What is the primary energy substrate used during high-intensity exercise?

During high-intensity exercise, the primary energy substrate utilized by the body is carbohydrates. This is largely due to the need for rapid energy production that carbohydrates can provide through anaerobic processes. When engaging in high-intensity activities, the body requires energy quickly, and carbohydrates are broken down through glycolysis to produce adenosine triphosphate (ATP) efficiently.

Carbohydrates can be stored in muscles and the liver in the form of glycogen, and during intense exercise, this glycogen can be rapidly converted back to glucose, allowing for sustained energy output. This process is especially important during activities such as sprinting or heavy lifting, where energy demands exceed what can be met by other substrates.

Fats, while a significant energy source during lower-intensity, longer-duration exercise, require more oxygen for metabolism and are not as effective during high-intensity bursts. Proteins serve primarily as a building block for tissues, rather than as a primary energy source. Vitamins play crucial roles in metabolic processes, but they do not serve as energy substrates themselves. Thus, carbohydrates are the most efficient and readily accessible energy source during high-intensity exercise.