Lie prone on ball, with front of feet apart on floor or with feet against base of wall. Cross arms, hands in front of shoulders.
Raise torso off of ball by hyperextending spine. Lower torso onto ball allowing spine to flex. Repeat.
If no wall is available, hips can be positioned lower on ball and toes can be positioned out wide on floor for balance.
Movement can be made easier by placing hands behind hips or positioning hips low on ball.
Exercise can be made more challenging by positioning ball lower toward hips or positioning hands behind head or arms to sides of head. See Arm Position During Waist Exercises. Exercise is also more challenging on hyperextension apparatus.