Dexter's statement is possibly the most absurd lie in bodybuilding, which means it is likely the most absurd lie in history.
There is a relatively fast man named Justin Gatlin. He won a gold medal in the 100 meters at the 2004 Olympics at 9.85 seconds.
He has an official 40 time of 4.42.
I think the "official" record according to the NFL is 4.25 seconds, by Fabian Washington.
But, that's just for the National Football League. It's highly probable that some dipshit in high school ran a faster time than anyone else in the history of the NFL.