Back Extensions on the Ball

Using a ball for back extensions will give you more range of motion than you get on the floor and you'll also have a balance challenge since the ball is unstable. You may want to prop your feet against the wall to get more leverage.

1. Lie down with the ball under the belly and hips, legs straight out behind you (or knees bent for a modification).
2. Place the hands behind the head or under the chin - you can also keep the hands resting on the ball if you need a modification.
3. Round down over the ball and then squeeze the lower back to lift the chest off the ball.
4. Raise up until the body is straight (don't hyperextend), lower down and repeat for 1-3 sets of 10-16 reps.

http://exercise.about.com/od/strengthtrainingworkouts/ss/backexercises2_2.htm