China’s Liu Xiang sits on the track after suffering an injury during his men’s 110m hurdles round 1 heat at the London 2012 Olympic Games at the Olympic Stadium

Liu Xiang sits on the track. (Stefan Wermuth/Reuters)

Liu Xiang sits on the track. (Stefan Wermuth/Reuters)

China’s Liu Xiang sits on the track after suffering an injury during his men’s 110m hurdles round 1 heat at the London 2012 Olympic Games at the Olympic Stadium August 7, 2012. Liu crashed out of the heats in the 110 metres hurdles in an echo of his injury-induced withdrawal from the same stage of the Beijing Games four years ago. REUTERS/Stefan Wermuth (BRITAIN – Tags: OLYMPICS SPORT ATHLETICS)