I've been doing these for about two months, I do three sets of 50 reps only twice a week. Gals, I can't believe the shape difference in my legs. My partner even commented on it! It's works the core muscles and the hamstrings, but I think it really shapes the quad too.

Give them a try. And doing them single-legged is a real burn. I do find that you really have to pump out the reps to get the burn. But learn the balance and form first.

Lisa