Components - Pointer/Mouse
Pointing devices such as a mouse
now come in many sizes, shapes, and configurations. In
addition to the conventional mouse, there are trackballs,
touch pads, finger tip joysticks, and pucks, to name a
few. Selection and placement of a pointer/mouse is an
important factor in creating a safe computer workstation.
- Keep the pointer/mouse close
to the keyboard.
- Alternate hands with which
you operate the pointer/mouse.
- Use keyboard short cuts
to reduce extended use.
Consider the following factors when evaluating your computer
- If the pointer/mouse is not near the keyboard
(Figure 1) you may be exposed to awkward
forceful hand exertions while using the
device. Working in this position (Figure 2)
for prolonged periods places stress on the shoulder
and arm and increases the likelihood that you
will assume awkward wrist and shoulder postures,
which may lead to musculoskeletal disorders.
Mouse placement that is too far away
because of a small keyboard tray
Mouse placed too far from the user and not
in the same plane as the keyboard
Appropriate mouse placement
Keyboard with a built-in touchpad
Mouse wrist rest
- Position the pointer/mouse to allow you to
maintain a straight, neutral wrist posture.
This may involve adjustments in your chair,
- If the keyboard tray/surface is not large
enough to accommodate both the keyboard and
mouse, try one of the following to limit reaching:
- Use a mouse platform positioned over the
keyboard. This design allows the mouse to
be used above the 10-key pad.
- Install a mouse tray next to the keyboard
tray (Figure 4).
- Use a keyboard that has a pointing device,
such as a touchpad, incorporated into it (Figure
- Use a keyboard without a ten-key pad, which
leaves more room for the pointer/mouse.
- Install keyboard trays that are large enough
to hold both the keyboard and mouse.
- Use a mouse pad with a wrist/palm
rest to promote neutral wrist posture (Figure
- Substitute keystrokes for mousing tasks, such
as Ctrl+S to save, and Ctrl+P to print.
- Inappropriate size and shape of pointers
can increase stress, cause awkward postures,
and lead to overexertion. For example, using
a pointing device that is too big or too small
may cause you to increase finger force and bend
your wrist into awkward positions. Using the
left hand to operate a device that is designed
for right-hand use can also create force and
posture issues and may create contact stress
to the soft tissue areas in the palm of the
hand. Contact stress can create irritation and
Fingertip joystick for a notebook computer
- Select a pointing device designed to fit the
hand that will normally operate it. Many devices
are available in right hand/left hand models
and also come in sizes to fit large and small
hands. A device that is designed for either
hand use may be desirable, since changing from
right- to left-hand operation provides periods
of rest for one hand. You should test a device
prior to purchase and long term use to ensure
proper fit and feel.
- Select pointing devices that are appropriately
sized and that require minimal force to generate
movement. For example, a puck device (Figure
7) must be small enough for single-handed operation
(generally, 1.5 to 2.5 inches wide, 2.5 to 4.5
inches long, and 1 to 1.5 inches high).
- Reduce the strain on hands by reducing pointing
device use. Using keyboard functions, such as
page down, may reduce mouse use and provide
rest for hand and arm muscles.
- Use another type of device that fits the hand
better or doesn't require bending the wrist
while gripping. A fingertip joystick (Figure
8), touchpad, or trackball (Figure 9) may be
less fatiguing for certain tasks. Always try
out any new product prior to selection and long
- When the sensitivity for the input device
is not appropriately set, you may need to use
and awkward hand postures to control the device.
For example, a mouse that is too sensitive may
require excessive and prolonged finger force
to provide adequate control. A mouse that has
insufficient sensitivity may require large deviation
of the wrist to move the pointer around the
screen. Exerting prolonged force or repeatedly
bending the wrist can fatigue the muscles of
the hand and arm and increase the risk of musculoskeletal
- Sensitivity and speed (how fast the pointer
moves on the screen when the pointing device
is moved by the hand) should feel comfortable
and be adjustable. The pointer should be able
to cover the full screen while the wrist is
maintained in a straight, neutral posture.
- Sensitivity should be set so you can control
the pointing device with a light touch. Most
current devices have sensitivity settings that
can be adjusted through the computer control
- Avoid tightly gripping the mouse or pointing
device to maintain control.
- A trackball's exposed surface area should
be at least 100 degrees (Figure 9). It should
feel comfortable and rotate in all directions
to generate any combination of movement.