Exercise and Stress
By Barbara A. Brehm, Ed.D.

Participation in regular physical activity is one of the most effective ways to reduce feelings of stress. Physical activity has both short- and long-term effects. Many people report feeling less stress both during and after a single exercise session. Regular exercise, which generally means performing some sort of physical activity at least three times a week, has a cumulative effect as well, and exercisers report feeling less stressed even on days when no physical activity occurs. What's more, the mental health benefits of exercise go far beyond stress management. Regular physical activity has been shown to decrease both anxiety and depression, and to improve self-esteem.

Fight, Flight or Exercise

On an intuitive level, it certainly makes sense that exercise should help reduce our physical stress response, at least in the short run. After all, the fight or flight response gears you up to respond physically to stress. The physical changes associated with the stress response are practically begging your muscles to move. While it is certainly not feasible to run right out of a stressful meeting and track down your favorite tennis partner for a vigorous game or two, exercise later in the day will still allow your body to "act out" the fight or flight response.

Exercise high: Endorphins, hormones and neurotransmitters

Many exercisers report feelings of euphoria and states of consciousness similar to those described by people using drugs such as heroin. Such accounts are responsible for the term "runner's high," since these descriptions first came primarily from long-distance runners. These reports have intrigued both exercise scientists and the lay public, and have suggested the possibility that certain types of exercise, particularly vigorous exercise of long duration, may cause biochemical changes that mimic drug-induced euphoria.

As scientists have come to better understand brain biochemistry, some interesting hypotheses have emerged. The most publicized of these has focused on a group of chemical messengers found in the central nervous system called opioids, since they are similar in structure and function to the drugs that come from the poppy flower: opium, morphine and heroin. Beta-endorphin belongs to this group. Opioids not only inhibit pain, but seem to have other roles in the brain as well, such as aiding in memory and learning and registering emotions. It is difficult for scientists to measure opioid concentrations in the central nervous system of humans, but animal research has suggested opioid concentrations increase with level of exercise -- more exercise, more opioids.

Why are opioids produced? Some will answer, "Because exercise is painful." These chemicals may help the body recover from prolonged exercise, as they seem to enhance mechanisms important during this period -- raising pain threshold, slowing heart rate, decreasing blood pressure and enhancing relaxation while inhibiting the fight or flight response.

Other biochemicals may be involved in the exercise high as well. Some research suggests that changes in the concentration of certain chemical messages called neurotransmitters may play a role in causing the positive mood associated with exercise. In particular, norepinephrine and serotonin concen- trations have been shown to change with exercise, at least in animals. Since abnormal levels of these chemicals have been associated with depression in humans, it has been speculated that the antidepressant effect of exercise may involve improving regulation of these substances in the brain.

Muscle relaxation

Muscle tension increases during stress, and can cause a wide array of stress-related musculoskeletal problems, as well as general feelings of fatigue, and mental and emotional stress. Physical activity, on the other hand, leads to muscle relaxation. A feeling of physical relaxation characterizes a good workout's afterglow. After working hard, muscles relax. One study measuring the electrical activity of muscle found that activities such as walking, jogging and bicycling decrease muscle tension by more than 50 percent for up to 90 minutes after exercise. Physical relaxation translates into mental relaxation as well. This exercise afterglow of relaxation is an important part of exercise's anti-stress value for many people.

Rhythmic exercise: Relaxed brain waves

Rhythmic exercises such as walking, running, rowing and swimming increase alpha-wave activity in the brain. The electrical activity of the brain can be monitored in the laboratory using an instrument called an electroencephalogram (EEG). Alpha waves are associated with a calm mental state, such as that produced by meditation or chanting. The rhythmic breathing that occurs during some forms of exercise also contributes to an increase in alpha-wave activity. Rhythmic activity performed to music may be stress-relieving in other ways as well.

Physical response to stress

Some research suggests that regular exercise of moderate intensity may provide a sort of dress rehearsal for stress. Several studies have found that people who exercise regularly have less of a physical response to laboratory stressors, such as difficult mental arithmetic tests. Other studies have found that physically fit subjects recover more quickly than sedentary peers from stressors such as cold exposure or emotional frustration.

Why? Your response to a session of moderately vigorous exercise resembles your response to stress -- elevated metabolic rate, cardiac output, energy substrate levels, muscle tension, stress hormones, etc. Regular exercise may "train" the body to cope with and recover more quickly from emotional stress, as well as exercise stress.

Mind games

The physical part of physical activity may be only part of the stress-management story. Physical activities may provide a diversion from sources of stress. When you are actively engaged in tasks demanding concentration and motor skills, it's hard to keep your mind on your worries. Exercise may relieve boredom or provide opportunities for social interaction. Perhaps most important of all, physical activity can be fun, and, to quote the famous children's author Dr. Seuss, "fun is good."

Copyright 2001, Fitness Management Magazine.