You have no idea what you are talking about. Seriously. 300+ lb men, going balls to the wall EVERY play takes cardio. Yes, they do get little rest periods between plays, but like i said, they are 300+ lb men. And if you honestly think they don't run EVERY practice, along with doing resistance training, you are insane. Especially if you go look at these freaks that weigh 320 lbs and are running 4.5s and 4.4s. Come on dude..
You would know if you actually played.
It's ironic that you're name is sports nerd yet you know absolutely jack shit (obviously) about football.
I'm sure they have great cardio compared to other 300lb men.
They have poor cardio compared to guys who compete in actual cardio intensive sports, like... say... Overeem, for example.
And I'm sure they do run in practice. Except they do sprints. Football is largely an anaerobic sport, while MMA is largely an aerobic one.
I know these guys are sick athletes. I know they can sprint like lightning. I'm not trying to disrespect them. But there's a fundamental metabolic difference between what they do and what Overeem does.