Mental fatigue can affect physical...( BETHESDA Md. (Feb. 24 2009) − ...)

BETHESDA, Md. (Feb. 24, 2009) − When participants performed a mentally fatiguing task prior to a difficult exercise test, they reached exhaustion more quickly than when they did the same exercise when mentally rested, a new study finds.

The study also found that mental fatigue did not cause the heart or muscles to perform any differently. Instead, our "perceived effort" determines when we reach exhaustion. The researchers said the next step is to look at the brain to find out exactly why people with mental fatigue perceive exercise to be more difficult.

Samuele M. Marcora, Walter Staiano and Victoria Manning of Bangor University, Wales, the United Kingdom, did the study, "Mental fatigue impairs physical performance in humans." The study will appear in the March print edition of the Journal of Applied Physiology. The American Physiological Society published the study.

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. The trials took place in the laboratory on different days. The participants got the same amount of sleep, drank the same amount and had the same meal before each of the sessions.

The mental fatigue sessions began with a challenging 90-minute mental task that required close attention, memory, quick reaction and an ability to inhibit a response. After undergoing this session, participants reported being tired and lacking energy. The control session consisted of watching neutral documentaries for 90 minutes and was not mentally fatiguing.

After each of the 90-minute sessions mentally fatiguing or non-fatiguing the participants did an intense bout of exercise on a stationary bicycle. They rode until exhaustion, defined as the point when they could not maintain a cadence of at least 60 revolutions per minute for more than five seconds.

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