Start in a standing position with your back facing a wall. Position the stability ball between you and the wall in the thoracic region of your back. Balancing on your right foot, slowly squat down and perform a single leg pistol squat by lifting your left foot off the ground. Squat as deep as you can. Rise and return to the starting position. Switch legs and repeat by balancing on your left foot. Repeat for a total of 5-10 reps on each leg