BERLIN, Germany (CMC):

Sprint phenomenon Usain Bolt hopes his mind-boggling exploits can clean up track and field's image, which has been tarnished in recent years by several doping scandals.

The Jamaican, who has broken the 100 metres and 200 metres world records four times in the space of 12 months, said he wanted to send a strong message athletes could do fast times without the help of drugs.

"It (drugs) is always going to be in the sport and I'm trying to clear that up, but continuing to run fast and being clean and letting people know that you don't have to take something to run fast," said Bolt, who celebrated his 23rd birthday on Friday.

"I'll just continue doing that (running fast), and one day people will stop asking that question (about drug use)."

Over the last year, Bolt has come under heavy scrutiny and has been subject to repeated drugs tests, as he has broken one record after another.

Following on from his astonishing performances at the Beijing Olympics last year where he captured the sprint double in record-breaking fashion, Bolt again stunned the world by setting two new world records in the 100 and 200 metres.

Last Sunday, he crushed his field to clock 9.58 seconds in the 100 metres and returned on Thursday to dismiss his rivals in the 200 metres, posting an amazing 19.19 seconds.

Bolt said, however, he was not fazed by suggestions that he could not run that fast naturally.

"I don't get offended because year after year people run fast and then they get tested positive," he pointed out.

"I'm not worried. I keep telling people, I get tested all the while and I'm going to be tested after this (event), so I'm not worried because I come out here and train hard, and I'm always ready."