I run a lot. Last month, I reached my fourth consecutive annual kilomile. And yet, for all that running, the very longest distances I compete in are marathons. 26.2 miles is more than enough for me.

There’s another breed of runners who compete in ultramarathons, races which are 50, 100, 200 miles (and even longer). Courtney Dauwalter is probably the world’s greatest ultrarunner, female or male. How does she do it? Why does she do it?

Outsiders can’t always understand why she would put herself through something like this—or why anyone would. If only they could stand with her on these mountains after a run, out of breath and full of fire, feeling the profound satisfaction that comes from putting one’s body on the line to see how strong one’s mind can be.

That satisfaction is certainly a motivator. But another factor is the persistent exploration of the pain cave, as Mirin Fader details in a tremendous profile for The Ringer. The distances Dauwalter and her fellow adventurers run can seem unfathomable, but the mental battles they wage can be relevant to all of us.