Competitive athletes may know this: you train and train and yet the performance drops off. The reason is usually overtraining - a chronic overload of the body, which can be caused by too high training intensities. Concomitants are often insomnia, headache, loss of appetite and even depressive moods.
That excessive training does not necessarily do the body good is well known. Researchers have now found that even certain areas of the brain can become tired from excessive endurance training.
French scientists compared a group of 19 male triathletes around the age of 35, whose training volume was increased by about 40 percent for three weeks, with a peer group of 18 triathletes who continued to follow their normal training schedule. The competitive athletes who trained too much showed not only excessive physical but also mental fatigue.
Better 80 euros immediately, than 100 euros in two weeks
More specifically, after training, the activity of the brain area responsible for conscious decision-making was restricted: cognitive control. This neural control system is used whenever habitual processes need to be monitored, disrupted, and modified to better align behavior with long-term goals.
The fatigue of this brain area was also reflected in the behavior of the athletes: they acted impulsive, as the researchers report in the journal "Current Biology". In the study, the athletes could decide, for example, if they would rather get 80 euros immediately or 100 euros in two weeks. The group's athletes, who pursued too much training intensity, opted for the immediate reward rather than the longer-term and larger one.
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The scientists also derive a cause for overtraining: The athletes did not stop training despite aching muscles, as they had a higher sense of achievement at that moment. They do not consider the long-term, performance-reducing consequences that overtraining can have, the researchers believe.
"The region of the prefrontal cortex that responded to excessive sports training was exactly the same as it had in previous studies of extreme mental stress," said Mathias Pessiglione, one of the authors of the study. This area of the brain seems to be the weak point responsible for the ability to make rational decisions.
For the training period this means: "One must consciously decide to stop when the muscles or joints are aching during endurance training," says Pessiglione. "To achieve a long-term training success."
Although endurance sports are generally good for the health, overtraining can have unfavorable effects on the brain, the scientists conclude. "We figured out that you do not make the same decisions when your brain is tired," says Pessiglione.
