LONDON - At 16, the Chinese swimmer Ye Shiwen is one of the youngest competitors in the Olympics and so far the most remarkable. What she has done in the pool is the water-based equivalent of what Usain Bolt did on the track four years ago in Beijing.
On Saturday night, Ye not only shattered the world record in the 400 individual medley, winning gold in 4 minutes 28.43 seconds, she also swam the final 50 meters faster than Ryan Lochte did in winning the men's race.
On Monday, Ye returned to the pool for the heats and semifinals of the 200 individual medley, her best event. There is nothing to indicate that Ye is anything more than a great swimmer from a country that holds about a fifth of the world's population, a teenager who relies on the latest scientific training and the kind of adolescent certainty that makes her unaware of her own limitations.
And yet women's swimming does not permit itself naive and untempered salute. Not after the systematic East German doping of the 1970s and '80s. Not after repeated Chinese scandals in the 1990s. Not after Michelle Smith of Ireland won four medals at the Atlanta Games in 1996 under disputed circumstances and was later barred from competition for tampering with a urine sample.
The response to unsurpassed achievement now falls somewhere uncomfortably between amazement and incredulity, that gray area between celebration and suspicion.
Euphemism serves as scar tissue that has formed around guileless trust.
"That's pretty unbelievable," David Sharpe, a Canadian swimmer, said of Ye's finishing kick on Saturday, in which she covered her final 50 meters in 28.93 seconds, faster than Lochte's 29.10. "No one really understands how that happened."
Ye swam her final 100 meters of the 400 IM in 58.68 seconds. Lochte was only three-hundredths of a second faster. No one could immediately remember a woman closing faster than 61 seconds.
"Interesting," said Natalie Coughlin, the American with 12 career Olympic medals.
"Insane," said Stephanie Rice of Australia, the 2008 Olympic champion and former world-record holder in the 400 IM. "Fifty-eight is out of control."
Lochte made a cordial joke about being outkicked. On Monday, Michael Phelps, who finished fourth in the men's 400 IM, smiled at a question about Ye's closing speed and said: "She almost outswam me, too. We were all pretty shocked. It's pretty impressive that she went that fast."
No swimmers accused Ye, who is 5-foot-8 and weighs 141 pounds, of using illicit substances to fuel her kick. The default reaction became: No comment.
John Leonard, an American who is executive director of the World Swimming Coaches Association and has for years spoken vehemently about his suspicions of doping in China, told the Guardian on Monday that he found Ye's performance "disturbing."
Other officials were more gracious.
Frank Busch, national team director for USA Swimming, called Ye's final 100 meters "more than remarkable, phenomenal."
"My hat's off to her training," Busch said. "Whatever she's done has paid off."
Was he concerned that what Ye had done was not legitimate?
"I would never go there," Busch said.
Yet, China has brought uncertainty upon itself. Ye has never tested positive for banned substances. But in the 1980s and '90s, according to news accounts, more than 50 Chinese swimmers have. Seven were caught by a surprise test at the 1994 Asian Games in Hiroshima, Japan. One swimmer, Yuan Yuan, was caught with 13 vials of human growth hormone at the 1998 world championships in Perth, Australia.
There has long been a debate about whether doping in China was state sponsored or directed by individual coaches. A former chief doctor for the Chinese gymnastics team told the Sydney Morning Herald last week that in the 1980s, it was state sponsored.
Some believe that embarrassment over doping scandals led China to more carefully scrutinize its athletes. In any case, the dominance of China's female swimmers in the mid-1990s has ebbed. China won only one gold medal in swimming at each of the past two Olympics, including the 2008 Beijing Games.
Already in London, it has won two. This follows a recent report by the official Xinhua News Agency that in March a 16-year-old swimmer named Li Zhesi, a former relay champion, tested positive for the blood-boosting drug EPO. While Ye's achievement might have once brought only commemoration, it now comes with questions.
According to state-run media, Chinese coaches and athletes have taken an oath to remain clean. Some athletes are even said to be avoiding meat, fearing that it might be tainted with a banned, performance-enhancing substance called clenbuterol.
"There's absolutely no problem with doping," Ye said Monday in translated remarks. "The Chinese team has always had a firm policy about anti-doping."
Ye has repeatedly said hard work, not banned substances, have made her a champion.
"If the coach asks me to practice 10,000 meters," she told the Beijing Morning News, "I would never be lazy to swim 9,900 meters instead."