1 While lying on your back, place your lower legs on a Swiss ball. Then, put your hands flat on the floor next to your hips. 

2 Push your hips up so that your body forms a straight line from your shoulders to your knees. Without pausing, pull your heels toward you and roll the ball as close as possible to your butt.

3 Pause, then roll the ball back until your body is in a straight line again.