Semenya is classified as a woman, was raised as a woman and races as a woman.

But for the IAAF, women like Semenya, with certain masculine attributes due to DSD, are classified, biologically, as men. It is a position hotly contested by South African officials.

In the build-up to the 2009 world championships in Berlin, where Semenya went on to win gold in the 800m, the South African had to undergo gender verification testing to confirm her eligibility to compete in the women’s category.

She was subsequently put on medication to reduce her testosterone levels, spending six months sidelined by the IAAF.

Semenya, born with the “46 XY” chromosome rather than the XX chromosome most females have, described the experience as like that of being treated like a “human guinea pig” and vowed never to again allow the IAAF to enforce medication upon her in order to compete.

The Swiss Federal Tribunal, in its ruling released Wednesday, was also not optimistic for Semenya’s ongoing appeal.

It concluded, “in a first summary examination, that Caster Semenya’s appeal does not appear with high probability to be well-founded”.

“The CAS, after thoroughly evaluating the expert evidence, found that the ’46 XY DSD’ characteristic has a direct impact on performance in sport, which could never be achieved by other women,” the tribunal said.

“Thus, with the participation of a female athlete with ’46 XY DSD’ in the ‘protected class women’, a basic principle of top-class sports, namely fair competition, is disregarded from the outset.”

Semenya on Tuesday expressed her disappointment at being ruled out of defending her title, adding: “This will not deter me from continuing my fight for the human rights of all of the female athletes concerned.”

She later tweeted: “People can be mean. Don’t take it personally. It says nothing about you, but a lot about them.”

Semenya followed that up on Wednesday by saying: “Determined spirit is unstoppable.”