"Scientists and many athletes have known for years, of course, that a cup of coffee before a workout jolts athletic performance, especially in endurance sports like distance running and cycling." Caffeine increases the number of fatty acids in the bloodstream, which allows athletes' muscles to absorb and burn those fats for fuel, therefore saving the body's small reserves of carbohydrates for later on in the exercise."

At some point it becomes a banned substance in competition. Now you know why you're getting dropped.