Trans and cisgender women have comparable fitness despite differences in muscle mass, finds a review of 52 previous studies.
The systematic review and analysis by overseas scientists in British Journal of Sports Medicine looked at data on body composition – fat and muscle mass – and physical fitness of trans and cisgender people.
After 1-3 years of hormone therapy, transgender women didn’t show observable differences to cisgender women in upper and lower body strength, or in a key measure of heart and lung fitness (VO₂ max).
The authors say there are many limitations to their review and we need more long-term studies, but conclude that current evidence doesn’t show “inherent athletic advantages” for transgender women.
The Science Media Centre asked local experts to comment.
Research Associate Professor Kim Meredith-Jones, Director of the Bone and Body Composition Research Unit, University of Otago, comments:
“I am not a clinical expert in gender-affirming hormone treatments. My perspective comes from experience measuring body composition, and some very cursory clinical experience working with adolescent transgender populations. With that context in mind, these findings are interesting, but they need to be interpreted carefully.
“Although this review included a large number of transgender participants overall, most were adults. This means the results cannot tell us what happens for young people who use puberty blockers or begin medical transition during adolescence. That remains an important evidence gap.
“The finding that transgender women had higher lean mass than cisgender women, but did not differ in strength or aerobic fitness, should also be interpreted with caution. These outcomes were often measured in different groups of participants, rather than in the same individuals. In addition, only a small number of studies included fitness data, and strength testing was carried out in far fewer participants than body composition measurements. This makes it difficult to draw firm conclusions about how muscle mass relates to physical performance.
“Finally, the studies included in the review varied widely in methods, hormone treatment duration, and measurement techniques. While the results add useful information to an evolving area of research, they should not be seen as definitive and highlight the need for better-designed, long-term studies that measure both body composition and physical performance in the same participants.”
Our colleagues at the AusSMC, SMC Spain, and UK SMC have also gathered comments. A selection follows – full comments available on their websites: SMC Spain, UK SMC, AusSMC.
Professor Ada Cheung is a Professor of Endocrinology at The University of Melbourne, Australia
“Blanket bans on transgender women in sport are not supported by the best available evidence. This large new review, combining data from more than 6,000 people across 52 studies, shows that after gender-affirming hormone therapy, transgender women are no different from cisgender women in body fat percentage, muscle percentage, strength, or cardiorespiratory fitness. While trans women are, on average, taller and may retain slightly more absolute muscle, this does not translate into meaningful advantages in performance, such as strength or aerobic capacity.
“What we still do not know precisely is how long these changes take to fully converge after starting hormone therapy, which is why sport needs evidence-based, sport-specific guidelines rather than one-size-fits-all rules.
“The idea that male puberty creates permanent athletic advantage is not supported by current data if someone is using gender affirming hormone therapy. Restrictive bans also harm cisgender girls and women by policing bodies and reinforcing narrow ideas about how women are supposed to look or perform. Fairness and inclusion can coexist.
“Instead of blanket bans, we need eligibility criteria for elite sport, and we should focus on the real work of supporting women’s sport: improving visibility and pay, reducing sexual harassment and assault, expanding access to facilities and coaching, and ensuring fair media coverage. These changes actually advance equity, while building sporting systems that are safe, inclusive, and grounded in evidence.”
Ada has declared the following: Professor Ada Cheung is a clinician scientist and member of the World Triathlon Transgender Athlete Eligibility Expert Panel and Formula Fixed Sport Science and Equity Panel. Ada Cheung has received research funding from NHMRC, Heart Foundation, Suicide Prevention Australia, The Paul G. Allen Frontiers Group, University of Melbourne, Endocrine Society of Australia, Royal Australasian College of Physicians Foundation, Austin Medical Research Foundation, Sir Edward Dunlop Medical Research Foundation and Viertel Charitable Foundation. She is currently a member of the Endocrine Society (US), European Society of Endocrinology, Australian Medical Association, Endocrine Society of Australia, World Professional Association for Transgender Health and Australian Professional Association for Trans Health.
Associate Professor Phoebe Toups Dugas is from the Department of Human-Centred Computing & Exertion Games Lab at Monash University, Australia. She is a transgender woman.
“Physical characteristics impact sports performance. This affects players’ chance at a fair go and their ability to socially enjoy their bodies. It affects how interesting a competition is. Many sports segregate based on sex, assuming that women and men have knowable inherent characteristics that impact performance – it turns out they’re neither knowable nor predictably affect performance. This paper points out that:
- identifying the impacts of hormones and sexual development on athletic performance is complex and poorly understood – there’s not consistent data, nor do physical characteristics predict performance;
- transgender women on hormone therapy become similar to cisgender women in terms of performance, despite retaining lean mass; and
- athletic performance is multifaceted, and attention to gender is not very useful.
“Adding in my experience as a transgender woman in dance who studies transgender play – being active and athletic in a trans body is transcendent, and taking such an opportunity away is not backed by science.
“We should identify IF and what characteristics matter for a sport, non-invasively test for them, and segregate using them instead. For example, if long arms make one better at a sport, then maybe divisions based on arm length make more sense than gender!”
Phoebe Toups Dugas has declared: My positionality is that of a transgender woman who is interested in justice and equity.
Professor Vincent Harley is from the Centre for Endocrinology and Reproductive Health (CERH) at Hudson Institute of Medical Research, Australia
“This study is interesting and large and shows no difference in upper or lower body strength or oxygen consumption amongst sedentary transgender women after one to three years of sex hormone therapy, when compared to cisgender women. On this basis, the study suggests that trans women do not have an athletic advantage at a baseline level. So, from a community sport perspective there is no reason to think transgender women would have an advantage.
“This study does not inform performance at an elite level. That would require a study of the performance of transgender athletes in a specific sport – a difficult task given their rarity. Exclusion of transgender athletes from sport would hinder data collection. The International Olympic Committee has stated inclusion of trans athletes should be the default. So many factors weigh in to success at the elite level – physique, genetics, sports infrastructure, socio-economic and psychosocial – so I’m not sure if being trans is another factor, especially considering the very small number of individuals involved.”
Vincent declares that he has no conflicts of interest.
Connor Macdonald is a Researcher and Lecturer from the College of Business and Law at Adelaide University, Australia
“As the authors of this study have stated, those who advocate for blanket bans of transgender women from participation in sport hinge their argument on transgender women having inherent physical advantages over cisgender women. These bans are most obviously seen in the US at the federal level, and in Canada at the provincial level in Alberta. As has been recognised for some time, the science around inherent sport advantage is inconclusive, yet those who have pushed campaigns against inclusion have often relied on ‘common-sense’ arguments that essentialise transgender and cisgender women. This study challenges not only the taken-for-granted views that transgender women retain sport-specific physical advantages over cisgender women, but also the social construction of transgender women and men.
“While the authors conclude with a call for further study and developing nuanced and context-dependent inclusion policies, I think there needs to be further conversation around the social constructions of sport and gender. Sport’s history as a domain exclusively for men has produced discrepancies in all women’s equitable access and participation in sport. And while these historical implications are constantly contested, there are still further opportunities to change how sport can be practiced, and that starts with inclusion.”
Connor declares that he has no conflicts of interest.