Philosophy

Cardiovascular exercise before breakfast burns 300% more fat than cardio after breakfast. Stored bodyfat is burned because glucose, glycogen, and insulin levels are low after the 8-12 hour fast. You can do whatever you want as long as the intensity is high enough. You could go to cross country practice, do 20 min. of HIIT biking or running, bike for a long distance, or kayak. Don't sit around letting yourself starve after the exercise, though; consume at least some protein and maybe carbs very shortly after the workout.