Is Fatigue A Figment of Your Imagination?

Yesterday on my way to work I listened to an interview about a new book on sports science on NPR.  The guest was Mark McClusky, an editor with WIRED.com, who discussed his new book Faster, Higher, Stronger - a book on sports science.  The interview discussed Mark's research into a number of methods that elite athletes use to attain better performance - many of which I have or intend to explore - so I decided to get a copy.  My copy arrived today and I dove into a chapter in the middle called "What Getting Tired Means".

The chapter highlights the theories of sports scientist Tim Noakes, who contends that fatigue is not a physiological state caused by the increase in lactate (or acidification) of muscles but rather a mental state, "a combination of the brain reading various physiological, subconscious and conscious signals and using these to pace the muscles in order to ensure that the body does not burn out before the finish line is reached."

Faster, Higher, Stronger implies that Mr. Noakes' view remains controversial in the sports science field and, in my opinion, with good reason (although I do think there are some interesting ideas and takeaways).  For one, muscle fatigue is not limited to elite athletes or endurance sports.  Muscle fatigue and fatigue in general has an entirely different context in the world of chronic illness.  Just the other night, while blow drying daughter's hair, turning the two pound hair dryer quickly back and forth so as not to leave the heat concentrated in any one place for too long, my forearm muscles began to tire.  They got heavy, much the same as used to occur when I was able to exercise at a high level, and ultimately struggled to hold up the two pound hair dryer.  I think it unlikely that muscle fatigue in this case was my brain trying to pace the use of my forearm to dry my daughter's hair.

That said, the correlation between the mind and exercise performance appears real from what I have read.  The brain is the control center of the body, regulating your body's systems (e.g. circulatory, nervous).  Each of those systems includes various organs and other tissues that have different functions, require different resources (e.g. oxygen, minerals, vitamins), and produce different waste products.   The brain cannot override the number resources required or eliminate the waste products; however, it can push through the normal safety limits for short periods of time. 

It is possible that Mr. Noakes' view is more nuanced that implied in Faster, Higher, Stronger by Mr. McClusky - that he is attributing the very small increase in exercise performance of "gold medal" athletes that allows them to temporarily push through the body's safety switches (by trickery or mental fortitude) - but the notion that fatigue is somehow an emotional or mental state does not seem plausible in the context of illness induced fatigue.