HOW: Begin this exercise laying on your back with your heels resting comfortably on a swiss ball with your knees straight. Once in this position, gently bend your knees bringing your knees towards your chest in a controlled manner. As you bring your knees into your chest, allow the knees to do as much work as possible with the ball assisting to perform the motion. Once the knees are bent as far as you feel comfortable or recommend, return to the starting position.
FEEL: You should feel the muscles of the hamstrings and core working as you bend your knees, then your thigh muscles working as you straighten your legs.
COMPENSATION: Keep your hips and low back resting on the ground, avoid lifting this area off the ground as you perform this exercise.