Caster Semenya will compete in her final 800 metres in Doha on Friday before new IAAF rules regulating the testosterone levels for athletes with a difference in sex development take hold.
The first Diamond League event of the season will be the last time Semenya can compete in her favourite event before the new regulations are introduced.
Athletes with differences in sex development will now be required to take medication to reduce their testosterone.
Double Olympic champion Semenya, who will now have to take hormone suppressants if she wants to defend her world title in September, has arrived in Doha ahead of Friday's race.
The South African was not at a press conference on Thursday to hear IAAF president Sebastian Coe welcome the Court of Arbitration for Sport's verdict as upholding the principle that fair competition in women's sport should be protected.
But she posted a strongly-worded message on her Twitter account, saying: "They laugh at me Because I am Different. I Laugh at them Because they're all The same."
Lord Coe, however, told reporters: "It's very straightforward for any international federation in sport.
"Athletics has two classifications, it has age, it has gender.
"We are fiercely protective about both and I'm really grateful that the Court of Arbitration has upheld that principle."
The ruling has provoked fury among the South African's supporters, but the principle of a testosterone limit has been backed by one of the witnesses who gave evidence for Semenya at her CAS hearing in February, Ross Tucker.
The South African was one of three experts who challenged the statistical evidence the IAAF presented as the basis for its limit, which currently only applies to track events between 400m and a mile, although other events could be added in the future as the governing body has described its eligibility regulations as a "living document".
Last year, Tucker, Norwegian biologist Erik Boye and American academic Roger Pielke Jr wrote to the British sports science journal which published the research and called for its retraction, citing several fundamental errors.
Despite admitting that some mistakes were made, the IAAF's experts refused to withdraw the research and it was presented to CAS in February.
"Testosterone is crucial," Tucker told Press Association Sport.
"As a concept the IAAF has a very strong position and its final legal argument in Lausanne was excellent.
"But their evidence is really weak and that was exposed quite early – Roger, Erik and I were calling for the retraction of that paper last year.
"What they managed to do was sidestep the weakness of their evidence and make a conceptual argument. CAS has clearly decided to weigh the concept and theory more highly than the evidence."
That last point would appear to be supported by CAS' suggestion that the IAAF does not impose the testosterone limit on athletes in the 1500m or mile events, as it did not believe there was sufficient evidence to justify it.
The IAAF, however, has shown no indication it will heed this advice.
Another expert who has sympathy for the IAAF's dilemma in trying to balance the rights of intersex athletes with the desire to create a level playing field is American sports scientist and athletics coach Steve Magness.
"They've been given an impossible task," Magness told Press Association Sport.
"They need to prove that having naturally high testosterone leads to better performance at the elite level in women's sport.
"That's much more difficult than it seems because you can't run a standard experiment and increase testosterone as it's not a natural rise.
"What you're left with is comparing a whole slew of world-class women to see if the ones who have higher testosterone are faster.
"Sounds easy, but the problem with this approach is you have to use blood samples taken from anti-doping tests.
"Now, if we believe the latest research that 30-40 per cent or more of elite athletes are doping, a large proportion of that sample is providing inaccurate data – that's why a study like the IAAF's is likely rife with errors."
