prolonged, sub-maximal exercise
this is
exactly the issue. Everyone operates at altitude with submaximal exercise ( compared to sea level). Anything that uses air suffers the same loss of performance, in parallel with the "thinning" of the air. For example, gasoline engines (unless they are super/turbocharged).
Anyone with a reasonable degree of fitness should be able to do Whitney. You do not need to be a champ. The last two times I was there, I was with a 30 yo once, the other time a 73 yo (I am 63). There is no race. The only competition is AMS (that can stop anyone no matter what degree of fitness) and your own self. Pace, pace, pace works better than race, race, race.
and now a word from a famous British climber/explorer
One must shut out from one’s mind all but the immediate task of making the next step. To start fretting about the slowness of one’s progress or about the time it is going to reach the goal would render the whole business unbearable. Eric Shipton,
Nanda Devi , page 145
