I was skeptical about this workout since it's quick (about 20 minutes) and I just didn't think i could work up a sweat in that amount of time. Well, I was wrong! The workout is tougher than I thought and I'm noticing a difference already. Yes, it's fast but Jillian makes you work the entire time. I'm in good shape and I typically do the Insanity, P90X, etc., DVDs but I prefer this one now!