Yet no one really knows why, says Edward McAuley, professor of kinesiology at the University of Illinois. Few studies have successfully identified the mechanism underlying this relationship.

Based on a study being published this month in the journal Health Psychology, at least part of the connection appears to come from a person's self-confidence about exercise, McAuley said. The emotional, or "affective," benefits you get from physical activity are dependent, in part, on what you believe you're capable of, what researchers call your exercise "self-efficacy," McAuley said.

The study, co-written with graduate students Heidi-Mai Talbot and Suzanne Martinez, shows that the higher a person's self-efficacy, the more likely he or she is to feel emotional benefits from exercise, McAuley said. "It suggests that changing the environment, providing information that enhances efficacy, can improve the exercise experience, at least emotionally. That becomes important particularly if the enjoyment, the emotions that are experienced in exercise, are implicated in getting people to do it again."

In the study, funded in part by the National Institute on Aging, McAuley and his research colleagues fed bogus data to 46 low-active college women, most of whom exercised less than once a week.

Half of them, chosen at random and labeled as "high-efficacy," were told after individual fitness tests on a stationary cycle that they placed in the top fifth for fitness among women of similar age and level of activity. The other half, labeled "low-efficacy," were told after the same tests that they placed in the bottom fifth. All the subjects were shown false computer printouts to show how their heart rates compared with their peers', and all were given positive messages about exercise.

In a follow-up test given several days after the first, each subject was first reminded of her previous test results, then was asked to work out for 20 minutes on a Stairmaster. At intervals before, during and after the exercise, each was asked to respond to questions from two measures designed to assess sense of well-being, psychological distress and fatigue.

The results showed the high-efficacy group responding with a significantly greater positive response and reduced negative feelings, McAuley said. The low-efficacy group showed no correlation between efficacy and affect (or emotional response). In the high-efficacy group, however, efficacy was "positively and highly correlated with affective responses in all the right directions, at every single time point."

McAuley thinks the results suggest efficacy influences how one deals with the body's signals during exercise. A person with lower efficacy might feel themselves getting tired or reaching their limit earlier. In the person with higher efficacy, "the belief in your capabilities is actually overriding what the body's telling you, you're thinking 'I can go further, I can work harder, this is a good feeling.' "

Note: If no author is given, the source is cited instead.

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