During aerobic exercise, what fuel sources are utilized?

During aerobic exercise, the body primarily utilizes fats, proteins, and carbohydrates as fuel sources, and this process occurs in the presence of oxygen. The utilization of these substrates allows for the production of ATP (adenosine triphosphate), which is the energy currency that fuels muscle contractions and cellular processes during extended physical activity.

In aerobic metabolism, carbohydrates are converted into glucose, fats are broken down through lipolysis, and proteins can also contribute when carbohydrates and fats are insufficient. Oxygen is essential for these processes, as it participates in the oxidative phosphorylation pathway in the mitochondria, where most ATP production takes place.

While carbohydrates are often the preferred source of energy, especially during higher-intensity activities, fats provide a significant energy yield during prolonged, lower-intensity exercises. Proteins serve as a last resort source of energy and are typically used more for recovery and rebuilding muscle than for fuel during exercise. This comprehensive use of multiple fuel sources, in conjunction with oxygen, highlights the efficiency of the aerobic energy system during sustained activities.