Usain Bolt talks about doping and fast times Jamaican sprinter Usain Bolt listens to questions during a news conference in central London. Leon Neal / AFP/Getty Images / July 25, 2013 July 25, 2013, 9:43 a.m. With the world championships only a few weeks away, sprinter Usain Bolt found himself answering questions about recent doping scandals in track and field. "It's surprising what's been going on," he said. But there are a lot of details still to be discussed. The last month has brought revelations that top sprinters Tyson Gay, Asafa Powell and Sherone Simpson failed drug tests. Several additional Jamaican athletes were found to have banned substances in their systems. Speaking to reporters on Thursday before a Diamond League meet in London, where he will compete in the 100 meters and 400-meter relay, Bolt knows the public is watching his sport with a suspicious eye. The world's fastest man insisted he is clean and pointed to a long record of success, saying he was born to sprint. "If you've been following me since 2002, you will know that I've been doing phenomenal things since I was 15," he said. I was the youngest athlete ever to win the world juniors. I broke a world junior record at 18. Earlier this week, track's governing body said it will have a comprehensive blood-testing program in place for the world championships in Moscow next month. Bolt also talked about his inconsistent performances of late, acknowledging that "it's been an up-and-down season so far." He said his training has improved over the last three weeks. "My confidence is really high and I am ready to run fast," he said. I don't really worry about times but I know I'm now in great shape. I'm going to run fast and hope to break the record. Tim Hudson suffers gruesome broken ankle [video]