Researchers have now shown experimentally that mental work is physically exhausting.

In a British study published in The Journal of Applied Physiology, researchers recruited 10 men and 6 women to perform a computer exercise requiring concentration, memory and reaction speed. Then the participants exercised on a stationary bicycle until they were exhausted - unable to maintain a cadence of 60 revolutions per minute. On another day, as a control, their physical exercise was preceded by 90 minutes of watching documentary films about cars and trains.

Even though there were no significant differences in physiological measures under the two conditions, bicyclers consistently tired about 15 percent more quickly after the mental exercise than after watching the movies. Apparently, their poorer exercise results after mental effort were caused by exhaustion of their minds.

“This tests whether the brain on its own can limit physical performance, and it turns out that it can,”said Samuele M.Marcora, the lead author and a senior lecturer in physiology at Bangor University in Wales.“If you want to improve fitness at maximum levels, you’re probably better off doing training when you’re not mentally fatigued.”


NICHOLAS BAKALAR