A strenuous workout can not only make you feel better, but some researchers say it can help improve self-esteem.

"All I have is anecdotal information, and it appears those who persist in exercise say, 'Yeah, it enhances self-esteem,' " said Wynn F. Updyke, project director of the Chrysler Fund-AAU Physical Fitness Program. The nationwide program tests the athletic abilities of elementary and high school students.

Fifty to 60 percent of teachers who work with the program believe that self-esteem is the most important psychological benefit of exercise, said Updyke, associate dean of health, physical education and recreation at Indiana University in Bloomington.

Updyke is setting up a study to check the relationship between exercise and self-esteem. He and his colleagues intend to give physical and psychological tests to approximately 800 students from fourth grade on for at least three years. They want to study changes over time so they can search for possible cause and effect.

The researchers plan to test the idea that confidence in a student's physical abilities generalizes into confidence about himself, and they want to see if improved exercise performance translates into better grades.

Previous research has reported that people who exercise tend to have higher self-esteem, according to Robert J. Sonstroem, a professor of physical education at the University of Rhode Island in Kingston.

However, it hasn't been proved if exercise causes a change and, assuming it does, how important exercise is compared with other causes, he said.

Although Sonstroem believes exercise might raise a person's opinion of his body, which could lead to higher overall self-esteem, others are skeptical.

"I think that question is still out," said Don Hellison, a professor of physical education at California State University at Chico. "Do we think about ourselves as a holistic way, or in terms of roles and abilities?"

Self-esteem about physical appearance, fitness and competence in sports might correlate with each other without generalizing into an overall feeling, said Hellison, who is working with Updyke to plan the study.

Another issue is that self-esteem seems to have a lot of behavioral roots, making it difficult to find a measurement system that can tell the roots apart, Updyke said. In physical education, for instance, "it's never just exercise, it's always sports or some other sort of skillful activity," he said.

The fitness tests to be used in the study will try to reduce the skill component by including such standard laboratory measures as stationary bicycle riding, Updyke said.

If the results are positive, they may indicate something else about self-esteem -- that simply trying and succeeding is good for your emotional health, Updyke said.