South African athlete Caster Semenya has won in her first race since losing her landmark legal case against the IAAF.
The athletics governing body will put in place rules designed to decrease naturally high testosterone levels in some female runners, which would mean Semenya could be forced to take medication to permit her to race, otherwise she could be forced to retire.
Athletes have until May 8 to reduce their testosterone levels to five nanomoles/Litre of blood serum - change events, given all events from the 400m to the mile are affected by the IAAF's new regulations, or retire.
The Court of Arbitration for Sport ruled that the regulations are discriminatory, but concluded such discrimination is a "necessary, reasonable and proportionate means" of preserving the integrity of female athletics.
The Olympian was challenging a proposal by athletics' governing body to limit testosterone levels in female athletes competing in distances of between 400m and one mile.
Semenya could potentially appeal the ruling but her social media output in recent days has suggested she could walk away from the sport permanently.