Ball roll-ins exercises your central abdominal muscles.
1. To begin, place your hands on the ground and the top of your feet atop the ball.
2. Keep your hands anchored in place then, bend at the knees to bring the ball toward your chest.
3. Hold this position for 1-3 seconds and roll the ball back out. Remember to squeeze your abs throughout the movement and do not use your hip flexors to move the ball toward you.