Supposed to be the best ab workout ever

I don't think I am coordinated enough to try it! My co-workers and I discussed it this morning. They promised to visit me in the hospital!

It's really only good if you already have pretty amazing core strength...otherwise you WILL use your lumbar paraspinals for stabilizing (to keep from collapsing in your lower back) and probably will use your rector femoris or other hip flexors to draw in the ball. Also, I think you are more likely to use upper back muscles (serratus anterior and rhomboids) to stabilize during the part where you push all the way forward than to use your oblliques.

Still a hard/useful exercise (lots of transverse abdominus, which is important, and rectus abdominus, which it less useful but does give men that nice six-pack), but for core strength I would concentrate on front/side planks keeping your head, neck, rib cage, and pelvis and heels all in one straight line and abs engaged so there is no collapsing in the lower back. Oncd you can hold all three (front, right side, left side) for 90 seconds each without rest, THEN I would try something like this.

Just my $0.02 (from a PT-in-training).