Carpal Tunnel 101

June 1, 2001
Dr. Alan Hedge, director of the Human Factors and Ergonomics programs at Cornell University, talks about the causes and symptoms of carpal tunnel syndrome and suggests preventative measures to combat the debilitating condition.

Today, roughly 3 to 5 percent of the general U.S. population suffers from carpal tunnel syndrome (CTS). However, many people don't really know what carpal tunnel syndrome is, its causes or how to prevent it.

Dr. Alan Hedge, a practicing ergonomist and researcher at Cornell University with 25 years experience in the field, answers the basic questions about CTS.

CTS and Causes

"CTS is a disorder that effects the median nerve as it passes through the carpal tunnel of the wrist," said Hedge. "Typically with CTS, the median nerve becomes inflamed and ultimately the fibers within the median nerve begin to die."

Several factors can cause CTS, however, when looking at the disorder from an occupational standpoint, Hedge said there are five main causes.

  • Working with the hands in a deviated position. Hedge said the worst deviation is for the hands to be in what is called wrist extension, that is when the hand is pulled upward so the knuckles are pointed upward rather than downward. This is most often the case when using a keyboard.
  • Repetition and high rates of movement are another causes. In particularly, repetition when you are changing postures, for instance moving so your hand is going up and down.
  • The amount of force you exert when you make those movements is also a factor.
  • Stress. Stress acts to tense the muscles in your arm, so it puts more of a load on the tendons as they pass through the carpal tunnel.
  • Contact stress. Anything that presses on the carpal tunnel itself, such as resting the crease of the wrist on the edge of a desk, resting the crease of the wrist on a wrist rest.

If you are subject to any or all of the previous occupational risk factors, how do you identify if you have CTS?

"This syndrome and many other musculoskeletal disorders always start by people experiencing discomfort," said Hedge. "So, if you are experiencing any type of discomfort in your arms or wrist while you are typing or after you are typing, you need to pay attention to that. That is the earliest warning sign."

Hedge said another warning sign of CTS is if you feel strange sensations in your hands during the night.

For instance, you may lay down in bed and feel some tingling or numbness in your hands or fingers, especially the first two fingers.

"This happens because when you lay down at night the fluids in the body redistribute themselves so that the pressure inside the carpal tunnel increases when you lay down," said Hedge.

The most dramatic sign of the disorder comes as a result of ignoring the symptoms.

"If you ignore that symptoms, then you will start to get pain in the hands whenever you make movement," said Hedge. "Simple tasks such as buttoning clothing or using a toothbrush become painful. You become clumsy and may start dropping things."

"CTS really can be a life changing disorder if you let it run its full course because you will find you won't be able to do things you normally could do," continued Hedge.


Hedge said taking preventative measures is the best way to stop CTS from accelerating into a completely debilitating disorder.

"The first thing we do, is make sure the keyboards and the input device people are using can be used with the hands in a neutral posture," said Hedge. "The best way of doing that is by putting the worker on a negative slope keyboard tray. That is a tray that will drop the keyboard down below the level of the users desk and will tilt the base of the keyboard away so the tops of the keys are flat to the hands as the user begins to type of the keyboard."

Hedge said he then encourages the user to type in that position and then rest their hands in neutral.

A second method of prevention is to break up work day.

"It is very easy to sit and type at the computer for several hours and not realize how quickly the time is passed," said Hedge. "If possible, a computer user should try to break the work day up by taking a brief break every 15 or 20 minutes and doing something different. Or software program that keeps track of how much you are keying and then alerts you that it is time to take a break." Hedge said there are some programs available that will even suggest stretching exercises for those rest times.

Wrist Rest and Braces

If used properly, Hedge said, wrist rests and braces can be supplemented with prevention but overall they are not the suggested methods of prevention.

"Wrist rests are a dreadful way to keep your hands in the proper position while typing," said Hedge. "What I suggest as an ergonomist is trying to get people to type with their hands completely free of anything."

Hedge noted that if a computer user is typing in a proper position, a wrist rest is not necessary.

The proper positioning would include bringing the hands from the keyboard and resting the palm of the hand, the base of the thumb and the little finger, on a flat surface, rather than resting the wrist on anything. Hedge noted that wrist rests tend to pull the hands backwards and exposes the carpal tunnel to unusual pressure.

Hedge said the type of wrist brace used determines whether or not it is actually a useful device

"If you are wearing a brace that actually pulls the hand backwards into wrist extension, then I don't think its a good idea," said Hedge. "If you wear a wrist brace or a type of supporting glove that keeps your hands relatively level and doesn't put any pressure on the wrist crease, than that could be satisfactory, providing it isn't changing the position of some other part of body. For instance, it doesn't cause you to put your arms in an awkward position so your elbow is bent."

In general, Hedge said he suggests minimizing the use any type of additional support device while typing. However, he did note that using the supports at times of the day a user is not typing or when they are sleeping can be useful.

What Next?

Now that you know what CTS is and the symptoms associated with it, what should you do if you think you have it? Hedge suggested asking the following questions to determine the right course of action:

  • Consider your own risk factors. Ask yourself what you do that involves you using your hands most of the day?
  • Ask yourself if you are working in a neutral posture? If not, can I get myself into a neutral posture.
  • Can you break you work day up to give your hands a rest?
  • Give yourself 1 to 2 weeks trying to improve how you are working. If the symptoms aren't getting better, than seek out medical advice.

For more information on carpal tunnel syndrome and safer computing visit the Cornell University Ergonomics Web Site at or the Healthy Computing Web site at

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