Cornell University Ergonomics Web
COMPUTER KEYBOARD DESIGN
What is the problem with the design of standard computer keyboards?
Alternative computer keyboard designs have been available for over 30 years.
The main concern with the design of the conventional computer keyboard is that
people bend their hands to the side when they are typing on the keyboard. This
lateral bending of the hands is called ulnar deviation. We know that extremes of
all our deviation increase pressure on the median nerve inside the wrist, and
this can increase the risks of developing problems such as carpal tunnel
syndrome. The original alternative keyboard designs split the keyboard laterally
to allow people to type with the hands straight rather than bend to the side. A
second problem with the design of the conventional computer keyboard is that the
hands of in full pronation when typing on the keys. There is a suspicion that
working with the hands fully pronated increases the risk of developing
musculoskeletal injuries in the forearms. Consequently, alternative keyboard
designs have been developed that allow the keyboard slant to be adjusted
laterally, so that the keyboard can be tented up or lowered to be used in a
flatter position. This tenting of the keyboard reduces wrist pronation. Some
keyboards are completely split so that the left and right hand positions and the
adjusted independently. What ever the keyboard design, ergonomists agree that
the healthy way to type at a keyboard is to have the hands as straight and flat
as possible in a posture that we called the neutral posture.
What injuries and they need to and why have their being so many interests?
Before the advent of the personal computer, people who were professional typists
were relatively few in number and they were properly trained in wrist posture.
In the 1980s, with the widespread adoption of the personal computer in the
workplace, suddenly a very large number of people began using keyboards in an
intensive way. The vast majority of these people had no training in how to
position the hands on the keyboard so that they could type in a healthy manner.
These days, we have probably in excess of 100 million regular keyboard uses in
the U. S. A. The result of this widespread use of keyboards is that, over time,
people who work in suboptimal wrist postures are more likely to develop a
variety of musculoskeletal injuries. This is why we have seen a rise in the
number of injuries and a growing awareness of the importance of good ergonomic
design.
What is the optimum arrangement for a standard keyboard?
Modern computer keyboards are much flatter than their predecessors. Research
studies have shown that when people use these keyboards they often do not type
with the hands in such extreme ulnar deviation as was found with the smaller
keyboards used on earlier computer systems. There are two considerations that
are particularly important with a standard keyboard. First, the keyboard is
usually an asymmetrical design, with the alphabetic part of the keyboard to the
left and a numeric keypad to the right. This means that if the user aligns the
center of the whole keyboard with the center of their body they will be typing
with the right hand more bent because the alphabetic part of the keyboard will
be to the left of their body. So the first thing that a user, who types
intensively, should do is to align the alphabetic part of the keyboard with
their body, this means aligning the ‘H’ key with the center of the body. The
second consideration is the angle of the keyboard relative to the angle of the
wrist. Most keyboards slope upwards from front to back, and this means that
users bend their hands upwards when they are typing on the keyboard. This
posture is called wrist extension, and we know that it is a source of injury
risk for the wrist. Once the hand is extended beyond about a 15° upward angle,
there is a very significant increase in the compression on the median nerve and
other structures inside the wrist. So it is extremely important to type with the
hands as flat as possible. The best way of achieving this with a standard
keyboard is to place the keyboard on a height adjustable, downward tilting
keyboard tray (often called a negative slope keyboard tray). This arrangement
allows the keyboard to be positioned below the uses elbow height, and an ideal
position is 1 to 2 inches above the users thighs. With the keyboard tray angled
slightly downwards, following the angle of the thighs, the user can place his or
her hands on the keyboard while keeping their wrists in a flatter position. In
this position, it is also useful to have a board flat palm support on the
keyboard tray so that the user can rest their hands in a flat, neutral posture,
in between bursts of typing activity.
What are the advantages of alternative keyboards, split keyboards?
There is a variety of different keyboard designs currently available in the
market. The choice of an alternative keyboard depends on the needs of the user.
Generally, we categorize alternative keyboards into the following types:
- Modified Standard Layout (e.g. Kensington Comfort Type Slim
Keyboard – www.kensington.com). This
keyboard looks like a standard keyboard except that the keys are angled so
that there should be less ulnar deviation when typing. - Fixed-angle split keyboards (e.g. Microsoft natural –
www.microsoft.com). These keyboard
designs split the alphanumeric keys at a fixed angle and they slightly tent
the keyboard. There is some research evidence of reduced discomfort because
of reduced ulnar deviation (lateral bending of the hands). These designs
work better for broader, larger frame individuals or pregnant women because
they put the arms in a better position to reach around the front of the
body. However, the designs usually address the issue of wrist extension, the
upwards bending of the hands, which turns out to a more important
musculoskeletal injury risk factor than ulnar deviation. Hunt n’ pecker
users will find that split keyboards are more difficult to use. The
keyboards generally are more expensive than conventional keyboards, and
usually they are larger and wider, which in some situations can put the
mouse too far out to the side of the keyboard. - Adjustable-angle split-keyboards (e.g. Goldtouch –
www.goldtouch.com). These keyboard
designs allow the user to change the split-angle to suit their own needs.
Often the split angle is linked to the degree of tenting of the keyboard as
well. There is some research evidence of reduced discomfort with this kind
of design, because of reduced ulnar deviation. These designs do not usually
address wrist extension issues. The fact that the use has to decide on the
split-angle means that they may need some training and it is always possible
that some users might end up with a split angle that is inappropriate for
them. Split
keyboards are always difficult for hunt n’ peck typists to use, and often
these designs are fairly expensive. - Completely split keyboards (e.g. Kinesis –
www.kinesis.com). In these designs the
left hand and right hands portions of the keyboard are completely split
apart. In some designs the keys are presented in a scooped design that
allows the hands to rest in a more neutral posture for typing. There is some
research evidence of reduced discomfort because of reduced ulnar deviation
and also reduced wrist extension. However, there is more of a learning curve
and research shows that initial performance can suffer a 50% slowing of
typing speed. Completely split keyboards are hard for hunt n’ peck typists
to use, and some of them are very expensive. A chair-mounted split keyboard
also is available (Kinesis Evolution Fully
Adjustable Keyboard) and this has been studied in a research project (view
research presentation). - Vertically split keyboard (e.g. Safetype –
www.safetype.com). The design is
rather like that of an accordion and the user types with the hands facing
each other, consequently the keys cannot easily be seen. This design works
well to reduce ulnar deviation and wrist extension, but it is important not
to have the keyboard too high otherwise the chest and shoulders can fatigue.
The design is pretty well impossible for hunt n’ peck typists to use, and
because it is a specialist keyboard it is expensive. A report of this
keyboard is available (download
research report). A presentation on this keyboard is available (view
research presentation). - Chordic keyboards (e.g. Twiddler -
www.handykey.com/). Chord keyboards
have a smaller number of keys and letters and digits are generated by
combinations of keys in chords. One-handed and two-handed designs are
available. Research shows that it is like learning stenography and there is
a high learning curve (about 80 hours to get to moderately fast) to learn
the chords that correspond to characters. The keyboards are more expensive
than regular keyboards but can be useful to some users, especially those
with special needs, such as a blind user or one with severely arthritic
hands. - Specialist keyboards (e.g. Datahand –
www.datahand.com, Orbitouch –
www.orbitouch.com). Several different
keyboards designs have been developed to assist users who have some physical
limitation or who wish to type in a different way. The Datahand allows the
user to rest their hands on a series of switches that detect different
directions of finger movements, and these generate the characters. The
Orbitouch lets users rest their hands on two domed surfaces and then to move
these surfaces to generate the characters. Specialist keyboards often result
in slower typing and can have significant learning curves, so they aren’t
for the masses. Like other alternative keyboard designs, they are expensive. - One-handed keyboards (e.g. Half-QWERTY -
www.aboutonehandtyping.com).
Sometimes users can have a physical limitation, such as one hand, or they
perform work where one hand needs to key while the other does something
else. Several alternative designs for one handed keyboards are available.
The Half-QWERTY users the same kinds of keys that are found on a regular
keyboard, but each key functions in two modes to generate all of the
characters of a regular keyboard in a smaller area. One-handed chordic
keyboards (e.g. BAT –
www.aboutonehandtyping.com, Twiddler -
www.handykey.com) are also available. So which keyboard design is
best? Given that people vary in size, shape, and ability the answer is that
no single design is for everyone. The reason why the conventional keyboard
remains the commonest design rather is that it is mass produced at low cost,
and it is the familiar design. However, it most certainly is not the best
design for all users in all situations. Consequently, the various ergonomic
designs described here have been developed to address different user needs
and different work situations.
Is there any one keyboard alternative design and that is overruled the best
from your point of view? No, the choice of a keyboard design depends on the
needs of the user. Most people can use a standard keyboard design without any
risk of injury, if this is correctly positioned in a negative slope arrangement.
However, if this is not possible then an alternative design might work. For
people with very broad shoulders or large individuals who may have difficulty in
reaching the keyboard when this is placed in front of them, a split-angle
keyboard can work well. For people with a specific injury or a specific in it,
then one of the other types of alternative keyboard designs may be most
appropriate.
Voice recognition as a supplement to keyboard input?
Recently, we have started to look at the benefits of using voice recognition
software as another means to supplement information input to the computer. What
we and others have found, is that the use of a combination of voice, keyboard,
and mouse operations may be the most efficient and effective way of entering
information into the computer. Up until now, most people have seen voice
recognition as an alternative to keyboard or mouse input rather than as a
supplementary tool, and trying to do everything by voice requires considerable
skill. However, using voice as a way of entering a first draft of text
information into the computer is a very efficient process. Subsequently, this
first draft can be edited using the keyboard and mouse as would happen with any
typed information. Together, this process really can speed a person’s work
performance, and also it rests the hands and wrists and reduces the chances of a
musculoskeletal injury.
Note: inclusion on this page does not constitute any endorsement of the
product.
