Final answer:
Carbohydrate supplementation is most important for exercises lasting over 60 minutes, where maintaining blood glucose levels is crucial for performance. Shorter events rely on ATP and creatine phosphate or glycogen stores which are typically sufficient without additional carbohydrates.
Step-by-step explanation:
Carbohydrate supplementation during exercise is most important in performances lasting longer than 60 minutes. This is when glycogen stores tend to be depleted and maintaining blood glucose levels becomes critical for continued performance and endurance. Carbohydrate loading is a strategy used before endurance events like marathons to maximize glycogen stores in muscles and the liver. During shorter high-intensity activities, such as those that last 3 to 20 minutes or 30 to 180 seconds, the body primarily relies on stored ATP and creatine phosphate, followed by glycogen stores. However, these stores can supply the needed energy without the immediate need for additional carbohydrates. For very short-duration exercises of less than 10 seconds, energy is supplied almost exclusively by ATP and creatine phosphate, with no need for carbohydrate supplementation.