Here's some info about the movements of CrossFit.
There are nine basic movements that, when learned, unlock the CrossFit's weightlifting regimen. They are the: squat, front squat, overhead squat, shoulder press, push press, push jerk, deadlift, sumo deadlift high pull, and medicine ball clean.
Crossfit attacks and taxes pretty much all of the body's energy systems. 3-4 minutes into a Crossfit workout and both the musculoskeletal and cardiorespitory systems will be screaming bloody mary! Mastering form and technique are at utmost importance. When fatigue sets in, form follows, which is understandable.
Review this video and see what I mean about form breaking after fatigue. These guys are developed athletes and their bodies are well-conditioned for the errors in technique. If you're not quite there, take it slow, control your movements, and scale down accordingly to prevent injury.