Abdominal Crunch Sit on the ball with your feet resting on the floor, about hip-width apart. Keep your back straight. Cross your arms on your chest. Tighten your abdominal muscles. Lean back, as shown, until you feel the muscles in your midsection tighten. Hold for three deep breaths. Return to the start position and repeat.
Also on these boards
30 Exercise Ball Core Workouts.