1. Sit on top of an exercise ball, feet placed firmly on the floor. Slide forward, rolling the bottom half of your glutes off the ball, until your lower back is centered atop of the ball. Place your hands at the sides of your head.
2. Crunch your upper body forward, rolling your shoulders toward your hips. Squeeze your abs at the top of the movement, lower and repeat.
Weighted Swiss-Ball Crunch
Grab a weight plate and lie back on a Swiss ball. Hold the weight against your chest [1]. Tuck your chin to your chest and crunch your rib cage toward your pelvis [2]. Lower your body to the starting position. That's one rep.