I met Felix when he was in Charleston for the WSM. He unfortunately tore a bicep during the Atlas Stones, so he was out of action for the finals. However, I found him to be the most impressive physical specimen of all the strongman competitors at that event.
Mark is not a young man. He's in his early to mid 40s. He's unreal thick. But the thing that impressed me the most was the sheer length of his fingers. I'm not kidding. His index finger had to be nearly 7" long.
I have large hands, and his hand and fingers completely wrapped mine and could have doubled. Phil Pfister has enormous hands, but his palms are bigger than Mark's. Felix's fingers don't look human. They're like Bananas hanging from his palms. Unreal.
There's some great youtube videos of him lifting at the Addington Weightlifting Club. He pulled 908 about two weeks before the WSM - no straps, just a belt.
There's some impressive human beings among us.