If you want shredded abdominals, you need less than 10-percent body fat. There is nothing on this planet that will lean you out as quickly as sprinting. According to Kalama, sprinting in soft sand adds the benefit of improving your stability. "It targets your toes, your feet, your ankles, calves, and the fronts of your shins," Kalama says. "It gets all of that really strong, and that equates to board control."
If you haven't been sprinting, start out with 10 reps at 40 yards each. Add two more to your routine every time you train, and watch your body transform.