Carbohydrates are the main fuels during exercise at intensities above 65 percent of maximum effort. Carbs are important fuels during intense exercise because they provide more energy per unit of time than fats. While people have plenty of fat to fuel exercise, carbohydrate stores
are limited to approximately 400 grams distributed in the liver and skeletal muscles. Post-exercise meals are critical for restoring depleted glycogen stores, but should these meals be high or low in simple sugars?
British researchers found that the glycemic index of a meal consumed between two intense bouts of endurance exercise (90 minutes at 70 percent of maximum effort, on two consecutive days) had no effect on the depletion rate of muscle or liver glycogen. Glycemic index is a measure of how fast foods increase blood sugar. High-glycemic index meals are high in simple sugars, while low-glycemic index meals contain more complex carbohydrates and fats. During the second exercise session, intramuscular fat use during exercise was higher following the high-glycemic index meal. This was an interesting and sophisticated study, but we need more research on the influence of diet during repeated days of intense exercise.