Oh...Now I feel awkward...
Now, that being said, these programs are great at getting you into a very high degree of athleticism, burn shit tons of calories, make you lose weight and lower your body fat percentage. These programs work! But, if your goals are to build muscle and build a physique that is maintainable, these programs are simply not effective enough in terms of Hypertrophy.
Hypertrophy: The increase in the volume of an organ or tissue due to the enlargement of its component cells. (Makin muscles bigger)
Muscle confusion is a hype word used by media and commercials to get you to buy their products. The primary purpose of employing this type of training is to keep you entertained and focused on the product. You can achieve very similar results from doing Bur-pees for extended periods of time...but that would be both physical and mental torture.
The recipe for building muscle is as such: Training, Eating in a caloric surplus, Rest and Progressive Overload. Or TERP as I have just now named it. (I'm a genius)
You obviously train in these programs.
You control your eating (unless you're a prisoner...Asylum!!!).
Rest is something you control whether you want to admit it or not.
Which leaves us with progressive overload...
Progressive overload: The gradual increase of stress placed upon the body during exercise training. This basically means, in terms of building muscle, increasing the amount of resistance or weight in order to recruit more muscle fibers.
Some people argue that this is possible with P90X. Our buddy here built lots of muscle using only P90X. But get this, he didn't do the cardio sessions, and he used weighted pull ups and push ups...So, basically, he applied progressive overload to big prime mover exercises that don't require a gym (Something I would recommend to pretty much everybody who didn't want to invest in a gym membership but wanted to build muscle [more of this coming soon]), didn't do a good portion of P90X and called it building muscle on P90X.
The program as written does not incorporate enough Progressive overload in terms of resistance to build muscle efficiently, especially when one is combating the atrophy caused by the intense cardio. (Dems calories could be turned into muscle!)
Why I don't recommended these programs to everybody:These programs are difficult. And I don't mean that they make you work hard (I'm all about hard work), I mean that they are really really difficult and demand a lot out of you. The programs are designed to be difficult, high intensity calorie burners. There is a high chance of injury just due to the fact that it is intense unmonitored circuit training.
And, as we all know, nutrition and fitness go hand in hand when it comes to results. Exercise, especially high intensity interval training speeds up metabolism and increases appetite. As well it should! After burning out all of the glycogen in your muscles, your body is demanding for calories to replenish those stores so it can repair itself. However, your body is a little bastard and often times thinks it needs more than it does, and every calorie beyond what you need to repair and replenish is stored up in your fat cells, turning into those delightful love handles we all adore. The average Joe is not very aware of what a calorie is, let alone how many there are in his peanut butter, nutella, and jelly cronut sandwich. This is why people will often go through programs (Not just the DVD wonders) and not lose an ounce of weight. Calories in vs. Calories out.
Once you have finished this program, you're often left with an increased appetite that is hard to satiate and left with the task of continuing your hard core training to match the appetite, or accept being hungry. You do have the option of spending more of your money on a nutrition plan (Often times sponsored by the company that brought you the DVDs!) that will keep you in a caloric deficit using weight watcher style meal portions. (I can starve myself, thank you.) It takes someone who is both smart and disciplined enough to ignore their body and feed themselves with the correct amount of nutrition to either maintain or lose weight.
Now, don't get me wrong, and please don't accuse me of saying you're going to gain every bit of weight you lost on this program right back the minute you indulge in a muffin. I want nothing but happiness for everybody, and I want to see people accomplish their goals. I've seen success stories and people who have leaped off the wagon and everything in between. (These are very popular programs, don't you know.) Your success on any path is determined by you and your dedication.
Who do I recommend these programs to:If you're a person who used to play sports, is already athletic, or a person who just loves a challenge, these programs are for you. If you're looking for a quick 90 day path to getting in really great shape temporarily and don't mind hard work, then why not, go for it. If you're a person that likes that boot camp type scenario and the motivation given by an intimidating instructor, you'll be in heaven. If you're on top of your nutrition or are not a chronic over eater (Unlike ol' Yeargain) and have a good understanding of calories in vs. calories out and you won't be screaming "yolo!" as you pound that whole cheesecake, you'll get some great results. Or if you just like to be a rebel and give ol' Yeargain the bird...I respect that. Go for it.
Also, don't pay for these programs. Look for them on the internet, talk to some friends, pass around some thumb drives, and steal the crap out of them. These people don't need your money, and fitness doesn't need to be expensive, it can cost you however much you want.