This is the phenomenon known as "Ultra-Running" (I think, the ultras even run further than 50 miles but I'll go with that) and not that I agree with it. I guess, it's the way Cross-Fit seems to be an excessive workout.
![](http://media-cache-ak0.pinimg.com/736x/12/a5/fe/12a5feafa7a08991ed43a1e0e919c0b8.jpg)
They do it a lot in the desert, Death Valley, in mountains, Grand Junction, canyons and so forth. Just be in the condition to do this.
![](http://www.ultrarunningltd.co.uk/wp-content/uploads/2013/01/ultra-running.jpg)