Swim demon Michael Phelps won his 8th gold medal of the 2008 Olympics last night, his 14th overall. How does he do it? It's that crazy 6'4" bod of his! "Generally, a man's arm span equals his height but in his case it's 6'7"-three inches more than his height. Naturally his arms work as powerful propulsive paddles, giving him a clear edge over others. His lower body, interestingly, is shorter than that of an average man of his height. His relatively short legs result in less drag or resistance. In short, Phelps has an upper body of a 6'8" person but his lower body seems to be of someone who is only 5'10", which also make the perfect plane in water." More science after the jump.