GERALD IMRAY, AP Sports Writer

STELLENBOSCH, South Africa (AP) — It seems the sports world just doesn't know what to do with an athlete like Caster Semenya.

The South African runner, and others like her, may present one of the greatest dilemmas for the perception of fairness in sports.

Athletes like Semenya with intersex conditions — those that don't conform to standard definitions of male or female — debunk any presumption that everyone fits neatly into those definitive categories in sports.

According to sports scientist Ross Tucker, "the biology isn't quite as simple as that."

Semenya's story is well-known. As an 18-year-old newcomer at the 2009 world championships, she dominated the best women's 800-meter runners. The gap between her and the defending world champion, who finished second, was astounding. Semenya celebrated by showing off her bicep muscles, stoking a controversy sparked hours earlier by revelations that she had undergone sex verification tests.

She was later sidelined for 11 months by world track's governing body, the IAAF, and was only cleared to run again in 2010. She returned and won a silver medal in the 800 at the 2012 Olympics.

Now 25 and the favorite for gold at the Rio Olympics, Semenya has been pursued by gender questions. But her case has never been about a man masquerading as a woman.

Semenya is a woman because she says she's a woman, was legally recognized at birth as female, treated as female, and identified as female. Nobody can dictate to Semenya what gender she is.

But since the 1950s, track and field has conducted sex testing to protect women's competitions, initially using very basic sexual anatomy tests, and later using chromosomes. The tests didn't work.

Sex testing in sports should be about preventing an unfair advantage and, therefore, not about genitalia or chromosomes, which don't make athletes run faster, jump higher or throw farther.

What does, according to the IAAF, is testosterone.

The IAAF says testosterone is the most significant factor in athletic performance. Men, generally, have more testosterone than women. In 2011, the IAAF officially drew a line between men and women in terms of testosterone.

The issue it sought to resolve was hyperandrogenism — high levels of naturally occurring testosterone in some women that apparently gave them a competitive advantage.

Tucker said research conducted by the IAAF showed six women with intersex conditions competed at the 2011 world championships. Joanna Harper, an expert on gender in sports and a consultant to the IAAF, thinks two female medalists at this year's indoor world championships are probably intersex, and estimated 5-10 intersex athletes will compete in track and field at the Rio Olympics.

Six years after Semenya was subjected to the IAAF tests, the lid was lifted on her situation in 2015. That's when Indian sprinter Dutee Chand went to the Court of Arbitration for Sport — the highest court in world sports — and challenged the IAAF rules that regulated testosterone in hyperandrogenic women.

The case forced the IAAF to publicly defend its rules that for hyperandrogenic women to be eligible to compete as women, their testosterone levels must be below a certain mark. It came down to a tiny measurement: how many nanomoles — a billionth of a mole — of testosterone a woman had per liter of blood. It couldn't be 10 nanomoles or more per liter, roughly the lower end of the male range. If it was 10 or higher, it had to be lowered.

Harper said the testosterone levels of these hyperandrogenic women could be lowered either through the removal of internal testes or with hormone-suppressing medication.

Former Olympic runner Bruce Kidd, a professor of physical education and an adviser to Chand, opposes the testosterone-limiting rule. He argues that the testosterone is natural in these women, and although men produce more of it, "there is nothing to say that testosterone is a male hormone."

"Dutee and Caster are (competing) with their own chemicals," Kidd said. "They are fully in keeping with the Olympic spirit of being true to yourself and playing without doping. So why are they being castigated for that? I think it is so unfair."

Significantly, the IAAF accepted that its rules were basically discriminatory but were devised in search of a greater justice: fairness for women's track and field.

Opponents of the testosterone rule pointed to the natural advantages of other athletes that aren't regulated, such as Usain Bolt's fast-twitch muscle fibers, Michael Phelps' big wingspan and former cyclist Miguel Indurain's huge lung capacity.

Harper, who supports the testosterone-limiting rules, explained that sports competitions don't have categories for athletes with slow twitch, short arms or small lungs. But women's sports are protected because if they weren't, there would be serious ramifications for Olympic qualification.

Chand — and by default, Semenya — won an interim decision last year in the Court of Arbitration for Sport case, but on a different reasoning. The IAAF didn't have definitive evidence to show how much of an advantage the extra testosterone gave hyperandrogenic women. CAS gave the IAAF until July 2017 to provide the evidence needed to reinstate the rule, which won't be in place in Rio.

The IAAF said it doesn't comment on individuals who were managed under its hyperandrogenism regulations, but it still believes in the rules. Work is ongoing to find evidence.

Harper is involved in that process and expects to be an expert witness for the IAAF when the case returns to court.

The best evidence might be provided right now by Semenya.

Since the testosterone regulations were shelved, Semenya has won every major 800-meter race she entered this season — running a personal best last month and the fastest time anywhere in seven years. Her best time this year is around four seconds faster than last year.
Tucker predicted it.

At the start of the season, when Semenya was competing at the South African national championships, Tucker posted a tweet saying she could break Jarmila Kratochvilova's 33-year-old
world record of 1:53.28 for the 800 this season. He thinks that without testosterone regulation, Semenya, a good athlete anyway, could become untouchable.

"You need a person who comes along and has got all the attributes that would make an elite athlete, plus they have high testosterone. Then you will get a freakishly good athlete, and that's the case with Semenya," Tucker said. "If I was a woman 800-meter runner right now, I'd be looking to change careers. You can't beat this advantage. It's too big."

But Alice Dreger, a historian of medicine and science who has written about Semenya, poses a question with regard to the testosterone regulations and what the IAAF is trying to achieve with its proposed limits:

"The data they have indicates it causes the athlete's performance to drop precipitously, basically eliminating them from play," Dreger said. "So what does it really mean to say 'you can compete if you get these interventions,' if the interventions mean you can't really compete anymore?"

Semenya, often media-shy, smiled and spoke easily with reporters at the nationals, saying she was starting to enjoy the sport again.

"I haven't had fun, you know, in a while," she said.

Gordon Mack of FloTrack interviewed Semenya after her 1:55 performance in Monaco