Caster Semenya has become the unwilling face of an issue plaguing the Olympics.
The South African runner won the gold medal in the women's 800-meter final, beating the next-closest runner by more than a second.
But she reportedly has a condition called hyperandrogenism, which causes much higher levels of testosterone than women typically have.
There's speculation other athletes have the condition, as well — and it's led to criticism that they have an unfair advantage.
In 2010, the International Association of Athletics Federations had Semenya sidelined while she underwent gender testing. She was eventually cleared to compete.
For the 2012 Olympics, athletes with the condition were forced to take drugs that lower testosterone levels, but those rules were thrown out for the Rio Olympics.
That's because The Court of Arbitration for Sport ruled that there was no clear evidence that athletes with hyperandrogenism have an unfair advantage over other athletes.
Medical experts say hyperandrogenism can affect people in different ways, and athletes with the condition aren't necessarily guaranteed a competitive advantage.
But there is still frustration among the athletes. Lynsey Sharp, one of the runners competing against Semenya, said, "Everyone can see it's two separate races, so there's nothing I can do."
Semenya told the BBC that all the criticism is only helping her grow as a person.
"They're making you a better person," she said. "People should learn how to unite. Sport is all about uniting people and not discriminating."