"Phelps is also faster at processing lactic acid, the fluid which makes muscles ache, than any other known human."

I wish I could recall some details, but that comment reminded me of something I heard about Lance Armstrong, that he possessed some way-out-of-the-norm physiological characteristics that provided some key advantages for bike races.

You have to wonder how common this is, plus the odds of someone with some physiological gift also being attracted to and motivated to pursue a well-matched sport.