Capitalize on the instability of an exercise ball, and try the tuck crunch. This move strengthens your core while toning your arms, chest, shoulders, and lower abs.
- Get into a plank with your shins on the ball.
- Pull your knees toward your chest, and then shoot your legs back out. Keep your body in a plank position the entire time.
- Do three sets of 15 to 20 crunches.