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A workout can be the perfect antidote to a stressful workday filled with endless emails and demanding deadlines. But that “my brain is fried” feeling could make your sweat session less effective, according to new research published in the Journal of Sport and Exercise Psychology.
In the study, 20 subjects ran two simulated 1.86-mile (3,000-meter) races on different days. Immediately before one of the races, the runners took a difficult test conducted on a computer for 90 minutes. The researchers wanted to see if mental burnout would affect physical performance. And in fact, the runners were about 15 seconds slower after taking the test, finishing in 11 minutes and 58 seconds, on average.
“Brain tissue is similar to muscle tissue—at some point the tissue is going to fatigue,” said Ranjana Mehta, a biomechanics researcher at Texas A&M Health Science Center who was not affiliated with the study.
Mental fatigue can occur when you have a lot of taxing meetings, when you have to solve a complicated problem, or even when you’re planning an elaborate party. “You can be tired after a hard day using your mind at work and with things going on in your life, and then not realize that this is the reason for a decline in your performance, not your level of fitness,” said study author Clare MacMahon of Swinburne University of Technology in Australia.
Another reason for the runners’ weaker finishes: Both physical and mental exhaustion affect the same region of the brain, the anterior cingulate cortex. “It’s possible that there was a decrease in the runners’ muscular endurance because the brain region responsible for sending the signals to the muscles became tired,” Mehta told Yahoo Health.
Brain drain may also make physical activity feel more difficult, which can diminish performance, previous research suggests. In one study, scientists from Bangor University in the United Kingdom asked 90 cyclists to ride a stationary bike as long as possible. The cyclists finished in an average of 12 minutes and 34 seconds. But when they played a challenging brain game before the ride, they gave up after 10 minutes and 40 seconds and said the workout felt significantly more difficult.
In the running study, however, the subjects said both races were equally as difficult. They may have slowed down in order to keep their level of effort the same, the study authors wrote.
The encouraging news: It’s not difficult to recharge your brain before your workout. “Some research indicates that taking a walk in nature, or even just watching a video of nature scenes, can help regenerate cognitive resources,” MacMahon told Yahoo Health. “There are two five-minute videos of outdoor scenes that we use experimentally, and both [study coauthor] Linda Schuecker and I have been known to go pull them up from our computers and play them and watch them when we ourselves feel a little zapped and need a boost.”
Watch the video below for your own 5-minute zen break: