Caster and the CAS decision

After a tough week which saw Caster Semenya fail in her attempt to block new IAAF rules in the Court of Arbitration for Sport, the World Champion bounced back on Friday and won what may be her final 800m race.

On Wednesday the Court of Arbitration for Sport (CAS) ruled that the IAAF is allowed to introduce rules which are aimed at restricting the testosterone levels of certain female athletes in the 400m to 1-mile distances.

Semenya is classified as one of the athletes who will have to reduce her testosterone levels if she wants to compete in her beloved 800m event. The new IAAF rules come into effect this week, which means the opening leg of the Diamond League in Doha was the final major athletics meeting before athletes needed to comply with the controversial new rule.

Semenya was a late entry to Doha and produced a stunning performance to convincingly win what could be her final official 800m – depending on CAS court appeals and her decision to comply with the rules or not.

Semenya, the defending series champion in the women’s 800m event, won the two-lap race in 1:54.98, a meeting record and the best of 2019. She finished nearly three seconds clear of Burundi’s Francine Niyonsaba who was second in 1:57.75.

Despite the controversial week, after the race Semenya showed no emotion as she crossed the line for her 30th 800m win in a row.

Asked if she would take medication to allow her to run in the 800m, she replied: “Hell no.” She did however insist she will be in Doha for the World Championships in September.

“With a situation like this you can never tell the future but the only thing you know is that you will be running,” she said before adding: “Actions speak louder than words. When you are a great champion, you always deliver.

Caster Semenya cruising to victory in the 1,500m heats at the SA Championships recently. Photo: Tobias Ginsberg

“It’s up to God. God has decided my life, God will end my life; God has decided my career, God will end my career. No man, or any other human, can stop me from running.”

“How am I going to retire when I’m 28? I still feel young, energetic. I still have 10 years or more in athletics.

“I’m going to keep on doing what I do best – which is running.”

Under the new IAAF rules, Semenya, and any other female athletes with differences of sexual development (DSD), must take medication to lower their testosterone levels. The ruling is limited to athletes with “46XY DSD”, a condition where the individual has XY chromosomes.

This fact has been largely ignored by the mainstream media and is arguably the most crucial factor in the ruling. As the LetsRun website so succinctly puts it: “It’s absolutely mind-boggling that virtually every major outlet in the world reporting the Court of Arbitration for Sport ruling has failed to mention one of the most important facts of the entire case. Caster Semenya has XY chromosomes.”

But what does that mean?

Very simplistically, according to, “Humans (and most mammals) have an additional pair of sex chromosomes for a total of 46 chromosomes. The sex chromosomes are referred to as X and Y, and their combination determines a person’s sex. Typically, human females have two X chromosomes while males possess an XY pairing.”

It is important to point out that the presence of XY chromosome does not simply make that individual a male. This was thought to be the case in the early years of the debate (in the 1980s) when the line between male and female athletes was simple drawn between those who had XX and XY chromosomes.

South African sports scientist Ross Tucker, on his Science of Sport website says: “A 46XY DSD is not necessarily biologically male,” and “The very nature of a DSD is that they are not able to use male hormones in the “typical way” – this is why they exist as DSDs.”

The IAAF have the difficult task of trying to define at what point a female with atypical XY chromosomes, gains an advantage. They produced a scientific study and concluded that affected female athletes with the XY pairing, who also have high natural levels of testosterone, have an advantage. On the basis of that, only females with 46XY DSD will have to reduce their levels through medication to under 5 nmol/L. The 5 nmol/L is double the normal female range of below 2 nmol/L. Females with only XX chromosomes do not have to reduce their testosterone levels, even if it is naturally elevated above the 5 nmol/L level.

It is important to note the studies on which the IAAF have based their rule are disputed, notably by Tucker, and that is probably going to form the basis of an appeal by Semenya’s legal team.

In the current ruling, CAS acknowledged the IAAF rule is not perfect and that their decision is the better of two bad options. In their decision the three-man CAS panel found that “… the DSD regulations are discriminatory, but the majority of the panel found that, on the basis of the evidence submitted by the parties, such discrimination is a necessary, reasonable and proportionate means of achieving the IAAF’s aim of preserving the integrity of female athletics in the restricted events.”

In other words, discriminating against a small group of 46XY DSD athletes who may have an advantage was better than discriminating against all other female athletes who may be at a disadvantage.

NOTE: This is a complicated issue and anybody interested in further reading should visit The Science of Sport, and specifically Tucker’s comprehensive look at the issue here, or listen to his podcast here.