With any computer input device, it’s how you use it that is important.
The prevalence is for keyboard users to use ‘clawed’ hands when using a keyboard to enter text. By this I mean when a user readies their hand position over the keyboard before they type, or whilst in thought between text entries, the hands can be seen to be extended into the air from the wrist in a ‘claw’ like shape (as pictured below). Often the wrists are leaning on a wrist rest, or worse still, leaning on just the hard desk surface .
Even worse, some users can actually continue typing with their hands in this claw like manner, with the fingers being held high over the keys like an eagle’s talons over it’s prey.
The risks involved in this practice can be significant when done over a continuous period of time. The forearm extensor muscles are in continuous tension, as well as the tendons over the back of the hands and fingers. If held tense like this for long periods, the forearm muscles can fatigue very easily, ie they are being used in a way that they were not designed to be used for over protracted periods.