During exercise, the body utilizes glycogen as a key energy source, particularly during high-intensity workouts. Glycogen, stored in the muscles and liver, breaks down into glucose for immediate energy production. As exercise intensity increases, the demand for quick energy rises, making glycogen the preferred fuel. However, prolonged exercise can deplete glycogen stores, which is why replenishing these stores with carbohydrates post-exercise is important. This process supports endurance and performance in subsequent workouts and aids in overall recovery for athletes and fitness enthusiasts alike.