1, Abdomen reduction: Sit on the ball first, adjust your body's center of gravity, put your center of gravity in front of the ball, keep your body balanced, and don't shake your body.

2. Lie on your back, bend your legs, and touch your knees left and right: your back doesn't have to be lifted off the ground too much, and your waist can't be lifted. It is enough to lift the shoulders and part of the lower back.