MUSCLES ENGAGED Abdominals The abdominal muscles (abs) provide movement and support to your core area. The deeper and closer to the spine the particular abdominal muscle is, the more effect over body posture it will have, and this often contributes significantly to a healthy back. Equipment Used Stability Ball A stability or exercise ball is a ball constructed of soft elastic and filled with air until firm.Most stability balls range from a diameter of approximately 35 to 85 centimeters (14 to 34 inches). Bench A weight training bench is a piece of equipment that has a resemblance to a normal (e.g. park) bench, but is cushioned and designed for use in the weight room. Exercise Instructions Step 1 Start lying down on a bench. Lift your shoulders up off of the bench to engage your upper abs. Place the stability ball between your legs and hold it there by contracting the abducutors in your inner thighs. Step 2 Slowly raise the stability ball up by contracting your lower abs. Control your breathing throughout he exercise and be sure to keep your lower back pressed firmly to the bench. Step 3 Lower the stability ball back down to the starting position and repeat the action.