The South African middle-distance runner Caster Semenya will compete in the women’s 800-meter final this Saturday in Rio de Janeiro, and she’s favored to win. Her potential victory is already being described as a “dilemma.

At best, her detractors will give the credit for her win to the 25-year-old's body chemistry rather than her skill. It might even prompt international sporting agencies to once again rethink what it means to be a female athlete.

No one is accusing Semenya of using illicit substances. Quite the opposite: Some have suggested she should be taking drugs in order to bring her hormone levels more closely in line with those of average women.

Semenya was raised and identifies as female. But according to a leaked medical test, Semenya’s testosterone levels are three times as high as those of most women, and she has internal testes instead of ovaries.

Semenya quite literally burst onto the scene in 2009, tearing swiftly past her rivals at the world track and field championships in Berlin, and she took home a silver medal at the 2012 Olympics. The more successful she became, the more speculations swirled that she’s not fully female.

Soon after her 2009 victory, the International Association of Athletics Federations general secretary Pierre Weisse cracked, “She is a woman, but maybe not 100 percent.” Russia’s Mariya Savinova, meanwhile, invited people to “Just look at her.”

And look at her they did. Track fans were quick to note that Semenya, with her beefy biceps and flat chest, doesn’t look like most women. The New Yorker called her “breathtakingly butch,” noting that, “Semenya became accustomed to visiting the bathroom with a member of a competing team so that they could look at her private parts and then get on with the race.”

Semenya was banned from competing for several months and underwent a gender test. In 2011, the IAAF capped the amount of testosterone female athletes could naturally possess and still compete with other women.

It’s unclear how much of an advantage testosterone gives women in running—or in anything else. Men are faster, on average, than women, but testosterone is not the only reason: Men also have more red blood cells and bigger hearts and lungs. Due in part to the lack of scientific clarity, in 2015 the Court of Arbitration for Sport suspended the IAAF’s testosterone regulations for two years.

That policy change allowed women like Semenya and Dutee Chand, an Indian runner who was at one point banned for her elevated testosterone levels, to compete in this year’s Olympics.

But as the New York Times reported, several female athletes had already gone to extreme lengths to comply with the testosterone rules:

At the London Olympics, four female athletes, all 18 to 21 years old and from rural areas of developing countries, were flagged for high levels of natural testosterone. Each of them subsequently had surgery to remove internal testes, which produce testosterone, as well as procedures that were not required for resuming competition: feminizing vaginoplasty, estrogen replacement therapy and a reduction in the size of the clitoris.

Chand, meanwhile, refused to take testosterone-reducing hormone drugs, telling officials, “I want to remain who I am.” (Chand performed poorly in her heat in Rio, further underscoring that testosterone isn’t exactly “jet fuel,” as Stanford University bioethicist Katrina Karkazis put it to the Times.)

Regardless of where sports’ governing bodies ultimately land on gender tests for female athletes—the IAAF has signaled it may challenge the Court of Arbitration’s decision—the controversy is unlikely to rest, since athletes are more likely to have intersex features than the general population. The growing societal acceptance of transgender athletes is also bound to complicate things for gender-sticklers.

The debate over Semenya, Chand, and others like them should make viewers question what, specifically, it is we want from Olympic events and athletes. In analyzing a related issue, Oscar Pistorius’ carbon-fiber legs, David Epstein quoted philosopher Bernard Suits in defining sports as “the voluntary acceptance of unnecessary obstacles.” Sports have rules because it’s just not fun to watch someone drive a Ford F-350 across the finish line, leaving a pack of honest runners in the dust. But if you’re born with a V8 engine in your bones, is it against the rules to use it?

As the historian and writer Louisa Thomas pointed out recently, integrity is at the core of the Olympics. The modern Games were founded by a French baron who sought to forge not just strong bodies, but characters: “The Olympics were an elaborate ritual constructed around the idea that a running race—or a wrestling match, or a ski jump—could tell you something about the virtue of its competitors,” she writes.

So pure of heart were these early Games that professional, as opposed to amateur, athletes were banned until the 1980s. These notions of athletic righteousness live on with the near-universal rejection of doping, at least by Olympics fans and judges. It’s no longer considered crude for athletes to earn money, but drugs to boost performance are clearly verboten. Russia’s extensive doping program was met with worldwide scorn.

Still, it’s not considered unsportsmanlike to simply be strange-looking. Countless Olympians are celebrated for unorthodox features that give them an edge in their sports. Much has been made of Michael Phelps’s preternatural wingspan and ultra-flexible feet that turn into “virtual flippers.” Biostaticians have said Usain Bolt’s 6-foot-5-inch height and fast-twitch muscle fibers make him perfectly suited to sprinting. Other athletes have less obvious advantages, like high levels of hemoglobin or diminutive heights tailor-made for tumbling passes.

It takes something special to become an Olympian, even if it’s an unusually gritty mindset. For Marla Runyan, the first legally blind runner to have competed in the able-bodied Olympics, the path to Sydney involved living hand-to-mouth on disability insurance, battling intense foot pain, and begging Nike for free shoes. And that’s on top of the small issue that she couldn’t see the track.

To be an Olympian, is, in other words, to be abnormal. The event draws people from the ends of every bell curve, and a zen attitude or shaved torso can make all the difference.

And judging by the fascination with Olympians’ body measurements, audiences like that the athletes are all so singular. Just as it wouldn’t be enjoyable to see the aforementioned pickup trucker square off against marathoners, we probably wouldn’t glue ourselves to our TVs to watch tubby Midwestern accountants hurl themselves through the air.

Sports must have rules, in other words, but the Olympics are already filled with social, cultural, and biological rule-breakers. The fact that people are alarmed about the masculinity of athletes like Semenya, but not the myriad other ways Olympians deviate from the norm, suggests that our anxieties about her might be rooted in something other than a love of fairness.