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.
These recent findings, although done in a small group, provide evidence to support a hypothesis advanced by Tim Noakes, the well known author on endurance training, which is that physical fatigue is typically less about mechanical failure (in other words, the tissues themselves say “enough!”) and more about neurological and cognitive failure (in other words, the brain and central/peripheral nervous system say “enough!”).