Mental Fatigue Can Feel Like Physical Fatigue

Does your workout feel more strenuous after a long day of thinking, problem solving, and decision-making? New research suggests that it’s normal to feel more physically exhausted when you’re mentally exhausted—but your body may be fooling you.

A study published in Medicine & Science in Sports & Exercise found that men who undertook mentally tiring tasks before exercising claimed to tire more quickly during physical exercise—but a test of the muscles they were working revealed that they were overestimating how tired they really were.

For the study, researchers in England and France had a group of men perform leg exercises under a variety of circumstances. During one, the men performed a test to induce metal fatigue, which involved sitting in front of a computer screen for ninety minutes, counting letters that passed by, and hitting keys depending on the configuration of the letters. During another session, the men watched a calming ninety-minute nature documentary. After both of these activities, the men performed leg exercises to the point of exhaustion, reporting how demanding they felt the exercises were.

After this, they were subjected to a contractile muscle test, where a small amount of electricity was shot through their legs, showing what their maximum contractile force available was; a more tired muscle ought to perform worse than a less tired one.

The men reported being exhausted thirteen per cent faster after their mental exercise compared to when they watched the nature documentary. Also, they reported that the exercises felt tougher. However, the results of their contractile test was the same—their muscles were just as able to perform difficult exercises during both sessions, suggesting that they weren’t as tired as they thought they were after being mentally exhausted.

So, something to keep in mind when you’re planning out your gym sessions: you’ll get your best performance not only with a well-rested body, but with a well-rested mind.


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