Carb Loading: What is it and how do you incorporate it before a race? Carb loading is a widely used nutrition strategy among endurance athletes, including triathletes, to maximize muscle glycogen stores - the stored form of carbohydrates that serves as a primary fuel source during prolonged, high-intensity exercise like a triathlon. During events such as Olympic-distance, 70.3, or full Ironman races, your body relies heavily on glycogen for energy, especially when pushing