It started with a splash, but the ripples continue to be felt.
When 16-year-old Chinese swimmer Ye Shiwen touched home to win a gold medal in the 400m individual medley, accusations began to fly.
She had beaten her personal best in the final by about five seconds and her world championship winning time from a year earlier by seven seconds, leading one American swimming coach to label it “suspicious”. Suggestions of foul play were rife. Ye, who has never tested positive for performance enhancing drugs - in or out of competition - called the accusations “sour grapes”. The International Olympic Committee declared her post-race drug test clean.
Her world record-setting victory has now been dissected more times than a medical school cadaver. Sports commentators, scientists, and swimming fans have produced charts, statistics and thousands of words both defending and questioning the authenticity of Ye’s performance.
The controversy hasn’t ended there, as I found out when I wrote a short explainer article for Nature News. While the arguments and counter arguments continue, the debate has shined light on a little-studied area of sports science called “performance profiling”.
This fledgling field melds sports statistics and computer modelling to flag performances that on the surface seem to defy human physiology or an athlete’s career trajectory. Profiling has already highlighted past wins that were heavily suspected of involving some form of cheating. But performances as they happen in the pool, track or road is a different matter – how can authorities instantly distinguish a clean athlete who has put in a superlative performance from one who has cleverly evaded drug tests? When opinions and conjecture can make or break an athlete’s reputation, not to mention relationships between sporting nations, can science reveal when fast is too fast?
As Australian swimmer Ian Thorpe told the BBC, he and other elite swimmers like Michael Phelps took large chunks out of their personal best times in their youth. And at the same games 15-year old Lithuanian swimmer Ruta Meilutyte improved her personal best by three seconds in the 200 metres freestyle event – a comparable amount to Ye.
Ye’s final 100m – and her last 50m in particular – has become the most scrutinised leg of her race. Reporters and commentators were quick to point out that she swam her final 50m faster than American Ryan Lochte’s gold-medal-winning performance in the men’s event. It’s an incredible, though not unheard of, feat for a female. But Ye’s supporters have said that comparing like-for-like in terms of the last 50m times doesn’t tell the whole story.
Lochte had a huge lead going into the final lap and may have eased up as a result, whereas Ye was down nearly one second at the start of the freestyle leg. Her performance could have been the product of an extraordinary, yet inexperienced athlete who didn’t know how to pace herself. However Ross Tucker, an exercise physiologist at the University of Cape Town, South Africa noted on his blog that athletes performing at their physiological limit tend to slow down as fatigue sets in, whereas Ye seemed to have a lot left in her tank after swimming 300m a couple seconds off world record pace. Also, her final 100m was only 10% slower than the best times in the women’s 100m freestyle swim; typical 400m individual medley performances are 18-23% slower.
Unusual trends
Using these types of statistics to establish whether a single performance is down to fair means or foul can raise questions but not answer them, say advocates for performance profiling. Critics may put an exceptional performance down to doping, but many other factors influence an individual run, swim or shot put, such as training, weather, sleep and diet.
