Monday, December 5, 2011

Muscle tiredness starts in the brain

A mechanism in the brain has been linked to inducing the feeling of being unable to gather the strength for certain tasks during physical exercise. It appears to be a key factor in determining the limits of our muscle capabilities. Though we are inclined to think that our muscles are the most important in determining our limits, it is actually the brain that sets them. Modifying this mechanism can prove to be interesting for athletes, that want to push themselves to the extreme.

Motor neurons
Scientists from the University of Zurich have shown that impulses from the muscles inhibit an area of the brain that is responsible for control over muscles. This was shown by letting participants perform a tiring task, while their brain was being scanned.  This revealed that the motor cortex, that regulates voluntary muscle movement, was inhibited by the physical activity. When the muscle information was artificially shut out from the brain, the fatigue-driven performance decrease was found to be delayed, highlighting the importance of the brain in regulating muscle activity.

A protective mechanism
The neuronal system that inhibits muscle activity during activity that requires energy protects the body from damage. Information about muscle state enters the brain through the thalamus, which integrates signals coming from the body and relays them to parts of the brain that need to be aware of it. The brain then alters our behaviour to prevent any damage. It has to be noted that not all protective behaviour is something we are aware of. Our body handles various processes automatically, and only a few involve our awareness. When it comes to physical activity, becoming aware of muscle fatigue was long thought to be a protective mechanism itself: the pain would make us stop doing what we are doing.

Informing and instructing the brain
It was known that signals coming from the body are necessary to inform the brain. It is what we use to make certain decisions. For muscles specifically, we already knew that the thalamus and a few other parts receive information from the muscles when we are putting them to the test. We did however not know that signalling to the brain plays such a distinctive role in determining our physical limits. That shows that the muscle does not only inform our brain, but it also instructs it to shut off motor activity by inhibiting the responsible parts.

Increasing endurance
The newly discovered neural mechanism indicates we can improve our athletic performance by sheer will power. by wilfully modifying our brain behaviour we may be able to reverse the inhibition of the motor cortex induced by tired muscles signalling to the brain. Professional athletes already focus on willpower: to be the best, you need to have the right mindset, something that is now backed up by science. 

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