Caster Semenya's domination of women's middle-distance running is likely to end with the introduction of new rules set to be announced.
The IAAF will reveal their highly controversial rule changes for athletes with hyperandrogenism, with the decision expected to force Semenya either to take medication to reduce her naturally occurring testosterone levels or move to longer-distance events.
Semenya, 27, a double Olympic champion over 800m, underlined her superiority at the Commonwealth Games when she took gold in the 1500m as well as over 800m.
But the new IAAF rules will apply to any distance from 400m to the mile, forcing Semenya to switch to the 5,000m and 10,000m if she refuses to take medication that can be used on a daily basis in tablet form.
When the IAAF introduced a similar rule in 2011 in response to Semenya's stunning victory at the 2009 World Championships — a limit for natural testosterone for female athletes was set — it had a significant impact on the South African.
She lost to Mariya Savinova at the 2011 World Championships and the 2012 Olympics. It was only after Savinova was exposed as a drug cheat that Semenya was upgraded to gold in both events.
Last month the IAAF council approved a proposal to limit naturally produced testosterone for female competitors in distances from 400m to the mile with a view to implementing the rule by November.
In July 2015 the Court of Arbitration for Sport issued a decision to suspend the regulations on hyperandrogenism — excessive levels of testosterone in the female body — after an appeal by the Indian government on behalf of their sprinter, Dutee Chand. But CAS is not a regulatory authority and a new rule would sidestep the issue unless an athlete makes a fresh legal challenge.
Until now Semenya has not challenged the rule changes.
She has been publicly critical but complied with the new regulations in 2011 and in Australia last month hinted at a move up to longer distances, no doubt in anticipation of a development that is now expected to be confirmed this week.
It will reopen the debate about the human rights of athletes born with the condition and will cause outrage in Semenya's native South Africa.
At the IAAF council meeting last month the world governing body's president, Lord Coe, insisted it was important to protect the rights of female athletes by ensuring a "level playing field".
"It is clear that this is one of the toughest subjects the council and I have been discussing," he said.
"I want to make one point crystal clear, this is not about cheating, no athletes have cheated.
"This is about our responsibility to ensure, in simple terms, a level playing field. It is our sport and it is up to us to decide the rules. We draw the lines at two classifications for our competitions, men's events and women's events.
"This means we need to be clear about competition criteria for those two categories. Athletes need to abide by competition rules we set."
Last year a Yale University professor raised concerns about the potential health risks of medically reducing testosterone levels and also claimed to have exposed serious flaws in the scientific study being used by the IAAF.
Katrina Karkazis said: "Lowering testosterone can have serious life-long health effects. If done via surgery, women are at high risk for osteoporosis."
Gideon Meyerowitz-Katz, a chronic disease epidemiologist in Australia, wrote in The Guardian in 2016: "Semenya's athleticism was attributed to a single molecule — testosterone — as though it alone earned her the gold, undermining at once her skill, preparation and achievement."
Karkazis also says it is completely wrong to compare naturally occurring testosterone to testosterone doping and pointed out the inaccuracy in referring to it as a male sex hormone.
Others argue that if athletes like Semenya are abiding by anti-doping rules there is no justification for denying them the chance to compete.
"If we implement it the way the sport has wanted to, we could actually prevent female athletes from competing and that seems to be a human rights violation," said Paul Melia, CEO of the Canadian Centre for Ethics in Sport. "Testosterone naturally occurring is not a banned substance.'
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