Guide to Keyboard and Mouse Use
A number of factors should be taken into consideration with respect to
keyboard and mouse use. Discussed throughout much of this site, the workstation should facilitate a
comfortable posture. Making improvements may be simple and effective; however, depending on circumstances and
the possible combinations of equipment, optimizing a workstation can be complex.
Typing
 |
 |
|
It is generally recommended that the operator float their hands over the keyboard while typing, so their hands are maneuvered
by (larger) shoulder muscles, and not the wrists. Inbetween periods of typing, the operator can rest by placing their hands
on a palm rest or another comfortable surface. A separate palm rest may not always be necessary; as an example, many
alternative keyboards will include a built-in palm rest. To minimize resistance and strain on soft tissues, a bend of
less than ten degrees at the wrist should be maintained while typing.
|
Resting Palms, Not Wrists
 |
It is also important to distinguish between resting palms and resting wrists. Resting palms
is recommended because the palm of the hand contains two protuberances which support the weight of the hand while keeping
pressure off of blood vessels, tendons, and nerves that run through the wrist. Resting wrists, on the other hand,
increases pressure on these soft tissues. |
 |
Avoiding Wrist Extension
 |
Bending the hand back at the wrist, also known as wrist extension,
should be avoided when typing because this will increase resistance on the soft tissues in the wrist. As far as typing is concerned, this is the most discomforting posture of one's hand
and wrist. To avoid this posture, the keyboard should not be used in a positive tilt, so
operators may want to consider closing the feet that are on the bottom of the keyboard. A
palm rest may also be used to help avoid wrist extension. |
 |
Tilting the keyboard away from the operator by about seven degrees will further help to
minimize wrist extension. This is usually achieved by using an appropriate adjustable keyboard tray, though other
measures may be as effective. |
Equal Height of the Keyboard and Pointing Device
It is necessary to keep the mouse and keyboard at the same height. Having to lift the arm and
hand to switch between the mouse and keyboard will lead to discomfort and should be avoided. Here are some situations
where this configuration is found. They should be corrected when identified:
- The workstation may include a keyboard recess that doesn't provide enough room for both the mouse and keyboard
- The workstation may be equipped with a keyboard tray that doesn't support both the mouse and keyboard. In many cases,
this is because there is insufficient clearance beneath the work surface for an appropriate tray.
|
 |
Mouse Selection and Use
 |
- Make sure that the size and shape of the mouse are comfortable. When the hand is relaxed, in a position where it is
halfway opened and halfway closed, tension between the extensor and flexor muscles of the fingers is balanced.
If the mouse is too large or too small, the hand will have to open or close to grip the mouse. This prevents the hand
from relaxing during mouse use which can lead to discomfort
- Avoid wrist extension associated with mouse use
- Use the mouse with a gentle grip, not a tight grip
|
Mouse Position
| When using a pointing device on the right-hand side of most standard keyboards, the operator must
reach past the numeric keypad, bringing their hand away from their midline and opening the angle of their shoulder. This
may not lead to discomfort for taller individuals; however, shorter individuals, relatively speaking, will have to reach
farther and maintain awkward postures while using their pointing device. There are three common solutions to this concern,
all can be used to improve posture by allowing the operator to bring the pointing device closer to the midline of their body. |
 |
 |
An inexpensive solution is to configure the computer operating system to reverse the mouse buttons
and use the pointing device on the left-hand side of the keyboard. |
 |
Mouse bridges are inexpensive, and they can be used to position the pointing device over the
numeric keypad of the keyboard. |
 |
Many manufacturers offer an adjustable keyboard tray with a mouse platform that
swivels over the numeric keypad of the keyboard. This is often a good solution for petite office workers who
may also need the keyboard and mouse lowered to a comfortable height. |
Additional Measures
|
Further measures may be used to reduce discomfort associated with
keyboard and mouse use. These are not usually considered to be necessary though they
may still be helpful. |
Injury Prevention Software
Several computer applications are available which remind the
computer operator to take breaks and microbreaks based on their keyboard and pointing device use.
This can be very helpful in avoiding discomforting levels of repetitive motion and strain by
helping the operator to make sure that they have adequate recovery time; it is usually
recommended for individuals who find that they tend to work for long periods of time
without breaks or change.
|
Reducing Load from Mouse Use
There are a number of software and hardware features that can be used
to reduce the load on the body associated with mouse use. Unfortunately a complete guide
isn't available; it may not be practical given the variety of operating systems, applications,
and hardware. Operators are encouraged to check their hardware and software for similar
features. A few examples are listed below.
- Auto-scrolling:
This feature is found in many applications. Pressing the mouse wheel places the application
in auto-scrolling mode. This allows the operator to scroll in any direction corresponding to
a slight movement of their mouse. The application will continue to scroll without further
movement of the mouse until the operator counters the scrolling by moving their mouse in the
opposite direction. Press the mouse wheel again to shift out of auto-scrolling mode.
This can help avoid excessive use of the mouse wheel or click-and-drag mouse use when scrolling.
- Keyboard shortcuts:
Both Microsoft Windows and Mac OS include keyboard shortcuts which can be used to reduce
dependence on point-and-click mouse use to issue commands such as cut and paste. Refer to
the operating system documentation for further information. Lists of these commands may
be found at the following web pages:
http://support.microsoft.com/kb/126449
http://support.apple.com/kb/HT1343
- Keyboards:
Many hardware manufacturers offer keyboards with
controls that issue common commands to the operating system or applications. This can help reduce
dependence on point-and-click mouse use for these actions. Some examples include: volume control,
web browser launch and navigation, and media navigation.
- Using the control key and mouse wheel to adjust text size:
In a number of common applications, holding down the control key while operating the scroll wheel
of the mouse will increase or decrease the size of the text or images. These adjustments can
help the operator improve the ease of viewing the application in their display.
|
Load Sharing
To reduce the amount of repetitive motion on their dominant hand, operators can move
their pointing device to the side of the keyboard that is opposite of their dominant hand.
When making this change, it is important to configure the operating system to reverse the
buttons on the pointing device.
|
Voice Recognition Software
Voice recognition software is available that will allow the operator
to dictate into many software applications. This may be particularly useful for e-mail and
word processing. In addition, this lets the operator stand up at their workstation when they
may otherwise be limited to sitting. The disadvantage of voice recognition software is that
it may not be practical in shared spaces or when confidential information is involved.
This, and other useful applications can be evaluated at PSU's
Assistive Technology Center.
|
Alternative Keyboards
 |
In most cases, people should be able to avoid discomfort by properly using a straight keyboard. There are alternative
keyboard designs that can be used to improve the posture of the hands and wrists; however, research has not shown that
they substantially reduce the risk of discomfort. Size, shape, contour, or circumstances may also affect the usefulness
of an alternative keyboard. Refer to this NIOSH publication for further information.
|
 |
One of the more common alternative keyboards designs is a split keyboard which is designed to help avoid wrist
deviation (horizontal bending of the wrists) while typing. People may want to consider obtaining a split keyboard if they
have broad shoulders which increase wrist deviation during keyboard use, or if they have prior, positive experience with
one and prefer it over a straight keyboard.
|
Revised July 1, 2009
This information is made available to assist office workers at
Portland State University to maintain safe work practices with respect to office ergonomics.
It has been developed to be consistent with current standards, regulations, and research intending
to reduce risk factors of work related injuries at video display terminal (VDT) workstations.
This guide is not case specific and should be used as a suggestion only. For additional
information, contact Jason Mitchell at mitchelj@pdx.edu.
|
