How Exercise Makes You Smarter
Exercise does more than build muscles and help pr heart disease．New science shows that it also boosts brainpower--and may offer hope in the battle against Alzheimer(痴呆症).
The stereotype of the 'dumb jock' has never sounded right to Charles Hillman．A jock himself, he plays hockey four times a week, but when he isn't body-checking his opponents on the ice, he's giving his mind a comparable workout in his neuroscience and kinesiology lab at the University of Illinois．Recently he started wondering if there was a vital and overlooked link between brawn and brains--if long hours at the gym could somehow build up not just muscles, but minds．With colleagues, he started an experiment．He rounded up 259 Illinois third and fifth graders, measured their body-mass index and put them through classic PE routines: the 'sit-and-reach', a brisk run and timed push-ups and sit-ups．Then he checked their physical abilities against their math and reading scores on a statewide standardized test．Sure enough, on the whole, the kids with the fittest bodies were the ones with the fittest brains, even when factors such as socioeconomic status were taken into account．Sports, Hillman concluded, might indeed be boosting the students' intellect.
Hillman's study, which will be published later this year, isn't definitive enough to stand alone．But it doesn't have to: it is part of a recent and rapidly growing movement in science showing that exercise can make people smarter．Other scientists have found that vigorous exercise can cause nerve cells to form．dense, interconnected webs that make the brain run faster and more efficiently．And there are clues that physical activity can stay away from the beginnings of Alzheimer's disease, ADHD and other cognitive disorders．No matter your age, it seems, a strong, active body is crucial for building a strong, active mind.
Some scientists have always suspected as much, although they have not been able to prove it．Now, however, armed with brain-scanning tools and a sophisticated understanding of biochemistry, researchers are realizing that the mental effects of exercise are far more profound and complex processes than they once thought．The processes start in the muscles．When the exercise is available, the muscle sends out chemicals, including a protein called IGF-1 that travels through the bloodstream, across the blood-brain barrier and into the brain itself．And then the brain issues orders fuels almost all the activities that lead to higher thought.
With regular exercise, the body builds up its levels of BDNF, and the brain's nerve cells start to branch out, join together and communicate with each other in new ways．This is the process that underlies learning: every change in the junctions between brain cells signifies a new fact or skill that's been picked up for future use．BDNF makes that process possible．Brains with more of it have a greater capacity for knowledge．On the other hand, says UCLA neuroscientist Fernando G6mez-Pinilla, a brain that's low on BDNF shuts itself off to new information.
Most people maintain fairly constant levels of BDNF in hood．But as they age, their individual neurons (神经)slowly start to die off．Until the mid-90s, scientists thought the loss was permanent-that the brain couldn't make new nerve cells to replace the dead ones．But animal studies over the last decade have overturned that assumption, showing that 'neurogenesis' (神经发生)in some parts of the brain can be induced easily with exercise．Last week's study, published in the Proceedings of the National Academy of Sciences, extended that principle to humans for the first time．After working out for three months, all the subjects appeared to regain new neurons．This, too, might be BDNF at work, transforming stem cells into full-grown, functional neurons．'It was extremely exciting to see this ex