With her expressive face and childlike glee, Chinese swimmer Fu Yuanhui has become a walking meme and social media sensation thanks to the Rio Olympics. She's one of the most popular athletes in China and has won hearts the world over.

But her influence now stretches beyond funny gifs and a quirky catchphrase. She has brought to the fore a topic that remains taboo in Chinese sport and society: periods. Specifically, the debilitating effects they can have on women's bodies.

After the final of the women's 4x100 metre medley relay race on Sunday, in which her team came a disappointing fourth, Yuanhui was spotted hunched over in pain.

The 20-year-old told a journalist: "I didn't swim well enough this time," the BBC reported. When asked if she had a stomach ache, she said: "It's because my period came yesterday, so I felt particularly tired – but this isn't a reason, I still didn't swim well enough."

Periods are rarely spoken about openly in Chinese sport, and women took to social media to thank and empathise with Yuanhui.

One blogger wrote (in Chinese): “[Menstruation] is an unspeakable issue in the public for women, but Fu actually talked about it in a live interview with CCTV. That’s exactly her personality. Cool!”, Quartz reported.

For many Chinese people, it was the first time they realised it was even possible for women to swim while on their periods. Let alone that it is hygienic, perfectly safe and even recommended as a way to ease cramps.

Confused people of both sexes also took to Weibo to ask: “Why there was no blood in the swimming pool?”, later finding out that the answer lay in tampons, Quartz reported. Tampons are not widely used in China and have never been popular. Not a single tampon was made by a Chinese manufacturer in 2015, compared to 85 billion sanitary pads. Only this month is a domestic tampon brand launching in the country.

There is still a high value placed on virginity in China and women still undergo hymen restoration surgery. Many believe that using tampons can break a woman's hymen, so they are never mentioned in Chinese sex education classes, reported Quartz.

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China's Fu Yuanhui competes in the Women's 100m Backstroke heats during the swimming event at the Rio 2016 Olympic Games Photo: FRANCOIS-XAVIER MARIT/AFP/Getty Images.

So why is menstruation so taboo in China? And why is there such mystery and squeamishness surrounding the methods women use to deal with them?

The answer is inherently tied to the position of women in Chinese society. "Despite huge social changes and reforms in the last three decades, China is in some ways still a conservative, Confucian and – at least in its politics and public face – patriarchal society," said Kerry Brown, Professor of Chinese Studies and Director of the Lau China Institute at King's College, London.

Despite "constituting an empowered minority " in China, due to the country's unbalanced sex ratio, women are largely absent from the top echelons of Chinese politics and only make up about a third of the main business leaders, Brown told Refinery29.

All of these factors help to create an environment in which maleness is the default, and women's concerns are not a priority.

When it comes to periods and why menstruation is a sensitive topic in particular, Brown told Refinery29: "I guess you have to think about the fetishisation of the female body, the ways in which in protocapitalist [early capitalist] Chinese modern society, the female body has become a commodified form, and how very ideal and unrealistic expectations towards women's physical appearance are promoted in the Chinese media – witness the huge numbers of plastic surgery places now, and the plethora of dieting and other regimes."

So while women in China have gained influence and other benefits during the last six decades of Communist rule, they still suffer discrimination and face glass ceilings, Brown said. "The swimmer Fu has managed to contribute at the Olympics by opening up another area of discourse which was closed down till now. And that is a good thing," he added.

Ignorance surrounding menstruation is far from confined to China, however, and periods remain a taboo and sensitive topic in societies around the world.

Less than a week ago, before Yuanhui's comments, it emerged that a gym in Georgia banned women from using the pool when on their periods. Unfortunately it seems there's a long way to go before everyone grasps the truth behind one of the most basic facts of life.

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