PARIS -- Usain Bolt blames his laid-back personality for last season's injuries and insists he has learned from his mistakes, pledging not to be complacent heading into the world championships in South Korea.
The Jamaican sprinter said the back and Achilles' tendon problems that hampered him in 2010 came about because of his casualness in failing to stretch properly.
"My coach said that I will never get an easy year again because when I get it easy, I get lazy," Bolt said Wednesday. "I think I got a little bit too laid-back last season because it was an offseason for us and I was trying to take it easy not to pressure my body too much. I backed off doing my back exercises, stuff like that. That's part of the reason I got injured last year.
"For me, the key thing is just to learn from your mistakes. So now I have learned. All I have to do now is work toward just being a better person and just being a better athlete."
Bolt made a belated start to the season because he was exempt from the Jamaican championships to have to qualify for worlds, which will be Aug. 27-Sept. 4 in Daegu, South Korea. He still has the fastest 200 time of the year after running a 19.86 in Oslo last month.
The three-time Olympic gold medalist will have a new bulked-up physique when he faces European champion Christophe Lemaitre of France in the 200 meters of the Areva meet Friday.
"I've been working a lot on my back. I've been strengthening my hamstring. As you can see, I've got a little bit more muscle this year because I've been really putting a lot of emphasis on that," Bolt said. "I've set a standard for myself which is really high. People don't understand that with sport comes injury. When you get injured, it's hard to get back sometimes. You got to really work hard."
The last sprinter to beat Bolt, top rival Tyson Gay, pulled out of the U.S. championships last month with an injured hip and won't even run at worlds on a relay team.
"This season, I personally think he pushed himself a little bit too much," Bolt said. "When you get injured, you got to make sure you're fully fit before you start going back into 100 percent work."
Despite the absence of Gay, Bolt said he won't underestimate the rest of the field in Korea.
"I can't get complacent because Tyson dropped out," he said. "I won't get complacent, because it's all about business.
"My goal is just to defend my titles. I want to become a legend in the sport."
Those titles he won in 2009 brought world records of 9.58 seconds in the 100 and 19.19 in the 200, breaking the marks he set a year earlier at the Beijing Olympics.
Bolt said former world record holder Asafa Powell is a contender at worlds after his Jamaican teammate ran the fastest 100 in 2011 with a time of 9.78 last week in Lausanne, Switzerland. The best Bolt has run is 9.91, in Rome and Ostrava, Czech Republic.
"Asafa just posted a wonderful time," Bolt said. "That meant he's back in business."
For now, however, Bolt's sights are set on Lemaitre. They have squared off only once this year, the Jamaican coming out on top in the 100 at the Golden Gala meet in Rome in May.
But Bolt's priority will be refining his technique.
"In this race, I'll try to get the perfect execution," Bolt said. "When I go out there, I should really focus on trying to get everything together, trying to get the right technique.
"If my technique works, it should be a good time because when I'm fluid, I go fast. A fast night should come if I get it right."