Bolt wants to fly the flag for drug-free athletics

Usain Bolt rocked his huge frame back into his too-small chair, wrapped his arms behind his head and prepared to deliver his well-worn defence after another bombardment of doping-related questions at his news conference on Thursday.

Ahead of his return to London for this weekend's Diamond League meeting the script was supposed to be all about his happy memories from 12 months ago when the Jamaican lit up the Olympic stadium with another superlative triple-gold medal performance in front of 80,000 dazzled fans.

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Yet the number one topic was the recent positive dope tests on his fellow Jamaicans Asafa Powell and Sherone Simpson as well as that of American Tyson Gay, leading one journalist to ask Bolt if the public could trust the fastest man in history.

"How long have you been following Usain Bolt - maybe since 2008?" he said.

"If you'd been following me from 2002 you would know I've been doing phenomenal things since I was 15.

"I was the youngest person to win the world juniors at 15, I set a world youth junior record at 17, I've broken records in every race I've ever done so I've proven myself. You could say I'm underperforming right now!

"I was made to inspire people and to run I was given a gift and that's what I do. I'm going to continue running and using my talent and help the sport."

Bolt is long used to his role as his sport's beacon of hope and with every failed test his position becomes more important to athletics' credibility.

Next month he will race the world championships in Moscow where his main rival is likely to be American Justin Gatland, a twice-convicted doper now back in the big time.

Powell and Gay, the fastest man in the world this year, will be watching from afar and working on their defence that their failed tests were the result of inadvertently taking contaminated supplements.

INCREDIBLE REGIME

Bolt was cagey when asked about the latest batch of positive tests and though he stopped short of condemning his rivals, he did issue a reminder of the principle that every athlete is responsible for what they put into their body.

"I think there are a lot of details that are still to be discussed, a lot of things that haven't been said so I'm just waiting to see what happens," he said.

"In life things happen and people make mistakes but as an athlete you have to be very careful and aware, it's hard but that's why you have a team to have to help you out with these things."

Powell was said to be on an incredible regime of 19 supplements, including some injectable, but Bolt, who said he had spoken to his compatriot and told him to "stay strong" said he trod a far safer path.

"I have vitamins that I take, every athlete does, but I don't really take supplements," he said.

"I work hard every day go out with one focus and don't worry about other athletes.

"I'm not going to stress about it (doping). I know I am clean and I just want to improve the sport and that is what I am going to do.

"Definitely it's going to set us back a little bit but I can't focus on this I still have the worlds ahead of me and everyone is stepping up their game."

Bolt will run the 100 metres on Friday in the final event of the night and return on Saturday as part of a Jamaican 4x100m relay squad.

His best time of the year so far is 9.94seconds - pedestrian alongside his 2009 world record of 9.58 - but he has looked sharper over 200m where his 19.73 is world-leading.

He says he is unconcerned as he seeks to regain the 100m title he lost to Yohan Blake in 2011 after he was disqualified for false-starting in the final.

"I could have run faster at the national trials, the main aim was to go there and qualify," he said.

"I've had three weeks of solid training, technique work, speed endurance, working on my core. I'm feeling in great shape.

"This year I wanted to try to break a world record but its been an up and down season. Hopefully tomorrow will put me on the right path to run fast at the worlds."

Photograph: Harry Engels/Getty Images