Nirmal Purja stands out as one of the fittest people. You maybe saw the film 14 Peaks.

This guy trained and was selected into the Gurkhas and Special Boat Service. Then he summits 14 of the 8000er (meters) in six months and six days. This has since been broken but this guy is still doing mountain summits.

There’s a few scenes where he Carries other climbers- already a feat to do so with your own gear but then fireman carry someone else your size at that altitude is wild.

Freak guy. I think Jack Kruse was onto something with the Sherpas and their mitochondria.