Why are Jamaican sprinters so fast?

In the race to decide the fastest man on earth, Usain Bolt was unconcerned when US rival Justin Gatlin stole an early lead.

“If you see it in replays, it looks worse than it felt in the race,” he said in Rio de Janeiro on Sunday. “I know he always gets a good start and I knew I had to take my time and chip away at the lead.”

The Olympic final of the men’s 100 metres would not seem to afford much time for chipping away, but Bolt reeled in his rival by the halfway mark, overtaking him to become the first man to win the Olympic title three times – and confirm his status as the greatest sprinter in history.

Finishing in 9.81 seconds, Bolt also notched another mark on the 50 fastest 100m times ever recorded. Before Sunday, 29 of those runs belonged to fellow Jamaicans – many from Bolt himself and contemporaries Asafa Powell and Yohan Blake.

Women sprinters follow the pattern: most recently, Elaine Thompson picked up gold in the women’s 100m in Rio on Saturday.

So why does Jamaica, an island nation of 2.7m, produce athletes that so handily trounce those from the US, a far richer country with a population of around 320m?

For Bolt, it’s the island’s unique sporting culture. Sprinters, rather than footballers, are the nation’s superstars; the annual schools athletics competition, called “Champs”, is played to packed stadiums and televised. The times set by these juniors can trump those of national champions in most other countries.

So the 29-year old Bolt in the starting blocks in Rio was long-trained in the ways of bruising battles played out before big audiences. He has previously suggested that repeated victories over Powell, his fellow countryman, is partly because of Bolt’s experience in the schools athletics competition. Powell’s school did not always qualify for the event.

“It’s just that we have a good system,” said Bolt. “Boys and girls Champs keep producing more and more athletes. For years to come, we will have the great athletes to win.”

Then there is genetics. A 2010 study into Jamaica’s sprinting success delved into the impact of a gene associated with explosive running, whereby a bigger than average heart facilitates a faster flow of oxygen to the muscles. If was found that the frequency of this gene is higher in Jamaicans than West Africans, who in turn have it more than Europeans.

Athletes of African descent are also known to have more “fast twitch” muscle fibres required for elite sprinting. The list of the ten fastest humans in history contains only black men from Jamaica, the US, Canada and Nigeria.

Yet, suspicions remain. Gatlin has twice been banned for doping offences, and on Sunday the US runner was loudly booed in the Olympic stadium, while Bolt was received rapturously.

“It was surprising,” said Bolt. “I didn’t really expect that. I guess there’s a different culture in different places.”

The Jamaican system has also had problems with drugs cheating. In The Bolt Supremacy: Inside Jamaica’s Sprint Factory, the investigative sports journalist Richard Moore explored whether Bolt’s victories could be explained by superior training, natural talent or more surreptitious means.

It was published after revelations in 2013 about the lax nature of Jamaican doping controls, with a number of sprinters, including Powell and Shelly-Ann Fraser-Pryce, subsequently serving bans for drugs offences. Fraser-Pryce won bronze in the women’s 100m final on Saturday, while Powell will race alongside Bolt in Jamaica’s 4 x 100m relay team next Friday.

Earlier this year, Nesta Carter, a sprinter who won gold with Bolt in Jamaica’s 4 x 100m relay team during the Beijing Olympics was found to have a banned stimulant in his system following the retesting of doping samples from the 2008 games.

Moore has concluded that Bolt is likely to be clean athlete, while also arguing that chaotic administration in Jamaica made it unlikely the nation could execute a sophisticated state-doping system such as that in East Germany in the 1970s. Bolt has never tested positive for performance enhancing drugs.

The Jamaican runs again in the 200m on Thursday, where he will face rivals such as Wayde van Niekerk. The South African won the 400m on Sunday by breaking a 17 year-old world record set by Michael Johnson, the US runner dubbed “Superman”.

Is he concerned that van Niekerk, who has been training with Bolt in Jamaica, could block the reigning champion’s bid for more gold in Rio? “He can’t beat me over 200m,” said Bolt with a broad smile. “Don’t worry about that.”