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Overtraining may be reversing the benefits of exercise. Getty Images
  • Researchers say that ‘overtraining’ not only leads to an exhausted body, it can also exhaust the mind.
  • They say this mental fatigue can lead to misjudgment when making important life decisions.
  • Some experts say rest for the mind is just as important as rest for the muscles when it comes to exercise.

Excessive exercise can certainly have an effect on the body: Tired and sore muscles, strains, and even injuries can result from overtraining. But can too much exercise also have a weakening effect on the mind?

The answer is… possibly.

A study published today in Current Biology indicates that excessive athletic training can result in mental fatigue in addition to physical fatigue.

The study looked at the training load on triathletes. It found reduced activity in the portion of the brain that’s vital to decision-making.

Overtraining syndrome, as the study calls it, is a form of burnout. In endurance athletes, burnout is defined by an unexplained performance drop associated with intense exhaustion.

The researchers conducting the study aimed to demonstrate that physical training overload shares a link to the form of fatigue demonstrated after intense mental work.

The athletes in the study acted more impulsively in subsequent decision-making tests, opting for instant gratification rewards instead of goals that would take longer to achieve.

The study determined this is because both sport training and excessive cognitive work affect the same region in the brain, the lateral prefrontal region.

“The ‘overtraining syndrome’ causing declined cognitive abilities makes sense,” said Dr. Elan Goldwaser, sports medicine specialist at New York-Presbyterian/Columbia and its Sports Performance Institute.

“In fact, overtraining does more than just contribute to temporary cognitive fatigue. ‘Overdoing it’ can cause a lot of other health effects as well. A whole panel of abnormalities can afflict the body from overtraining, and the brain is no exception,” he said.

There’s no one definition of overtraining. All people are different. That said, there is a way to determine what might be overtraining per individual.

“When you start to feel fatigued during exercise, meaning winded or that you have difficulty thinking, speaking, or collecting your thoughts, it’s important to slow down and take a break,” said Dr. Robert Glatter, assistant professor of emergency medicine at Lenox Hill Hospital, Northwell Healthcare. “These are early signs that there is an importance to scale back and go easy on yourself.”

The initial idea for the study came from the National Institute of Sport, Expertise, and Performance in France, which trains athletes for the Olympics.

According to the researchers, some of the athletes were experiencing overtraining syndrome, which resulted in diminishing performance because of fatigue.

“The study looks at decision-making and the ability to have executive control when fitness levels are pushed,” Glatter said.

“The lateral prefrontal region of the brain is shared by physical and cognitive activity,” he said. “The study makes the important distinction that we need to look at those areas. Decisions that are made [when] fatigued reflect loss of control and lack of judgment.”

Such mental control is important in intense athletic training, the research suggests, because to maintain physical effort and reach a distant goal requires cognitive control.

“You need to control the automatic process that makes you stop when muscles or joints hurt,” Mathias Pessiglione, PhD, one of the corresponding authors of the study, said in a statement.

Just as an athlete would rest muscles and joints, it’s equally important to rest the brain between workouts.

Moderation is the key to exercise in general. Pushing to capacity is ultimately not the safe or beneficial decision.

The study suggests that athletes must recognize their limits not only because of how overtraining affects the body, but also how it affects the brain.

While you might think you’re being healthy, you could be hurting your ability to make important decisions about life.

“From a structural standpoint, the brain will be fine,” Goldwaser said. “But from a functional standpoint, there are theoretical micro injuries that begin to accumulate, similar to how concussion affects the brain, from overtraining.”

Goldwaser and Glatter suggest rest and letting the brain recover the same as we let muscles recover. Hydration, nutrition, and rest are imperative to the body’s recovery.

“One’s optimal fitness is a coin. On one side is our training — intensity, frequency, and repetition — while on the other side of that coin is our recovery,” Goldwaser said.

The study reveals the importance of planned and controlled workouts. Exercise can absolutely optimize our cognition and sharpen our brain, but as with anything, too much of a good thing can go awry. Overtraining may be reversing the benefits of exercise.

“With too much training and too little recovery, we end up hurting ourselves,” Goldwaser explained.