Begin lying on your back with your legs in the air, toes toward the ceiling, holding the medicine ball over your chest. Engage your abs to press your lower back into the mat while lifting your head, neck, and upper back off the mat.
Exhale, and round your lower back, so the bottom of the pelvis raises as you lift your upper body an inch higher off the mat. Aim the medicine ball higher up your leg as you perform this double crunch, engaging both the upper and lower abs.
Inhale, and lower your pelvis and upper back an inch toward the floor. This completes one rep.