Usain Bolt is a freak of nature. There's the size, for starters: 6ft 5in with size 13 feet (ideal sprinters are thought to be between 5ft 11in and 6ft 1in). Then there's the condition that should have ruled out a career in sport – scoliosis, or curvature of the spine, which resulted in one leg being half an inch shorter than the other. And the attitude – at warm-up, a do-or-die intensity is etched on the faces of his rivals, but Bolt smiles, hangs out, even dances. And, of course, the records: Bolt is the fastest man ever – at both 100m and 200m. Finally, and most outrageously, he wasn't even giving his all when he broke them.

Bolt has just flown in from Germany and is curled up in his chair like a sleepy cat. His voice is deep, soft and slow. He recently lost his first 100m race in more than two years, to Tyson Gay, and it has been splashed across newspapers that he is injured and will miss the rest of the season. But he's already focused on the two biggies – next season's world championships and, most important, the 2012 Olympics in London.

The world has been blessed with phenomenal sprinters, but nobody can hold a light to Bolt. In 2002 he became the youngest gold medallist at the junior world championships, winning the 200m. He was only 15, beating boys four years older than him. To put it in context, if Bolt didn't exist, his two major rivals, Gay and Asafa Powell, would be battling it out to be the fastest men in history. As it is, they barely figure in the conversation.

Bolt, 24, grew up in a small rural town in Trelawny, Jamaica. When he was a young boy, his parents, who ran the local grocery store, took him to the doctor because he couldn't stay still. "I was all over the place, climbing things. My mum goes, 'There must be something wrong with this kid', and the doctor goes, 'Nooooo, he's just hyperactive.' " His mother, a Seventh Day Adventist, was gentle and forgiving, his father a disciplinarian who had two other children with different women. Respect was an important word in the Bolt household. And when young Usain didn't show enough of it, he knew his father would beat some into him. He says he could always tell when he was for it, because his dad became quiet. "I'll do something and he'll talk and talk, but when he's going to beat you, he just says, 'Come here', he holds your hand and then he goes off."

Look, Bolt says, he doesn't want to give the wrong impression – his dad may have been tough, but both parents were loving in their own way, and shaped his values. "Manners is the key thing. Say, for instance, when you're growing up, you're walking down the street, you've got to tell everybody good morning. Everybody. You can't pass one person." When he talks about his childhood, he does so in the present tense. It's a reminder of how young he still is.

Cricket was his first love. He grew up when the West Indies were still a force, and he wanted to be the new Courtney Walsh or Curtly Ambrose. He was gifted, too, opening the batting and bowling for his local side. "But I just happened to run fast. They said, try track and field, and I continued because it was easy and I was winning."

By the first year of high school, he was already absurdly fast. His dad told him to give up the cricket and concentrate on track and field. "He said I should do running because it's an individual sport, and if you do good, you do good for yourself." He cracks his fingers – they're the longest I've ever seen.

Back then, he hated his name. Everybody got it wrong – Husain, Tusain, they'd call him, anything but Usain. But friends and family just called him VJ. That was the way it was in Jamaica, he says – you got a nickname and it stuck. Why VJ? "My mum just said, he needs a nickname, so let's call him VJ... That's a boring story, innit?" His laugh is loud, guttural and full of fun.

In Bolt's likable autobiography, his brother Sadeeki is quoted as saying he was the better cricketer. Is that true? "That's what he thinks," Bolt says. And is he a good runner? "Ah, don't even go there. My brother is really, really slow." Sadeeki, eight months younger than Usain, also claims that he is the cool one, the handsome one, more popular with the girls. "Oh my God! He's always saying that. But he's more laid-back. In that sense, he's cooler."

More laid-back than Bolt? Surely that's impossible. "Yeah, he doesn't get stressed. There are things that bother me. I try not to let them, but they do." For example, he says, he was so uptight before that junior world championships final that he put his shoes on the wrong feet. "I've never been so nervous in my whole life. I was shaking because everybody was expecting me to win or get a medal. That one moment changed my whole life, because after that I was like, why should I worry?"

He still thinks it's the greatest race of his life. "I saluted the crowd, they were screaming. I was 15, in front of my home crowd – no better feeling. Gold, record, make your country really proud."

But for much of the next three years he was injured. That's when Jamaica turned on him. His own people said he was undisciplined, he partied too much, he was a good-time boy. And, yes, he did like to party, but the truth was he was suffering with the scoliosis. Jamaicans, he says, are always quick to criticise. Even now. He talks about losing to Gay. "I lost one race and it's this big thing. I went to a party and I met this girl I know, we're good friends. I got pictured with her, and I got injured, and all of a sudden it's the girl's fault. 'Oh Usain, he's this, he's that.' It doesn't bother me, because I know that's how they are."

He stops and looks at me. "But they're not as bad as you. You guys are awful, man." The press? "Yeah, you guys are rough on everybody. You put people under so much pressure." Take the England football team, he says. "You guys set them up by saying they've got to get married early. That's the English way. But you're not ready to settle down, and that's where all the girlfriends come in, and all the problems. You do not want to get married at 22! Especially if you're famous, because girls are going to be throwing themselves at you."

He says there's an inevitability to the way our footballers are undone – marry young, have affairs, get exposed by the tabloids, and that's when the real problems begin. "I wouldn't get married now. It would be awful. Wayne Rooney's the same age as me – he's married and got a kid. I don't think these guys are ready to get married yet. There's less stress on me. If they say, 'I saw Usain out with a girl last night', whatever, cos I'm not married."

I've never met a sportsman quite like Bolt. While so many are a frustrating mix of buttoned-up, conservative and grand, he is opinionated, funny and grounded. He's not quite finished with the rights and wrongs of partying. "With me, people say he's always partying – well, I do party. I work hard, and I do good, and I'm going to enjoy myself. I'm not going to let you restrict me. That's when the stress comes in, that's when you start to lose it."

When he parties these days, he says, he enjoys "a couple" of Guinnesses. And in the old days? "Ah, I don't want to talk about the old days! I was really bad, because I wasn't really focused yet. I'd go all night. But I never got drunk. I don't do drunk."

Not surprisingly, people have questioned whether somebody can run so fast without taking drugs. "There was one interview, and this guy was saying, 'You've just come on the scene and now you're running world records, why should we believe you?' And I was like, first, go check your history. I was world junior champion when I was 15. I got injured, and that delayed me, but you can't come here saying I just popped up."

Was he angry? "I was annoyed, because he was really saying he didn't believe me. I understand why people ask, and I say it's fine to ask the question, because sportsmen have been through so much."

The thing is, he says, he's probably the most tested athlete in the world, so he has nothing to worry about. When he was growing up in Jamaica, all his track friends were clean, too, he says. But they must have been aware of all the drug scandals? "Of course. It was really bad with sprinters – they'd break the record, and a year down the line you'd hear they were on drugs." In 2007, Marion Jones admitted she had taken steroids just before the 2000 Olympics, was stripped of the five Olympic medals she won and was subsequently sentenced to six months in prison for perjury. For Bolt, the discovery was heartbreaking: "Everybody had loved her and looked up to her, especially the female athletes. Then to discover their idol was on drugs all those years kind of messes you up."

Bolt couldn't have arrived at a better time – just when athletics looked as if it had fallen into permanent disrepute, here was a man who looked and acted so differently from those who had gone before. But he still managed to bring his own unique brand of controversy with him. In 2008, he had to plead with his coach to let him run the 100m in Beijing. He had been running the distance for less than a year, and was surviving on a diet of chicken nuggets at the Olympics. Not only did he win gold, he broke the 100m world record with a time of 9.69 seconds and, most astonishing, started beating his chest in celebration 15m before the finish. He was accused of showboating, of not trying hard enough. International Olympic Committee president Jacques Rogge said, "I think he should have more respect for his opponents."

How did he feel about the criticism? "It caught me off guard. I was worried that I really overdid it. But then I went to a couple of the other guys and said, 'Did you feel I disrespected you?' And they said, 'No, if we'd won we'd have probably done the same thing.' I was just happy. That was all the joy coming up."

In the build-up to his "proper" event, the 200m, he played around with his hair, demonstrated his new signature pose (based on a Jamaican dance rather than, as often assumed, a lightning bolt) and set a new world record of 19.30 seconds. He followed that with a third gold, in Jamaica's 4 x 100m relay team. A year later, at the world championships in Berlin, he smashed his own world records to win golds at 100m in 9.58 seconds and 200m in 19.19. Again, it looked as if he could have gone faster.

His team say, without a hint of a smile, that once he knuckles down he can break 9.4 seconds. Bolt himself says he can run faster. So does that mean he's lazy? "Yeah," he says enthusiastically. "Yeah, I am lazy. There's no doubt about that."

Ricky Simms, his manager, is sitting in with us. Does he agree with that assessment? "Yes, he is lazy. But when he trains, he trains very hard. The image on the track is that he just turns up and runs, but it isn't true. If you play football with him, he wants to beat everybody. He's very competitive."

The thing is, Bolt says, being laid-back ultimately helps him run faster. "On the track, that is just my personality coming out, me having fun. But it also helps me to relax. Back in the day, these guys were so tense, and then you make mistakes. So I have to let everything flow – that's my way."

Tyson Gay, on the other hand, looks as if he could explode with tension when he prepares. "That's just who Tyson is... I don't think Tyson goes out. He's a real shy person, just loves track and field, does everything right. We don't talk that much, because he doesn't really socialise. I've never seen him at a party."

Did it bother him when Gay beat him? "No," he says convincingly. But there seems to be a tension between the two of them, I say. He nods. "Of course. When Tyson was beating me early on, we were friends, and then, when I started beating him, everything went the opposite way. He didn't talk to me that much. I guess he's just one of those athletes who always wants to be winning."

But what if the situation were reversed and Bolt was regularly losing to Gay? "That would be hard for me. I couldn't deal with that." Would he regard it as failure if, say, he won a couple of silver medals in 2012? "Yes, I would, because you set a standard for yourself." Would he quit? "No, because I'd want to redeem myself."

We're talking about sporting legends, and I ask whether Carl Lewis won gold for sprinting at three Olympic games. He laughs. "I don't know the history of my sport. I'm not like those people who know everything."

What does he think makes him such a great runner? He looks a little blank. Perhaps the height helps and those huge strides, he suggests. "A lot of tall people don't have good coordination, but my coach says the one thing he can relax about is that I learn really quickly."

"Take off your clothes," Simms says to him, out of the blue. We both look shocked.

"I can't ask him to do that in an interview," I say. "It's not professional." Bolt just sits there giggling.

"Look at his body," Simms says with pride. "He's a specimen. The first time I took him to the track, the stride was like nothing I'd seen before. You know on the Discovery Channel, you see cheetahs, the way their feet move, the way the mechanics of their body work? He's similar. The mechanics are so perfect, and the strength he can generate from his hips, his hamstrings and his quads, everything is perfect for running."

We head off to a makeshift studio to get Bolt's picture taken and this time he does strip down to his undies. Simms is right, he is a specimen – more racehorse than man. What's it like to run so fast, to race the wind? "You don't really think during a race," he says. He clicks his fingers urgently. "It's just, what do I need to do now? Bang bang. When I get out of the blocks, I need to get this first turning, bang bang. There's no time to think. I'm just happy when I'm finished."

I ask about his ambitions. Ultimately, he says, he'd love to make a go of playing football professionally. He's being deadly serious. One of the perks of being Usain Bolt is that sporting stars love to meet him, so whenever he's travelling and there's time, he tries to train with a top football team. Last year it was Manchester United, a few days ago it was Bayern Munich. He's still carrying a copy of the French sporting newspaper L'Equipe, which features a spread on his football skills and praise from Bayern manager Louis van Gaal. He shows me a photo of himself with his arm wrapped round the dwarfed 6ft German forward Miroslav Klose. "If I keep myself in shape, I can definitely play football at a high level," he says.

"With his physical skills, I reckon he could play in the Premier League," Simms says.

But before that, Bolt says, there is so much more he has to achieve on the track. He can't wait for the 2012 Olympics; he says it will be like a home gig, because there are so many Jamaicans in London. And if he wins double gold there, then he might be prepared to rest on those considerable laurels. "People always say I'm a legend, but I'm not. Not until I've defended my Olympic titles." He smiles. "That's when I've decided I'll be a legend."

• Usain Bolt: 9.58 is published by HarperSport at £20.