Transgender Women Show Comparable Fitness to Cisgender Females, Study Claims
A controversial new study from the University of Sao Paolo in Brazil suggests that transgender women undergoing hormone therapy possess no significant physical advantage over those who were born female. The research, which has sparked intense debate within the scientific community and sporting world, analysed strength, fitness, and body composition across multiple studies.
Methodology and Key Findings
The team conducted a comprehensive review of 52 studies involving more than 5,000 transgender individuals and over 1,000 cisgender participants, all aged between 14 and 41. Their analysis revealed that while transgender women maintained greater muscle mass following hormone treatment, their overall physical fitness levels were comparable to cisgender women.
Specifically, the researchers found no observable differences in body strength or maximal oxygen consumption between transgender women on hormone therapy and cisgender women. Based on these findings, published in the British Journal of Sports Medicine, the authors argue their evidence does not support theories of inherent athletic advantages for transgender women and suggests blanket bans may be unjustified.
Scientific Criticism and Counterarguments
However, several prominent scientists have strongly criticised the study's methodology and conclusions. Professor Alun Williams, an expert in sport and exercise genomics at Manchester Metropolitan University, highlighted several fundamental problems:
- The research did not track fitness levels over time or before treatment began
- Comparisons were made without tight assessment of training history
- Hormonal treatment after puberty doesn't change skeletal dimensions like height, limb length, or shoulder width
I don't agree with the authors that the studies published to date, or their review of them, overturn the evidence for inherent athletic advantage in transgender women, Professor Williams stated, adding that male advantages in many sports remain regardless of hormone changes.
Current Sporting Landscape and Policy Implications
The question of transgender participation in women's sports remains fiercely contested across multiple jurisdictions. In the United Kingdom, numerous sporting bodies implemented bans on transgender women competing in female categories last year following a Supreme Court ruling that defined women under the Equality Act based on biological sex.
Meanwhile, in the United States, former President Donald Trump issued crackdowns on strict definitions for male and female competitors after transgender swimmer Lia Thomas won a major women's freestyle title. The International Olympic Committee has established working groups to examine the issue, with a potential ban on transgender women in Olympic sports expected for the 2028 Los Angeles Games.
Study Limitations and Ongoing Debate
The Brazilian researchers acknowledge significant limitations in their work, noting that most included studies did not involve elite athletes and lacked representation across different ages, sports, and competitive levels. They specifically highlighted the under-representation of transgender athletes who may retain more muscle memory from pre-transition training.
These findings contradict previous research, including a 2022 study that found male-to-female transitioners remained faster, stronger, and fitter than most women even after taking hormone drugs. Critics argue that physiological advantages from testosterone exposure during early development cannot be fully eliminated through hormone therapy alone.
Expert Perspectives and Future Research Needs
Dr Blair Hamilton, a research associate in applied sport and exercise physiology at Manchester Metropolitan University, offered a measured response to the study. Overall, the findings make sense and are consistent with what we've seen in the wider scientific literature, he commented, while noting the fierce debate surrounding this area.
Dr Hamilton emphasised that having slightly more muscle doesn't automatically translate to better sporting performance, as studies measuring muscle size and those measuring performance weren't always conducted on the same groups. However, he stressed the need for research involving elite athletes to draw definitive conclusions, noting that at the moment, there are very few openly transgender elite athletes anywhere in the world.
The study has prompted criticism from sex-based rights organisations, with Fiona McAnena, director of campaigns at Sex Matters, stating: Men do not shrink or magically lose all their male advantages when they identify as women, no matter what hormones they take. She argued that academic analysis cannot prove that men should compete in women's sport based on claimed female identity.
As sporting bodies continue to grapple with this complex issue, researchers agree that more comprehensive studies involving diverse athlete populations are urgently needed to inform evidence-based policies that balance inclusion with competitive fairness.
