South African runner Caster Semenya must start suppressing her natural testosterone levels to compete as a woman in certain track events, which could affect her impressive speed.

Semenya, the 28-year-old who holds two Olympic gold medals, lost her appeal to the Court for Arbitration in Sport in Switzerland on Wednesday afternoon. The 2-1 decision marks the end of a nearly yearlong battle between Semenya and the International Association of Athletics Federations (IAAF), track’s governing body.

“I know that the IAAF’s regulations have always targeted me specifically,” Semenya said in a statement through her lawyers. “For a decade, the IAAF has tried to slow me down, but this has actually made me stronger. The decision of the CAS [court] 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.”

In 2018, the IAAF announced a new rule concerning female athletes with a condition called hyperandrogenism, which results in increased testosterone production. The IAAF decided that elevated testosterone levels give them an unfair advantage in races ranging from 400 meters to one mile and instituted a new policy that mandated that female athletes with the condition take medication, such as contraceptives, to reduce their testosterone levels.

Semenya and her legal team argued that she shouldn’t have to alter her body to compete and pointed out that other athletes are celebrated for their genetic variations.

Complying with the regulations could also hamper Semenya in the 800-meter race, her strongest event. One sports scientist predicted that suppressing her testosterone levels could make her five to seven seconds slower.

The decision will also affect Semenya’s biggest rival, Burundian athlete Francine Niyonsaba. She recently revealed in an interview with the Olympic Channel that she also has hyperandrogenism and criticized the IAAF proposal as “discrimination.”

In its decision, the court acknowledged that the rules are discriminatory but added “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."

Though the judges sided with the IAAF, they also expressed concerns about the practical implementation of the regulations and the lack of concrete evidence that elevated testosterone gives a performance advantage for two specific distances: 1500 meters and 1 mile. The panel determined enough evidence existed to limit participation in other distances, but recommended that those two races be exempt from the rules until more scientific evidence is produced.

If the IAAF agrees, Semenya may still be able to compete at those longer distances without taking testosterone-suppressing medication, but she couldn’t defend her 800-meter gold title at upcoming events like the Tokyo 2020 Olympics.

Semenya’s lawyers now have 30 days to file an appeal with Switzerland’s highest court. Her legal team said it’s still reviewing the decision and considering whether to appeal.