JOHANNESBURG, South Africa (AFP) — Anger is mounting in South Africa over new athletics rules prescribing maximum testosterone levels in female competitors widely seen as targeting the country’s Olympic champion Caster Semenya.

Her backers at home and abroad have denounced the International Association of Athletics Federations’ (IAAF) new policies that target women who naturally produce unusually high levels of testosterone of being “sexist”, “racist”, “homophobic”, “dehumanising” and “humiliating”.

From November 1, athletes classified as “hyper-androginous” will have to chemically lower their testosterone levels to just 5 nanomoles per litre of blood to be eligible to run any international race of 400 metres up to the mile.

The IAAF has defended the rule change as scientifically sound.

According to a study financed by the IAAF, high testosterone levels in some athletes give them a “significant” advantage in certain competitions.

The first athlete to be affected by the change is double Olympic 800 metres champion Semenya — who also runs the 1,500 metres.

The IAAF insists that the new rules “are about levelling the playing field to ensure fair and meaningful competition in the sport”.

“The regulations are solely to ensure fair and meaningful competition within the female classification for the benefit of the broad class of female athletes,” said the IAAF in a statement.

But the decision has provoked an explosion of anger.

South African law professor Steve Cornelius described it as “ostracising certain individuals, all of them female, for no reason other than being what they were born to be” in a stinging letter resigning from the IAAF’s disciplinary tribunal.

“I cannot in good conscience continue to associate myself with an organisation which insists on… female classification (that) is based on the same kind of ideology that has led to some of the worst injustices and atrocities,” he wrote to IAAF president Sebastian Coe.

South African sprinter L.J. van Zyl told AFP that the decision was “unfair because there are only certain events that are targeted”.

Canadian Olympic wrestler Erica Wiebe tweeted that “I believe in #fairsport, #cleansport and #sportsocialchange but I don’t believe in policing women’s participation in sport because they don’t fit within Western conventions of femininity. C’mon” IAAF.

Semenya, who has undergone several sex tests since her first title in 2009, responded defiantly to the new IAAF rules.

“God made me the way I am and I accept myself. I am who I am and I am proud of myself,” she wrote over an image of herself looking skyward posted on Twitter.

Semenya has a deep voice, strong build and is considered “intersex” — born with sex characteristics not typically male or female — along with between 0.1 and 0.4 per cent of people globally.

Heightened testosterone levels among androgenous women can contribute to increased muscled mass and heightened sporting performance — a competitive advantage caused by involuntary genetic traits.

Semenya, who was previously suspended for 11 months as a result of her genetic makeup, has tackled her situation head-on — winning the backing of former South African president Nelson Mandela.

The chair of the country’s parliamentary sport committee Beauty Dlulane said she was “appalled” by the decision which she alleged was part of “a plan to suspend Caster”.

“This should be challenged,” she said.

Athletics South Africa said on Thursday it would take the IAAF to the Court of Arbitration for Sport in Switzerland if it did not back down over the new rule.

The scandal has also taken on a racial edge in the rainbow nation which was for decades run according to apartheid laws.

Sports minister Tokozile Xasa called the regulations “a very sexist, racial and homophobic… way to discourage her”.

Mandela’s party, the ruling African National Congress, called the rule “unjust and blatantly racist”.

“The regulations are a painful reminder of our past where an unjust government specifically legislated laws for (activists) to stifle their fight,” it said. “The IAAF uses the same tactic.” The outcry has not been confined to South Africa.

Canada’s athletics federation has jumped to the defence of “hyper-androginous” athletes calling for athletics to be “free of discrimination”.

Cornelius, the South African law professor who resigned from the IAAF disciplinary panel, said “the big problem is the science is not conclusive”.

“The science on which the IAAF relies has been questioned in academic journals,” he told AFP. American athletic champion Tianna Bartoletta said she was not surprised the IAAF had acted, but wished it had “sought a more inclusive solution”.

“Athletes have been outspoken about the unfairness of competing against women who have higher testosterone levels,” she said.

Bartoletta suggested the IAAF could have acted more fairly if it had contacted “all of its participating elite females for a snapshot of their hormone panels.”

Cornelius said the IAAF study that led to the rule change centred on the pole vault and hammer throw competitions — and made no direct reference to the 1,500 metres.

“They are going to struggle in a court of law to explain,” added Cornelius.