Should You Use a Wrist Rest?
Perhaps the most ubiquitous object associated with computers these days (with the possible exception of wrist braces!) is the keyboard wrist rest. It would be more accurate to refer to it as a "palm support," since you really don't want contact pressures on your wrist. Some suppliers have gone as far as to say they can "prevent carpal tunnel syndrome," which has led some people and organizations to believe that giving everyone a wrist rest comprises a complete ergonomics program.
Like any other ergonomic device, no one thing alone will prevent cumulative trauma injury. Many factors are involved, including both the physical arrangement of the workstation, and many issues of safe work and personal health habits. A wrist rest is only one of many items that may contribute to increased safety.
The term "wrist rest" is actually a misnomer. We don't want to have anything in contact with the wrist itself while we are typing at a keyboard or controlling an input device, whether a mouse or a trackball. One of the worst things we can do is increase pressure on the wrist while we use our hands in this way. A more accurate term would be a "palm" rest, a point of view shared by increasing numbers of people involved in ergonomics. I will adopt it for the rest of this article.
What Are They Supposed to Accomplish?
The main intent of a palm rest is to prevent the hands from dropping off the edge of the keyboard while we type. Extension of the wrist (bending it back toward the body) has been shown to cause the greatest increase in pressure in the carpal tunnel. Also, just think of what the tendons of the wrist must do to turn the corner at the palm, and the irritation and friction created in the process.
A palm rest also provides a soft surface for the hands that is more comfortable than the hard surface of the desk. For many people this means the sharp edge of the desk, often making direct contact with the wrist.
When you place your palms on the rest, some of the weight of your arms is taken off of your shoulders and back. Spinal pressure is actually measurably reduced. This spares much muscular effort in your neck and shoulders, the place where most people experience chronic soreness.
All of these issues are valid goals, but other factors bear some thought.
It's Supposed to Be a "Rest."
The most common mistake in the use of a palm rest is to plant the hands on it at all times when typing. This is a habit that is unfortunately encouraged by the many catalog photographs of people typing in this way. It's a "rest," and is intended for the times between actual keying.
Some very significant problems result from planting the hands on the rest.
First, if you don't move your hands to reach outer keys, you must instead stretch the fingers and bend the wrists. The computer keyboard has many more keys than a typewriter did - such as Fkeys - so there are more times when the hands should travel to the keys. Stretching the fingers pulls on tendons in the hand and into the forearm all the way to the elbow, as well as demanding the contraction of various muscles.
Even more often you need to reach keys to the side, such as Enter, Return, Tab, Delete, Escape, and many others that did not exist before the computer. If the palm is planted, then you are made to bend the wrist to the side (ulnar deviation) in order to reach these keys. This is another demanding use of tendons and muscles, plus the fact that any bend of the wrist increases pressure in the carpal tunnel.
Remember that, at its core, ergonomics is about preventing unnecessary exertion of our body tissues so they don't become inflamed and injured. This is a perfect example, because there is a simple alternative. When you need to reach keys in the farther reaches of the keyboard, move the hands to keep the fingers relaxed and the wrists straight. Only keep your hands on the palm rest when the fingers can reach keys (often the home row) without straining tissues.
Related to Keyboard Height
Many keyboards are being used at tables that are much too high, having been designed for doing paperwork, a task which is better performed higher up than keyboard entry. (For more info on keyboard position, see Where Should the Keyboard Be?) If the keyboard is too high, then use of a palm rest is likely to create too much pressure against the palm (or the wrist) simply because one would have to lift the arms up from the shoulders to prevent contact. That means it is harder to move the hands during typing, as discussed above, so almost demands that one stretches the fingers and bend the wrists.
Some people prefer not to use a palm rest. For some of them it may because they used it in conditions like this. Once they get the keyboard down to the level where the arms and shoulders are relaxed and the wrists are straight, they may find they value an appropriate palm rest. For others they recognize that they become lazy when the rest is there, so do without in order to maintain some self-discipline. This is fine until you have had to spend so much of the day keeping your arms afloat that the shoulder and back become overworked. This is less likely to happen in a properly adjusted chair with armrests to the arms have a place to get a break.
When the keyboard is low enough that you are not forced to have pressure on the hands while keying, then a palm rest becomes a place of comfort, and can contribute what it does best, namely relieving effort from the shoulders in carrying the weight of the arms.
Some Early Research
Some initial, unpublished research which I am quoting from a recent presentation, compared carpal tunnel pressure in three conditions. One with a palm rest but the hands floating during keying, another with the hands planted on the rest, and the third with no rest at all. Carpal tunnel pressures were lowest when the hands were afloat over the rest. This suggests that the rest kept the hands from dropping off the edge of the keyboard and that having no rest at all entailed increased rest.
Most important, it points to the need to use a palm rest properly, that it can increase the risk of injury when misused.
Proper Use of a Palm Rest
Clearly, one should not plant the palms on a rest during keyboard work. Use it as a rest, not as a crutch.
The real goal here is to keep the hands and fingers relaxed, to avoid stretching the fingers and bending at the wrist in any direction. Don't let the palm rest lead you to be lazy with your hands. Allow them to move over the keys as you type. Don't be afraid of contact with the rest, just be certain you are not performing the abovementioned evils.
Be sure to use a palm support with a comfortable surface. Some are a bit rough, and any such irritant will be a source of stress.
For multi-user workstations, shared by many people, many palm rest fabrics will absorb oils and aromas that could become a health concern. There are hygeinic, washable materials used in some products that are recommended for such use.
Be careful of the depth of the rest. Too deep, and it could have the effect of pushing the keyboard too far from your body, leading you to reach forward with the arms, overworking the shoulders. As compensation you may be pulled forward, and may end up too close to the screen. This in turn may lead you to slump to get your head farther from the screen, while still having to reach ahead to the keyboard. These issues are worth preventing even at a small scale.
Which reminds us that there is an array of ergonomics issues that must be kept in balance in how one sits, and their relationship to all elements of their work. The keyboard, monitor, documents, telephone, writing surfaces, and any other aspect of your work needs to be taken into account. A palm rest can affect the overall balance of these things, so proper use is a matter of both the physical ergonomics as well as learning appropriate habits so the rest is a benefit, not an irritant.
Additional ergonomics articles from Onsight