South African Olympic champion Caster Semanya is taking the International Association of Athletics Federation (IAAF) to court over its latest rules.

The IAAF carried out a study on testosterone in female athletes, and found out that elite female track and field athletes with higher levels of testosterone enjoy a 1.8 percent to 4.5 percent competitive advantage over women with lower testosterone levels, especially in the 400m, 400m hurdles, 800m, hammer throw, and pole vault events.

The report, titled “Serum androgen levels and their relation to performance in track and field,” was authored by Dr. Pierre-Yves Garnier, director of the IAAF Health and Science Department, and Dr. Stéphane Bermon in support of the IAAF appeal to the Court of Arbitration for Sport (CAS), which two years ago suspended the IAAF rule on limiting female athletes’ naturally occurring testosterone levels.

“If, as the study shows, in certain events female athletes with higher testosterone levels can have a competitive advantage of between 1.8-4.5 percent over female athletes with lower testosterone levels, imagine the magnitude of the advantage for female athletes with testosterone levels in the normal male range,” Bermon commented.

The IAAF rule, which comes into force on November 1, is not directly aimed at Semenya but she will be most affected by it.

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When the IAAF first introduced the rule in 2011, Semenya underwent the required hormone therapy and quickly saw her times slow, though she still managed to win a silver medal at the 2012 London Olympics.

This time, however, she’s ready to fight against it.

Law firm Norton Rose Fulbright said in a statement that the legal challenge would be filed on Monday at the Court of Arbitration for Sport (CAS) in Lausanne.

“Ms Semenya, like all athletes, is entitled to compete the way she was born without being obliged to alter her body by any medical means,” Norton Rose Fulbright said.

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