Sit on floor facing wall with knees bent. Hold medicine ball with both hands.
Lie back with ball over head and tap ball to floor. Immediately throw ball to wall from over head while sitting up. Ball rebounds off of wall. Catch ball slightly above and in front of head. Continue to volley ball against wall.
Perform prescribed repetitions or for time. Wall should be impact resistant to avoid structural damage. Feet may also be secured under weighted or anchored structure. If feet are not being supported by fixed object, legs may need to be extended somewhat to offer adequate counter balance to upper body.
If upper back does not come completely down at end of movement, abdominal muscles may only be isometrically involved in exercise. See Spot Reduction Myth. Also see Medicine Ball Sit-up Throw with partner and Medicine Ball Sit-up on Machine.