ABOVE: One of the study’s subjects during a training session
MIKAEL FLOCKHART
As a researcher at the Swedish School of Sport and Health Sciences, Filip Larsen would hear anecdotes about the downsides of too much exercise—a common enough phenomenon that nevertheless puzzled him. “All athletes know if you train too much, something’s happening. . . . Your legs feel terrible after a while, and then if you just continue, you have these psychological disturbances too, like mood disturbances,” he says. “That hasn’t been really described in the literature—no one knows exactly what’s going on.”
To find out, Larsen and his colleagues recruited 11 healthy young people and put them through a four-week, increasingly intense regimen of sessions on a stationary bike while monitoring their glucose tolerance and mitochondrial function. During the toughest week, the subjects displayed insulin resistance and other deleterious metabolic changes, the team reported last week (March 18) in ...
