How to do it: Lie facedown with your elbows bent out to the sides, palms stacked, resting your chin on your hands. Bend your knees and open them to the sides. Flex feet and press heels together. From there, press your heels up to the ceiling, lifting thighs off the floor as high as possible. Lower thighs to floor and immediately repeat (be sure to keep upper body steady as legs lift). Try up to 3 sets of 20 reps.