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 Medicine Ball A medicine ball (also known as an exercise ball, med ball, or fitness ball) is a weighted ball roughly the diameter of the shoulders (approx. 14 inches). Medicine balls come in a variety of weights from 2lbs. to 30lbs. and can be made of hard plastic, dense rubber or synthetic leather material. Exercise Instructions Step 1 Start with you back pressed firmly against the mat, the stability ball between your feet and a medicine ball of appropriate weight in your hands. Step 2 Lift your legs up using your lower abs while crunching up with the medicine ball by contracting your upper abs. Meet and touch at the top and lower yourself back down. Step 3 Open your body back up, lower yourself back down to the starting position and repeat action.