I have seen this question being argued over and over again and the kids did not get an honest answer. Yes, there is a limit age below which it is not smart to start working out on such an extreme level because your bodies are still developing and your muscles can only grow normally if you workout normally. Your bones are also subjected to this.
If you are asking what is the perfect to start the P90X weight loss program I would say that around 19-20 years of age. I have done such a workout when I was still playing professional basketball. I was around 17 and now I am paying the price. My back hurts, I am fat and I probably couldn’t get through one day of the P90X workout DVD. So, unless you want to be like me have a little patience and keep in mind that there are a lot of other things that you can do to stay in shape until you can approach the extreme power program.
I really think that they should tell younger kids about this. As far as I am concerned it is dangerous for younger kids and they should be directed to other workouts program before they start the P90X weight loss DVD. Kids, make sure that you are prepared to pay the price if you can’t have a little patience. In any case, you should make sure that at least you are warmed up well before starting to work out.