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Ergonomic Concepts > Considerations for One-Handed Input
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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.


Last edited December 9th, 2013

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