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Trauma. A blow to the wrist or forearm can make the tendons swell and cause or encourage the onset of CTS.

Prevention

Computer keyboard users can take several steps to lower their chances of developing CTS. Some of these center around the configuration of the workplace, or "ergonomics." Others have to do with human factors.

Ergonomics. Proper seating is crucial to good ergonomics. The height of your seat and the position of your backrest should be adjustable. The chair should be on wheels so you can move it easily. Arm rests on the chair, though optional, are often helpful.

Table height. To adjust the chair properly, look first at the height of the table or desk surface on which your keyboard rests. On the average, a height of 27-29 inches above the floor is recommended. Taller people will prefer slightly higher tables than do shorter people. If you can adjust your table, set your waist angle at 90 degree, then adjust your table so that your elbow makes a 90 degree angle when your hands are on the keyboard.

Wrist angle. If your keyboard is positioned properly your wrists should be able to rest comfortably on the table in front of it. Some keyboards are so "thick" that they require you to bend your hands uncomfortably upward to reach the keys. If so, it will help to place a raised wrist rest on the table in front of the keyboard. A keyboard that requires you to bend your wrists is a common cause of CTS among computer users.

Elbow angle. With your hands resting comfortably at the keyboard and your upper arms vertical, measure the angle between your forearm and your upper arm (the elbow angle). If it is less than 90 degree, raise the seat of your chair. If the angle is greater than 90 degree, lower the seat. Try to hold your elbows close to your sides to help minimize "ulnar displacement" - the sideways bending of the wrist (as when reaching for the "Z" key).

Waist angle. With your elbow angle at 90 degree, measure the angle between your upper legs and your spine (the waist angle). This too should be about 90 degree. If it is less than 90 degree, your chair may be too low (and your knees too high). Otherwise, you may need to alter the position of the backrest or adjust your own posture (nothing provides better support than sitting up straight). (Note: If making your waist angle 90 degree changes your elbow angle, you may need to readjust the height of your chair or table.)

Feet. With your elbows and waist at 90 degree angles, your feet should rest comfortably flat on the floor. If they don't, adjust your chair and table height and repeat the steps above. If your table isn't adjustable and your feet don't comfortably

reach the floor, a raised footrest can help. Otherwise, you may need a different table.

Work routine

You need very little recovery time between keystrokes to cool and lubricate the flexor tendons. If you type constantly, however, the need for recovery builds. Further, working with your hands bent upward at the wrists or frequently bending your wrists sideways heightens the friction within the carpal tunnel. It takes longer to recover from these motions. Working under stress (deadline pressure, anger, or other anxiety) can make matters even worse.

Many studies recommend a 10-15 minute break each hour to give yourself the recovery time you need. This needn't be a break from productive activities - just a break from your keyboard. Exercises can help, too. Try the following:

a) Make tight fists, hold for one second, then stretch your fingers out wide and hold for five seconds. Repeat several times.

b) With arms outstretched in front of you, raise and lower your hands several times. Rotate your hands ten times (make circles in the air with the fingertips).

Variety is the key. CTS occurs most frequently in workers whose motions are not only repetitious but are kept up for hours at a time. If you use a keyboard, structure your workdays to include a mix of activities each hour. For example, instead of typing all morning and filing all afternoon, mix typing and filing throughout the day.

Early detection

The most painful cases of CTS are those that have gone undetected or untreated over a long time. CTS can be caught easily in its early stages, however, and much of the pain and all of the disability avoided.

Early symptoms include a tingling in the fingers, often beginning several hours after work activity has stopped. Because of this delay in the appearance of symptoms, many CTS sufferers don't make the connection between their work activities and the pain they feel until it's too late. The tingling can lead, over time, to stiffness and numbness in the fingers and hand, and then to severe wrist and hand pain.

For many individuals the early symptoms of CTS go unnoticed. Employers and co-workers can help one another identify the onset of CTS by watching for and pointing out any unconscious shaking of the hands, rubbing of the wrists, or unusual postures or hand positions at the keyboard.

At the first sign of CTS, you should be examined by a doctor who specializes in hand and wrist disorders. The doctor can perform a number of simple tests to detect CTS, and can prescribe specific steps for avoiding the problem.

Summary

Carpal tunnel syndrome is common among computer keyboard users. It can strike anyone, and its consequences are serious. Awareness of the problem and its causes is crucial to preventing CTS. With proper ergonomics and attention to the work routine you can prevent CTS; with early detection and treatment it need never become debilitating. The employer's attention to stress levels, proper ergonomics, and the early warning signs of CTS are important in keeping the ailment at bay in the workplace.

Summary

We hear a lot about hazards associated with working with computers, and learn from experience that long hours at the keyboard can bring on eyestrain and various aches and pains. These concerns, and the steps we can take to make computer work safer

and more comfortable are the subject of many books and articles.

The good news is that problems can be avoided through well-designed offices, properly set-up workstations, and sensible work habits. Checklists and guidelines for setting up and using computers abound. The bad news: there is substantial variation in opinion as to what constitutes proper workstation set-up, quick and easy solutions to ergonomic problems are not always possible, and checklists don't capture the complexities of the possible combinations of people, task, equipment, and workspace. Fortunately, there are measures that really do work. A few quick and universally agreed upon precautions:

• Use the minimum force necessary to press the keys.

• Vary your tasks during the day to avoid sitting in one position for several hours or performing the same hand motions without interruption.

• Take periodic breaks.

• Keep your wrists in a natural, unforced, straight position.

Bibliography of computer and health materials

• Ross, Randy. "VDTs: Are They Safe?" PC/Computing . March, 1989, pp. 146-7.

• Sheehan, Mark. "Avoiding carpal tunnel syndrome: A guide for computer keyboard users," University Computing Times (Indiana University, Bloomington). July-August 1990, pp. 17-19.

• Updegrove, Kimberly H., Daniel A. Updegrove. "Computers and Health - Issues and Protective Measures." Penn Printout. February, 1991.

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