After the UK Prime Minister Boris Johnson entered the debate on transgender women’s inclusion in female sport, BBC Sport breaks down some of the key questions.
What is the debate about?
The heart of the debate on whether transgender women athletes should compete in women’s sport involves the complex balance of inclusion, sporting fairness and safety.
Trans women have to adhere to a number of rules to compete in specific sports, including in many cases lowering their testosterone levels to a certain amount, for a set period of time, prior to competing.
There are concerns, however, that athletes retain a biological advantage from going through male puberty that is not addressed by lowering testosterone.
Sports – at both elite and non-elite level – have been encouraged to come up with their own policies.
Why is it being discussed now?
Transgender cyclist Emily Bridges was due to compete in her first women’s event last month, but was barred by cycling’s world governing body.
Bridges, 21, came out as transgender in 2020 and began hormone therapy a year later as part of her gender dysphoria treatment.
She raced in male events while transitioning, including finishing 43rd out of 45 riders in the elite men’s criterium at the Loughborough Cycling Festival in May 2021, while in September she was second to last in the Welsh National Championship road race, a 12km lap behind the winner.
Last month, Bridges won a men’s points race at the British Universities Championships in Glasgow – her final men’s race.
Then, having met British Cycling’s requirements, Bridges was set to compete in the women’s National Omnium Championships.
But three days before she was due to take part in her first women’s race, Bridges was ruled ineligible to compete by cycling’s world governing body, the UCI. British Cycling later suspended its transgender policy, meaning transgender women could no longer compete at its elite female events while a full review is undertaken “in the coming weeks”.
Last month, American Lia Thomas became the first known transgender swimmer to win the highest US national college title with victory in the women’s 500-yard freestyle – prompting more discussion and debate across sport.
What are the current rules?
The rules around transgender women competing in elite sport vary depending on the sport in question.
They focus on testosterone levels in athletes, with most rules stating that transgender women have to lower and then maintain those levels in their body.
For example, World Athletics, which governs track and field events, has set five nanomoles of testosterone per litre as its benchmark.
British Cycling, before suspending its policy, had ruled that athletes should have below five nanomoles per litre for a 12-month period prior to competition, a level which is maintained from then on.
World Rugby has banned trans women from playing at elite level – saying “safety and fairness cannot presently be assured” – while the Rugby Football Union’s domestic policy in England does allow trans women to play, under certain testosterone-based conditions.
The International Olympic Committee (IOC) first permitted transgender athletes to take part in the Olympics in 2004 – as long as they had undergone “appropriate surgery”.
Then in 2015 the IOC stated athletes who had transitioned from male to female could compete in women’s sport without requiring surgery, as long as they have declared their gender identity is female for at least four years, and kept their testosterone level below 10 nanomoles per litre for at least 12 months.
A revised framework was issued after last year’s Tokyo Olympics which said there should be no assumption that a transgender athlete automatically had an unfair advantage in female events.
It said that the individual sports which come under its umbrella needed to set their own guidelines.
The updated guidance was criticised by a group of medical experts in January, who said it could undermine integrity in sport.
According to NHS data, men’s testosterone levels range between 10 and 30 nanomoles per litre dependant on factors including age and time of day.
A younger, healthy male typically ranges between 20 and 30.
Women have lower levels of testosterone, with one NHS Foundation Trust giving a reference range of between 0.7 and 2.8.
What does the most recent research say?
There is limited research into what effect transitioning can have on an athlete – because there are so few transgender athletes, and even fewer in elite sport.
The NHS states that hormone therapy – such as taking oestrogen to suppress testosterone – is “limited by factors unique to the individual, such as genetic factors”.
An 18-month review developed by Sport England, Sport Scotland, Sport Northern Ireland, Sport Wales and UK Sport concluded that “testosterone suppression is unlikely to guarantee fairness between transgender women and natal females in gender-affected sports”.
The report also said that there are “retained differences in strength, stamina and physique between the average woman compared with the average transgender woman or non-binary person registered male at birth”.
Their guidance applies to transgender inclusion in community sport up to national level – not international, professional or elite sport, and said that ‘open’ or ‘universal’ categories may be needed in future to improve transgender inclusion.
It said existing policies were not fit for purpose, needed a reset and that “for many sports, the inclusion of transgender people, fairness and safety cannot co-exist in a single competitive model”.
Joanna Harper, a scientist at Loughborough University and a trans athlete herself, has been carrying out two studies on the impact of transitioning on athletes which has not yet been published.
She said: “The data that I have seen suggests that there is a substantial performance loss with testosterone suppression.
“I think that in most sports, probably including cycling, that will be sufficient not to eliminate all the advantages, but to ensure meaningful competition.”
Bridges told Cycling Weekly in March that she had been participating in a study at Loughborough University to track her power data. She said the data showed a 13-16% drop in her power outputs across six-second, one-minute, five-minute and 20-minute durations.
An earlier study by Harper found that hormone treatment also reduced haemoglobin levels to that of women.
Haemoglobin is found in red blood cells that carry oxygen through the body and to the muscles. The NHS says women usually have a lower red blood cell count than men.
“All of the transwomen athletes that I have data on have testosterone within the typical female ranges, which are well below any limit set by a sports governing body,” Harper added.
“And this is because transwomen don’t transition for sport; we transition to be more like other women and the primary therapy to do that is to bring our hormone levels to the same values as other women.”
What have previous studies found?
A 2020 study looked at people who transitioned while serving in the US military.
The research, published in the British Journal of Sports Medicine, found trans women who underwent hormone therapy for one year continued to keep an athletic advantage. One finding was that after two years the gap did close, but trans women ran 12% faster than the other women in the study.
Dr Timothy Roberts, a paediatrician and associate professor at the University of Missouri-Kansas City who carried out the research, said this was slower than they would have to run in order to be an elite runner.
He told German broadcaster dw.com: “To be in the top 10% of female runners, you have to be 29% faster than the average woman. And to be an elite runner, you’ve got to be 59% faster.”
Sports scientist Professor Ross Tucker told BBC Sport in August how the physiological differences established during puberty can create “significant performance advantages [between men and women]”.
“When human males go through puberty… the heart becomes larger, the lungs become larger, the body fat percentage goes down, and the skeleton changes,” he said.
“The collection of those things creates significant performance advantages [between men and women]. Those differences are between 10-12% in swimming and cycling.
“Then you get to sports like weightlifting, which involve upper body muscle strength, where the differences are even bigger. We’re talking 30-40%.”
What are the legal provisions and human rights issues?
Bridges said in a statement on social media that she simply wished to race competitively again, adding: “No-one should have to choose between being who they are and participating in the sport that they love.”
The Equality Act 2010 legally protects people from discrimination in the workplace and wider society.
There are exceptions within the Act when it comes to sport. Those exceptions can also apply to services such as bathrooms and domestic abuse refuges in certain circumstances.
Section 195 of the Act, which deals with sport, says it is lawful to restrict the participation of transgender people from sporting competitions where physical strength, stamina or physique are important factors in deciding who wins.
However, the restriction can only be done to ensure the competition is fair or the other competitors are safe.
Essentially that means it would not be unlawful discrimination to refuse participation to a transgender athlete if the competition organisers can show they would have an unfair competitive advantage.
Cycling’s world governing body, the UCI, requires riders to have had testosterone levels below five nanomoles per litre for a 12-month period prior to competition.
However, those same regulations state that the UCI must establish conditions that “protect health and safety” and “guarantee fair and meaningful competition that displays and rewards the fundamental values and meaning of the sport”.
What have the athletes at the centre of these stories said?
A number of transgender women have spoken in detail about the debate and what it means to them to compete in women’s events.
Bridges is still registered as male on British Cycling’s website and raced in men’s events until February as she underwent treatment to meet the requirements.
“After starting hormone therapy I didn’t want to race in the male category any more than I had to – obviously, it sucks, getting dropped, racing as a man when you’re not one,” she told Cycling Weekly.
“It was quickly apparent that that was the wrong category for me.”
The 21-year-old said she had received “little clarity” on why she was deemed ineligible to compete and described how she had received “targeted abuse” on social media.
Swimmer Thomas became the first known transgender swimmer to win the highest US national college title with victory in the women’s 500-yard freestyle in March.
Thomas swam for the Pennsylvanian men’s team for three seasons before starting hormone replacement therapy in spring 2019.
She told ESPN that it “means the world to be here” following her victory at the college event.
New Zealand weightlifter Laurel Hubbard was hesitant to speak to reporters before the Tokyo Olympics last year.
But she said in 2017 she hoped people would accept her competing in women’s events.
“People believe what they believe when they are shown something that may be new and different to what they know. It’s instinctive to be defensive,” she said.
“It’s not really my job to change what they think, what they feel and what they believe. I just hope they look at the bigger picture, rather than just trusting whatever their gut may have told them.”
What about their competitors and peers?
A number of former and current athletes have spoken about the issue and how it impacts them.
British 800m athlete Ellie Baker tweeted about Bridges competing: “How this has been allowed to happen is just ridiculous. I would refuse to race and hope that the other women would stand with me on this too.
“This is totally unfair. The advantages a trans women [sic] has had from going through puberty as a boy to a man can never been undone.”
Britain’s 400m hurdler Jessie Knight also praised Baker for “speaking out, something most female athletes (including myself) are not brave enough to do”.
BBC Sport understands discussions were taking place among British cyclists about taking action against Bridges’ inclusion in the British Omnium Championships prior to her being ruled out, but they feared voicing their opinions would be interpreted as transphobic.
This stance was largely confirmed in a letter sent to the UCI by a group of elite female cyclists on 6 April.
The group – including retired Olympians, scientists and researchers – called on cycling’s world governing body to “rescind” its rules around transgender participation and testosterone levels and implement eligibility criteria for women “based on female biological characteristics”.
One of the signatories was Sara Symington, head of Olympic and Paralympic programmes at British Cycling.
Former marathon runner Paula Radcliffe believes the best place to start is “more research” with “honesty on both sides”.
“If you have gone through male puberty there is an undeniable advantage and the cases going on at the moment undoubtedly prove that,” she told BBC Radio 5 Live.
“I don’t necessarily think there should be an outright ban from the start, but I do think that the current IOC rules, where there should be no presumption of physical advantage, are completely wrong.”
US swimmer Erica Sullivan, who competed against Thomas at the college event, said that Thomas deserved “to be celebrated for her hard-won success”.
“Like anyone else in this sport, Lia has trained diligently to get to where she is and has followed all of the rules and guidelines put before her,” Sullivan wrote for Newsweek.
“As a woman in sports, I can tell you that I know what the real threats to women’s sports are: sexual abuse and harassment, unequal pay and resources and a lack of women in leadership.”
Kent cricketer Maxine Blythin also received support on social media from her team-mates after she was criticised on social media.
What have sport chiefs said?
British Cycling performance director Stephen Park said the inclusion of transgender athletes was the “single biggest issue for Olympic sport”.
World Athletics president Lord Sebastian Coe, speaking in the aftermath of Thomas’ victory, said the future of women’s sport was “very fragile”.
“There is no question to me that testosterone is the key determinant in performance,” Coe told The Times.
“Look at the nature of 12 or 13-year-old girls. I remember my daughters would regularly outrun male counterparts in their class but as soon as puberty kicks in that gap opens and it remains. Gender cannot trump biology.
“I think that the integrity of women’s sport if we don’t get this right, and actually the future of women’s sport, is very fragile.”
UCI president David Lappartient told BBC Sport he was “worried” the inclusion of transgender athletes could affect the fairness of competition in cycling.
However, he added that the UCI “fully recognises the rights of transgender athletes to do sport”.
World Rugby, when it banned transgender athletes, said: “It is known that biological males (whose puberty and development is influenced by androgens/testosterone) are stronger by 25% to 50%, are 30% more powerful, 40% heavier, and about 15% faster than biological females.
“That combination of mass, strength, power and speed means that in a direct physical contest, ciswomen in all these domains will be at significant risk of injury.”