A thin X criss-crosses Ye Shiwen's broad back. It is a mark left by the lines of her swimsuit, her skin darker around it, testament to the hours the teenager spends in an open-air pool; branded by her work ethic.
To many the 17-year-old is a marked woman for a different reason. Last summer, on the opening day of London's Games, Ye produced a landmark swim, obliterating a four-year-old world record with a performance that defied belief. There were plenty who did not believe her achievement and innuendo was already her companion as she stepped onto the podium to collect gold for the 400m individual medley.
Ye, then 16, was not the youngest gold medallist in the pool but neither of the 15-year-olds, Katie Ledecky, who left Rebecca Adlington in her wake, or Ruta Meilutyte, the Plymouth-based Lithuanian, had their victories asterisked by the doubters. Ye's tests in London and since have been negative for drugs but this remains a suspicious sporting world.
Last month she won three titles at her national championships, a first step towards her aim of repeating her London double – she also won her signature event, the 200m individual medley. At August's World Championships in Barcelona, she will step warily into the global spotlight again because London bruised her.
"I was very depressed and angry after London," says Ye, "but everything is fine now." She gives the barest nod of her head while her answer is translated as if adding her own full stop. She wants wants to look forward to Barcelona and then the next Games three years from now, in the city where we are talking and where she is attending the Laureus World Sports Awards. Out of the window behind her as she sits on her hands on a hard-backed chair there is a view of Copacabana Beach, a golden sprawl that is surely otherworldly to Ye.
Beaches suggest downtime, leisure, a concept almost alien to Ye, who has trained relentlessly for a decade – around two thirds of her young life. She has one morning off a week, Thursdays, otherwise it is five hours a day in the pool plus extra sessions on land. Much of the hard aquatic yards are done open-air at altitude in Yunnan Province in China's south-west.
"It is pretty tough, but I'm committed to it," she says. This regime, Ye says, is why she is potentially the best all-round female swimmer in the world and part of a Chinese team that has made remarkable strides since hosting the Games. "First of all it is hard work by the team and the coaches, they have paid a lot of attention to detail," adds Ye. "The nation provides very good conditions for training and supporting the athletes. It is a combination of hard work and good support.The training has been taking place at a very high altitude in China and I believe my fitness has improved because of the lack of air at altitude."
Her success in London earned her acclaim back home in Hangzhou. "People recognise me now – especially when I go shopping. I feel quite excited when that happens," she says, looking up and laughing, suddenly just a teenager. She was named Zhejiang Model Worker by her home province, accompanied by a bonus of 1.8m yuan (£193,000). That was 800,000 yuan less than handed to Sun Yang, the male swimmer who also took two 2012 Olympic golds. Sun shone in London and none of the gloss was taken off his wins by accusations of doping.
There is still doping in Chinese swimming – 17-year-old world champion freestyler Li Zhesi is serving a ban for taking EPO – but the country no longer stands accused of widespread abuse as in the 1990s, when more than 40 swimmers were banned. Suspicion surrounds Ye because of her dramatic improvement in London. Her 400m gold medal-winning effort was five seconds quicker than any she managed before the Games. She swam her final freestyle length faster than Ryan Lochte, the men's 400m winner.
"Any time someone has looked like Superwoman in the history of our sport they have later been found guilty of doping," suggested the respected US coach John Leonard. He drew parallels with Michelle Smith, the Irish swimmer who won the same event in 1996 and was found to have tampered with a dope test sample two years later. Smith has always denied doping. Ye too denies doping. She is, she says, tested regularly. A question about doping – should she be more blunt and vehement in her denials – elicits an exchange between Ye and the translator who has accompanied her from Beijing. Ye exhales loudly.
"She says," the translator instructs finally, "she uses the evidence from Wada [the World Anti-doping agency] and their results to answer this question." It has become her default defence after being asked again and again in London. Did it hurt being accused of being a doper? "Yes," nods Ye.
The responses may be curt but there is no refusal to answer questions about doping, nor instruction to move on from the topic issued by the athlete's entourage, as would be the norm in an interview with a Western sports star; and back home Ye is a star.
She says she felt "burnt out" after London, an experience she got through via daily phone calls to her parents. "During the Olympics it was pretty challenging so every day my parents would call me to relax me and calm me, make me stronger," she says. "I was pretty angry when I was asked the questions about doping but after a while it was OK and everything is fine for me."
There is a case to be laid out for her startling improvement. At her age, development can be ferociously quick, and erratic, just as happened with Ledecky, and when Ye's times are broken down that last length can be laid next to Adlington swimming the last length of her 800m freestyle at the 2011 World Championships in an even faster time. Two Australian coaches, Ken Wood and Denis Cotterell, who have had turns overseeing her development, are enthusiastic backers, each pointing to her work ethic and mental toughness in the pool – outside it she is quiet, bordering on shy. The model worker, they say, is also a model swimmer.
However her achievements have come – and there are many in the swimming community who remain utterly convinced she has, possibly unknowingly, doped – hard work has been its cornerstone. A teacher at her kindergarten spotted her large hands and feet and pushed her towards swimming. From the age of seven she has trained intensively, much of it away from home. During her teenage years she was allowed one phone call home a week. Her parents called her their "little ghost".
Her rise has been rapid and if she continues to develop she will become one of the world's dominant swimmers. After her five different events at the Chinese championships, she revealed that her coach had decided to work her even harder because he thinks she is "fat". It is a judgement that is cruelly harsh and elsewhere would have been greeted with disbelief. She is back in Yunnan, churning out length after length accompanied, as she probably always will be, by a flotilla of doubters.
"It is a long journey," she says of the career that lies ahead, via Barcelona and Rio. "Different people have their different views but I will just keep on going."