There's actually a documentary about it. Some guy dominated it for like 15 years and he was a pretty small guy (which while there's classes he's beaten a lot of guys way bigger than him).
Oh wow, it was 25 years.
Here's the movie: (Pulling John)
http://www.imdb.com/title/tt1289451/
It was pretty entertaining I thought.
There's also some guy that has a genetic defect where one of his arms is just massive compared to the rest of his body and so he's been doing arm wrestling.
Seems like I remember reading about the guy in the OP a few years back as well, or maybe it was another guy that had a similar genetic "defect" that caused him to grow outlandishly large hands and forearms.