How excessive exercise affects our brains

According to the U.S. Centers for Disease Control and Prevention, two and a half hours of moderate-intensity exercise or 75 minutes of high-intensity exercise performed each week can improve memory, protect against cognitive decline, and enhance learning. But does excessive exercise also affect the human brain? UNN looked into this.  

Exercise stimulates physiological changes in the body, such as stimulating the production of growth factors, chemicals that affect the growth of new blood vessels in the brain and even the number, survival, and overall health of new brain cells. 

Many studies have shown that the parts of the brain that control thinking and memory are larger in volume in people who exercise than in people who do not. Exercise can also indirectly improve memory and thinking by improving mood and sleep, as well as reducing stress and anxiety.

Bigger doesn't mean better 

But regular excessive exercise does not improve cognitive function. Scientists have concluded that serious physical activity has a negative impact on cognitive control, which jeopardizes the capacity of our brain. But there is no way to predict in advance how much of an impact this will have.

A 2019 study was conducted with 37 male athletes under the age of 35. Part of the participants were allowed to do their normal workouts, while for others the workout was increased by 40%. The experiment lasted for 3 weeks. All participants underwent MRI scans to check their cognitive abilities. The scientists then concluded that increased exercise affects the brain's ability to think and understand, and decreases the ability to make decisions. The results of this study were published in the journal Current Biology. The article indicates a decrease in brain activity observed in the lateral prefrontal cortex, an area of the brain that plays a role in decision-making and cognitive control. The scientists also noted a decrease in motivation in the study participants whose physical activity was increased.

Similar findings were reported in a 2023 systematic review published in Sports Medicine - Open. In preparing the review, analysts examined the results of seven different studies related to athlete overtraining and cognitive function. Although the studies used many different methods of data collection, one method, namely the Stroop verbal-color test, was common to all. The results of the test showed that athletes who were diagnosed with functional overtraining (increased activity of an organ or organ system), a short-term decline in performance caused by increased training intensity, showed slower performance on cognitive tasks than other participants in the experiments. Participants with overtraining took longer to read the name of a color as well as the color the word was written in (e.g., the adjective "blue" was written in red).  In their findings, the reviewers emphasized that overtraining can pose a health risk to athletes if they are not given adequate recovery time.

What intensity of exercise is good for the brain?

Researchers lean toward the need to aim for at least regular exercise of moderate intensity  -  such as brisk walking - for 150 minutes per week. Start with a few minutes a day and increase this amount by five or 10 minutes each week until you reach your goal. Most experts notethat aerobic exercise is better for the brain. But even if you prefer a different type of exercise or are no longer new to the sport, it's important to remember that overtraining is not something to strive for.

It should also be remembered that the real benefits, not only for the body as a whole, but also for the brain appear when we exercise regularly. For example,  a study published in the journal Nature human behavior showed that people who exercise several times a week, on average, have higher cognitive test scores than people with sedentary lifestyles. Another study showed that human cognitive performance tends to improve after participating in a new aerobic exercise program for several months.

Scientists don't guarantee that exercise will have the same positive effect on everyone's brain. But they note a general positive trend, if only because sport improves mood, reduces stress and depressive manifestations.