I have mentioned before that my primary method of staying in shape (and hobby) is Muay Thai kickboxing. I picked it up originally to compliment my biking, but it has pretty much taken over my life and everything I do now compliments my Muay Thai.
After our Muay Thai lessons at the gym, we have always done conditioning, whether it be running outside, ab work, cardio kicks, pushups, or a combination of all of the above. As of late, we have been doing circuits. They look something like this.
Of course the guy in the video is a professional, training for a professional fight. Our circuits are not as long and not as many (in the video, you are supposed to do each exercise for one minute, then go on to the next exercise for a total of a five minute circuit and then to 2-5 circuits), but the idea is the same. Different exercises to the point of exhaustion, short rest, then do it all over again. It almost sounds something like what Zenpundit posted the other day. Maybe this is a fad. I like it though. And after 45 minutes of Muay Thai training, and then doing several circuits, I guarantee you that you will get in shape. I don’t know much about Crossfit, but from the way Zen was describing what was going on in his gym, it seems like perhaps it is an extreme form of circuit training.