[zxcdw]

I wouldn't be so sure. There's this woman[1] who ran 366 marathons in a year -- that is one per day and two durnig the last day of the year since she started. (And despite the interview was done after she had ran 100 marathons, she finished her project last July with 366 marathons as intended.) Yes, it's not ultramarathons, but I guess she still stretches the boundaries what some of us would consider humans being capable of.

That's almost 15450 kilometers in a year(~9550 miles).

1: http://blog.endomondo.com/2012/11/07/annette-fredskov-366-ma...

[daliusd]

Well, I think marathon each day is possible. I believe that's not far from what average persistence hunter runs a day (I have not checked my facts however). Running 3-4 times that is impossible IMHO. I have found this:

http://en.wikipedia.org/wiki/Self-Transcendence_3100_Mile_Ra...

It is 60 miles / day. Maybe it is upper limit?