Which substance is known for its role in enhancing endurance performance?

Caffeine is well-documented for its ability to enhance endurance performance, making it a popular choice among athletes. It acts primarily as a central nervous system stimulant, which can reduce the perception of fatigue during prolonged physical activity. By increasing adrenaline levels, caffeine can enhance the ability to perform high-intensity exercise and improve overall endurance. Additionally, it has been shown to promote the mobilization of fatty acids from body fat, making them available for energy use during prolonged workouts. This helps in preserving glycogen stores, which is crucial for sustained performance.

In contrast, casein is a slow-digesting protein that is beneficial for muscle repair and growth but does not have a direct role in enhancing endurance performance. Glutamine, while important for recovery and immune function, is not primarily associated with endurance enhancement. DHEA (dehydroepiandrosterone) is a hormone that may impact overall energy levels and hormone balance but lacks strong evidence in enhancing endurance capabilities effectively.