just like the old machines with the oscillating belts that shook your entire body. My mother had one and after 10-15 minutes of use, I felt like I had bugs crawling all over my body.
I can see lots of guys buying this just so they can watch thier wives butts... "Oh, yeah, that thing is WORKIN!!!!!
But, if their wives' butts are in shape- they don't have to get on one of those things for the guy/partner/husband to watch it.
If her butt is not in shape - is that something anyone really wants to watch like that?! Just wondering.