The body uses glucose during physical activity as a primary source of energy. When exercising, glucose is broken down through the process of glycolysis to produce ATP (adenosine triphosphate), which fuels muscle contractions. During high-intensity workouts, the body relies more heavily on glucose compared to fat stores for quick energy. The body stores glucose in the form of glycogen in muscles and the liver, which is mobilized during exercise to maintain blood sugar levels and sustain energy output. Understanding this process can help athletes optimize their nutrition and fuel for optimal performance.