Trans Women in Sport: What Does the Science Say?
- Trans Health Research team
- May 16, 2024
- 9 min read
Updated: 6 days ago
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.
In recent years, significant attention has been directed at trans women in sport. This has included the spread of misinformation and disinformation including inaccurate depictions of trans athletes in the media. In turn, some international, national, and local sporting bodies have developed policies regarding trans women that are based on assumptions and opinion rather than scientific evidence.
Many of these ‘debates’ and trans-exclusionary policies are based on the presumption that trans women have a performance advantage over cisgender women. This presumption is based on the fact that generally speaking, cisgender men have an advantage over cisgender women when it comes to strength, speed, and endurance. However, even though trans women may have gone through a testosterone-dominant puberty, this does not automatically mean they will have the same advantage over cisgender women in sport. Trans women are different to cisgender men and feminising gender-affirming hormone therapy (GAHT) results in rapid and dramatic changes in the body.
Below, we will debunk some common myths and discuss the latest research surrounding trans people and sporting participation.
Trans participation in sport
Trans people are vastly underrepresented in sport. Our Australian research found only a third of trans adults regularly participate, compared with around 80% of the general population, and very few compete at elite levels. This gap reflects both the small size of the trans population (<1%) and the many barriers they face; unsafe or unwelcoming environments, gendered uniforms, lack of inclusive facilities, fear of harassment, and exclusionary rules. These challenges deter many from taking part at all. Yet participation matters: sport improves physical and mental health, builds confidence, and fosters community. To unlock these benefits for everyone, sporting organisations need to dismantle barriers and ensure equitable access.
Common myths: are trans women a threat to women’s sport?
Women’s sport isn’t threatened by trans women. The real problems are big-picture ones: not enough funding, lower pay, less media attention, limited support for community clubs, and old stereotypes that undervalue women’s performance. People who say they’re “protecting women’s sport” by excluding trans people rarely tackle these issues.
The lack of trans women dominating women’s competitions speaks volumes and stands in stark contrast to the intensity of media coverage and political attacks. In over two decades of eligibility at the Olympics, only two trans women have ever qualified, and none have won a medal.
It’s also misleading to call trans women “biological men.” Men’s and women’s categories in sporting competition exist because, on average, men and women’s bodies perform differently. But trans women are not men. Many trans women use gender affirming hormones, which increase estrogen and lower testosterone and lead to marked changes in muscle, strength and endurance over time. That’s the fairness question we should focus on - how gender affirming hormones change performance, not slogans or scare campaigns.
When it comes to concerns about “safety”, there’s no robust empirical evidence or even any case studies that trans women increase injury risk in women’s sport. Reviews consistently note a lack of epidemiological injury data; where bans exist, they’re typically based on theoretical modelling and extrapolation (incorrectly equating trans women to cisgender men) rather than observed injury rates.
If we care about women’s sport, let’s invest in it: pay, facilities, coaching pathways, media coverage and community participation. Inclusion and fairness can go hand in hand.
Gender-affirming hormones have a dramatic impact on physical performance
Trans women who use GAHT are prescribed oestrogen on its own, or oestrogen with a testosterone blocking medication (anti-androgens). Using GAHT, it is possible to reduce an individual’s testosterone blood levels and increase oestrogen blood levels to within the cisgender female range.
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. The research shows that when testosterone blood levels are reduced and oestrogen levels are increased, this affects muscle, fat mass and other aspects of the body that factor into physical performance. In nonathletic trans women, GAHT increases fat mass by approximately 30%, and decreases muscle mass by approximately 5% after 12 months, with ongoing decline beyond 3 years.
One thing that GAHT cannot change, once a trans woman has been through testosterone-dominant puberty, is bone structure. Trans women are, on average, taller and broader than cisgender women. However, with the effects of GAHT on muscle and fat mass, taller and broader does not necessarily equate to a performance advantage.
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.”
Trans women have minimal to no performance advantage over cisgender women
In our review article we outline the currently available research comparing nonathletic trans women and cisgender women on performance measures. There is an absence of sport-specific research on physical performance including trans people, so much of the research looking at absolute physical performance relies on retrospective studies (i.e fitness tests performed in the US miltary). The research shows that after 2 years of GAHT, trans women appear to have little to no advantage over cisgender women in a 1.5 mile run and sit-ups, and by 4 years of GAHT there is no performance difference between the two groups. While push-up performance declined in trans women once starting GAHT, they still maintained an advantage over cisgender women. While absolute lean mass remains higher in trans women, relative percentage lean mass and fat mass (and muscle strength corrected for lean mass), hemoglobin, and VO2 peak corrected for weight was no different to cisgender women.
Whilst research suggest some areas where there may be a residual advantage compared to cisgender women (i.e. push ups or hand grip strength), other aspects of physical performance suggest a disadvantage (i.e. lung function or fitness).
Recent research has shown some unexpected results when it comes to lung function in trans women on hormone therapy. Two studies found that, compared to both cis women and cis men, trans women had more obstructed airflow and less efficient breathing on lung function tests. This was surprising, since lung size itself isn’t thought to change with estrogen therapy or testosterone suppression. One possible explanation is that respiratory muscles may become weaker, which could affect breathing efficiency even if overall lung capacity stays the same.
When it comes to cardiorespiratory fitness, research shows a clear pattern. Several studies of non-athletic trans women have found that their fitness levels, measured by VO₂ peak, are very similar to cis women but lower than cis men (Braga et al., Saitong et al., and Alvares et al.). In other words, trans women’s fitness capacity aligns more closely with cis women than with cis men.
One common critique of studies on trans women and sport is that they often don’t involve trained athletes. To address this, Alvares and colleagues carried out a study of national-level volleyball players, comparing adult trans women with cis women and cis men. The groups were matched as closely as possible: the trans women had been on hormone therapy for an average of seven years, were similar in height to cis women (but shorter than cis men), and trained a similar number of hours (though fewer than cis women). The findings were clear: trans women performed on par with cis women but below cis men across multiple measures, including fat and muscle mass, hand grip strength, jump height, and cardiorespiratory fitness (measured by both absolute and relative VO₂ max).
Hamilton and colleagues in the UK also studied athletic trans women and trans men, comparing them with cis women and cis men who trained at similar intensities. On average, the trans participants had been on hormone therapy for 4 to 6 years. The results showed that athletic trans women had higher absolute handgrip strength, but in many other areas including lung function, jump height, and relative VO₂ max they performed worse than cis women. Trans men, meanwhile, had lower absolute handgrip strength and VO₂ max, but their relative VO₂ max was similar to cis men.
What this means for sport depends on the sport. Different sports rely on different combinations of strength, endurance, power, hand-eye coordination, teamwork and strategy. A small edge in one area, such as upper body strength, may matter in some sports but not in others, and could be offset by lower performance in other measures. A further limitation is that most existing studies are small, cross-sectional, and short-term, so we do not yet know how long hormone therapy takes to produce lasting changes in physical performance. Larger and longer-term studies are needed to fill this gap.
Trans women are required to meet strict criteria to compete in elite-level women’s sport
Most international sporting bodies have eligibility guidelines for trans inclusion. Typically, trans women who want to compete in elite-level sport must meet strict criteria related to the time they have been on GAHT, their sex hormone levels, and specific performance measures.
For example, the Australian Football League Gender Diversity Policy for Elite Football stipulates that trans women are eligible to compete in the women’s category, provided they demonstrate their testosterone blood concentration has been maintained at below 5 nmol/L for at least 24 months. Additionally, they are required to provide as much data as they have from the previous 24 months on their height, weight, bench press, squat, 20m sprint time, vertical jump, match raw GPS data from three Australian Football matches, and 2km run time. All of this data is used to assess whether the trans woman has any relevant and significant competitive advantage compared to cisgender players. There is also assessment of safety risk of the trans woman’s potential participation – considering the safety of both her and other players.
Recently, some sporting bodies have implemented bans that prevent any trans women from competing in the women’s category. However, these ‘blanket bans’ are not based on evidence (given there is no definitive evidence that trans women on long-term GAHT have a performance advantage over cisgender women) and do not recognize that trans women are as diverse as cisgender women when it comes to their height, weight, and various other factors that may impact physical performance.
Community-level sport is for everyone
When talking about who can play sport, it is important to make a distinction between elite level and community sport. Whilst guidelines should be in place for the participation of trans people in elite sport, the line distinguishing community sport and elite sport is at times difficult to define and may be different for individual sports or disciplines. Sometimes rules and policies made at the elite level have trickle down effects to community sport, even if this is not the intention of the policy.
Participation in physical activity and sport are deeply ingrained in Australian society. The immense benefits of engaging in sports and physical activity go beyond just physical health and extend to mental and social well-being. Community sport at the grassroots level is all about inclusion, community/social connection, fitness, fun and which should be welcoming of everyone, trans people included.
In Australia, the inclusion of trans people in community sport is covered by the Sex Discrimination Act 1984 which prohibits unlawful discrimination on the basis of sex and gender identity in certain areas of public life. In 2019, the Australian Human Rights Commission and Sport Australia released the Guidelines for the inclusion of transgender and gender diverse people in sport, which provide clear guidelines for sporting bodies and highlight the need to centre the wellbeing of trans people in any policy development process.
Most Australian sporting bodies have clear guidelines regarding the inclusion of trans people in community sport. For example, in comparison to strict criteria for trans inclusion in AFL Elite Football outlined above, the Australian Football League Gender Diversity Policy for Community Football states that: “... in Community Football, considerations of social inclusion have greater priority than concerns that may exist with respect to competitive advantage in relation to the participation of gender diverse players”. Under these guidelines all trans women are eligible to compete in women’s Community Football competitions, with a clear process to address any unacceptable safety risks to either the trans player or other players.
Trans women still face significant barriers to sport participation
Even with guidelines in place to facilitate trans inclusion in sport, trans women still face significant barriers to participation. Many trans women have had previous negative experiences or anticipate discrimination from coaches, officials and other players, and bathroom/changeroom facilities may be inadequate for trans people, in terms of providing privacy and safety.
Because of actual and anticipated discrimination, trans women participate in sport at lower rates than cisgender women. At an elite level, there are very few trans women.
There is clearly a lot of work to be done to improve the inclusion of trans women (and all trans people) in sport, at both an elite and community level. In many respects, Australia is leading the way. For example, in addition to the Australian Human Rights Commission guidelines and the growing number of sport-specific trans inclusion policies, there are 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 terms of research, in a world-first, Trans Health Research at University of Melbourne, Monash University and Victoria University are currently conducting the GAME Study, which aims to uncover the effects of GAHT on skeletal muscle health, fitness, and performance. High quality research, like the GAME Study, is vital in improving trans inclusion in sport.