What is the primary fuel source during high-intensity, anaerobic activities?

During high-intensity, anaerobic activities, the primary fuel source is carbohydrates. This is because carbohydrate metabolism can rapidly provide the energy required for explosive movements, which usually occur in activities like sprinting, weightlifting, or high-intensity interval training.

In the absence of oxygen, the body relies on a process called glycolysis, which breaks down glucose to produce ATP—the energy currency needed for muscle contractions. Glycolysis is much quicker than the process of oxidizing fats or proteins, making carbohydrates the preferred source when quick bursts of energy are necessary.

While fats and proteins can be utilized as energy sources during prolonged or lower-intensity activities, they do not provide the same rapid energy output as carbohydrates. Additionally, amino acids, although they can be converted to glucose through gluconeogenesis, are generally not a primary energy source during high-intensity efforts.