Side Crunch On Ball
Instructions: Firmly place your left hip on a Swiss ball and lean into the ball; make sure that your torso is off the ball. Support yourself by pressing the sole of your right foot against the bottom of a wall or a sturdy object. Place your hands by your ears and contract your right oblique muscles, lifting your torso up as far as you can. Hold for three seconds and release.
Do 10 reps and repeat on the opposite side.