In his most recent post, RunnersWorld blogger Amby Burfoot discusses a fascinating new paper by Dr. Tim Noakes. Entitled "Fatigue is a brain-derived emotion that regulates the exercise behavior to ensure the protection of whole body homeostasis," the paper (published in the journal Frontiers in Physiology) expands upon Dr. Noakes conception of the Central Governor Model of exercise.
The Central Governor Model (CGM) suggests, broadly speaking, that maximal exercise is regulated by parts of the brain so as to maintain homeostasis throughout the body; in other words, a kind of sub-conscious network that ensures you don't kill yourself while exercising. It should be noted that critics are quick to point out that people do sometimes die in athletic events, suggesting the CGM may not account for all cases in which catastrophic failures in the body lead to a loss in homeostasis.
With that said, the CGM does provide a fascinating (and unique) perspective on the notion of fatigue in exercise, and is therefore worth exploring. Indeed, the big difference between this paper and other writings on the CGM centers on the notion of fatigue; that "A key component of the CGM is its proposal that fatigue is not a physical event but rather an emotion (St Clair Gibson et al., 2003) that is used by the brain to regulate the exercise performance (Tucker, 2009)." Consequently, Dr. Noakes re-imagines "fatigue" primarily as a brain-based phenomenon, described succinctly by Bainbridge in 1931 as:
"…the sense of fatigue is often a very fallacious index of the working capacity of the body…there is not necessarily any correspondence between the subjective feelings of fatigue and the capacity of the muscles to perform work … it is a protective feeling, which tends to restrain a man from continuing to perform muscular work when this would react injuriously upon his whole system” (Bainbridge, 1931, pp. 176–177)."
An important implication of this theory, as Dr. Noakes describes in the final section, is the possibility that athletic success "...will be strongly influenced by the manner in which the brains of the respective runners generate the sensations of fatigue during exercise." Indeed, if fatigue is an "emotion" rather than a "physical event," it is possible that the limitations of what our bodies can do are not simply a consequence of physiology, but rather a nexus of physiological and psychological phenomenon interacting together. In short our perceptions of fatigue, both in training as well as racing, appear to play a significant role in how hard we can push ourselves.
Interestingly, this point appears to share great affinity with those on the same subject made by Jerry Lynch and Warren Scott in their 1999 book Running Within. In chapter 12 of the work, they discuss strategies for dealing with in-race fatigue. One thing all these strategies share is a process of redefining fatigue as something less harmful than it at first appears, stating, "...if you change your beliefs about physiological limits, you will the change the pain's effect on you" (Lynch and Scott 1999, 126). Such strategies include:
"...[interpreting] it [fatigue] simply as a feeling you get when your muscles are working hard. See it as an important indication that you are exploring the outer boundaries of your running potential. Think about how necessary fatigue is if you wish to experience significant breakthroughs in your performance. Fatigue is there because you are exploring your potential and giving your best effort...When you create this shift in consciousness, notice how there is a subsequent shift in the fatigue as well" (Lynch and Scott 1999, 126-127).
According to everything we've now considered, it appears that our perceptions of fatigue may heavily influence our performance regardless of physiology. Furthermore, both sub-conscious and conscious factors appear to play a role. Differences in perception, be they cases of individual variation or the result of training, may yield large differences in performance. Something to consider maybe.
Happy Thursday, friends :)
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