Hold a medicine ball (or unweighted ball) and lie flat on your back with knees bent, legs hip-width apart, abs engaged, and ball next to your chest, elbows bent. Have a partner kneel in front of you, placing pressure on your feet (optional) to help stabilize your legs.
EXHALE: Keep your back straight and use your abs to sit up, bringing your chest toward your thighs and your back off the floor as you simultaneously toss the ball to your partner. INHALE: Slowly lower back down toward the floor (as your partner tosses the ball back to you) and catch the ball before you return to the starting position to complete one rep.
Practice extreme caution with this exercise, which requires good hand-eye coordination. Try it with a light or unweighted ball first and gradually progress to a heavier ball. Try to toss and catch the ball in line with the chest (not overhead or near your abdomen) as much as possible. Keep your shoulders relaxed and your spine neutral. Make sure your spine doesn't arch or round during the exercise. Do not let your feet come off the floor.
Muscles Worked: Abs