I think that she says not to do imax back to back because this is a very high impact workout. You really don't want to be doing, nor is there any reason whatsoever (unless you are some type of athlete) that you need to be doing a high impact workout every day. I don't really know the biomechanics of it all, BUT, high impact is very hard on your body (your joints etc). Your body needs a break from this. You probably don't want to do it more than twice or three times a week at the most. In my opinion doing high impact every day could very well lead to injury. Good luck and enjoy your workouts!!
Kristie Schultz
AFAA certified instructor