Target Muscles: rectus abdominis, transverse abdominis
What to Do: two to three sets of 10 to 15 reps.
Set Up: Get into push-up position with your hands directly under your shoulders; place your feet on top of a stability ball. Action: Contract your abs as you raise your hips up, directing your tailbone toward the ceiling as you bring the ball in towards you; your body should resemble an upside-down V as shown. Make sure the movement occurs only at your hips, and don't round your shoulders. Slowly reverse to return to the start and repeat for the remainder of your set.