Usain Bolt says stiff back has caused problems

Usain Bolt says he has recovered from a stiff back that caused him hamstring problems and is ready to defend his Olympic titles in London.

Bolt says "it was a slight problem. I got that fixed and I'm ready to go."

Bolt lost to training partner Yohan Blake at the recent Jamaican trials. And while he hardly enters the London Games as the dominant force he was four years ago in Beijing, he is still the reigning Olympic champion in the 100 and 200 meters.

He also still holds the world record in both events.