Lol, Tony Horton just took the extremely basic concept of periodization and coined it as "muscle confusion" to make it sound novel. Yeah, variety is good. If you do the same thing over and over again then the law of diminishing returns comes into play. You make progress by disrupting homeostasis and eliciting a change in your body's equilibrium. "Muscle confusion" has no monopoly on this fundamental premise. It's outlined through much more scientific detail in professor Vladimir Zatsiorsky's Science and Practice of Strength Training
Basically, any routine that doesn't have you doing the same workout every day is using "muscle confusion", although again, this is such a basic principle that there isn't really any one technical word for it. It's like calling eating "muscle nutrient infusion".
P90X as a program sucks. I did a write-up on it awhile ago:
"The choice of exercises are poor. Upright rows internally rotate the shoulders to their limit and aren't a very healthy movement in the long-run. Same with chair dips (which also suck because they have no range). Tricep kickbacks are mediocre because gravity does much of the work for you. They include these two for tris but no Tate press (http://ironechelon.webs.com/TatePress.htm)?
The "Ab Ripper" workout contains sit-ups ("Crossed Leg, Wide Leg Sit Up") which are bad for your back and target the hip flexors, not the abs. There's something even worse called the "V-Up Roll-Up". You can see that at about 1:13 here: http://www.dailymotion.com/video/x7tcqp_p9...x-part-2_school
That would be even worse on your vertebrae than regular sit-ups. In sit-ups, you anchor your feet down and pull with your back, activating the psoas attachment and grinding the vertebrae in your back. With these, you don't even have your feet to anchor down and pull with your hip flexors. It's all back, and I can see this leading to very herky-jerky tendencies in novices.
There's a weird theme against the posterior chain, which are your hamstrings, glutes, and lower back. Your hammies in particular are very important, moreso than the quads for many respects. The workout "Legs and Back" doesn't mean "back" as in your posterior chain, but your upper back, as in your lats. Huh? Does anybody over there know anything about resistance training? Instead of hamstring movements like bootstrappers, there are more pull-ups and chin-ups. There's something called a "deadlift squat", which is deadlifting on one leg, but by itself that diminishes hamstring usage because you'll have to bend your leg more to balance.
The nutritional plan has unexplainable carb cycling periods for no reason. In one phase you'll go low-carb, and the next will introduce carbs again. This is done without increasing fat intake to compensate for the lack of glycogen you'll be experiencing from the low-carb portions. A carb deficit causes your body to convert alanine into glucose in the absence of regular glycogen, which catabolizes muscle. More credible low carb diets like the Anabolic Diet by Pasquale or the Paleo Diet will at least advocate increasing lipid intake to give glycogenic processes an alternative source of glycogen."
QUOTE(serotonin @ Jun 2 2010, 07:46 PM)
Yeah when you work out you tear the muscle then it rebuilds so if you work out day after day it's bad for it. IIRC the only muscle set exempt from that is the abdominal group.
Correct me if I'm wrong...
*waits for Reidar*?
Your abs apply to this but on a slower basis because their composition contains more slow-twitch Type I muscle fibers, which are more resistant to microtrauma. Same goes for your calves. Recovery is still needed but perhaps on a less strict timeframe.