Good post, its Brocks cardio that has me so impressed (in addition to his speed, strength and agility).
For such a large person to have such a big engine (cardio vascular ability) is rare.
Like you said having to supply blood to all that tissue and feed all that muscle mass is a big demand on your cardio. Most people think that the size of your heart and lungs is proportional to your body size but this just isn’t true.
Gaining weight, even if it’s muscle mass is a BURDEN on your cardio.
I think he could cut some size and still be just as dominating in wrestling but improve his striking and submissions (along with flexibility).
I’m guessing his training includes tons of anaerobic threshold work and intervals, I Sherk does this and he’s a cardio freak.