Thanks for the tag.

Although the business model is questionable, the physical training methods are generally tried and true... when they're being performed safely.

CrossFit is an extreme form of HIIT, something I've been putting myself through lately. Short of 'roids, HIIT is the most effective way to build muscle and/or burn fat, hands down. They're spot on in their incorporation of the "big lifts" - bench, deadlift, squat, and overhead press, but the looseness of their licensing and certification is an issue. No one should EVER be encouraging people to proceed with a lift when their form looks like this.

Back when I was 19, during the coursework for my B.S., I was required to take a kinesiology course. Being a procrastinator, by the time I signed up for classes, only a few kinesiology classes were left to choose from, and I reluctantly picked weight lifting. One lecture a week, and two sessions per week in a gym with weights. I couldn't bench my body weight, I could only manage 5 or 6 pull-ups, my max squat was just about my bodyweight, etc. The coach/professor was generally very competent, and would teach us proper form prior to introducing a new movement, then patrol around during the lifting session and correct anything that was too far from a safe form. I lucked out on stumbling into such a good learning environment for weight training.

So now, just to repeat what you've probably heard several hundred times: TECHNIQUE AND FORM ARE EVERYTHING, especially as you creep up towards amounts of weight that can seriously injure (or even kill you) if you aren't focused and trained properly. So no, you can't just saunter into a CrossFit "box" without prior weight lifting experience and hit a WOD without expecting to pull a muscle or two. Most people realize this. Indeed, CrossFit seems to appeal to those already in decent shape looking to "take it to the next level" and find like-minded friends (read: folks rabidly dwelling on physical fitness) to form support groups.

You don't need to join CrossFit to craft up and execute workouts that are comparable to their WODs. You say you've gotten a professional (personal trainer, I assume) to help you start weightlifting. Excellent choice. Depending on what you're training for, you could ask your trainer to put you through some HIIT-style workouts. Like CrossFit, you will be made to do some high-resistance, low-repetition movements in tandem with low-resistance, high-repetition exercises, often in a circuit. Just be sure, while you have this professional oversight, to learn correct form on the big lifts, with as heavy of a weight as you can manage while maintaining proper form. In addition to the four I listed earlier, I recommend pull-ups, incline bench, standing or seated row, and leg press.

Some people don't get CrossFit, and that's fine. It makes sense to me. I'm just one notch too low on the dedication meter, and quite honestly I don't want to make friends whose lives revolve around fitness.

One aside: Diet is probably 70% of "results". You can train your little heart out, but if you aren't eating right, you won't see the gains or losses you were looking for. The biggest thing to pay attention to is net calories.

Ummmm, also, if you have any questions, let 'em rip... may take me a while to answer though, life's been on warp speed for a few weeks now.