Sit on floor facing wall with knees bent. Hold medicine ball with both hands near chest.
Lie back while hold ball near chest. Raise upper body up by first flexing spine and then flexing hips. While completing sit-up, throw ball toward wall. Catch ball bouncing off of wall with both hands. Reposition ball near chest while laying back. Repeat.
Perform prescribed repetitions or for time. 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.
Exercise intensity can be decrease by keeping ball closer to hips instead of near chest during sit-up.