Plank Leg Lifts on the Ball prepare the core stabilizers for original Pilates mat exercises such as Leg Pull Front and Push Up. By varying the position of the ball, you can make the exercise easier (if the ball is under the thighs) or harder (if the ball is under the shins). This exercise strengthens the core, the shoulder stabilizers and arm muscles and tones the muscles of the legs. Please visit http://www.PilatesOnFifth.com (for more info), http://www.UltimatePilatesWorkouts.com (for more videos)and http://www.Shop.PilatesOnFifth.com (for store)