Glycogen serves as a primary energy source stored in the liver and muscles, critical for physical performance. During exercise, the body converts glycogen into glucose, fueling muscular activity. The liver releases glycogen into the bloodstream to maintain blood sugar levels during fasting or intense exercise. However, glycogen stores can become depleted during prolonged activity, leading to fatigue. Therefore, athletes focus on replenishing glycogen through proper post-exercise nutrition, which enhances recovery and prepares them for future performance.