Exercise physiology explains muscle fatigue as a complex process involving various physiological factors. Fatigue occurs when the energy supply in muscles diminishes, primarily due to depletion of creatine phosphate and glycogen stores. Accumulation of lactic acid from anaerobic metabolism also contributes to discomfort and decreased muscle function. Additionally, electrolyte imbalances and neuromuscular factors can lead to fatigue. Understanding these mechanisms allows athletes and trainers to develop strategies to enhance endurance, optimize recovery, and improve performance across various physical activities.