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Sources · Transgender women in women's sport

This house would let transgender women compete in women's sport.

Fact bank v1 · 11 cards

  1. TWS-01True

    “After puberty, males outperform females by about 10% in running and swimming, and by much more in strength and power events.”

    Confirmed: a review of sports records found the gap between males and females opens at puberty and is often 10–50%, depending on the sport. It is smallest in rowing, swimming and running (11–13%).

    The gap is biggest where upper-body strength matters. In Olympic weightlifting it was 31–37%, and in one study of moderately trained people, men's punches were 162% more powerful than women's. Another review found that before puberty, boys and girls have the same testosterone levels and perform about the same in sport. These figures compare males and females in general, not trans women.

    “We report that the performance gap between males and females becomes significant at puberty and often amounts to 10–50% depending on sport.”
    Sports Medicine (Springer), via PubMed Central, US National Library of Medicine·Transgender Women in the Female Category of Sport: Perspectives on Testosterone Suppression and Performance Advantage (Sports Medicine)Government / parliament · 8 Dec 2020 ↗

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  2. TWS-02Mostly false

    “One year of testosterone suppression removes trans women's muscle and strength advantage.”

    Studies that followed trans women over time found only small changes. After 12 months of treatment, muscle mass, muscle size and strength typically fell by about 5%, so the advantage was only slightly reduced.

    The 12-month figure matters because an older IOC rule let trans women compete after keeping testosterone below 10 nmol/L for at least 12 months. In one Swedish study of 11 untrained trans women, thigh muscle shrank by 5% in a year while strength stayed about the same. A 2026 review comparing trans women with other women found no clear difference in strength, but rated that evidence as very weak.

    “the loss of lean body mass, muscle area and strength typically amounts to approximately 5% after 12 months of treatment”
    Sports Medicine (Springer), via PubMed Central, US National Library of Medicine·Transgender Women in the Female Category of Sport: Perspectives on Testosterone Suppression and Performance Advantage (Sports Medicine)Government / parliament · 8 Dec 2020 ↗

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  3. TWS-03False

    “Taking hormones makes no real difference to a trans woman's body.”

    False: a review that looked at 24 studies found that hormone therapy lowered trans women's muscle mass, muscle size, strength and haemoglobin (the part of the blood that carries oxygen). Haemoglobin dropped to the same level as other women's within 4 months.

    Muscle and strength changed more slowly. Clear drops showed up after 12 months, but even after 36 months trans women's strength, muscle size and lean body mass were still higher than other women's. The authors say strength may be well kept during the first 3 years of hormone therapy.

    “Transwomen experienced significant decreases in all parameters measured, with different time courses noted.”
    British Journal of Sports Medicine (BMJ), via PubMed Central, US National Library of Medicine·How does hormone transition in transgender women change body composition, muscle strength and haemoglobin? Systematic review with a focus on the implications for sport participation (British Journal of Sports Medicine)Government / parliament · 1 Mar 2021 ↗
  4. TWS-04Mixed

    “After two years on hormones, trans women no longer have any physical advantage over other women.”

    Partly true. In a US Air Force study of 46 trans women, their extra push-ups and sit-ups had gone after 2 years of hormones, but they still ran 1.5 miles 12% faster than the average woman in the Air Force.

    Before hormones, they did 31% more push-ups and 15% more sit-ups, and ran 21% faster, than Air Force women. After 1 year, the waiting time World Athletics recommended at the time, they were still 9% faster. The study used military fitness test records, compared with averages for Air Force women under 30. They were not elite athletes.

    “After 2 years of taking feminising hormones, the push-up and sit-up differences disappeared but transwomen were still 12% faster.”
    British Journal of Sports Medicine (BMJ), abstract via PubMed, US National Library of Medicine·Effect of gender affirming hormones on athletic performance in transwomen and transmen: implications for sporting organisations and legislators (British Journal of Sports Medicine)Government / parliament · 7 Dec 2020 ↗
  5. TWS-05Mixed

    “A study paid for by the IOC found trans women athletes are actually at a disadvantage compared with other women.”

    Partly. In this small study of people who train or compete in sport, trans women did worse than other women on stamina (aerobic fitness) and jumping once body weight was taken into account. But their grip strength was higher (40.7 kg against 34.2 kg).

    The study tested 23 trans women and 21 other women once, and both groups had similar testosterone levels. A single snapshot like this cannot show how hormones changed anyone's performance, and the authors say long-term studies are urgently needed. It was funded by an IOC research grant. People from different sports and levels took part, so it may not reflect elite sport.

    “Transgender women athletes demonstrated higher absolute handgrip strength than cisgender women, with no difference found relative to fat-free mass or hand size.”
    British Journal of Sports Medicine (BMJ), via PubMed Central, US National Library of Medicine·Strength, power and aerobic capacity of transgender athletes: a cross-sectional study (British Journal of Sports Medicine)Government / parliament · 10 Apr 2024 ↗
  6. TWS-06Mixed

    “A big 2026 review of 52 studies proved that trans women have no athletic advantage over other women.”

    Partly. The review (52 studies, 6,485 people) found no clear difference between trans women and other women in strength or stamina. But it rated how sure we can be about this as "very low", the lowest grade, so it cannot prove there is no advantage.

    The studies were of trans people in general, not only athletes. The authors also say trans women had more lean (muscle) mass than other women, even though their fitness looked similar. The journal has since published two corrections to the paper, in July and September 2026.

    “Current evidence is mostly low certainty and has heterogenous quality but does not support theories of inherent athletic advantages for transgender women over cisgender.”
    British Journal of Sports Medicine (BMJ), abstract via PubMed, US National Library of Medicine·Body composition and physical fitness in transgender versus cisgender individuals: a systematic review with meta-analysis (British Journal of Sports Medicine)Government / parliament · 11 Feb 2026 ↗
  7. TWS-07Mixed

    “A systematic review found no evidence that trans women have an athletic advantage.”

    That 2017 review did say there was no direct or consistent research showing an advantage. But that mostly reflected how little had been studied: only 1 of its 8 research articles was an experiment, with 36 people, and it did not test sports performance.

    That one study found a year of hormones cut trans women's muscle mass, but it stayed above that of trans men who had not yet started hormones. Newer studies since 2020 have tested strength and fitness more directly, and they disagree on how much advantage remains.

    “Currently, there is no direct or consistent research suggesting transgender female individuals (or male individuals) have an athletic advantage at any stage of their transition”
    Sports Medicine (Springer), via PubMed Central, US National Library of Medicine·Sport and Transgender People: A Systematic Review of the Literature Relating to Sport Participation and Competitive Sport Policies (Sports Medicine)Government / parliament · 3 Oct 2016 ↗

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  8. TWS-08Mostly true

    “Many trans people avoid sport because they do not feel welcome.”

    Mostly true: a 2017 review of the research found that a lack of welcoming, comfortable places to play was the main barrier stopping trans people from taking part in sport. But that finding rests on very few, very small studies.

    Six of its eight research articles involved 12 people or fewer, and some described things like feeling uneasy in changing rooms. In the one survey (80 people), trans people reported less physical activity and less social support than the non-trans people in the survey. The review also said most of the experiences of competitive sport it found were bad ones, and that sport rules seemed to play a big part in that.

    “this review found the lack of inclusive and comfortable environments to be the primary barrier to participation for transgender people”
    Sports Medicine (Springer), via PubMed Central, US National Library of Medicine·Sport and Transgender People: A Systematic Review of the Literature Relating to Sport Participation and Competitive Sport Policies (Sports Medicine)Government / parliament · 3 Oct 2016 ↗
  9. TWS-09False

    “Trans women can compete in women's events at the Olympics as long as they lower their testosterone.”

    Out of date: in March 2026 the IOC said that from the Los Angeles 2028 Games, a test for the SRY gene will decide who can enter women's events. Lowering testosterone does not change a person's genes, so it no longer decides whether a trans woman can take part.

    The SRY gene sits on the Y chromosome and plays a key role in male development. An older IOC rule had let trans women compete after keeping testosterone below 10 nmol/L for at least 12 months. By 2024, rules already differed from sport to sport: some banned trans women from women's events, and some asked for lower testosterone. World Athletics and World Boxing brought in SRY tests for women's events in 2025. For now, these tests mainly apply to elite athletes at selected international events, not everyday sport.

    “In March 2026, the International Olympic Committee announced an updated policy confirming SRY gene screening as the basis for determining eligibility in the female category”
    South African Journal of Sports Medicine, via PubMed Central, US National Library of Medicine·From policy to practice: A South African clinical toolkit for SRY gene screening in sport (South African Journal of Sports Medicine)Government / parliament · 15 Sept 2026 ↗

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  10. TWS-10Mostly false

    “The US Supreme Court has banned trans women and girls from women's sport across America.”

    The Court did not bring in a nationwide ban. On 30 June 2026 it ruled 6-3 that states are allowed to limit girls' and women's sports teams in schools and colleges to biological females. It did not decide whether states that let trans girls play on girls' teams are breaking the law.

    The case, West Virginia v. B.P.J., upheld laws in West Virginia and Idaho. More than 25 states have passed laws like these. All nine judges agreed the laws did not break Title IX, the US law against sex discrimination in schools and colleges that get federal money; three disagreed on the constitutional question. Separately, a February 2025 order from President Trump told the Education Department to make it a priority to act against schools that let trans girls and women play on female teams.

    “The decision does not, however, resolve the related question as to whether other states may nonetheless permit transgender athletes to participate”
    Congressional Research Service, US Congress·West Virginia v. B.P.J.: Supreme Court Upholds State Laws Restricting Eligibility of Transgender Girls to Compete in Athletics Competitions (CRS Legal Sidebar LSB11454)Government / parliament · 10 Jul 2026 ↗

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  11. TWS-11True

    “Most Americans think trans athletes should have to compete on teams that match their sex at birth.”

    Confirmed: in a February 2025 Pew survey of 5,097 US adults, 66% favoured requiring this, 15% were against it and 19% were neither.

    Support was up 8 points since 2022. It was much higher among Republicans (88%) than Democrats (45%). In a November 2025 survey, 73% said they would be uncomfortable with trans athletes on teams that don't match their birth sex. In the same February survey, 56% backed laws protecting trans people from discrimination in jobs, housing and public places. These are US results only.

    “66% of adults favored a law or policy that would require trans athletes to compete on teams that match their sex at birth.”
    Pew Research Center·Most Americans are uncomfortable with transgender athletes on sports teams that don't match their birth sexIndependent research institute · 11 Aug 2026 ↗

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