What substance primarily fuels the body during high-intensity exercise?

During high-intensity exercise, carbohydrates serve as the primary fuel source for the body. This is due to the fact that carbohydrates, particularly in the form of glycogen stored in muscles and the liver, can be rapidly broken down to provide energy through anaerobic glycolysis. This metabolic pathway is crucial during intense activities such as sprinting or heavy weightlifting, where the demand for energy exceeds the oxygen availability for aerobic metabolism.

Carbohydrates can be used efficiently at high intensities because they provide quick energy, while fats and proteins do not meet the immediate energy requirements as effectively. Fats require more oxygen to oxidize fully and are predominantly used during prolonged, lower-intensity exercises. Proteins have a minimal role in energy production during exercise and are typically utilized for muscle repair and growth rather than as a primary energy source. Minerals, while essential for various metabolic processes, do not serve as fuel but rather support functions such as enzyme activity and muscle contraction.

Thus, carbohydrates are uniquely suited to meet the energy demands of high-intensity activities, making them the primary fuel source during such exertions.