Answer:
transition from almost exclusively carbohydrate to mostly fat
Step-by-step explanation:
When an athlete is performing high-intensity aerobic exercise, this is for strength and hence exercise for strength needs an athlete to take more of food with carbohydrates and not that of fats, as what is needed is energy. However, when the reason for the exercise is now for endurance, longer-duration submaximal exercise is performed and then the best food for such exercise is fat, as the exercise turns most of the fats into muscle.