Muscles involved: Rectus Abdominus, Obliques, Hip Flexors and Shoulder Girdle.
Action: Start by getting into a pushup position with the tops of your feet on a Swiss ball. Your body should form a straight line from your toes to your shoulders with your hands positioned just slightly wider than your shoulders.
Keeping your back flat and abs tight, bend your knees and roll the ball toward your torso. Squeeze your abs for a second and then roll the ball back to the starting position. Repeat for the desired number of repetitions.
Comments: Keep the movement smooth and be sure to keep your spine in a neutral position. In other words, don’t let your hips drop.