Your brain triggers exhaustion long before your muscles reach their physical limit.

The Central Governor Theory was first proposed by Professor Tim Noakes of the University of Cape Town in 1997. The theory suggests that the brain, specifically the motor cortex, regulates exercise performance to maintain homeostasis. Rather than muscles failing from physical exhaustion, the brain subconsciously reduces neural drive to those muscles to protect the heart and other vital organs.Research published in the British Journal of Sports Medicine shows that fatigue is an emotional state rather than purely physiological. Studies demonstrate that when athletes receive a placebo or are told they have more distance to cover than they actually do, they often perform at higher intensities. This proves the body has significant "emergency reserves" that the brain normally keeps locked away.Elite endurance athletes—such as Olympic marathoners and Tour de France cyclists—undergo psychological conditioning to override these signals. By repeatedly exposing themselves to high-intensity discomfort, they increase their mental tolerance and access a higher percentage of their physical potential. However, even the most elite athletes rarely utilize more than 65–70% of their absolute muscle fiber capacity during sustained aerobic exercise.