When the world's fastest women race for gold over 800m in Tokyo, all three medallists from the 2016 Olympics will be absent - barred as intersex athletes who refuse to alter their natural hormones to meet the rules of sport.
The ban is one of many controversies dogging a sporting spectacle that opens on Friday - a year late - amid a global pandemic, a slew of scandals and deep disquiet over potential risk to life of staging a mega event between 206 nations.
For some of the women who have trained relentlessly for the chance at middle-distance glory, the intersex dispute is a mere distraction. For those sidelined - a disaster.
"It broke my heart when I was told I couldn't run in my favourite 400m event because I had higher testosterone," Aminatou Seyni said in an email sent by her athletic federation in Niger.
"I didn't want to take any medical steps... My hormones are natural," said the 24-year-old, who will run in the 200m where high testosterone is no barrier.
Seyni ranks 44th in the world for the 200m, some 40 places behind her timings over the longer race she can no longer run.
Intersex people are born with atypical chromosomes or sex characteristics. Women like double Olympic 800m champion Caster Semenya have some male sex characteristics, including internal testes that produce average male levels of testosterone.
World Athletics, the sport's governing body, says this lends an unfair advantage over middle distance and, in 2019, mandated lower testosterone to "ensure fair competition for all women".
But many women such as Semenya and fellow 2016 medallists, Burundi's Francine Niyonsaba and Kenyan Margaret Wambui, refuse to use drugs or surgery to alter the makeup of their bodies.
Semenya is challenging the rules - the bar covers races from 400m to a mile - but the ruling won't come in time for Tokyo.
Namibian medal contenders Christine Mboma and Beatrice Masilingi were also pulled from the 400m due to their high testosterone and must race over 200m instead.
World Athletics says intersex women - most of the athletes do not use the term - must lower their testosterone by taking the contraceptive pill, having monthly injections or surgically removing their internal testes.
Otherwise, it says intersex athletes race with "all the same advantages" a typical man holds over a typical woman.
In 2019, the United Nations Human Rights Council criticised the rules, saying sports bodies should not "force, coerce or otherwise pressure women and girl athletes into undergoing unnecessary, humiliating and harmful medical procedures".
Semenya raced to fame in 2009 when she won the 800m at the World Championships. Her speed and build led to questions and she was made to take a sex verification test by World Athletics.
In 2011, the governing body said athletes could only race with testosterone "below the male range". To comply, Semenya took contraceptive pills that made her feel "constantly sick".
Her times also slowed, though her 2012 Olympic silver was upgraded after the winner was stripped of her gold for doping.
When restrictions were lifted in 2015, after a court challenge by Indian 100m sprinter Dutee Chand, Semenya returned to dominance, winning the 800m at both the 2016 Olympics and 2017 World Championships.
World Athletics introduced new rules for middle-distance races that came into force in 2019.
Semenya challenged - and lost, accusing the governing body of taking it upon itself to decide who was "woman enough".
World Athletics says intersex women like Semenya, who have XY male chromosomes instead of XX female ones, account for 7.1 in every 1,000 elite female athletes, or 140 times more than in the general population, with a still higher podium presence.
"The current World Athletics regulations are not anything that anyone would come up with out of the blue," said Joanna Harper, an expert on intersex and transgender female athletes at Britain's Loughborough University, who is trans herself.
"They're kind of inelegant and awkward," said Harper, who supported World Athletics in Semenya's case. "But I think they are a reasonable solution to an extremely complicated problem."
Other experts disagree.
"The idea that... women with intersex variations are everywhere and taking over can very easily become completely overstated," said Morgan Carpenter, executive director of advocacy group Intersex Human Rights Australia. "There aren't that many women with intersex variations."
World Athletics did not reply to a request for comment.
Burundi's 2016 800m silver medallist Niyonsaba, 28, is now racing in the 5000m and 10,000m in Tokyo. However, Semenya and Wambui, 25, failed to qualify for the 200m or the 5000m.
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