Trans Women in Sport: What Does the Science Say?
- 5 days ago
- 7 min read
Authors: Dr Sav Zwickl, Eli Ward-Smith, Arden Wong, and Prof Ada Cheung.
Content Warning: This blog contains reference to exclusion of, and discrimination against, trans people in sport.
Sport discussions involving trans women often spark strong opinions and heated debate. Below, we aim to lay out what we do know from the research, where uncertainty remains, and how inclusion and fairness might both be supported.
Why this matters
Sport offers huge benefits — improved health, connection, confidence, community. Yet many trans people don’t participate at all, much less at competitive levels. In Australia, we found only ~1/3 of trans adults engage in regular sport, compared to 80% in the general population.
Barriers include unsafe or unwelcoming environments, gendered uniforms, exclusionary rules, lack of privacy in facilities, and fear of discrimination. So, the question shouldn’t just be “can trans women compete?” but also “how do we remove unfair obstacles so everyone can participate?”
What are the common worries?
Three major concerns tend to dominate public debate:
1: Performance advantage.
That trans women might have superior strength, endurance, or speed.
2: Safety.
That trans women might pose injury risk to cisgender women.
3: Fairness of competition.
Whether the playing field remains level.
To evaluate these, we need to see what the science says — and also where evidence is lacking.
How hormone therapy changes the body
Most trans women who compete are on gender-affirming hormone therapy (GAHT) — typically oestrogen plus medications to lower testosterone. This therapy leads to measurable changes in body composition and function.
Trans Health Research and collaborators have recently published two articles that review the research on the impact of GAHT on trans sporting participation and physical performance. Some key effects observed (in non-athletic trans women) include:
Increase in fat mass (about 30% over 12 months).
Decrease in muscle mass (around 5% over 12 months).
Bone structure (e.g. height, skeleton width) does not change after puberty.
So, while GAHT brings substantial bodily changes, it doesn’t erase everything that developed before treatment if it was started after puberty — and that is part of the uncertainty.
For example, trans athlete Hannah Mounsey described her experience of GAHT:
“... it’s massive. I lost 20 kg in the first month I was on hormone treatment, simply due to the lack of testosterone. This obviously slowed significantly because the body doesn’t want to lose muscle, but the effects on my central nervous system and hemoglobin levels, things people can’t see, continue at a much faster rate. The central nervous system plays a huge role in strength and force production, while hemoglobin impacts your endurance capabilities. What this means is that essentially the external doesn’t necessarily match the internal. As the saying goes, don’t judge a book by its cover.”
What the evidence says about performance
Because there aren’t many long-term, sport-specific studies, we mostly rely on smaller, cross-sectional ones. While research is still limited, especially in elite athletes, we can draw some key conclusions from existing studies. Here’s a summary of what we do see:
After 2 years of GAHT, trans women show little to no advantage over cis women in tests like running 1.5 miles or number of sit-ups.
By 1–3 years on GAHT, many performance differences in studied metrics narrow substantially or disappear.
However, in strength tests (e.g. push-ups, grip strength), some small residual advantage may persist.
In contrast, some areas suggest worse performance: lung function, efficiency of breathing, and fitness (Braga et al., Saitong et al., and Alvares et al.) when normalised to body size.
In one study of national-level volleyball players, athletic trans women performed similarly to cis women (but below cis men) across multiple physical metrics.
In a UK study, athletic trans women (on hormones for 4–6 years) had worse performance in lung function, jump height, and relative VO₂ max (a measure of fitness) than cis women, but absolute grip strength was higher.
The most comprehensive synthesis to date, a 2026 systematic review and meta-analysis (Sieczkowska et al., British Journal of Sports Medicine) of 52 studies and 6,485 participants, found that trans women on 1–3 years of GAHT had upper-body strength, lower-body strength and relative VO₂ max comparable to cis women, despite higher absolute lean mass. The authors concluded the evidence does not support theories of inherent athletic advantage for trans women over cis women.
A 2025 longitudinal study (Harper et al., European Journal of Sport Science) tracked 9 trans women runners and 1 trans woman swimmer before and after starting GAHT. Race times slowed by around 15% in runners (with bigger decrements in longer-distance events) and around 5% in the swimmer. After adjusting for training volume, the runners’ age-graded performance scores did not differ pre- versus post-GAHT, meaning they were roughly as competitive in the women’s category as they had previously been in the men’s category. This is the first study to use both retrospective and prospective data on the same trans women athletes before and after GAHT.
In short: any advantage that exists is likely to be small, context-specific, and not universal.
Safety concerns
Despite frequent public talk, there is no robust empirical evidence that trans women increase injury risk to cisgender women in sport.
Most policies that cite safety are based on theoretical models (assuming trans women are the same as cis men, and comparing cis men to cis women), not on observed injury data.
What rules currently exist
Many sporting bodies have eligibility policies. These often require:
Maintaining testosterone levels below a threshold (e.g. < 5 nmol/L) for a set duration (e.g. 24 months).
Submission of performance data (times, strength metrics, prior competition data).
Some sports, however, have banned trans women entirely — but these bans tend to lack scientific justification, and they ignore the diversity among trans women in body size, physiology, training history, etc.
The Australian context and the IOC sex testing debate
In 2025, World Athletics and World Aquatics introduced mandatory sex testing or genetic screening (for the SRY gene) for all athletes wanting to compete in the female category. The International Olympic Committee is reportedly considering a similar framework. This is a significant shift: it applies not just to trans women, but to every woman who wants to compete, including cisgender women with naturally higher testosterone or innate variations in sex characteristics (sometimes called intersex variations or differences of sex development).
Australian athletes are already feeling the impact. Australian 800m runner Catriona Bissett, reflecting on submitting to genetic screening to compete at the 2025 World Athletics Championships, wrote: “If I want to be in this sport I don’t have a choice but to comply.”
The Human Genetics Society of Australasia, the peak body for clinical genetics in Australia and New Zealand, has called for ethical, non-discriminatory and inclusive practices and opposes the use of mandatory genetic testing to determine biological sex in sport, noting that biology and gender identity are complex and distinct, and that genetic tests should only be used for health-related purposes.
Mandatory genetic screening raises serious concerns about privacy, bodily autonomy and the psychological impact on athletes, including minors on elite pathways. It also sits uneasily with Australia’s Sex Discrimination Act, state and territory anti-discrimination laws, and the National Integrity Framework safeguarding obligations that Australian sporting organisations are bound by.
Australia already has world-leading, pragmatic frameworks that show inclusion and fairness can coexist: the Australian Human Rights Commission’s Guidelines for the inclusion of transgender and gender diverse people in sport, and the Australian Sports Commission–Australian Institute of Sport’s Transgender and Gender Diverse Guidelines for High Performance Sport. These frameworks are evidence-informed, sport-specific, proportionate, and grounded in human rights.
Adopting a more restrictive international approach would mean stepping back from standards that Australia should be championing globally, not abandoning.
Community-level sport: inclusion first
At grassroots and community levels, the aim should be to welcome everyone. In Australia, the Sex Discrimination Act prohibits discrimination based on gender identity, which applies to sporting settings.
Sport Australia’s 2019 guidelines for the inclusion of trans and gender diverse people in sport emphasise that inclusion, wellbeing, and non-discrimination should be central to policy-making.
Many community-level sports put social inclusion ahead of competitive fairness. For example, in community-level Australian Football, all trans women may compete, unless there is a clearly demonstrated safety risk.
What we don’t yet know
How long exactly it takes for GAHT to eliminate residual advantage in different sports and for different individuals. Is it 1 year, 2 years or longer?
Sport-specific evidence in high-level athletes in disciplines that rely heavily on power, speed, or strength.
Longitudinal studies following the same athletes before and after transition.
Broader data on injury incidence in mixed or women-only competitions involving trans women.
How to move forward with fairness and inclusion
Here are guiding principles:
Use evidence-based eligibility criteria (e.g. hormone levels, treatment duration), and avoid blanket bans not grounded in data.
Distinguish elite sport (where fine margins matter) from community sport (where inclusion and wellbeing may carry more weight). The Australian Sports Commission has separate guidelines for both.
Invest in more rigorous, long-term research, ideally following trans athletes over time. Our world-first GAME study is currently addressing this.
Focus on perennial problems in women’s sport (pay inequity, infrastructure, media exposure). Policies excluding trans athletes don’t solve those concerns.
Create welcoming environments (inclusive bathrooms, changing rooms, coach education) to reduce non-policy barriers.
For further information, Australia has two national sporting inclusion programs designed to assist sporting organisations with the inclusion of people with diverse sexualities and gender; Pride in Sport and Proud 2 Play.
In summary
There is very low participation of trans people in sport due to a large number of barriers such as actual or anticipated discrimination.
Hormone therapy leads to substantial physical changes in trans women, which often narrow or eliminate many performance differences over time.
Any remaining differences are small and vary by sport. Some studies show a slight residual advantage in certain measures (e.g., handgrip strength) and a disadvantage in others (e.g., lung function and aerobic fitness). How much this matters depends on the demands of the specific sport.
Safety concerns are mostly hypothetical. To date, there is no solid evidence that trans women pose a greater injury risk to cis women in sport.
Fairness and inclusion can coexist. With thoughtful, evidence-based policies, both can be achieved without resorting to blanket bans.
Published: 16 May 2024.
Updated: 28 May 2026.