I (27F) am a relatively fit person. Not an athlete, but I work out 5x/week, take walks nearly every day, and go on reasonably long hikes \~2-4x/month. But when I do really long, strenuous 8+ mile hikes at elevation I hike slow and I hurt the next day or am just exhausted.
I really want to pick up backpacking so I can make it to peaks that I wouldnt be able to get to in one day but after a long strenuous day hike I can't imagine getting up and doing that long of a hike again the next day. I hear about people doing about 8-10 miles a day backpacking and I dont understand how you sustain that for multiple days in a row. I've known people who never hiked before that just went out and did the entire AT spontaneously and it makes me feel like there's something wrong with my body.