SECRET OF CHAMPIONS: "Carbohydrate loading" is a proven method of increasing endurance in long-lasting athletic events. Three to four days before the event, the athlete begins limiting his training to very mild workouts (running only one to three miles if he's a marathoner, for example) & eating a diet that takes 70 percent of its calories from carbohydrates, instead of the usual 50 to 60 percent. Some runners find that this nearly doubles their staying time.