A scientific paper published Monday found that women who produce higher-than-normal amounts of testosterone have up to a 4.5 percent advantage over their competition on the track, evidence the sport's governing body will use to potentially sideline Olympic gold medalist Caster Semenya and others with so-called intersex conditions.
The International Association of Athletics Federations will use the new study in its appeal to the Court of Arbitration for Sport, which suspended an IAAF rule that enforced a limit on female athletes' naturally occurring testosterone levels. The appeal will not affect this year's world championships, where Semenya is expected to go for her third title at 800 meters.
The study, funded by IAAF and the World Anti-Doping Agency, and published in the British Journal of Sports Medicine, analyzed more than 2,100 androgen samples from athletes participating in the 2011 and 2013 world championships.
It found females with higher testosterone levels received a competitive advantage of 1.8 percent to 4.5 percent over female athletes with lower testosterone levels in 400- and 800-meter races, hammer throw and pole vault.
''If, as the study shows, in certain events female athletes with higher testosterone levels can have a competitive advantage of between 1.8 to 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,'' said one of the study's authors, Stephane Bermon.
In 2011, the IAAF enacted a rule to force athletes with hyperandrogenism to artificially lower their testosterone levels to be eligible to compete.
Dutee Chand of India contested the rule and CAS overturned it in time for last year's Olympics. CAS gave the IAAF two years to produce evidence that hyperandrogenism led to an unfair advantage. IAAF will submit the paper, but said it would have no further comment until the case is concluded.