Research of the Week: Why Hard Training Makes You More Impulsive
/In her exploration of the epidemic of overtraining syndrome among ultrarunners a few years ago, Outside contributor Meaghen Brown told the story of Mike Wolfe, a North Face pro from Montana whose career had ground to a halt in the face of a debilitating but unexplained set of symptoms. Over the years, scientists have kicked around numerous possible theories about overtraining: unbalanced hormones, an immune system gone haywire, energy deficits, stress overload, and so on. But Wolfe was ready to consider a simpler possibility: "[A]t some point," he mused, "the mind quits before the body and just says, 'Enough.'"
There are some intriguing echoes of that idea in a recent study, published by French researchers in Biology Letters-but, far from closing the book on overtraining, the results raise as many questions about the nature of extreme fatigue as they answer. The most telling conclusion is that the distinction between mental and physical fatigue, at least when it comes to prolonged tests of endurance, is thin to the point of vanishing.
The study involved 37 serious triathletes, half of whom increased their training load by 40 percent for a three-week period in order to induce a mild and reversible form of overtraining (what sports scientists call "overreaching"). At the end of this period, they completed a series of cognitive and decision-making tasks in a brain scanner, answering questions like "Would you prefer $10 now or $50 in six months?" The eye-catching result is that the overtrained triathletes became more likely to choose immediate rewards over delayed (and superior) gratification compared to the control group. This is the finding that led to headlines like CNN's "Too much exercise could lead to bad decisions on what you eat and buy"-which is, to put it mildly, a bit of an extrapolation.
