Exercise Ball Crunch
To perform the Exercise Ball Crunch, you sit on an exercise ball with your feet flat on the floor. Move your feet forward allowing the ball to travel down your back until it supports your lower back. Cross your arms on your chest or place them lightly behind your head. Tighten your abs and lift your torso off the ball, pulling the bottom of your ribcage down toward your hips. Lower back down, getting a stretch in the abs, and repeat.