By Dr. Alexei Koudinov, editor of the Israel-based Doping Journal Web site.
"I first noticed that before his first gold swim on August 10: Phelps removed earphones 2 minutes before the start, and he was the only swimmer who worn earphones at the pool deck. Intriguing scientific evidence testifies: Listening to music improves blood oxygen capacity and is a performance enhancement."
Such an enhancement is "a bio-chemical feedback mechanism from an external source."
Forget the hard work, intensive training and complete dedication to his sport. He's doing it by listening to an iPod.
http://weblogs.baltimoresun.com/sports/specialevents/blog/2008/08/does_music_give_phelps_an_unfa.html