Caster Semenya has made a last-minute decision to run in the 800m in Doha on Friday, which will be the last time she can compete in her favourite event before the IAAF’s new rules requiring athletes with differences in sex development to take medication to reduce their testosterone are introduced.

Semenya’s agent has confirmed the South African has flown to Doha for the first Diamond League event of the season where she will compete against her closest rival Francine Niyonsaba – the Olympic and world championships silver medallist in the 800m, who last month revealed she was also a differences in sex development (DSD) athlete – as well as Britain’s Lynsey Sharp.

Semenya was not at a press conference to hear the IAAF president, Sebastian Coe, welcome the court of arbitration for sport’s verdict on Wednesday as upholding the principle that fair competition in women’s sport should be protected.

Caster Semenya v IAAF: behind the scenes at sporting trial of the century | Sean Ingle Read more

“I think this is pretty straightforward and it is very straightforward for any international federation in sport,” he said. “Athletics has two classifications: it has age, it has gender. We are fiercely protective about both. And I am really grateful the court of arbitration for sport has upheld that principle.”

Cas’s ruling means all DSD athletes, such as Semenya, will have to take medication to reduce testosterone for at least six months if they want to run internationally at events between 400m and a mile. It also appeared to offer some hope to the South African by suggesting the IAAF may consider delaying the implementation of its ruling in the 1500m and a mile “until more evidence is available”. However, speaking in Doha, Lord Coe rejected that suggestion with a flat-out “no”.

Meanwhile Semenya’s lawyer, Jim Bunting, told the Guardian her team were already scrutinising the 165-page Cas document with a view to a possible appeal to the Swiss federal tribunal, which would have to receive it in the next 30 days. He also urged the IAAF to reconsider implementing its policy over the 1500m and a mile until it gathers more evidence and suggested an independent tribunal should be appointed.

Sign up to The Recap, our weekly email of editors’ picks.

Bunting said: “While a majority of the three arbitrators said it was discriminatory but necessary and was proportionate, all three judges expressed significant concerns and reservations about the practical implementation of the resolution in the certain restricted events.

Cas tried to provide a clear verdict on Caster Semenya but left a tangled mess | Andy Bull Read more

“At a broad level we would hope there is still hope. We believe the IAAF should pause and consider carefully what is the correct way to proceed. And we would encourage them to appoint an independent group of experts to look at the 1500m data.”

If Semenya decides not to take hormone medication to reduce her testosterone levels to five nmol/L she could decide to step up to 5,000m without falling foul of the IAAF’s rules for DSD athletes. Another option would be to step away from the sport completely, a prospect she appeared to raise on Thursday when she tweeted: “Knowing when to walk away is wisdom. Being able to is courage. Walking away with your head held high is dignity”.

The British 100m and 200m star Dina Asher-Smith, who is also competing in Doha on Friday, said she did not want to speak about Cas’s decision because she was not a lawyer and did not have “an informed opinion on it”. However she added: “Caster is my friend and I hope she is going to be OK.”

Meanwhile the World Medical Association has reiterated its advice to physicians around the world not to take part in implementing the IAAF’s new eligibility regulations for classifying female athletes. The latest guidance follows a WMA council meeting last month where the doctors warned that compelling female DSD athletes to take hormone suppressants were contrary to international medical ethics and human rights standards.

The WMA president Dr Leonid Eidelman added: “We have strong reservations about the ethical validity of these regulations. They are based on weak evidence from a single study, which is currently being widely debated by the scientific community. They are also contrary to a number of key WMA ethical statements and declarations, and as such we are calling for their immediate withdrawal.”