World record holder Usain Bolt gestures after crossing the finish line to win the 100m semifinal heat at the Jamaica's Olympic trials in Kingston, Jamaica, June 29, 2012. (AP Photo/Collin Reid)

World champion Yohan Blake, left, celebrates after finishing ahead of current world-record holder Usain Bolt, second from right, to win the 100m final at Jamaica's Olympic trials, June 29, 2012. Blake pulled a stunner finishing in 9.75 seconds to upset Bolt by 0.11 seconds. (AP Photo/Collin Reid)

Michael Phelps swims to victory in the men's 100-meter butterfly final at the U.S. Olympic swimming trials, July 1, 2012, in Omaha, Neb. (AP Photo/Mark Humphrey)

Ryan Lochte after swimming in a men's 100-meter butterfly semifinal at the U.S. Olympic swimming trials, June 30, 2012, in Omaha, Neb. (AP Photo/Mark J. Terrill)

Cuba's Dayron Robles in action during the men's 110m hurdles at the Zagreb Meeting IAAF World Challenge in Zagreb, Croatia, Sept. 13, 2011. Robles won the race. (AP Photo/Darko Bandic)

China's Liu Xiang crosses the final hurdle at the Men's 110m Hurdles of the Golden Grand Prix in Kawasaki, near Tokyo, May 6, 2012. Xiang clocked 13.09 seconds and won the race. (AP Photo/Shizuo Kambayashi)

Britain's Chris Hoy racing in the men's semifinal sprint at the Track Cycling World Championships in Melbourne, Australia. Winner of three gold medals in Beijing, Hoy is one of the host nation's top hopes for glory on home turf in the spectacular new velodrome. (AP Photo/Andrew Brownbill)

Sally Pearson of Australia wins the women's 100m hurdles at the IAAF Diamond League athletics meeting at Bislett Stadium in Oslo, Norway, June 7, 2012. (AP Photo/Terje Bendiksby)

Roger Federer of Switzerland poses with the trophy after winning the men's singles final against Andy Murray of Britain at Wimbledon, England, July 8, 2012. (AP Photo/Kirsty Wigglesworth)

Novak Djokovic of Serbia during a men's semifinals match against Roger Federer of Switzerland at Wimbledon, July 6, 2012. (AP Photo/Kirsty Wigglesworth)

Team USA forward LeBron James works to get past team Brazil guard Alex Ribeiro Garcia during an Olympic exhibition basketball game, July 16, 2012, in Washington. USA won 80-69. With 12 of the best players in the world and a coach (Mike Krzyzewski), who has four NCAA titles, USA is looking to come home with Olympic Gold. (AP Photo/Alex Brandon)

Brazil's Neymar controls the ball during a training session in preparation for the London 2012 Olympic Games in Rio de Janeiro, Brazil, July 11, 2012. (AP Photo/Felipe Dana)

Queen Elizabeth's eldest granddaughter, Zara Phillips, will be representing Great Britain in eventing at the London Olympics. Phillips, 31, will ride High Kingdom on her Olympic eventing debut, having missed Athens and Beijing because of injuries to previous horse Toytown. (AP Photo/Tm Ireland, PA)

Japan's oldest Olympian Hiroshi Hoketsu, 71, qualified for the individual dressage competition on Japan's team for London. He competed at the Beijing Games four years ago. When Hoketsu first went to the Olympics in 1964, he was 23 and the games were in his native Tokyo. (AP Photo/Martin Meissner)

Oscar Pistorius of South Africa, who wears carbon fibre blades, will become the first double amputee to compete in the Olympics. He was selected to run the 400 meters individual competition in London. (AP Photo/Paolo Giovannini)