About 30 years ago the wife, my son & I hiked up Pikes Peak, from Manitou Springs elev 6615, 7500ft up to the peak, 14,115 ft, up the Barr Trail. 13 miles, 7500ft elevation gain. Started at dawn. I was already acclimated to living here, albeit only about a mile high in Aurora. Was still a smoker - so was the wife. Timberline is 11,500ft here at this lattitude. For the last 3,000 ft I was miserable and taking baby steps. The wife had one cig at the top then quit cold turkey. Took me another couple years to quit. About 1/4 of the way up, a jogger ran past us. About the halfway point, here he comes back at us. I said "WOAH pal, where did you go?" "To the top and back." "I hate you." We were going as fast as we could so we wouldn't miss the last cog rail train back down. cursed if I was going to be battering my joints hiking back down, around midnight or so.
https://en.wikipedia.org/wiki/Barr_Trail