Crossfit Competitions and WOD's involve doing olympic lifts for massive reps that nobody who is a professional in weightlifting would ever recommend. Kipping Pullups and Muscleups put extreme stress on the joints which is not necessarily a bad thing however it is awful for beginners who do not have prepared joints. In short I like crossfit however I would not tell anyone who is a beginner in fitness to join a crossfit box unless I knew the coach there. Facts not dogma or popular opinion people.