Input devices: a usage-driven approach

Skeptical Remarks

The public should be skeptical about claims of ergonomic superiority...
Pascarelli & Quilter in Repetitive stress injury

Although some “ergonomic” accessories or devices may fit certain people, I believe that there are easily argued reasons why most of them may not work or may even be harmful. These opinions are examples only, offered to stimulate critical thinking.

Forearm rests

These often elaborate mechanical contraptions support your forearm even while in motion over the keyboard. But a fundamental misunderstanding may be a play here: the muscles of the forearm lift a heavy object, the hand, that is not supported by forearm rests. So, the full weight of these long, bony structures still have to be born by the forearms. And, perversely, the forearm rests may make it cumbersome to place the arms in a position where the hand and forearm can truly rest, because it takes quite an effort to get in and out of these devices. As a result, the strain on the forearms may be very significantly increased by using forearm rests.

Contoured keyboards

In these keyboards, the majority of the keys are placed inside a depression along a curvature. There is one depression for each hand, so that the keyboard may look like two bowls in a frame. By matching the movement patterns on the fingers—the theory goes—these keyboard are easier on the body. But precisely thanks to this property, the keyboard will force the hands into hovering in a specific position in space above it. In contrast, a flatter layout gives superior flexibility for striking the keys.

Microswitch keyboards

This paradigm stipulates again that motion is at the heart of injury. The keyboards accommodate each finger in an individual fixed area or well in close proximity to tiny switches. Then minuscule movements of fingers active switches. Phenomenal typing speeds are achievable. I got the feeling when using a design of my own of getting a kind of direct feed from brain to computer. But again, there is a fundamental misunderstanding at play if the aim is to reduce physical strain: the body must continuously adjust the position of all fingers so that they don't touch the switches. This compensation includes maintaining positions of hands, forearms, not to say the whole body. Again, the conventional keyboard is superior. With it, the hands are free all the time, except for the moment of strike, to rest or to hover over the keyboard.


It has been suggested that using a pen on a tablet is more ergonomic than using a mouse. Unfortunately, there is a condition called writer's cramp that has been known for hundreds, if not thousands of years, and it is likely to affect the tablet user as well. Holding a pen puts static load on the whole upper body, so that the pen is not dropped and does not touch the tablet when not in use.

Touch pads

So what about not holding anything at all? The touch pad offers such a solution, but as most people have experienced, this technology does not work to well either. The cramped space is anything but natural for tracing the movement of the cursor by using the index finger. Even if the touch pad was big enough that the whole hand could rest on it, it would still induce static stress: the hand must be turned so that the index finger does not touch the surface, whenever the cursor is not moved.


There are good things be said about trackballs: the hand may rest next to the device while the cursor is not being moved. Moving the cursor can be done with the thumb or side of the hand. Unfortunately, most trackballs that are on the market have large, easily depressed buttons surrounding the ball. This "ergonomic" look probably have the opposite effect: the hand constantly must balance itself to not touch the buttons whenever near the device. So, such trackballs may be as harmful as ordinary mice.

So, what helps?

I believe that no tinkering with keyboard or mouse design will lead to products that are radically less stressful on the body. Marginal improvements, perhaps along the lines I've suggested, may be possible. Ergonomic manuals consistently state that there is one way only to effectively address severe cases of overuse syndromes: complete and total cessation of the physical activity that led to the problem. Sometimes this cessation must be permanent, often implying a loss of ability to work. Finger and hand work must be avoided in any form that resembles the injury-causing way of working.

An approach to reduce physical impact might be: type with only the strongest fingers (thumb and index) and move a mouse by pushing it with two hands resting on the desk or keyboard tray. Such behavioral techniques may offer far greater potential for reducing injury than any changes in device design. But their use may also lead to further injury, given that they represent a very different approach than that of complete rest. For lesser injuries, other techniques are possible as is discussed in books on computer-induced injuries.

In conclusion, I believe that avoidance and technique are more important than device design. Avoidance can be achieved by a combination of speech recognition and foot pedals. I doubt that there are any other ways that are comparable in efficiency.