Froning weighs 200 lbs. High school girls weigh 95-110 pounds. His cardiovascular system might actually be significantly stronger and better than theirs.
But again who cares? His sport is not focused on running. So it's dumb to say he's not fit because some running specialists half his weight are faster than him. And if these decathlete's are so much better than him, why aren't they just easily hopping over to the cross fit championships and picking up half a million dollars or whatever the money is?