Let's see... Can you do a hundred pound dumbbell curl? He could. Do you think you could spar multiple rounds with ranked amateur boxers or go to the mat over and over again and roll with BJJ guys half your age? He did it at least twice a week. He was also an avid mountain biker who wouldn't flinch at the most challenging trails... all at an altitude of over 7000 feet.
You probably couldn't walk half a Klick at this altitude without sucking on an O2 bottle.