Which macronutrient is most critical for endurance athletes?

Carbohydrates are the most critical macronutrient for endurance athletes because they serve as the primary source of energy during prolonged physical activity. When engaging in endurance sports, such as running, cycling, or swimming, the body relies heavily on stored carbohydrates in the form of glycogen. During long-duration exercise, maintaining adequate glycogen levels is essential for sustaining energy output and performance.

Carbohydrates provide a quick and easily accessible source of energy, which is crucial for endurance athletes who need to maintain intensity over extended periods. When glycogen stores are depleted, athletes may experience fatigue, decreased performance, and an increased risk of injury. This is often referred to as "hitting the wall" in long-distance running.

In contrast, while fats can also contribute to energy production during lower intensity and longer duration activities, they are not as readily available as carbohydrates for quick bursts of energy, making carbohydrates a preferred fuel for endurance performance. Proteins primarily play a role in muscle repair and recovery rather than serving as a direct energy source during endurance activities. Vitamins, while essential for overall health and metabolic functions, do not contribute to energy production in significant amounts compared to carbohydrates, fats, and proteins.