Has anyone seen the "Bun and Thigh Roller"? There's a new infomercial about it on TV. Basically the same motion as the BTR, but no "bottom" to it. The man who developed it is a professional body builder, and he got his inspiration from stability ball work. That made me think that maybe the stability ball can be used in a similar way. I got out my ball and some dumbbells, propped myself up against the ball and put the dumbbells on my upper thighs and began to rock. Seems to work just like the BTR and the BTR (rocker and roller!). Of course, there is a much lower limit to how much extra resistance you can add (I wouldn't want to hold 30 pound dumbbells on my upper thigh!).