Strategies
for Individuals with One Functional Hand
(One-Handed Input Options)
What are some Considerations for
One-Handed Input?
One handed keyboards are usually used to assist people who
have limited or no functional use of a second hand.
They are not recommended except in these circumstances as
moving to single handed keyboard input creates a significant
increase in risk factors for that hand, as it is performing
twice as much activity. This is a decision that should
not be taken lightly, and moving to a one-handed keyboard
should be a course of action taken only after significant
consideration.
The primary concern for users performing one-handed input is
the Overreach for the mouse. A centrally located pointing device
might be an option, in conjunction with a compact keyboard
if the arrow keys are too much of a reach for the
individual. However most adults can comfortably reach
laterally around 13-14" for all the 'non-numeric' keys on a
standard keyboard, as long as the mouse is below the
keyboard (i.e. between the user and the keyboard).
Mouse options to consider include Central
Pointing Devices, Touchpads
and Compact
Keyboards.
For most individuals with a single functional hand, the
above solutions experience far more success than the 'single
handed keyboard' options due to learning curves and
cost. If there is any functionality in the second
hand, or the individual does not meet the criteria outlined
below, it is strongly suggested to use the above approach
before considering the solutions below.
Individuals who are good candidates for keyboards optimized
for one handed input would need to be:
- Motivated to overcome the learning curve / extended
decline in productivity for a long term benefit
- Keyboard intensive user who was formally a touch typist
- Typically younger individuals (under 40) who are more
adaptable and who are less likely to injure their single
functional hand with the double load it will now have to
endure
- Not worried about cost of the solution
What are the Approaches Keyboard Manufacturers Have
Taken to Designing Single-Handed Keyboards?
One approach arranges the keys on a 3 dimensional layout
which reduces the required reach for the keys. This is
an excellent way of load balancing a single handed user as
much as possible by employing a 3-D landscape to the keying
action, varying the movement and usage of muscles and tendon
sheaths in the fingers while typing. It is a
significant investment (temporally in terms of learning
curve as well as financially), as the layout by necessity
must be distinct from standard QWERTY or DVORAK layouts.
Another approach is to 'chord' the keys and create multiple
layers on a smaller number of keys which can be toggled
between with a toggle key. This chording solution allows the
keyboard to be toggled between various layers (the left
alpha, right alpha, symbols, etc.). This prevents the
forced movement of the hands from the left to the right side
of the keyboard which can be of some benefit. In
addition, the footprint can be quite small to reach all
characters. However, there is a significant load
factor placed on the thumb as the 'toggle' between the
various layers and the productivity is more limited than on
other solutions.
