Mind Over Matter – Prior experience and the perception of fatigue

Continuing on the topic of mind over matter, and specifically in relation to exercise, I am reminded of some work done by Professor Tim Noakes several years ago. Professor Noakes challenged a long established belief that fatigue originates in the muscles (when the muscles run out of oxygen, glycogen or ATP), or when there is too much lactic acid. This model was called the “Limitations Model”. Rather, Noakes and his colleagues proposed that fatigue originates in the brain (I can now hear all coaches saying “you’re not tired, it’s in your head). According to Noakes, “fatigue is a complex emotion affected by factors such as motivation and drive, other emotions such as anger and fear, and memory of prior activity” (read more here).

According to Noakes (and colleagues)…

the brain, when it senses that the athlete is overstretching him- or herself, sets off a series of sensations that the body translates as symptoms of fatigue. The brain does so to protect itself, the heart and the rest of the body. “Its main function is to make sure you don’t get into trouble in whatever exercise you’re doing” (read more here and here).

But how does the brain know when enough is enough? I should note that the Central Governor model is a highly complex one, and accounts for various interrelated factors, and I am skimming the surface.

One aspect, or conclusion I could draw was that the brain begins brain gathers “data” from early childhood on how far we we can push ourselves physically. So perhaps as a child you weren’t exposed to much sport. Whenever you were asked to participate in physical education you expected to feel tired (because you were unfit) and so you did (because you were unfit, but also because your brain acted against any threat of over doing it). In adulthood, your brain would sound the “I’m tired” alarm long before someone else who may, as a child, have spent hours running around a soccer field. You would need to ensure that your brain doesn’t trick you into thinking you’re tired, when in fact you could run further or faster. The risk for the soccer fan could be the opposite, his or her brain might ignore signs of real muscular fatigue and land up pushing too hard and result in over training.

So the next time you’re running and you feel fatigued, you might consider the possibility that it’s all in your head and push on. You might be right, and you might be wrong, and I think this is where a heart rate monitor might be a more reliable indicator of fatigue.

Thinking back to my previous post, I wonder if anything has been done on mood and the perception of fatigue. I shall see what I can find.