What is the primary substrate used during prolonged aerobic exercise?

During prolonged aerobic exercise, the body primarily relies on fatty acids as the main substrate for energy production. As exercise duration increases, glycogen stores (sugar) start to deplete, and the body shifts towards utilizing fats due to their abundance and energy-rich composition. This metabolic switch is advantageous because fatty acids provide a more sustained and efficient energy source for extended periods of activity, especially at lower intensities.

Additionally, fatty acids release more ATP per gram compared to carbohydrates, making them a preferred fuel source during prolonged endurance activities. While sugars do play a crucial role, especially in the initial phases of exercise, the increased reliance on fatty acids during longer durations is a key aspect of the body's energy management strategy in aerobic conditions.