Thirty-odd years ago, Arthur Jones described metabolic conditioning as something greater than the sum of anaerobic and aerobic conditioning.
In other words, if you got very strong and very fit, there would be room for improvement, and that would be the realm of metabolic conditioning.
To get it, though, you've got to train for it. You do so not by tacking a running session onto the end of a lifting session; you do it by training for strength, but training at a rapid pace.
He wasn't claiming to define something new, although I think he was the one who coined the MC name.
Bill Starr and Tommy Suggs, of course, experimented with "timed squats," which went in a similar direction.
The major difference was that controlled intervals is cyclical in nature (something I've become a big believer in).
The major similarity is that both involved squats.
This whole approach to conditioning has been shown as viable over and over.
Big, multi-joint exercises, particularly when they're done over a large range of motion, are what do the trick.
Heavy KG's seem to be important, but going against that particular grain are the results of at least two kettlebell studies, in which both strength and endurance results were greater than control groups; the experimental group used KB poundages that were modest.
In those cases, though, range of motion was extreme (think snatch and C&J) and reps were comparitively high.
Despite the modest poundages, strength improvement in such tests as pullups and standing broad jump still exceeded participants who had practiced those very exercises the whole time.
More recently, the CrossFit have emphasized how improving aerobic conditioning through anaerobic means can lead to improved performance and fewer injuries.
They stress a little more variety than you'd want if you're looking for cosmetic improvement, though.
Sticking with, say, clean and press for sets of six, with rest periods that diminish from one workout to the next, will not only build your metabolic conditioning, but you're also going to end up with a beautiful back and set of shoulders, along with other muscle groups, if you stick with it long enough and work in cycles.
You'd want enough variety, of course, to avoid strength imbalances across the joints, but you get what I'm saying.
