OK - good luck to you, I hope you recover smoothly and quickly. I personally do not believe that a workout that has you in front of the toilet for 20 minutes afterward is good for you. I get the "shock to the system" thing, but that is psychological, and not necessarily good for you in the short or long term. In a week or so, once you are recovered (trust me), I'd give it a good think whether you trust this person with your fitness. I just finished a month of crossfit, and made the decision not to join, but my gut feeling is that for the very unfit (no offense intended, that workout is not "hard" if you are even moderately fit), crossfit doesn't make much sense. If you can't do a "real" pushup or run say 1/2 mile, there is truly no need to go to the gym - you can easily work up to some basic standards on your own before joining crossfit. I intend this advice simply as helpful and hope it is not taken as any kind of criticism. Best of luck to you in your recovery (which does not need to be as painful as it WILL be) and your health!