A couple specific individuals I've known. Both ran 15-20 miles a day. They'd just go for runs most evenings or mornings and run and run. At least every weekday for one, the other I know ran daily. One was a Catholic seminarian (ran in the mornings, no family, obviously). The other was a middle-aged, family man, working as an engineer. He'd run most of his life. Both were African, one Nigerian (the seminarian), I don't recall where the other was from.

> One was a Catholic seminarian

That explains a lot. One of the true and tested recipes for libido suppression the Church takes to heart is to physically and mentally exahust their horny young men until they are not horny any more.

This of course is just my opinion, but an informed one. I went to a Catholic mid-school and highschool, and even when we were not 100% on board as a seminarist would be, sports was something the administration promoted very heavily. We'd also get to know lots of seminarists that would come to do field work there prior to taking their vows, and an almost universal trait of them was their passion for sports.

> He'd run most of his life. Both were African, one Nigerian (the seminarian), I don't recall where the other was from.

Now you're making sense. For someone who's not been doing serious long distance running since childhood, 20 miles in a week is quite good. From what I've read in running magazines, and personal experience, doing much more than 30-40 miles a week is not good for your body (esp. knees). 100+ miles per week is crazy.

I guess the confusing part was that you said "most". Unless you only know a few skinny people.

Ah, that "or they run 20 miles a day." was an aside at the end. The first part was what I typically see of healthy, skinny people, the second part of very few (substitute other sorts of crazy levels of physical activity for the running if you want).

Two hours a day is not a crazy number at all for some endurance sports. If you do cycle racing 10 hours per week is a good starting point to build up endurance.

But that works because cycling isn't weight bearing, so after the initial exponential learning curve you can pretty much do as much of it as you have time and motivation.

20 miles a day of running, on the other hand, is absolutely not typical. Other than ultra-runners no professional does >100mi/wk regularly simply because the diminishing returns don't justify the linear increase in injury risk and aggravation (it's running, injury incidence is already crazy high).