(Ivanhoe Newswire) -- Why does a marathon runner suddenly collapse to the ground after they reach the finish line?  Most people assume it is because the runner exerted all of their energy in their muscles, but few people know that it might also be a braking mechanism in the brain that swings into effect and causes them to be too tired to continue.  

 

What might be occurring is called “central fatigue.” Central fatigue is a phenomenon which has been known for about 80 years.  It is referred to as a tiredness that affects the brain and nervous system, instead of affecting the muscles. 

 

"Our discovery is helping to shed light on the paradox which has long been the subject of discussion by researchers. We have always known that the neurotransmitter serotonin is released when you exercise, and indeed, it helps us to keep going. However, the answer to what role the substance plays in relation to the fact that we also feel so exhausted we have to stop has been eluding us for years. We can now see it is actually a surplus of serotonin that triggers a braking mechanism in the brain. In other words, serotonin functions as an accelerator, but also as a brake when the strain becomes excessive," Jean-Francois Perrier, Associate Professor for the Department of Neuroscience and Pharmacology, was quoted as saying. 

 

Perrier hopes that mapping out the mechanism that prompts central fatigue will be useful in several ways.  By conducting scientific experiments, it is possible to measure and observe that the brain sends insufficient signals to the muscles to keep going, which means that we are unable to keep performing. This makes the central fatigue mechanism an interesting area in the struggle against doping. 

 

"In combating the use of doping, it is crucial to identify which methods athletes can use to prevent central fatigue and thereby continue to perform beyond what is naturally possible. The best way of doing so is to understand the underlying mechanism," Perrier said. 

 

The brain communicates with our muscles using what is called motoneurons, which refers to a neuron having a motor function.  Motoneurons are hyperactive in several diseases.  For example, it’s true for people suffering from spasticity and cerebral palsy who are unable to control their movements.  Perrier hopes that in the long term, this new knowledge can also be used to develop drugs against these symptoms.  Also, Perrier hopes to find out more about the effects of antidepressants. 

 

"This new discovery brings us a step closer to finding ways of controlling serotonin. In other words, whether it will have an activating effect or trigger central fatigue. It is all about selectively activating the receptors which serotonin attaches to. For selective serotonin re-uptake inhibitor (SSRI) drugs which are used as antidepressants, we can possibly help explain why those who take the drugs often feel more tired and also become slightly clumsier than other people. What we now know can help us develop better drugs," Perrier concluded.

 

SOURCE: Proceedings of the National Academy Of Sciences, March 2013

 

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