MIND OVER MUSCLE
It’s the brain that decides when you’re fatigued, new theory suggests
Pro cyclist Jens Voigt — who’s well known for his “shut up legs” mantra, which he repeats when pedalling becomes physically unbearable — offers a pretty accurate description of the battle between mind and body during a hard workout.
“Sometimes you can hear your body start talking to you like, ‘I can’t do it anymore, I can’t do it anymore,’ and your mind goes, ‘Shut up, body, and do what I tell you,’ ? Voigt has said.
The scientific community is at odds about the fatigue experienced by anyone who has pushed his or her body to its physical limits.
Traditional thinking suggests that fatigue occurs when athletic demands exceed the capacity of the heart to supply oxygen to the muscles.
That shortage of oxygen causes a buildup in metabolites, which leads to muscular distress and failure of the muscles to contract. In short, your muscles are spent. The only way to extend the time to fatigue is to improve the heart’s ability to pump blood at a greater rate as exercise intensity heats up.
It also suggests the most successful athletes possess a superior heart that delivers more oxygenated blood to the muscles.
But this theory doesn’t take into account the role the brain plays in fatigue.
Tim Noakes, author of the popu- lar book Lore of Running and a renowned sports scientist, believes fatigue isn’t the result of muscular failure. He suggests the brain signals the body to slow down as a protective response to keep it from overworking itself to the point of damage.
Noakes says there are too many unanswered questions about how muscular failure causes fatigue, including the fact that at the end of a race, when muscles should be exhausted, exercisers somehow find the reserves to speed up.
Noakes calls his theory that fatigue is more mental than physical the Central Governor Model, which suggests the brain, not the muscles, is calling the shots during a tough workout.
And unlike the muscles, which respond only to the level of oxygen delivery, the brain takes in all sorts of information.
That feedback includes the athlete’s emotional status, level of sleep deprivation, mental fatigue and recovery from a previous workout. Also taken into account by the brain is the duration of the workout and other intangibles like how strongly the athlete believes he can succeed.
Armed with all that information, the brain keeps the exerciser moving at an intensity the body can safely sustain using a continuous loop of physiological feedback.
Fatigue, suggest Noakes and others who believe in the Central Governor Theory, is not a measure of the capacity of the muscles to sustain high-intensity exercise, but rather a feeling the brain transmits to keep the body from overextending itself.
Noakes believes that somewhere during the course of the race, the brains of all those who fail to win have sent out a stronger sensation of fatigue than that experienced by the fastest competitor.
This doesn’t suggest a lack of mental fortitude, but rather that the level of fatigue felt by the exerciser is uniquely generated in an athlete’s brain based on physiological feedback.
It also suggests that having a winning attitude, or at the very least an “I can do it” attitude is an important component to achieving athletic goals.
Noakes’s theory of a Central Governor isn’t fully endorsed by the scientific community. But his idea that there’s more behind fatigue than just a physical response is worth exploring.
That said, there’s no agreed-upon strategy for training the brain to stop sending out such strong signals of fatigue as exercise intensity heats up. So while more intuitive than based in science, Voigt’s attempt at mind over muscle could very well be the key to achieving athletic success.