Exercise Ball Crunch

The exercise ball is an excellent tool to strengthen the abs and is the third most effective move for targeting the rectus abdominis. What makes this move a bit more effective than crunches on the floor is that the legs are often involved in floor crunches. On the ball, the abs do more work, but you still involve the entire body to help stabilize you throughout the movement, a nice bonus that floor crunches don't always offer.

How to:

1. Lie on the ball, positioning it under the lower back.
2. Cross your arms over the chest or place them behind your head.
3. Contract your abs to lift your torso off the ball, pulling the bottom of your ribcage down toward your hips.
4. As you curl up, keep the ball stable (i.e., the ball shouldn't roll).
5. Lower back down, getting a stretch in the abs, and repeat for 1-3 sets of 12-16 reps.

View this exercise in the Best Ab Workout.