Lie prone on ball. Position toes out wide on floor for balance. Hold weight under chin or behind neck.
Raise torso off of ball by hyperextending spine. Return torso to ball and repeat.
Movement can be made easier by using no additional weight or by positioning hips low on ball. In contrast, exercise can be made more challenging by positioning ball lower toward hip. In which case, feet may be placed against base of wall for stability. See Arm Position During Waist Exercises. If weight is positioned behind head, neck extensors act as stabilizers.