China's Liu Xiang (C) falls as Poland's Artur Noga (L) and Hungary's Balazs Baji compete in their 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 meters hurdles at the London Olympics on Tuesday in an echo of his injury-induced withdrawal from the same stage of the Beijing Games four years ago. REUTERS/David Gray (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS)

China's Liu Xiang (R) falls as Poland's Artur Noga pulls up in the 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 meters hurdles at the London Olympics on Tuesday in an echo of his injury-induced withdrawal from the same stage of the Beijing Games four years ago. REUTERS/David Gray (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS)

China's Liu Xiang falls after he crashed into the first hurdle near Poland's Artur Noga (L) and Hungary's Balazs Baji in their 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/David Gray (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS)

China's Liu Xiang falls after crashing into the first hurdle during his men's 110m hurdles round 1 heat at the London 2012 Olympic Games at the Olympic Stadium August 7, 2012. REUTERS/Lucy Nicholson (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS TPX IMAGES OF THE DAY)

China's Liu Xiang sits on the track after suffering an injury in his men's 110m hurdles round 1 heat during the London 2012 Olympic Games at the Olympic Stadium August 7, 2012. REUTERS/Lucy Nicholson (BRITAIN - Tags: SPORT OLYMPICS SPORT ATHLETICS)

China's Liu Xiang holds his leg after suffering an injury in his men's 110m hurdles round 1 heat at the London 2012 Olympic Games at the Olympic Stadium August 7, 2012. REUTERS/Kai Pfaffenbach (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS)

China's Liu Xiang falls onto the track during his men's 110m hurdles round 1 heat at the London 2012 Olympic Games at the Olympic Stadium August 7, 2012. REUTERS/Eddie Keogh (BRITAIN - Tags: SPORT OLYMPICS SPORT ATHLETICS TPX IMAGES OF THE DAY)

China's Liu Xiang falls while competing in his men's 110m hurdles round 1 heat during the London 2012 Olympic Games at the Olympic Stadium August 7, 2012. REUTERS/Mark Blinch (BRITAIN - Tags: SPORT OLYMPICS SPORT ATHLETICS)

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)

China's Liu Xiang hops down the track after crashing into a hurdle in his men's 110m hurdles round 1 heat during the London 2012 Olympic Games at the Olympic Stadium August 7, 2012. REUTERS/Lucy Nicholson (BRITAIN - Tags: SPORT OLYMPICS SPORT ATHLETICS)

China's Liu Xiang hops down the track after crashing into a hurdle in his men's 110m hurdles round 1 heat during the London 2012 Olympic Games at the Olympic Stadium August 7, 2012. REUTERS/Lucy Nicholson (BRITAIN - Tags: SPORT OLYMPICS SPORT ATHLETICS)

China's Liu Xiang hops down the track after crashing into the first hurdle and failing to finish 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/David Gray (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS)

China's Liu Xiang looks up after kissing the last hurdle in his lane 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 at the London Olympics on Tuesday in an echo of his injury-induced withdrawal from the same stage of the Beijing Games four years ago. REUTERS/Lucy Nicholson (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS)

China's Liu Xiang kisses the last hurdle in his lane after 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 at the London Olympics on Tuesday in an echo of his injury-induced withdrawal from the same stage of the Beijing Games four years ago. REUTERS/David Gray (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS TPX IMAGES OF THE DAY)

China's Liu Xiang kisses the last hurdle in his lane 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 at the London Olympics on Tuesday in an echo of his injury-induced withdrawal from the same stage of the Beijing Games four years ago. REUTERS/Lucy Nicholson (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS TPX IMAGES OF THE DAY)

China's Liu Xiang kneels 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/Kai Pfaffenbach (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS TPX IMAGES OF THE DAY)

China's Liu Xiang (R) is helped by Hungary's Balazs Baji after crashing into the first hurdle during their 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 at the London Olympics on Tuesday in an echo of his injury-induced withdrawal from the same stage of the Beijing Games four years ago. REUTERS/Lucy Nicholson (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS)

China's Liu Xiang (C) is helped by Britain's Andrew Turner and Spain's Jackson Quinonez after suffering an injury during their 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 at the London Olympics on Tuesday in an echo of his injury-induced withdrawal from the same stage of the Beijing Games four years ago. REUTERS/Lucy Nicholson (BRITAIN - Tags: OLYMPICS SPORT ATHLETICS)

China's Liu Xiang is assisted onto a wheelchair after suffering an injury during his men's 110m hurdles round 1 heat during 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/Lucy Nicholson (BRITAIN - Tags: SPORT OLYMPICS SPORT ATHLETICS)

Liu Xiang of China grimaces in pain during his warm-up before the start of his 110m hurdles heat of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 18, 2008. Liu failed to start his 110 metres hurdles first-round heat on Monday. After one false start Liu stopped before the first hurdle clutching his leg and then walked out of the stadium. REUTERS/Ruben Sprich (CHINA) 

China's Olympic champion Liu Xiang prepares to start his 110 metres hurdles first-round heat of the athletics competition at the Beijing 2008 Olympic Games, August 18, 2008. After one false start Liu stopped before the first hurdle clutching his leg and then walked out of the stadium. REUTERS/Kim Kyung-Hoon (CHINA) 

China's Olympic champion Liu Xiang prepares to start his 110 metres hurdles first-round heat of the athletics competition at the Beijing 2008 Olympic Games, August 18, 2008. After one false start Liu stopped before the first hurdle clutching his leg and then walked out of the stadium. REUTERS/Kim Kyung-Hoon (CHINA) 

China's Olympic champion Liu Xiang walks away after failing to start his 110 metres hurdles first-round heat of the athletics competition at the Beijing 2008 Olympic Games, August 18, 2008. After one false start Liu stopped before the first hurdle clutching his leg and then walked out of the stadium. REUTERS/Gary Hershorn (CHINA) 

Liu Xiang of China tears off a number tag signifying his lane number before the start of his 110m hurdles heat of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 18, 2008. Liu failed to start his 110 metres hurdles first-round heat on Monday. After one false start Liu stopped before the first hurdle clutching his leg and then walked out of the stadium. REUTERS/David Gray (CHINA) 

Liu Xiang of China tears off a number tag signifying his lane number before the start of his 110m hurdles heat of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 18, 2008. Liu failed to start his 110 metres hurdles first-round heat on Monday. After one false start Liu stopped before the first hurdle clutching his leg and then walked out of the stadium. REUTERS/Ruben Sprich (CHINA)

Liu Xiang of China grimaces in pain as he settles into the starting block of his 110m hurdles heat of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 18, 2008. Liu failed to start his 110 metres hurdles first-round heat on Monday. After one false start Liu stopped before the first hurdle clutching his leg and then walked out of the stadium. REUTERS/David Gray (CHINA) 

Liu Xiang of China leaves the track without starting his 110m hurdles heat of the athletics competition in the National Stadium at the Beijing 2008 Olympic Games August 18, 2008. After one false start Liu stopped before the first hurdle clutching his leg and then walked out of the stadium. REUTERS/David Gray (CHINA)