The possibility of injury is an increased risk with participation in anyhigh-intense fitness regimen like CrossFit, especially if you are new to Olympic-style weight lifting and plyometric workouts, or have a previous injury. Not only are the exercises themselves risky, but performing them under a fatigued state, such as during an intense circuit, increases the risk of injury even further.
WARNING: A very serious, yet rare muscular injury known as rhabdomyolysis is also a major concern with participation in vigorous exercise. In short, rhabdomyolysis is a condition in which skeletal muscle becomes so severely damaged that it rapidly breaks down. If this happens, muscle cells may rupture and important contents could leak out into the bloodstream, eventually damaging the kidneys even to the point of kidney failure. It must be treated in a medical facility as it is potentially life threatening.
Symptoms of rhabdomyolysis depend on severity but can include general weakness, extreme stiffness, soreness and swelling of the affected muscle, and abnormally dark colored urine. There are a number of factors that can cause rhabdomyolysis (e.g. alcoholism, genetics, dehydration), but it can be brought on by extreme physical exercise.
To prevent rhabdomyolysis, make sure you start slow and gradually increase the intensity of each workout. Drink plenty of water, and avoid exercise in a hot and humid environment.
If you are interested in CrossFit but are new to weight lifting or exercise in general, you should visit a CrossFit affiliate to receive the necessary personalized attention before attempting a WOD on your own.
If you take that route, however, be aware that the CrossFit coach may not have an appropriate educational background in sports conditioning. Strength and conditioning specialists spend years learning proper technique of explosive exercises and some have degrees in exercise science, biomechanics, or kinesiology.
Make sure you ask about credentials and references for any coach or personal trainer who is responsible for teaching you proper lifting technique. Be sure to let them know if any exercise makes you feel uncomfortable or causes pain.
It's best to have a sufficient strength base before starting a high-intensity, power-based training plan. If you are not strong enough to perform a certain exercise by itself, let the coach know so he/she can modify the regimen accordingly.