A team led by neuroscientist Arthur Kramer divided fifty-nine sedentary people ranging in age from sixty to seventy-nine into two groups that would hit the gym three times a week for one hour over the course of six months. Members of the control group embarked on a stretching routine, and the others walked on treadmills, starting out at 40 percent of their maximum heart rate and ramping up to 60 to 70 percent. The only variable was fitness, and indeed, after six months, the walking group averaged a 16 percent improvement in their maximal rate of oxygen consumption (VO2 max), which is a measure of the lungs’ capacity to process oxygen.
But the groundbreaking finding came from MRI scans before and after: those with improved fitness had an increase in brain volume in the frontal and temporal lobes. Scientists knew that this could happen in the hippocampus, but the suggestion that brain volume increased in the cortex was “out there,” in the estimation of neuroscientist Carl Cotman, the researcher who pinpointed the link between exercise and BDNF. “I’m sure he’s right,” Cotman says of Kramer. “He’s a very honest, accurate guy. But the findings are definitely on the outer fringe. I mean, I don’t think anybody with animal studies has shown that a brain region in an older animal gets bigger from a very short period of physical activity.”
The major implication is that exercise not only keeps the brain from rotting, but it also reverses the cell deterioration associated with aging.
According to Dr. Ratey, it remains to be seen whether Kramer’s findings can be replicated, but the idea that just six months of exercise remodels these crucial areas of the brain is incredibly heartening. In the scans, the exercisers’ brains looked as if they were two to three years younger than they were. The resolution of the images doesn’t show specifically what composed the growth, but given what we know from animal studies, Kramer has his suspicions. “It could be new vascular structure, new neurons, new neuronal connections,” he says. “I think it’s probably all of the above.”