I swiped the picture from an thread (http://www.freerepublic.com/focus/f-chat/2364770/posts) about him. He's a champion arm wrestler, so I suppose he just exercises that arm.
There is another picture of him, on another thread, that shows the arm better. It is quite muscular but not quite as grotesque as it appears in this picture. His left arm is also muscular but much smaller, evidently he works the he** out of his right arm and not so much his left. Kinda stupid IMO, but what ever floats his boat.