Double Olympic champion Caster Semenya will run her last 800-metres on Friday before the International Association of Athletics Federations imposes hugely controversial new rules limiting testosterone in female athletes.
Semenya, who has spent years trying to get the new IAAF regulations thrown out, will compete at the Diamond League meeting in Doha against 2016 Olympic silver medallist Francine Niyonsaba - who recently revealed she had similar difference in sexual development (DSD) characteristics to the South African.
Both must then begin taking medication to lower their testosterone levels if they wish to compete over that distance based on the new rules, which the Court of Arbitration for Sport (CAS) said on Wednesday were necessary to ensure fair competition.
The case is likely to have far-reaching consequences for women`s sport and has split opinion around the globe.
Athletics South Africa likened the new IAAF regulations to apartheid, and both it and Semenya`s lawyers have said they could contest the CAS ruling dismissing her appeal against their introduction.
Under the rules to take effect on May 8, female athletes with high natural levels of testosterone wishing to compete in events from 400-metres to a mile must medically limit that level to under 5 nmol/L, which is double the normal female range of below 2 nmol/L.
Barring further legal action, that leaves Semenya at a crossroads: Either she submits to the regulations or looks to compete in longer distances.
She claimed the 5,000-metres title at the South African Athletics Championships last week, an event not covered by the IAAF regulations, but in a modest time of 16:05.97, well below the qualifying standard for the world championships of 15:22.00.
This potential lifeline means Semenya may not abandon the 800-metres yet, though any advance to the Swiss Federal Tribunal could take months to reach a verdict and leave her career in limbo.
"I know that the IAAF`s regulations have always targeted me specifically," Semenya, 28, said in a statement released via her lawyers on Wednesday.
"For a decade the IAAF has tried to slow me down, but this has actually made me stronger. The decision of the CAS will not hold me back. I will once again rise above and continue to inspire young women and athletes in South Africa and around the world."
Semenya`s personal best of 1:54.25 will make her the quickest in the field in Doha’s Diamond League meet, the first time she will compete over the distance in 2019.