South Africa's Caster Semenya after competing in the women's 800m round 1 at the Rio 2016 Olympic Games.

Story highlights

Caster Semenya makes first appearance at Rio 2016

South African eases to 800m in heat

She has hyperandrogenism -- elevated testosterone levels

Huge support for athlete on social media

CNN —  

She’s the South African athlete who has been at the center of fierce controversy over whether she should be allowed to compete in women’s races.

But Caster Semenya, who advanced to the 800 meters semifinal at Rio 2016 in a time of 1:59.31 amid huge support in her home country, hasn’t let that controversy inhibit her.

Semenya won the world 800m title as an 18-year-old in 2009, but her triumph in Berlin quickly turned into a trauma amid scrutiny of her sex.

In the aftermath, it emerged that she had been ordered to undergo “gender verification” by the International Association of Athletics Federations (IAAF) amid concerns over the times she had achieved.

It was revealed that Semenya has hyperandrogenism – meaning elevated testosterone levels – and that sparked debate over whether, as an “intersex” athlete, she should be taking part in women’s events.

READ: Should a woman’s testosterone levels matter?

Semenya competes in the women's 800m heat at Rio 2016.

Semenya won 800m silver at the 2012 Games in London, losing out to Mariya Savinova – one of six Russian athletes who, an independent anti-doping report found, should not have been allowed to compete.

That race saw the emergence of Twitter hashtag #HandsOffCaster as people rallied to her defense – a hashtag that began trending in South Africa on Wednesday as she returned to the Olympic spotlight four years on.

The hashtag – along with #Caster4Gold and #TeamCaster – was used to demonstrate the groundswell of feeling in favor of the athlete.

Ahead of the race, South African Minister of Sports and Recreation Fikile Mbalula tweeted that Semenya was “focused like never before” and wrote: “It’s your day today, all the best.”

He added: “South Africa stands firmly behind Caster – unshaken. Go and show them who we are!”

South African newspapers, still reveling in Wayde van Niekerk’s sensational 400m final win, which saw him smash Michael Johnson’s 17-year-old record, were also swift to back Semenya.

“Run Caster, run” the country’s Times newspaper said in a front page headline, publishing a cartoon that showed Van Niekerk handing the baton of South African hopes to her.

Its front page article said Semenya had been “subjected to unprecedented scrutiny and humiliation” by having to undergo gender verification.

It said the row had resurfaced because her improved race timings throughout the year had made her “overwhelming favorite” to win gold in Rio.

But it added: “The uproar has sparked a backlash with South Africans rallying around the Limpopo star, who refers to her critics as ‘haters.’”

Two years after Semenya’s win in Berlin, the IAAF ruled that female athletes whose testosterone levels were above a set level would have to use medication to bring the levels down.

READ MORE: ‘That girl is the Olympic spirit right there’

After the race in the German capital, Italian runner Elisa Cusma Piccioni said: “She is a man,” while Canadian Diane Cummins described her as “on the very fringe of the normal athlete female biological composition from what I understand of hormone testing.”

Cummins added: “From that perspective, most of us just feel that we are literally running against a man.”

When a 2015 Court of Arbitration for Sport decision decreed the IAAF ruling was not based on sufficient scientific foundation, Semenya was able to compete without testosterone suppression – and the furore began all over again.

Jean Verster, the coach who has worked with her since 2014, told the Guardian recently he has been “trying to protect her” from the arguments that rage.

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He described her as “a fantastic human being, a down-to-earth person and a great athlete who is like a mother to some of the girl athletes in our group.”

Asked whether he expected a happy outcome for his star at Rio, he said simply: “Absolutely. We wouldn’t be doing this if we didn’t believe that.”

And on Wednesday, Semenya started proving him right.

Thabile Vilakazi contributed to this report.