team Unruly Bush wrote:
Hiking Mt. Shasta (less than half the height of Everest) was harder for me than a sub 3 marathon. Granted I trained for the marathon
I'd say the same, though I'd say Shasta was much harder than a sub-3. I didn't have to do "marathon training", mostly dog jogging with my dog (9:00 pace might be fastest run of week), to go sub-3 on my first try at age 43. When I was younger, I probably could do 2:35 as a training run if I wanted without knocking myself out.
It took me two tries to climb Shasta. First try was solo on Green Ridge over New Years (21 years ago). I started late afternoon maybe, and dug in and bivied mid-mountain in crazy wind gusts, where I could look down on the town lights between gusts, where people were likely celebrating the new year. I had to bail the next morning because it had turned into and stayed a blizzard. I couldn't see where I was going. Second try was a few months later, a solo walk up on Casaval Ridge. Went smoothly, but I probably lost some brain cells going to altitude without acclimatization.
The main reason Shasta was more difficult is the commitment and sound judgments needed to do the climb solo safely in the winter. If the weather changes for the worse, you have to be able to take care of yourself, with no help expected to come (maybe to pick up your body if you mess up). You need to be aware of potential avalanche paths, possible crevasses on glaciers if crossed, etc. I remember a poster on a climbing, really more peak bagging board I used to be on (Views from the Top) died on Shasta from exposure, so it can kill you just like Everest. Even if doing it in a group in the summer, I'd say it's harder than a sub-3 for a decent runner because of the length of time it takes and the altitude.
I interpret the OP's question as a question to me or runners who might be reading LR, not the average person. Many people, especially women, do not have the talent to ever go sub-3 no matter their training.