The following is an article that I wrote last year for the rather splendid running magazine Like the Wind. If you don't already subscribe, and you have even a passing interest in any type of running (if not, what on earth are you doing here?!), I thoroughly recommend giving it a look. It's not all idiots like me writing - some people know what they're talking about!
Running 100 miles in one go is a really stupid thing to do. I know this because people tell me so on a regular basis:
"I wouldn't even drive that far!"
"Pheidippides died after running only a marathon y'know!"
"Isn't it bad for your knees?"
You know the drill. Everybody knows these things. Nobody could possibly run 100 miles. Except that they do. All the time.