Split keyboard design
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Figure 9.
Tented and raised keyboard design |
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Potential
Hazard
- Most keyboards are manufactured with a 10 key keypad permanently affixed to the right side of the keyboard. This arrangement can be limiting to left handed workers or right handed workers who are recovering from injury and are attempting to remain functional during their recovery. This arrangement is also a problem if one is attempting to create work-rest regimens by alternating principle hand usage during the work day or work week.
Possible
Solutions
- Alternative left hand keyboards which have
the keypad permanently affixed to the left side
of the keyboard are available as are keyboards
with a detached keypad. These allow the user to
switch positions for either left or right hand
use. These may be especially useful for
applications where workers share computers.
- Programmable stand alone keypads are
available which can be programmed to facilitate
either right or left hand usage
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Figure 10.
Alternative keyboards allow the user to
place the keypad and mouse on either side of
the keyboard
Figure 11.
A programmable keypad allows keys to be defined to user preference
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