• A number of prominent former athletes, including Martina Navratilova and Paula Radcliffe, have been openly critical of transgender women competing in women's sports.
• One of their main arguments is that it is theoretically possible for a cisgender man to "decide" to be a woman, take hormones, win and earn money while competing as a female, then go back to living as a man.
• Leading trans athlete Rachel McKinnon told Business Insider this is a nonsense argument.
• It is also implausible from a medical standpoint, according to a prominent clinician at the Gender Identity Clinic in London.
• McKinnon said the idea that cisgender men could game the situation shows an "irrational fear" of trans women and is "the dictionary definition of transphobia."

An increasing number of former athletes are speaking out against transgender women competing in women's sports — but one of the main arguments they have against their participation may be fundamentally flawed.

The UK government estimates that there are between 200,000 to 500,000 transgender people in the country, which accounts for 0.3% to 0.75% of the British population. The statistic is similar in the US — in 2015, The New York Times cited a 2011 paper that estimated that 0.3% of the population, or 700,000 adults, identified as trans, a number that has likely risen since.

Despite this, it is uncommon for trans women to compete — let alone excel — in women's sports.

In 2003, the International Olympic Committee (IOC) allowed the participation of athletes who had undergone sex reassignment, ushering in the possibility that, from 2004, transgender athletes and indeed trans women could compete in the Olympics.

The IOC modified these guidelines somewhat in 2015 so that testosterone levels must now be kept below a certain limit for transgender athletes to compete.

Still, despite the fact that more than 50,000 total Olympians have participated in the tournament since 2004, there has never been an openly transgender athlete at the Olympics.

Trans women have attracted attention for their participation in sub-elite, national-level women's sport, however.

Sprint cyclist Rachel McKinnon, who competes in the women's 35-44 age range, won a track world title in her age category at the UCI Master Track Cycling Worlds in Los Angeles last year.

Afterwards, she received thousands of death threats and faced criticism against trans women participating in women's sports in the mainstream media.

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The former Olympic swimmer Sharron Davies said in The Telegraph that "those with a male sex advantage should not be able to compete in women's sport."

Paula Radcliffe, the former Commonwealth gold medal-winning long-distance runner, also told the BBC it would be "naive" not to think transgender women would become "a threat to female sport" because, in the future, "people will manipulate the situation."

Earlier this year, the 18-time Grand Slam tennis champion Martina Navratilova even said in The Sunday Times that "a man can decide to be female, take hormones if required by whatever sporting organisation is concerned, win everything in sight, earn a small fortune, and then reverse his decision and go back to making babies if he desired."

Interestingly, Navratilova was once coached by tennis player Renee Richards, who was the first trans woman to compete in women's sport. Richards notably played in the US Open before and after the sex reassignment surgery she underwent in 1975.

Her US Open results after her surgery were not markedly different to earlier in her career, though it's important to note she no longer had youth on her side.

Still, Navratilova said in her Times op-ed: "Letting men compete as women simply if they change their name and take hormones is unfair — no matter how those athletes may throw their weight around."

However, there is one big problem with Navratilova and Radcliffe's arguments, according to McKinnon, who called their comments "the dictionary definition of transphobia."

'The dictionary definition of transphobia'

Speaking to Business Insider, McKinnon said: "Martina and Paula's core argument is that we should ban all trans women, all innocent trans women because of a fabricated, fictional fantasy of a fraudulent cisgender man."

The term cisgender describes someone who personally identifies with the sex they were assigned when they were born.

McKinnon says a key component of Navratilova's argument is that she wants to ban "innocent" and "real" transgender athletes from competing in women's sports "because a cis man in theory, but not practice, could commit fraud" by gaming the system.

Fraud, in this case, could occur if a cis man managed to convince a gender clinician to diagnose him with gender dysphoria, live as a woman for the specified time period, and then compete in women's sports categories at events like the Olympics, only to detransition and return to living as a cis man.

"We should never deny people's rights because a select few, in theory, could commit fraud," McKinnon said.

"The idea we should ban all immigrants because one or two might be terrorists is the height of racism, bigotry, and xenophobia. So their argument is the very definition of an irrational fear of trans women, the dictionary definition of transphobia."

The IOC already grants trans women the right to participate in Olympic sports providing they have declared that they identify as a woman and that their blood testosterone level is below 10 nanomoles per liter, a number which is set to be lowered to five nanomoles.

But not all sports are this inclusive.

USA Powerlifting, the sanctioning body for the strength sport in the United States, does not allow trans women to lift competitively because it says that men "naturally have a larger bone structure, higher bone density, stronger connective tissue, and higher muscle density than women. The argument put forward by the organization could explain why the same debate doesn't occur for trans men competing in men's categories.

"These traits, even with reduced levels of testosterone do not go away,"the organization says. "While [trans women] may be weaker and less muscle [sic] than they once were, the biological benefits given them at birth still remain over that of a female."

Whether or not you agree with USA Powerlifting's line of reasoning, Navratilova's argument — that a man can just decide to be a woman, win, then go back to being a man — isn't a practical one.

"Generally, you can't just walk into a doctor's office and say 'give me hormones,'" McKinnon said. "Not in the Canada or UK. If you wanted a vasectomy, they don't just whip out the scissors. They ask questions, 'These are the risks, do you understand the risks?' It isn't the case where you walk in and they have a pocket full of hormones to give you like candy."

She went on: "You have to make an appointment with a mental health professional like a psychologist or a psychiatrist and generally, not always, they have to diagnose you with gender dysphoria."

The gender dysphoria diagnosis

Gender dysphoria, according to the Gender Identity Clinic's website, is "the distress experienced by those whose gender identity feels at odds with aspects of their body and/or the social gender role assigned to them at birth."

Treatment varies from individual to individual but can include hormone therapy, mental health support, and/or genital reconstructive surgery, according to Britain's National Health Service (NHS).

"They will want to see you for six to 12 months before they are willing to diagnose you," McKinnon said. "There cannot be a whiff of fraud the entire time. If the mental health professional thinks you're faking it for a moment, they will not support you."

Dr. James Barrett, the lead clinician at the Gender Identity Clinic in London, agreed.

We would notice that you didn't appear to be a trans person…we're not a shop. You can't just walk in and say you fancy living as a woman.

"We would notice that you didn't appear to be a trans person," Barrett told Business Insider. "We're not a shop. You can't just walk in and say you fancy living as a woman, and oh by the way you're a tip-top athlete."

He added that "hardly anyone" then tries to change back.

"It's an incredibly rare thing to detransition," he said.

"We've been doing this for a very large number of years and we'd be skeptical. The person would have to actually have gender dysphoria rather than talking athleticky stuff."

Barrett added that it would be incredibly impractical to just "decide to be female" only to change back to living as a man at a later date.

First, it would take a two- to three-year process simply to live as a woman.

"If you wanted to get to the stage where ... you were legally female, you'd have to live in a different gender role for at least two years according to current UK legislation," he said. "A couple of years just for a kick-off."

With the current legislation, you don't have to have any hormones or surgery to go from being a man to a woman on your birth certificate, he said.

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"But I think it would be surprising to have a certificate in the absence of any hormone treatment. You might end up with a certificate in the absence of surgery, but that's usually because the hormone treatment is such that it's rendered the testosterone levels down to where they'd be if someone had had surgery."

If you do get a diagnosis, you'll receive a letter, according to McKinnon.

"You now have to find a physician willing to treat a trans person," she said. "There are sometimes years-long waiting lists for an endocrinologist who will treat a trans person."

From there, it takes approximately six months of hormone suppression to get below the limit of 10 nanomoles of testosterone per liter of blood, although the IOC has plans to lower this further to five nanomoles per liter.

Then, McKinnon said you must keep that level below 10 for a 12 month period, and document it with tests.

Any sign of fraud and "you will be banned" before you can even begin to compete in events, she said.

Testosterone suppression has lasting effects

Another reason a cisgendered man may not want to "manipulate" the system and become a woman is that testosterone suppression has lasting effects.

"When you want to go back to being a man, you will now have breasts," McKinnon said. "The idea that anyone would do this, fine, it may be theoretically possible, but it's never happened."

McKinnon then said that over the last two Olympic Games there have been thousands and thousands of Olympians, but no trans person ever even qualified to participate in the events.

This could suggest that trans women aren't as big a threat to women's sports as critics would have us believe.

"The idea that this fantasy should stop real innocent people from accessing their right to sport is an irrational fear of trans women and the dictionary definition of transphobia," McKinnon said.

Speaking from a medical standpoint, Dr. Barrett from London's Gender Identity Clinic agreed that transgender athletes should be granted an equal chance to participate in sport

"Trans folk have every right to compete as everybody else," he said.

Martina Navratilova declined to comment to Business Insider regarding McKinnon's statements. A representative for Paula Radcliffe had not responded to Business Insider's requests for comment at the time of publishing.

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