At StoneAge Athletics we define "fitness" as the ability to DO...whatever it is you set out to do.
Swiss alpinist Ueli Steck is one of the best examples of what we mean. His goals may not appeal to everyone, but his results speak for themselves, and for what it takes to accomplish "impossible" things.
Just some fun facts. The Eiger's north face is 5,900 feet high. That is a vertical mile. It has killed 64 people since it was first climbed in 1938 earning it the nickname "Mordwand" or Death wall. Ueli's time of 2 hours and 50ish minutes means he was climbing an average of 34 vertical feet per minute up steep dangerous terrain to a summit that is 13,000 feet above sea level...
This one is longer but gets into his training and mindset more.