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Mental fatigue and physical performance

March 8th, 2009

There’s an interesting study in this month’s Journal of Applied Physiology about the link between mental fatigue and physical endurance. In a nutshell: “When participants performed a mentally fatiguing task prior to a difficult exercise test, they reached exhaustion more quickly than when they did the same exercise when mentally rested.”

This is a topic I’ve thought a lot about, in part because my occupation is so physically undemanding. I typically spend the day sitting in front of my computer, chatting on the phone, and reading. But if I try to do a hard running workout at the end of a day where I’ve been filing a story on deadline, I STINK! My performance really suffers compared to days when I’ve just been reading or researching. But I don’t get a lot of sympathy from my training partners when I say, “I’m exhausted, I was really typing hard today.”

I had thought it might have something to do with stress hormones, but the researchers (from Bangor University in Wales) suggest another mechanism. Apparently, concentrating hard requires the anterior cingulate cortex region of the brain. Studies have found that rats with a lesion in that area are unable to work as hard for a reward as normal rats — so it may be that our ability to accurately gauge physical effort is put out of whack by too much hard thinking.

This is also another clue that our physical performance limits are almost always mental rather than physical. What we perceive as our bodies reaching their outer limits may, in many cases, just be case of frazzled nerve endings in the anterior cingulate cortex…

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