What macronutrient is primarily responsible for providing energy during high-intensity exercise?

Carbohydrates are primarily responsible for providing energy during high-intensity exercise due to their ability to be quickly broken down into glucose, which can then be utilized for immediate energy needs. When engaged in high-intensity physical activities, such as sprinting or heavy weightlifting, the body relies heavily on anaerobic glycolysis, where glucose is converted to energy without the need for oxygen. This quick energy production from carbohydrates is essential for maintaining performance levels during such strenuous activities.

In contrast, proteins primarily serve as building blocks for muscle repair and growth rather than as a primary energy source during exercise. While fats are a significant energy source during lower-intensity, prolonged activities, they are not as efficiently utilized during high-intensity efforts due to their slower oxidation rate. Vitamins, although crucial for various metabolic processes, do not directly provide energy. Thus, carbohydrates are uniquely suited to meet the energy demands of high-intensity exercise, making them the key macronutrient in this context.