Ye won the women's 400m individual medley in a world-record time, and was heavily favoured to win last night's 200m individual medley as well. After her 400m gold, it emerged she had swum the final 100m freestyle leg as fast as the US's Ryan Lochte did when winning the men's equivalent.

That is remarkable enough, but consider also that Ye is only 16 and has improved her best time in the event by a staggering seven seconds since last year's World Championships.

Then, the final important piece of the puzzle is that she is Chinese.

The world of swimming, and indeed sport, is extremely mistrusting of sensational performances by Chinese athletes. That scepticism dates back to the 1990s, when China emerged from obscurity to produce a handful of the fastest women runners ever seen. In an astonishing period, they broke world records at 1500m, 3000m, 5000m and 10000m, and three of those records still stand today.

Even more suspiciously, the athletes came, saw, conquered, and then vanished soon after the 1996 Olympic Games. Their coach suggested at the time that they were powered by "turtle blood", which the rest of world quickly adopted as a euphemism for drugs.

The fact that China has failed to produce athletes at that level since the 1990s only reinforces the doping claim.

Back to the pool. The 1990s also produced a spate of dominant Chinese performances, but they were caught. An "epidemic" of positive drug tests in the 1990s saw China gain a reputation as a doping nation (rightly or wrongly). Since 1990, 40 Chinese swimmers have failed drug tests.

That is three times more than the next-highest nations, and so it should come as no surprise that Ye is under scrutiny.

Some will call this unfair discrimination, and I would agree that it is not good enough to condemn someone as a doper simply because of whose flag they compete under. However, there is a difference between judgment and asking the question, and, in this case, it is a question that simply must be asked.

In the same way that a cyclist who wears the yellow jersey as winner of the Tour de France is suspected because of the history of the sport, so too a young athlete from China will be questioned when they produce remarkable performances. The process of drug testing must be allowed to provide the proof, and we all remain innocent until proven guilty.

Ye's age of 16 does not, in itself, make her triumphs inexplicable. Swimming is a sport that does produce exceptionally young champions - Phelps was 15 in Sydney, Ian Thorpe was a world champion at 14.

The combined effects of training and physiology make it feasible for a 16-year-old to improve by seven seconds in one year. However, what is unusual is that Ye improved by seven seconds having already been a world-class swimmer at 15 - she was world champion in the 200m individual medley in 2011 and fifth in the 400m individual medley. To improve that much from world-class levels raises a red flag. Add to that the extraordinary fact that she outpaced the men's champion, and there's enough there to make her story "uncertain".

Sadly, sport has taught us that what is "uncertain" often ends up being "dirty". I hope she is competing clean, but sport has made fools of us before, and its history makes her performances seem more than a little suspicious.