Here’s a little science you can use: Researchers at Bangor University in the UK found that mental fatigue impairs physical performance. The subjects in the study cycled to exhaustion at 80% of their peak power output after either performing a 90-minute mentally-demanding task (a computer matching test) or watching a non-mentally demanding video. Subjects in the mentally fatigued group took significantly less time to reach exhaustion and rated their perceived exertion as higher than did subjects in the non-mentally fatigued group. The two groups did not differ on several physiological measures (e.g., heart rate, cardiac output, oxygen consumption), suggesting that subjects in both groups worked the same, but the mentally fatigued subjects tired more easily.

What’s this mean for you? The study suggests that mental fatigue can limit your endurance, and therefore can decrease your sport performance. So, the next time you’re tapering your physical training before a big competition, consider giving your mind a rest, too!