I don’t think I go a week without someone asking me about Crossfit, P90x, or Insanity. My response most of the time is that if it’s something you want to do, do it. Personally, I think all 3 of them are insanity and wouldn’t recommend them to your casual fitness enthusiast or weight loss client, and people often want to know why I think that. Listed below are my primary reasons.
1. For the vast majority of people, they are overkill. You can get the same or better results doing less than half as much total work. Dealing with the general population as much as I do, I can tell you the number of people who have asked me what is the most amount of work they need to do to lose fat is zero. Most, if not all, want to know the quickest, easiest way to lose fat. These 3 methods are none of the above. They require a ton of work and the results you get really aren’t any better than what I’ve seen with my clients who train 3-4 times a week for 30 minutes at a time with tons of rest between sets.
2. Pushing your stress response to the level these people do day in and day out almost always leads to more injuries or illnesses. The last thing someone who is trying to lose weight needs is a reason to quit and both of these reasons are probably the greatest contributors to quitting a fat loss plan.
3. Most people who need to lose fat are coming from sedentary lifestyles. While over time you can certainly prepare them for these types of activities, it would take at least a year just to correct movement dysfunction and learn proper exercise technique, let alone improve their stress response to the point this activity leads to positive adaptation. If you get sore in very specific areas chronically this is almost always due to either over-stressing that tissue or a movement dysfunction.
4. People who are more prone to obesity and Type 2 Diabetes tend to have higher percentages of Type II muscle fibers. These fibers fatigue more easily than Type I fibers and take longer to recover. In order to activate these fibers they cannot be in a fatigued state, they need full recovery. If organized properly you can do higher intensity exercise in a compressed time window while getting full recovery. None of these modalities do that.
5. I agree that intensity is key, but what these programs do isn’t intense by definition. While they are physically draining, intensity is defined by percentage of max force output. If I sprint as fast as I can for 30 seconds, get full recovery, and then sprint as fast as I can for 2 minutes, the second sprint will be more exhausting but the first will be more intense because it will be at a greater speed which requires more force. Also, if I sprint for 30 seconds, get partial recovery, and then try to sprint for 30 seconds again, the second sprint will not be as intense as the first because I will not be able to produce as much force. This is the primary drawback of these types of exercise; partial recovery means partial muscle recruitment. We want total muscle recruitment, not partial.
6. If you have problems regulating your appetite with no exercise, you are going to have a hell of a time regulating it by doing all of this work.
7. Muscle confusion does not exist. Don't get me wrong, I'm not about to compare sports science to heart surgery, but I don't intend on going to a heart surgeon who calls my heart the "Blood pumpy thing". I expect the people I pay to provide a service to know what they are doing and talking about. A muscle cannot be confused any more than a hammer can. Muscles are tools your brain uses to accomplish a task, they don't get confused. If they get used and haven't been used in a while they get sore via inflammation and waste products they are not capable of disposing of. This can both be a positive adaptation or a negative one depending on the magnitude of the soreness.
Don't get me wrong, if your goal is to become a Crossfit athlete you obviously need to join a Crossfit gym. Of the 3, Crossfit is obviously superior because you are getting instruction. I've noticed quite a push in the Crossfit community to develop bridge programs so that sedentary people who want to do crossfit can work their way up to doing it safely. This is a very good move and is causing me to soften on it, I would endorse a gym that does it properly. If you are interested in doing a crossfit program I highly recommend going to one that uses a Functional Movement Screen to drive corrective exercise and has a good bridge program. Realize that most programs that do this are going to be more expensive than ones that don't, but you get what you pay for. It is well worth it to take care of any movement dysfunction up front rather than deal with it after you have learned the movements and need to re-learn them after fixing the problem. As for the other 2 programs...fix your diet, go for walks, and foam roll and strength train 2-3 times per week for 45 minutes at a time. The rest is just overkill.