[MikeNice81]

I see a lot of Cross Fit, P90X, and Insanity guys get hurt. It is very rigorous and should only be attempted by those in good shape to start with. Even in great shape it is not something that should be done more than four times a week. You should also transition to something else about every eight weeks to twelve weeks to lower your chances of repetitive stress injuries.

From the American Council on Exercise

Due to the intensity and explosive muscle action of the exercises in a CrossFit workout, there are many benefits for the average exercise enthusiast; however, the intensity of the exercises which deliver the benefits could also increase the risk of injury if not done correctly. Before beginning a CrossFit program, work with a personal trainer to learn how to perform the movements required for the workout. An individual should first develop necessary joint mobility (especially at the ankles, hips and shoulders) as well as joint stability (particularly in the core region) to learn how to effectively perform hip hinge, squat, pushing, pulling and rotating movements. The explosive and plyometric exercises in a CrossFit workout require rapid lengthening and shortening of muscles so if a participant does not take the time to develop the necessary flexibility and movement skills first, the joints might not allow a full range-of-motion which could affect muscle tissue and cause an injury.

Also From ACE

CrossFit workouts are not for the weak at heart, and as some individuals reported when interviewed, the workouts “will wreck you.” While this raises significant concern with respect to technique and injury, it is important to recognize that they do value the importance of safety and this message is evident on their Web site and throughout their training manuals. However, they also acknowledge that in life, individuals face situations that push beyond the limits of appropriate overload where some sacrifices to technique must be made to accomplish the task at hand. They recognize the fact that danger lies in flawed mechanics, but their belief is that flawed technique is the key to making corrections. While this is certainly true for certain aspects of life, I must debate this point when training and designing programs to prepare for life’s challenges. A coach should not attempt to correct poor technique under conditions of high fatigue and load as this only promotes injury.

CrossFit has devoted significant time and energy to educating their coaches. Their CrossFit Level 1™ certificate offers a basic introduction to the fundamentals of CrossFit, and a cursory overview of movement mechanics, while the CrossFit Coach's Prep Course™ is an intermediate-level seminar building upon many of the foundational concepts and movements introduced in the Level 1 Course. While both appear remedial when one considers the nature and risk of the exercises performed,

Be careful when starting any new excercise program. Also be realistic about your abilities. Programs like P90X, Crossfit, and Rush Fit are good programs. They are considerred advanced programs though. It is best for the average person to consult with a trainer before begining any of them.

For an absolute beginer I usually recomend trying Kathy Smith's "Project You" or getting Mark Lauren's book "You Are Your Own Gym." Joining a gym and working with a personal trainer is the best starting point. However, not everybody can afford $35 a month and $40 an hour for a trainer.