You are so overcome with fatigue and aching muscles after running 15 laps that you just want to lie down and rest. Blame a brain mechanism rather than your physical prowess that limits performance and ensures one's own limits are not exceeded, a study reveals.

The study led by neuro-psychologist Kai Lutz from the University of Zurich with Urs Boutellier from ETH Zurich, Switzerland, discovered neuronal (brain cell) processes reduce muscle activity during muscle-fatiguing exercise, the European Journal of Neuroscience reported.