Cornell University Ergonomics Web
COMPUTER KEYBOARD DESIGN
What is the problem with the design of standard computer keyboards?
Alternative computer keyboard designs have been available for over 30 years. The main concern with the design of the conventional computer keyboard is that people bend their hands to the side when they are typing on the keyboard. This lateral bending of the hands is called ulnar deviation. We know that extremes of all our deviation increase pressure on the median nerve inside the wrist, and this can increase the risks of developing problems such as carpal tunnel syndrome. The original alternative keyboard designs split the keyboard laterally to allow people to type with the hands straight rather than bend to the side. A second problem with the design of the conventional computer keyboard is that the hands of in full pronation when typing on the keys. There is a suspicion that working with the hands fully pronated increases the risk of developing musculoskeletal injuries in the forearms. Consequently, alternative keyboard designs have been developed that allow the keyboard slant to be adjusted laterally, so that the keyboard can be tented up or lowered to be used in a flatter position. This tenting of the keyboard reduces wrist pronation. Some keyboards are completely split so that the left and right hand positions and the adjusted independently. What ever the keyboard design, ergonomists agree that the healthy way to type at a keyboard is to have the hands as straight and flat as possible in a posture that we called the neutral posture.
What injuries and they need to and why have their being so many interests? Before the advent of the personal computer, people who were professional typists were relatively few in number and they were properly trained in wrist posture. In the 1980s, with the widespread adoption of the personal computer in the workplace, suddenly a very large number of people began using keyboards in an intensive way. The vast majority of these people had no training in how to position the hands on the keyboard so that they could type in a healthy manner. These days, we have probably in excess of 100 million regular keyboard uses in the U. S. A. The result of this widespread use of keyboards is that, over time, people who work in suboptimal wrist postures are more likely to develop a variety of musculoskeletal injuries. This is why we have seen a rise in the number of injuries and a growing awareness of the importance of good ergonomic design.
What is the optimum arrangement for a standard keyboard?
Modern computer keyboards are much flatter than their predecessors. Research studies have shown that when people use these keyboards they often do not type with the hands in such extreme ulnar deviation as was found with the smaller keyboards used on earlier computer systems. There are two considerations that are particularly important with a standard keyboard. First, the keyboard is usually an asymmetrical design, with the alphabetic part of the keyboard to the left and a numeric keypad to the right. This means that if the user aligns the center of the whole keyboard with the center of their body they will be typing with the right hand more bent because the alphabetic part of the keyboard will be to the left of their body. So the first thing that a user, who types intensively, should do is to align the alphabetic part of the keyboard with their body, this means aligning the H key with the center of the body. The second consideration is the angle of the keyboard relative to the angle of the wrist. Most keyboards slope upwards from front to back, and this means that users bend their hands upwards when they are typing on the keyboard. This posture is called wrist extension, and we know that it is a source of injury risk for the wrist. Once the hand is extended beyond about a 15° upward angle, there is a very significant increase in the compression on the median nerve and other structures inside the wrist. So it is extremely important to type with the hands as flat as possible. The best way of achieving this with a standard keyboard is to place the keyboard on a height adjustable, downward tilting keyboard tray (often called a negative slope keyboard tray). This arrangement allows the keyboard to be positioned below the uses elbow height, and an ideal position is 1 to 2 inches above the users thighs. With the keyboard tray angled slightly downwards, following the angle of the thighs, the user can place his or her hands on the keyboard while keeping their wrists in a flatter position. In this position, it is also useful to have a board flat palm support on the keyboard tray so that the user can rest their hands in a flat, neutral posture, in between bursts of typing activity.
What are the advantages of alternative keyboards, split keyboards? There is a variety of different keyboard designs currently available in the market. The choice of an alternative keyboard depends on the needs of the user. Generally, we categorize alternative keyboards into the following types:
Is there any one keyboard alternative design and that is overruled the best from your point of view? No, the choice of a keyboard design depends on the needs of the user. Most people can use a standard keyboard design without any risk of injury, if this is correctly positioned in a negative slope arrangement. However, if this is not possible then an alternative design might work. For people with very broad shoulders or large individuals who may have difficulty in reaching the keyboard when this is placed in front of them, a split-angle keyboard can work well. For people with a specific injury or a specific in it, then one of the other types of alternative keyboard designs may be most appropriate.
Voice recognition as a supplement to keyboard input?
Recently, we have started to look at the benefits of using voice recognition software as another means to supplement information input to the computer. What we and others have found, is that the use of a combination of voice, keyboard, and mouse operations may be the most efficient and effective way of entering information into the computer. Up until now, most people have seen voice recognition as an alternative to keyboard or mouse input rather than as a supplementary tool, and trying to do everything by voice requires considerable skill. However, using voice as a way of entering a first draft of text information into the computer is a very efficient process. Subsequently, this first draft can be edited using the keyboard and mouse as would happen with any typed information. Together, this process really can speed a person's work performance, and also it rests the hands and wrists and reduces the chances of a musculoskeletal injury.
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