Most clients who benefit from biofeedback are trained to relax and modify their behavior. Most scientists believe that relaxation is a key component in biofeedback treatment of many disorders, particularly those brought on or made worse by stress. Their reasoning is based on what is known about the effects of stress on the body. In brief, the argument goes like this: Stressful events produce strong emotions, which arouse certain physical responses. Many of these responses are controlled by the sympathetic nervous system, the network of nerve tissues that helps prepare the body to meet emergencies by “flight or fight.”

The typical pattern of response to emergencies probably emerged during the time when all humans faced mostly physical threats. Although the “threats” we now live with are seldom physical, the body reacts as if they were: The pupils dilate to let in more light. Sweat pours out, reducing the chance of skin cuts. Blood vessels near the skin contract to reduce bleeding, while those in the brain and muscles dilate to increase the oxygen supply. The gastrointestinal tract, including the stomach and intestines, slows down to reduce the energy expensed in digestion. The heart beats faster, and blood pressure rises.

Normally, people calm down when a stressful event is over especially if they have done something to cope with it. For instance, imagine your own reactions if you’re walking down a dark street and hear someone running toward you. You get scared. Your body prepares you to ward off an attacker or run fast enough to get away. When you do escape, you gradually relax.

Clients usually are taught some form of relaxation exercise. Some learn to identify the circumstances that trigger their symptoms. They may also be taught how to avoid or cope with these stressful events. Most are encouraged to change their habits, and some are trained in special techniques for gaining such self-control.

Biofeedback cannot cure disease or by itself make a person healthy. It is a tool, one of many available to health care professionals. It reminds physicians that behavior, thoughts, and feelings profoundly influence physical health. Biofeedback helps both clients and doctors understand that they must work together as a team.

The word “Biofeedback” was coined in the late 1960s to describe laboratory procedures then being used to train experimental research subjects to alter brain activity, blood pressure, heart rate, and other bodily functions that normally are not controlled voluntarily.

At the time, many scientists looked forward to the day when biofeedback would give us a major degree of control over our bodies. They thought, for instance, that we might be able to “will” ourselves to be more creative by changing the patterns of our brain waves. Research has demonstrated that biofeedback can help in the treatment of many diseases and painful conditions. It has shown that we have more control over so-called involuntary bodily function than we once thought possible. But it has also shown that nature limits the extent of such control. Scientists are now trying to determine just how much voluntary control we can exert.