Clearly the heel of the left hand is pressed against the surface supporting the keyboard, causing the hand to bend backwards and the fingers to arch over into a keying position. This person will soon require a brace for their left wrist, but it will not be because they key a lot, as much as it will be for how they key.
Wrist supports or palm rests can virtually eliminate all wrist pain and the potential for an RSI to develop, but only if they are utilized properly, and other steps are taken as well. People must first make sure their chair is correctly adjusted. At a proper seat height, the thighs will be parallel to the floor, for an even distribution of weight. Chair backs must be independently adjustable, to firmly support the lower back when the user is sitting in an upright posture. However, if you are somewhat taller or shorter than average, taking these steps with your chair will be pointless; if all surfaces in your workstation are not also adjustable. How does all this lead to a Repetitive Strain Injury or a Cumulative Trauma Disorder?

Keyboards that are too high cause the user to 'shrug' to maintain a proper keying position, using the muscles across the top of the shoulders and up the neck, to support the weight of both the upper and lower arm. In fact over the 14 years that we have been planning and implementing workstation solutions for computer terminal operators, we have found the discomfort and pain this ,shrugging' causes, to be more prevalent than wrist pain. That is because most keyboard support surfaces are simply too high for the employee. Many people who drop their wrists or palms onto the surface supporting the keyboard, are actually seeking to relieve this discomfort, which then makes them a prime candidate for an RSI.
Leaving the keyboard too high but adding a wrist support will actually increase the potential for an RSI or CTD to develop, as the users will drop the shrugging of their shoulders when they rest their wrists, but increase the deflection of their hand in the process. Besides, the persons wrists will be at an angle to the wrist support and if its angle is not adjustable, and it has a sharply angled edge, it will be very uncomfortable.

Clearly, poorly designed or improperly utilized wrist supports can and will increase employee wrist pain, more so if used on non-adjustable or incorrectly adjusted keyboard surface. Especially if the chairs do not provide proper back support, as people would tend to lean on the wrist support, creating an uncomfortable pressure. There is a solution, but it is not to just provide everyone with an adjustable chair. As long as people come in different sizes, the keyboard height must be adjustable. Then the home row of keys can be adjusted to elbow height, after the user has adjusted their chair to support a proper sitting posture. A straight, hand in-line to the wrist position can now be maintained, without shrugging. In fact a proper keying height and correct sitting posture may reduce or eliminate the need for any kind of wrist support, especially for people with previous typing experience. They know what proper posture and hand position is and that it should be maintained.

Still, most people will benefit from a correctly utilized wrist support on an adjustable surface. Partly that is because there are far more people using terminals who are not properly trained typists, but mostly because of the keyboard sensitivity mentioned earlier. Yet using a wrist support at the wrist, can also cause discomfort. At that part of the arm, nerves and veins are very close to the surface of the skin. Having a support at this position, especially one that is too narrow or has a peaked shape, can actually impede blood flow or irritate the nerves. Watches or bracelets can increase the discomfort, as they are pressed into the wrist at point of contact. Perhaps this is why many people actually refuse to use a 'wrist' support.

Many 'experts' suggest they should be used as palm rests anyways, with the keyboards pulled right up against them. However, anyone who has tried this, will know that can cause discomfort as well. The 'pisiform' is a prominent bone located to the outside of the hand, near the wrist. With very little flesh between it and your skin, at least for most people, it is this part of your palm that will bear most of the weight. Since standard keying requires frequent movement of the hands across the keyboard, it is not long before this bone or the skin covering it becomes quite irritated by the 'palm' rest.
People might return to pressing the heel of their hand against the surface supporting the keyboard, because at least this can be done using the fleshiest part of the hand. Of course they will remain a prime candidate for a wrist or hand RSI, but will consider themselves to be better off, at least until some pain starts to develop. At which point that individual will simply blame all of their problems on the fact that they must use a keyboard as part of their task function. Especially if they read misleading media articles on the subject.