Primary Muscle Group: Core Muscles
Muscle groups worked in this exercise: Upper and Lower Abdominals
Preparation: Start by sitting on the ball with your knees bent and feet flat on the floor. Slowly walk your feet forward as you slide your torso down the ball. Your trunk should be parallel to the floor. Just let your hips clear the ball and let your lower back press into the ball; cross your arms over your chest.
Breathing: Exhale as you lift. Inhale as you relax back to starting point.
Execution: If you're really feeling strong, try extending your arms over your head, palms together, to increase resistance again. Now crunch!