Fatigue: It’s all in your mind. Or tastebuds.

July 22, 2009 at 6:31 pm Leave a comment

Fatigue

Conventional wisdom among most physiologists used to be that fatigue was a biochemical phenomenon. You get tired from running, for example, because of a buildup of lactic acid in one’s legs — or maybe because the muscles don’t have enough oxygen.

But what explains, then, the awesome sight of marathon participants who sprint the final hundred yards of a 26.2 mile race — an event that otherwise slowed them to a walk (or a crawl) until the “finish line” came into view? If fatigue is something that can be explained by reference to an anatomy and physiology textbook, how and why do people often finish exhausting exercises faster than at any other point in the workout?

Because the mind matters.

From Gretchen Reynold’s fantastic story in this past Sunday’s NYT Magazine, “Going All Out: Can Your Brain Fight Fatigue?“:

Recently, researchers in England discovered that simply rinsing your mouth with a sports drink may fight fatigue. In the experiment, which was published online in February in the Journal of Physiology, eight well-trained cyclists completed a strenuous, all-out time trial on stationary bicycles in a lab. The riders were hooked up to machines that measured their heart rate and power output. Throughout the ride, the cyclists swished various liquids in their mouths but did not swallow. Some of the drinks contained carbohydrates, the primary fuel used during exercise. The other drinks were just flavored, sugar-free water.

Phys Ed

By the end of the time trials, the cyclists who had rinsed with the carbohydrate drinks — and spit them out — finished significantly faster than the water group. Their heart rates and power output were also higher. But when rating the difficulty of the ride, on a numerical scale, their feelings about the effort involved matched those for the water group.

In a separate portion of the experiment, the scientists, using a functional M.R.I., found that areas within the brain that are associated with reward, motivation and emotion were activated when subjects swished a carbohydrate drink. It seems that the brains of the riders getting the carbohydrate-containing drinks sensed that the riders were about to get more fuel (in the form of calories), which appears to have allowed their muscles to work harder even though they never swallowed the liquid.

Time to hit the trails for a little mindful running.

play, think…
J.R. Atwood

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Jason R. Atwood

I'm an avid trail runner and doctoral student at U.C. Berkeley who studies motivation and the relationship between the mind and body. This blog is a forum to share research, news, and musings about these topics of interest. More

Play is the beginning of knowledge.

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