Olympic runner Caster Semenya’s battle against rules that would force women to lower their naturally high testosterone levels in order to compete has rekindled debates about the extent to which the hormone can improve athletic ability.

The ongoing controversy has also raised questions about the credibility of research conducted by the International Association of Athletics Federations, a global regulatory body. Some experts say that the organization’s base level of testosterone allowed in a female athlete is arbitrary and unscientific.

On Wednesday, the Court of Arbitration for Sport in Switzerland condemned the two-time Olympic 800-meter champion for her high testosterone levels. the CASE says that while the of the IAAF rules are discriminatory, “such discrimination is a necessary, reasonable and proportionate way” to “preserve the integrity of women’s athletics”.

Testosterone is a hormone that builds muscle tone and bone mass. For this reason, it is against the rules for athletes to inject or swallow testosterone supplements. Some women have what is called hyperandrogenismmeaning they have unusually high natural levels.

“What is clear is that there is strong evidence that men who take excessive doses of testosterone…clearly gain a competitive advantage in strength-related sports,” Bradley said. Anawalthormone specialist and chief of medicine at the University of Washington Medical Center.

The problem, says Anawaltis that attempts to try to quantify this competitive advantage in natural levels of the hormone are “fraught with interpretative pitfalls”.

Attempts at hormonal regulation

Last year, the IAAF released new eligibility rules for the “women’s classification” for the 400m/mile track events.

Among the regulations, a female athlete whose testosterone levels are five nanomoles per liter of blood or higher must reduce her blood testosterone level below that level to be eligible for women’s competition.

“The latest research we have undertaken and the data we have compiled shows that there is a performance advantage in female athletes with [Difference of Sexual Development] DSD on the track distances covered by this rule,” Stephane Bermon of the IAAF’s medical and scientific department said in a statement. DSD is characterized by higher than usual levels of testosterone.

Watch: Why Testosterone Isn’t Always a Competitive Advantage

Why Testosterone Isn’t Always a Competitive Advantage

Explain the science behind testosterone and why a dose doesn’t always equal a benefit. 1:55

But Peter Sonksena retired professor of endocrinology from St Thomas’ Hospital and King’s College, told Reuters in March that IAAF regulations “grossly overstate the role” of testosterone in performance.

In a recent editorial published in the British Medical Journal, co-authors Cara Tannenbaum, professor in the faculties of medicine and pharmacy at the University of Montreal, and Sheree Bekker, researcher at the University of Bath, set out what they consider problems of research on the issue.

For example, the authors noted criticism of an analysis commissioned by the IAAF which found that women whose serum testosterone levels were in the upper third performed significantly better than women whose levels were in the the lower third.

These results, Tannenbaum and Bekker claim, could not be independently reproduced, and the data does not reliably reflect the source track times of athletes from the 2011 and 2013 World Championships.

Data errors

“The authors of the analysis subsequently admitted data errors, leading to charges of alleged data tampering and a potential breach of scientific integrity by the IAAF,” Tannenbaum and Bekker wrote.

“Who’s to say that having higher testosterone levels makes you more likely to win a medal?” Tannenbaum said in a recent interview with the University of Montreal. “How do you know it’s not just because of the way you train or because of some genetic predisposition that gives you strong muscles?”

Eric Vilain, director of the department of genomics and precision medicine at George Washington University, said it’s difficult to measure how sensitive an individual is to testosterone.

Last year, the IAAF released new eligibility rules for the “women’s classification” for the 400m mile track events. (Michael Dodge/Getty Images)

Vilain also took issue with setting the testosterone threshold at five nanomoles per liter of blood, saying it was an “arbitrary choice.”

“There is no evidence that the performance of a female athlete with [five nanomoles per litre of blood level] turned out better than [with] four,” he said.

Still, Vilain thinks there’s a consensus that testosterone has an impact on athletic performance.

The question, he said, is what should be a “reasonable and fair threshold” of testosterone for an athlete.

In general, there’s a much higher prevalence of women who have naturally high levels of testosterone who are elite athletes than in the general population, Anawalt said.

“Inferential Evidence”

He said it has been discovered that 0.7% of all elite female athletes have naturally high levels of testosterone. In the general population, the frequency is one hundred and forty times lower. “So that’s inferential evidence that there is a difference.”

Ruth Wood, a professor of integrative anatomical sciences at the University of Southern California, said she doesn’t believe the one controversial study cited by the IAAF invalidates the claim that testosterone improves athletic performance.

look like Semenya’s lawyer reacts to the IAAF Decision:

Caster Semenya’s lawyer ‘deeply disappointed’ with defeat on appeal

Two-time Olympic champion Caster Semenya has lost her appeal against rules designed to lower naturally high levels of testosterone in some runners. 7:21

Wood agreed, however, that testosterone levels alone will not make someone an Olympic athlete.

But when the differences between eighth and first place in an Olympic race are tiny and all competitors have maxed out their training potential, she said a little extra testosterone can make a big difference “between winning and not winning.” not win”.