Tire your brain and your body may follow, a remarkable new study of mental fatigue finds. Strenuous mental exertion may lessen endurance and lead to shortened workouts, even if, in strict physiological terms, your body still has plenty of energy reserves.

Scientists have long been intrigued by the idea that physical exertion affects our ability to think, with most studies finding that short bouts of exercise typically improve cognition.

Prolonged and exhausting physical exercise, on the other hand, may leave practitioners too worn out to think clearly, at least for a short period of time.

But the inverse possibility that too much thinking might impair physical performance has received far less attention. So a team of scientists joined forces to investigate the matter. They found that exercise simply feels harder when your brain is tired, so you quit earlier, although objectively, your muscles are still somewhat fresh.

This finding has multiple implications for how we combine ratiocination and sweat. It suggests, for instance, that the morning of an important race or challenging training session may not be the ideal time to finish your taxes, since overthinking could lead to underperforming physically.

Inversely, the results also suggest that training our brain to avoid or limit mental fatigue could be a hitherto untapped means of improving physical performance.

Training yourself to speed through crossword puzzles, in other words, might improve your workouts, by subtly altering how mind and muscles communicate and making your brain less likely to consider your muscles easily enfeebled.

“But that possibility hasn’t been tested,” Lepers said. For now, his study’s most compelling conclusion is that, as he says, our feelings do not always reflect our physiological state and our bodies may in many instances be sturdier than own minds realise, an idea worth thinking about.

— New York Times News Service