Olympic and world sprint champion Usain Bolt believes the tainted image athletics has acquired after several high-profile drugs cases in the past few years will clear as time goes by.
"It'll take a couple of years for people to start believing that we are actually clean. Then this tainted image will go away," the 22-year-old Jamaican told a news conference at the launch of the Zeitz Foundation on Thursday.
"As soon as someone starts running fast there's always a problem, but I'll continue running fast. I'm clean without a doubt."
In the past decade American sprinters Marion Jones, Tim Montgomery, Justin Gatlin amd Kelli White plus Briton Dwain Chambers have been banned for doping offences.
Last month four of Bolt's compatriots were banned for three months after being found guilty of using the banned stimulant methylxanthine.
However, Bolt said he felt the International Association of Athletics Federations (IAAF), together with the World Anti-Doping Agency (WADA), were showing the way.
"People are always saying things, but it's changing because the IAAF are doing a very good job cleaning up the sport."
Former 110 metre hurdles world champion Colin Jackson, speaking alongside Bolt as an ambassador for the foundation which was launched by Puma chief executive Jochen Zeitz, paid tribute to the lanky Jamaican's effect on athletics since he stormed to triple Olympic gold last year.
"There's a lot of hope he's going to carry our sport forward because it's been dark for many years," the 43-year-old Briton told Reuters.
MAGIC FORMULA
"It's so good to have someone so fresh, so exciting and who appeals to so many people.
"He's taken on all the responsibilities really well. For me he's just got to keep on doing exactly what he's been doing. Don't change the magic formula."
Bolt was scheduled to fly to Africa later on Thursday with Jackson and Zeitz.
"Hopefully I can outrun a cheetah, but I won't be trying that anytime soon," Bolt told Reuters, grinning from ear to ear.
"Maybe some lions?" asked Zeitz.
"No way," replied Bolt. "I've heard some bad stories about lions."
