Here's the Link to the original question and one of the posts makes mention of my Body Sculpting Bible books:
http://www.mahalo.com/answers/weightlifting/is-the-muscle-confusion-concept-described-in-p90x-literature-for-real-or-a-load-of-marketing-crap

Hi, my name is James Villepigue, and I am the author of the Body Scultping Bibles. Muscle Confusion, like Quincy points out, is nothing more than helping your body/muscles avoid hitting the dreaded training plateau. Muscle don't have the intelligence that many have claimed they have, but your body, as a whole, will naturally adapt to a stress (the many variables of weight training) over time.

Muscle Confusion is nothing more than a glorified name for periodization training; a specific type of training completed in various periods or blocks of time.

Some refer to these blocks/periods of time as Micro (shorter periods of specific types of training) & Macro (longer periods of specific types of training).

My co-author and I have referred to our proprietary periodization system as, "The 14-Day Body Sculpting Program". It' simply a means of changing up many of our training system's training variables (the different types of exercises, the sequence of exercises performed, the number of sets, reps, the amount of rest between sets, the tempo AKA speed of your lifts, the Time Under Muscular Tension, the amount of weight lifted, the total duration of your workouts, etc.   

I am not one to put another training system down and to be truthful, I've personally heard some great things about P90X. I honestly don't think they claim to have invented a new concept known as their "Muscle Cinfusion". I believe that they simply coined a unique term to help differentiate their system from others and to me, that's just smart marekting. By the way, I have absolutely NO ties to P90X, I just like being straight forward with all of you.

My motto when it comes to training is this: The Best Workout Is The One That You're Not Currently On". This should sum up the muscle confusion concept, Periodization training or whatever you want to call it, as a whole.

Hope this helps clarify the confusion...Pun intended! ;)

Keep Going!

James Villepigue CSCS
www.BodyByJames.com