Fit 'N' Brainy

Perhaps you've resisted exercise all these years because you're more interested in the life of the mind than the oh-so-vain pursuit of corporeal perfection. But while all the news of exercise's benefits to your heart and lungs hasn't gotten your nose out of books and your sneakers out of the closet, you may now be persuaded to move. Physical activity, it turns out, could save not just your body but also your precious head. Lifelong exercise has been shown to decrease cellular aging in the brain: Moderately active rats have more robust brain cells than their sedentary fellow rats, researchers from the McKnight Brain Institute of the University of Florida found.

That means regular mild exercise can evidently prevent brain deterioration in humans, too, says Thomas Foster, Evelyn McKnight chair for brain research in memory loss at the University of Florida's College of Medicine. Oxidative damage, a natural consequence of aging, contributes to memory loss and has been implicated in development of Alzheimer's and Parkinson's disease. It occurs when oxygen molecules become free radicals, renegades that damage cell tissues. Rats that had access to an exercise wheel were found to have fewer byproducts of oxidative stress in their brains than those that did not.

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Fit rats also showed healthier DNA. "The DNA for these animals after two years looked as if it were from their younger counterparts of only about 6 months of age," Foster said. Because damage to DNA causes cell mutations and cell death, finding ways to preserve it may help prevent age-related memory failure and defend against loss of balance and motor function. "By age 50 almost everyone has mild memory deficits. We forget where we put the keys or jumble the names of our kids. If these losses increase, then we run into problems."

Cheer up, couch potatoes—we're not talking marathons or even hour-long spin classes here. "For this study animals were not forced to run; they did it because it was entertaining, the same as a pet hamster on a running wheel," said Foster. "In people, that translates to a daily 30-minute walk or a light 1-mile run."

The finding complements past research showing the mental benefits of light workout sessions. Scores of studies show that short stints of exercise increase a protein called BDNF, or Brain-Derived Neurotrophic Factor, which helps nerve cells grow and connect. In rat studies conducted by Fernando Gomez-Pinilla and his colleagues at UCLA, even a few minutes of swimming raised levels of BDNF.

The benefits of BDNF are many. Rats with boosted BDNF in their brains navigate mazes better, heal faster from brain injuries, and are even more likely to avoid a type a behavior that is akin to rodent depression than cage mates with lower levels of the protein.

Workouts don't just protect brains, it seems, but also improve thinking. In a comparison of 18 studies, inactive older adults who began an exercise routine got significantly better at cognitive tests that measured skills such as planning and paying attention. Again, these subjects' regimen was quite manageable: Just three days a week, they worked up from a slow 15-minute walk to a 45-minute jaunt. So put down your crossword puzzle and jog around the neighborhood. Don't be surprised if the answer to that inscrutable clue hits you when you return.

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