There is a growing debate among ergonomic and occupational health experts over the actual need for a wrist rest to perform keyboard and computer mouse work safely. One school of thought suggests that wrist rests do help align the user's hands and wrists while typing or mousing, while another suggests that they may encourage users to relax their hand positions too much while typing. Instead of decreasing the number and severity of carpal tunnel injuries, an improperly used rest may actually cause more repetitive stress injuries (RSI) for those who type or mouse for extended periods of time.
A wrist rest, especially a gel-filled one, is certainly better than no support at all. Without any form of support, a keyboard or mouse user tends to experience hand and wrist fatigue relatively soon. The user's unsupported wrists and lower hand may fall below the level of the keyboard, which is an especially dangerous position for repetitive typing. The rest also provides a soft cushion for the wrists, instead of an unforgiving desktop surface or no surface at all.
One of the main concerns about the use of a wrist rest, however, concerns the idea of the user resting his or her hands at all while actively typing or mousing. Proper typing technique stresses the importance of bending or cupping the hands in order for the fingers to strike the keys at a downward angle. If the user's wrists are resting on a pad while typing, the fingers must reach for the keys at a more stressful angle. For this reason, many occupational health experts suggest only using a keyboard or mouse wrist rest between typing and mousing sessions. The user's wrists should not touch the pad during active typing.
The same philosophy holds true for a mouse pad rest. A padded wrist rest may help keep the wrist to stay in alignment with the hand, but the entire hand and wrist need to move as one unit directed from the user's shoulders. Flicking or pushing the mouse with the fingers or wrist alone is considered improper mousing form and can lead to inflammation of the upper back and neck muscles. While carpal tunnel syndrome may be the most common office-related injury, the second-most reported injury is an inflamed trapezius muscle often caused by improper mousing techniques.
Installing a wrist rest for a computer keyboard or mouse is not inherently a bad idea, considering how uncomfortable it can be not to have any support for the wrists at all. But if you plan on doing extensive typing or mousing work, you may want to take a refresher course on proper typing and mousing techniques. Putting too much pressure on the bottom of your wrist can cause damage similar to carpal tunnel syndrome, and it can be difficult to resist pushing your wrist down on the wrist rest while typing.