Mental fatigue affects physical endurance

BANGOR , Wales, Feb. 24 (UPI) -- Performing a mentally fatiguing task prior to an exercise test can result in people feeling more exhausted, Welsh researchers said.

The study also found that mental fatigue did not cause the heart or muscles to perform any differently -- instead, people's "perceived effort" determines when people reach exhaustion.

Samuele M. Marcora, Walter Staiano and Victoria Manning of Bangor University in Wales said mental fatigue impairs physical performance in humans.

The 16 participants rode a stationary bicycle to exhaustion under two conditions -- once when they were mentally fatigued and once when they were mentally rested. Throughout both exercise sessions, the researchers tracked a variety of physiological measures -- such as oxygen consumption, heart rate, cardiac output, blood pressure, ventilation and blood lactate levels.

The study, published in the March issue of the Journal of Applied Physiology, found the participants stopped exercising 15 percent earlier, on average, when they were mentally fatigued.

The researchers speculate that mental fatigue lowers the brain's inhibition against quitting, or affects dopamine, a brain chemical that plays a role in motivation and effort.