Usain Bolt, who shattered the world record each time to capture Olympic gold in the 100 meters, 200 and 4x100 relay, dismissed speculation his sudden rise to supremacy was aided by doping.

"I know I'm clean. I work hard for what I want," the Jamaican said in a telephone interview on Friday.

Jamaican sprint king Usain Bolt

The 1.96-meter sprinter clocked 9.69 seconds for the 100 in Beijing last month to carve 3/100ths of a second off the previous record he set in New York on May 31.

Bolt had previously run only a handful of 100s and his performance raised eyebrows among some observers.

Carl Lewis, a nine-time Olympic champion who won one of his titles when Jamaican-born Canadian Ben Johnson tested positive for steroids at the 1988 Seoul Games, raised questions about Bolt in a recent interview in Sports Illustrated magazine.

"I'm still working with the fact he dropped from 10-flat to 9.6 in one year," American Lewis was quoted as saying.

"I think there are some issues...countries like Jamaica do not have a random (dope control) program so they can go months without being tested."

Bolt felt such speculation came with the territory.

"I know what he said," the Jamaican said. "To me it doesn't really matter what he said, a lot of people were saying that.

"When you run the 100 meters that's what you get. As long as you're fast they start saying that.

"It's like a trend. I'm trying to change that. It's a bad image for the sport.

"Carl Lewis can say whatever he wants. That's just his opinion."

Bolt said his 100 breakthrough was earned by hard training.

"The 200 is also sprinting, that was key," he said. "The only thing I had to do was get my start right and I got my start right.

"That's why my last 50 meters are so good because I've got speed and endurance."

Bolt, 22, said he would continue to run the 100 and 200. "In the future I'll probably step up to 400 meters," he said. "But it's a lot of work. I'm not ready for that kind of work."

(Agencies via Shanghai Daily September 28, 2008)