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"If the body is feeble, the mind will not be strong."

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Dr. Jennifer Etnier, Crews' colleague at ASU and also an assistant professor of exercise science and physical education, says that physical activity is probably very important for adolescents, though most of the research thus far has been on other groups—particularly the aging. A 1997 meta-analysis carried out by Etnier and a number of colleagues, however, found five studies–out of a total 134 looking at the importance of exercise—that focused on normal adolescents and cognitive abilities.

The results of these studies suggest that cognitive abilities are indeed benefited by exercise for this group. When the life cycle is broken down into six groups—elementary (age 6 to13); high school (age 14 to17); college (age 18to 30); adult (age 30 to 45); older adult (age 45to 60); oldest adult (age 60 to90)—the “high school” grouping is the second most likely group to benefit after the “older adults.”

There are all sorts of reasons why this might be the case, Etnier says.

“Exercise could be making a difference in a number of ways,” she says. “In puberty, exercise may be stabilizing children from having big hormonal level swings, which would allow them to concentrate better. Also, activity helps with tension; if a kid is having behavioral problems, exercise could bring about a fatigue preventing them from having as many outbursts. As soon as they do that, they start learning more, because they can pay attention.”

Etnier adds that another, subtler mental facet is affected a great deal by exercise: self confidence. “If you exercise and attain these accomplishments in the physical activity realm, you feel better, more confident, and that transfers to the classroom: you may be more participatory in class; if you feel better about yourself, you may perform better.”

The science behind all of this is still to be clarified. One leading theory is that exercise provides the brain with more glucose. The brain needs glucose both to power neurons and to produce acetylcholine, a neurotransmitter important to memory.

As it happens, short bouts of exercise do not appear to enhance cognitive abilities appreciably; it is through longer-term commitments that the effects seem apparent, which would seem to stress the importance of an exercise regimen.

“It's such a travesty that P.E. classes are being cut from the school system,” says Etnier. “Because there can be, if physical activity is used properly, an aerobic exercise component, a resistance exercise component, and a skill learning exercise in an enriched environment.”

Thomas Jefferson famously said that “not less than two hours a day should be devoted to exercise, and the weather little regarded. I speak this from experience, having made this arrangement of my life. If the body is feeble, the mind will not be strong.”