London, Jul 27 (IANS/CMC): Jamaican sprint sensation Usain Bolt has disclosed he had suffered a back injury but was quick to say he has gotten over the problems which had led to hamstring troubles.

Less than a week before his opening 100 metres race at the London Olympics here in the United Kingdom capital, Bolt said Thursday he was able to train fully over the last two weeks, most of which were spent at Jamaica's re-Olympic camp in Birmingham, CMC reports.

"My back was just a little bit stiff and it caused problems with my hamstring, but I am over that," he said while adding "it's fixed and I am training well over the last two and a half weeks."

Speculation was rife about Bolt's fitness, especially after he suffered two shock defeats to training partner Yohan Blake at the Jamaica national trials earlier this month.

In both 100m and 200m, Bolt was forced into second spot, raising considerable doubt about his ability to defend his Olympic sprint titles.

Bolt, who was fielding questions from over 200 journalists at Thursday's Jamaica Olympic Association/Puma press conference, brushed side questions about what his biggest challenge would be in coming days.

Asked if this challenge would be bettering his world record 9.58 or defeating his newest nemesis in Blake, Bolt said he was clear on what he wanted out of the July 27 to August 12 showpiece.

"I am just focusing on winning. That's the aim of every athlete coming here, to win the gold medal. I don't think any athlete would want to single out anyone to say I am focusing on this person," the 25-year-old stressed.

In Beijing four years ago, Bolt stunned the world with electrifying runs of 9.69 and 19.30 for the gold medals and then world record times over the 100m and 200m respectively.

He subsequently reset these times the following year at the Berlin World Championships, clocking 9.58 seconds in the 100m and 19.19 seconds in the 200m.