21-15-9 for time of:
Felt surprisingly good. My upper body has been amazingly sore since Tuesday's pull-ups/dips/sit-ups/squats workout, so banging out 21 push-ups in one shot in the first round was a nice surprise. Squats were easy all the way through, though I was definitely sucking wind like a champ by the 3rd round of 9. At that point, I was doing the push-ups in sets of three, but managed to minimize the rest times as best I could.
As a great example, one of my favorite CrossFitters is Rob Orlando, a beast of a guy who's sheer brute strength is phenomenal. For all that, his cardio-endurance has been severely lacking. Though he's won several strong-man competitions, his showings at past CrossFit events have been lop-sided: top tier in the strength events, and miserable in the distance/extended-time events. The upshot is that CrossFitting, and really any other multi-modal, constantly varied workouts is that there is an expectation of finding a weakness like that, engaging it, and removing it. Rather than focus just on his strength work, going into the 2010 CrossFit games, Rob has really worked on his endurance, and will hopefully have a more even showing this year.
At another point on the spectrum is Chris Spealler, who last I knew was 135# soaking wet, but can run for days, and throws multiples of his bodyweight around like no-one's business. There's no hiding behind being a "little dude" for Speal. He pretty much owns all the body-weight events, because he's small, fast, and *efficient,* but by working in the strength domain as well, he's made himself into one of the guys to beat.
So, to get back to the reason why metabolic conditioning workouts seem to work so well. Rather than doing a set number of exercises and reps, the focus is actually on doing them as fast (and safely) as possible. Rather than just focusing on strength, a cardio element is mixed in as well. And instead of just focusing on Long Slow Distance (LSD) for cardio, you get *that* while powering through a strength workout. Now, is 2:51 spent doing push-ups and squats the same as running a 4 minute mile? In most respects, no...unless you wanted to get stronger too, not just better at running a certain distance in a certain time.
The other big upshots are the post-workout effects. Mainly, by pushing your heart-rate up into the sprint zone, you cause a greater and longer-lasting adaptation to take place because your body is forced to recover from both duration and intensity of exercise, rather than just low-intensity duration. None of this is to say that merely running/jogging/walking won't have an impact...but looking at fitness as a whole, and including strength, ability to generate force, and therefore the ability to actually *do work,* multi-modal metabolic conditioning has a lot more impact than anything rated low- or no-impact.
That's my 2c, probably badly explained, and any and all errors in the philosophies are mine alone. I know these concepts have been discussed (and are still being hashed-out on various boards across the web, especially the CrossFit Forum), so if anything sounds half-assed or stupid, its almost guaranteed to be me not getting something, not the theories themselves.