Practical Science on Movement and Pain

Fatigue is an Emotion

I have been meaning to write part three in my series on central governors, which is supposed to cover fatigue. Well now I don’t have to, because I can just point my readers to an excellent article written by Tim Noakes, which describes in detail his central governor model for fatigue. The tile provides a good summary: Fatigue is a Brain-Derived Emotion that Regulates the Exercise Behavior to Ensure the Protection of Whole Body Homeostasis. The basic idea is that human exercise capacity is not limited by a failure of the body, but is instead regulated by the brain to ensure that such a failure does not occur. Here is a brief summary of some of the highlights of the article.

Looking for fatigue in all the wrong places

Noakes starts with a review of the history of the study of fatigue, which mostly focused on efforts to find the ultimate limitations of human exercise capacity in the body, such as the muscles or the heart. The problem with this approach is that it does not explain why athletes almost invariably simply choose to stop exercising before such bodily limits are reached (some of which would result in catastrophic injury or death.) For Noakes “the presence of the noxious symptoms of fatigue must indicate that exercise cannot be regulated solely by an inevitable and unavoidable failure of skeletal and or cardiac muscle functions.”

Here are some common observations that are not explained by the theory that exercise is limited by some single factor in the body:

  • athletes begin exercise at an intensity which is appropriate for the expected duration;
  • athletes run harder in competition than in training;
  • athletes speed up at the end of exercise (the end spurt).
  • skeletal muscle is never fully recruited during any form of exercise – 35-50% in prolonged exercise and 60% during maximal efforts.

To explain these and other observations, Noakes and his colleagues helped develop the Central Governor Model for fatigue.

The central governor – it’s all in your head

The essence of the central governor model is that fatigue is not a physical event but rather an emotion that is used by the brain to regulate exercise stress. An important implication is that all forms of exercise are submaximal since there is always a reserve of motor units that are never fully utilized.

Research shows that motor recruitment and fatigue during exercise will be affected by a huge variety of factors, including emotional state, mental fatigue, recovery from previous exercise, motivation, self belief, prior knowledge of the duration of exercise, cerebral and arterial oxygenation, muscle glycogen storage, fluid loss, thirst, heat, and more. In fact, “the prediction of this model is that potentially everything … can potentially affect athletic performance. But that the most important of these effects begin and end in the brain.”

Because fatigue is produced by the brain based on its opinions about what is going on in the body, it is subject to error, as noted by Bainbridge in 1919:

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 the man from continuing to perform muscular work when this would cause injury.

In support of this idea, Noakes cites to evidence that athletes can be “tricked’ into working harder in numerous ways, such as deceiving them about the time or distance they have exercised, cooling hands and palms to make core temperature appear less elevated, or using a carbohydrate mouth rinse to fool the brain about the availability of energy reserves.

Although Noakes does not mention it in the article, the idea that the fatigue can be a “fallacious index” of actual body state has interesting implications for chronic fatigue syndrome. And there are some obvious connections to what we are learning about pain science.

The difference between winning and losing?

Noakes ends the article with some very interesting speculations about the differences between coming in first or second in an endurance event. Here are some excerpts:

In the case of a close finish the CGM was clearly successful – neither athlete died. But if the second runner did not die, why did he not run just a little faster and so approach death a little closer? For surely he could have sped up by just a fraction without dying? Yet he did not. Why not?

My unproven hypothesis is it is that in the case of a close finish, physiology does not determine who wins. Rather somewhere in the final section of the race, the brains of the second, and lower placed finishers accept their respective finishing positions and no longer choose to challenge for a higher finish.

According to this model, the winning athlete is the one whose illusionary symptoms interfere the least with the actual performance

the winner is the athlete for whom defeat is the least acceptable rationalization.

“The fight,” wrote Muhammad Ali “is won or lost far away from witnesses, behind the lines, in the gym, out there on the road, long before I dance under the lights.”

A little romantic maybe, but it rings true. If it’s all about physiology, then why does this race feel meaningful?:

Or this one (complete with Rocky music):

I love it.

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5 Responses to Fatigue is an Emotion

  1. Mark Hollis says:

    Nice post (but then when isn’t one on this site?). The aspect I found most interesting about the second video clip, and ties in with the central govenor theory, is that Steve Jones ‘found’ the extra necessary power/strength upon what really was a visual (sensory) signal. He would have been mentally visualising coming first when he was out front (and psychologically aware (belief) of the runners behind him competing) however upon an increased sensory confirmation of this psychological awareness/belief (I can see someone in front of me and to win I need to not be seeing them in front of me)was able to significantly alter motor output.

    Do you think that ‘Because fatigue is produced by the brain based on its opinions about what is going on in the body’ … [and in the environment (the extrapersonal space where the future benefits/demands of the body's needs are met)]‘?. So Fatigue is a co-relative relationship between the brain’s representation of the previous body (memory (what’s gone on)), the current body (sensory/perception/cognition (what’s going on)), and the future body (belief/desire (what to come))?.

  2. Mark Hollis says:

    Nice post (but then when isn’t one on this site?). The aspect I found most interesting about the second video clip, and ties in with the central govenor theory, is that Steve Jones ‘found’ the extra necessary power/strength upon what really was a visual (sensory) signal. He would have been mentally visualising coming first when he was out front (and psychologically aware (belief) of the runners behind him competing) however upon an increased sensory confirmation of this psychological awareness/belief (I can see someone in front of me and to win I need to not be seeing them in front of me)was able to significantly alter motor output.

    Do you think that ‘Because fatigue is produced by the brain based on its opinions about what is going on in the body’ … [and in the environment (the extrapersonal space where the future benefits/demands of the body's needs are met)]‘?. So Fatigue is a co-relative relationship between the brain’s representation of the previous body (memory (what’s gone on)), the current body (sensory/perception/cognition (what’s going on)), and the future body (belief/desire/prediction (what to come))?.

  3. dwight pargee says:

    Soviet and eastern bloc sport scientists were aware of these ideas way back and incorporated them in their training techniques, here’s a great story:

    “Charles A. Garfield, author of Peak Performance: Mental Training Techniques of the World’s
    Greatest Athletes (1984), extensively studied the Soviet and East German sports training pro-
    grams. He found that mental training was widely taught, especially to athletes at the international
    class level. Garfield states in his book the following:

    In Soviet athletic training programs, two key skills must always be mastered. The
    first is the skill of voluntary relaxation — that is, the ability to relax the body
    consciously and put the mind in a quiet receptive state. The second skill is the ability to
    produce and creatively manipulate mental images. This is the process frequently re-
    ferred to as “visualization.” [10]

    Garfield is himself a former weight lifter. In 1976 he met Soviet sports psychologists at a sci-
    entific conference in Milan, Italy. The Soviet scientists demonstrated to him how mental training
    can greatly elevate athletic performance. Using Garfield as the subject in an improvised experi-
    ment, they assigned him the task of bench-pressing 300 pounds. Garfield had not worked out for
    months, and when he had done so, he rarely benched more than 280 pounds. So, it was only by
    generating a huge effort that he succeeded in lifting the 300 pounds. The Soviets then told Gar-
    field that they wanted him to attempt to bench-press 365 pounds, which was his personal record
    set eight years previous. Garfield informed them that it would take him 9-12 months of serious
    training to get in condition to lift 365 pounds again. The scientists thought otherwise. After taking
    various physical measurements of Garfield — body fat percentage, small blood sample analysis,
    metabolic rate, etc. — they had him perform a mental rehearsal technique:

    They asked me to lie on my back and proceeded to guide me into a deep state of
    relaxation. I was fully awake and alert, aware of everything going on around me. Yet
    every muscle in my body relaxed, and I felt more at ease than ever before in my life.
    They asked me to imagine my arms and legs becoming increasingly heavy and warm.
    A warm, tingling sensation spread over me.

    … I was told to mentally visualize myself approaching the bar, sitting on the bench,
    lying down, and then, with total confidence, lifting the 365 pounds. I was also in-
    structed to imagine the sounds I would hear, the dull metallic ring as the bar tipped
    slightly, jangling the weights together, the sound of my own breathing, and any vocal-
    izing I ordinarily did when working out.[l 1]

    This relaxation and visualization process lasted approximately 45 minutes whereupon Garfield
    proceeded, much to his surprise, to successfully bench-press the 365 pounds. The Soviet scientists
    informed him afterwards in a matter-of-fact way that they had calculated he could lift between
    345 and 395 pounds. The visualization procedure merely brought to the surface Garfield’s latent
    physical capabilities.

    Garfield presents in his book a comprehensive mental training program for athletes — the pro-
    gram being a synthesis of what Soviet and East German sports psychologists have their top ath-
    letes follow. He says that the program will yield “dramatic changes… in two or three months” with
    continued practice. Yet, Garfield’s own bench-pressing experience, under the guidance of the So-
    viet scientists, clearly shows that adoption of mental rehearsal techniques can, in many cases,
    bring about major improvement immediately (recall how Marshall Morris, after learning and then
    using self-hypnosis, improved his snatch from 198 pounds to 242 pounds — all this occurring in
    the same day). While athletes should not raise their expectations too high about the benefits men-
    tal training will provide them, still they should recognize and seek out the potential rewards one
    can experience from regularly practicing such mental disciplines as visualization and self-
    hypnosis.

    Soviet sports psychologists have investigated how various forms of mental training affect
    weight lifters’ performance. Some of their investigations are especially worthy of mention…..”

    the whole text of “The Super mental training Book” is available at: http://www.archive.org/stream/TheSuperMentalTrainingBook/SuperMentalTraining_djvu.txt

    -dwight

  4. Great topic. Please read everything you can get your hands on by Dr. Herbert Spiegel. Specifically “The Neural Trance.” He was far beyond his years!!!

  5. Todd Hargrove says:

    Hi Marc,

    Interesting speculation about the benefits of running in first. But I know that hanging in second is the preferred strategy for many (like Haile).

    Dwight,

    Thanks for the great story. Yeah those Russians knew some stuff.

    Chris,

    Never heard of Spiegel I will look into it. Thanks for the reference.

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