Usain Bolt celebrates after winning the exhibition race "Bolt Against Time", a 150m race on a track at Copacabana beach in Rio de Janeiro, Brazil, on March 31, 2013. (Xinhua/Fabio Motta/Agencia Estado) 

Usain Bolt celebrates after winning the exhibition race "Bolt Against Time", a 150m race on a track at Copacabana beach in Rio de Janeiro, Brazil, on March 31, 2013. (Xinhua/Fabio Motta/Agencia Estado) 

Usain Bolt celebrates after winning the exhibition race "Bolt Against Time", a 150m race on a track at Copacabana beach in Rio de Janeiro, Brazil, on March 31, 2013. (Xinhua/Fabio Motta/Agencia Estado)