And be careful about many ab exercises, since many can cause back
problems later on. In fact, most crunches work the lower back
as hard as they do the abs, and all that twisting can be a strain. Not that anyone knows how to best work the abs, though, as far as I can tell. For six pack abs, quite frankly, most who have them don't get them through exercise -- it's a sure sign of steroid use, since the belly should have some fat.