Michael Phelps of the U.S. swims the butterfly leg of the men's 4x100m medley relay final during the London 2012 Olympic Games at the Aquatics Centre August 4, 2012. The U.S. team of Matthew Grevers, Brendan Hansen, Michael Phelps and Nathan Adrian won the gold in the event. REUTERS/Toby Melville (BRITAIN - Tags: SPORT SWIMMING OLYMPICS)