Muscle fatigue is a temporary condition that occurs when muscles become less capable of generating force. This can happen during or after intense physical activity, leading to a feeling of weakness or tiredness in the affected muscles. Factors contributing to muscle fatigue include the depletion of energy sources, the accumulation of metabolic byproducts, and changes in the nervous system's ability to stimulate muscle contractions. During exercise, the body uses glycogen stored in muscles for energy. As these energy reserves diminish, the muscles may struggle to perform at their usual capacity. Proper rest, hydration, and nutrition can help alleviate muscle fatigue and promote recovery, allowing muscles to regain strength and function.