I'm on my 50th day. Honestly, great workout. I've gotten MUCH more cardiovascularly fit. But, its not a long term thing. None of these are. And any ultra repetitive workout like this get annoying after a while. Its good. If you're very out of shape, don't do it. You'll die. As a jump start to a lifelong fitness routine its OK. But you'd do just as well running stairs. That's my favorite workout. I live on the 11tg floor of my apartment building. I run down and up as many times as possible. Still not workout I've found tougher than that.