A new scientific paper finds that women who produce higher-than-normal amounts of testosterone have up to a 4.5 percent advantage over their competition on the track.
World track officials plan to use this evidence to potentially sideline Olympic gold medalist Caster Semenya and others with so-called intersex conditions.
The International Association of Athletics Federations will submit the study in its appeal to the Court of Arbitration for Sport. The top sports court suspended an IAAF rule that enforced a limit on female athletes' naturally occurring testosterone levels.
The appeal will not affect next month's world championships, where Semenya is expected to go for her third title at 800 meters.
The study analyzed more than 2,100 androgen samples from athletes participating in the 2011 and 2013 world championships.
Nearly 40 percent of the 296 athletes currently serving suspensions from international competition because of doping - taking performance-enhancing drugs - are women, and about half of these tested positive for androgens, the study team writes in the British Journal of Sports Medicine.
Some women, though, have naturally high levels of androgens, and there is controversy as to whether they should be allowed to compete, the authors note.
“The quantitative relationship between enhanced testosterone levels and improved athletic performance should be taken into account when the eligibility of women with hyperandrogenism to compete in the female category of competition is discussed,” the researchers write.
Dr. Stephane Bermon from the University of the Cote d’Azur in Nice, France, and the Monaco Institute of Sports Medicine and Surgery and Dr. Pierre-Yves Garnier from the International Association of Athletics Federations (IAAF) Health and Science in Monaco investigated whether androgen levels affected athletic performance in 1,332 women and 795 men who participated in track and field events at IAAF World Championships in 2011 and 2013.
Overall, 44 female athletes had elevated free testosterone levels and 101 male athletes had below-normal free testosterone levels, the researchers found.
Among the 24 female athletes whose total testosterone levels were high, nine had naturally elevated levels as a result of a condition called hyperandrogenic disorder of sex development, another nine were found to have been doping and six were impossible to classify.
Higher testosterone levels in female athletes translated into 2.73 percent better performance in 400-meter runs, 2.78 percent better performance in 400-meter hurdles and 1.78 percent better performance in 800-meter runs compared to women competitors with normal testosterone levels.
The difference was most pronounced in the hammer-throw events, where women with higher testosterone performed 4.53 percent better, and pole vault, where they did 2.94 percent better.
While these improvements sound tiny, in elite athletes they are enough to turn also-rans into medalists.
Interestingly, the researchers found no significant difference in performance when comparing male elite athletes with the highest and lowest free testosterone levels.
Dr. Bermon did not respond to a request for comments on this research.
