Trans Athletes in 2025: A Science First Direction
Transgender athletes are at the center of one of sport’s most heated debates. In 2025, political narratives often overshadow scientific evidence about performance, fairness, and safety. This article examines what research actually shows about hormone therapy, endurance, strength, youth inclusion, and elite competition. It argues that sport specific, evidence driven policies offer a fairer and more accurate alternative to blanket bans and presents a science first model for future regulation.
A Debate That Has Moved Faster Than the Evidence
In 2025, the participation of transgender athletes has become one of the most contentious topics in global sport. Legislative bodies in several countries have passed sweeping bans that restrict transgender individuals from competing in the category that matches their gender identity. These bans often cover an extraordinarily broad range of contexts, from mixed youth recreation leagues to elite Olympic pathways. In the United States, some laws have even been written so broadly that they apply to “mind sports” such as chess and eSports, despite a complete absence of physical performance considerations in those activities. The chess federation FIDE acknowledged in its own policy statements that chess performance does not differ by sex, but it still implemented restrictions on transgender women. Such contradictions reveal that the debate has drifted far from scientific reasoning and into political symbolism.
This moment requires a science first approach. The existing research on transgender athletes is not exhaustive, but it is significantly more detailed than public discourse usually suggests. The literature shows that athletic performance varies by sport, by physiological demand, and by the stage of transition. There is no universal advantage that applies across all sports, and there is no single policy model that fairly governs every competition context. The strongest findings indicate that prepubertal youth have no measurable sex-based athletic differences, and that adults undergoing gender-affirming hormone therapy experience substantial reductions in testosterone-mediated advantages, especially in endurance performance. Remaining differences are generally small and sport specific.
Despite this, policy decisions frequently rely on assumptions about “male physiology” or fears of competitive dominance. These arguments rarely reflect published research and often ignore the heterogeneity of sport. Combat sports present legitimate safety considerations, but even there, empirical injury data are extremely limited. Public arguments tend to rely on hypothetical scenarios rather than documented risk.
The purpose of this essay is to move the discussion back toward evidence. Transgender athletes deserve policies that respect both fairness and dignity. Athletes in women’s sports deserve clear rules that protect competitive integrity. These goals are not mutually exclusive. A science first framework, implemented through a sport-specific review system, offers the most rational way forward. To accomplish this, we need the creation of a Trans Sports Union, an independent multidisciplinary body with authority to evaluate each sport separately and create consistent, evidence-based guidelines.
Only by abandoning blanket bans and replacing them with precise, context-driven standards can the sporting world navigate the challenges of 2025 and beyond.
The State of the Science in 2025
A. Prepubertal Development
The scientific consensus is unequivocal. Before puberty, boys and girls do not differ in ways that affect athletic performance. There is no height difference, no sex-based muscle disparity, and no advantage in strength or speed. Multiple reviews of pediatric physiology confirm that prepubertal children share comparable hormone profiles, which means that the attributes commonly associated with male puberty, such as increased lean mass or bone density, simply have not developed.
Because there are no physiological sex differences before puberty, prepubertal transgender children pose no fairness issue in sport. They should be permitted to play in the category that matches their gender identity. Excluding them violates scientific knowledge and can harm their mental health, participation rates, and long-term wellbeing. Participation in sport at this age provides developmental, social, and psychological benefits that extend beyond competition. This is a point on which both medical experts and youth sport organizations widely agree.
B. Hormone Therapy and Adult Physiology
The central scientific question in adult transgender sport involves the impact of gender affirming hormone therapy. Testosterone suppression in trans women and testosterone supplementation in trans men lead to measurable physiological changes that influence athletic performance. The key is understanding which changes matter, to what extent, and for which sports.
The most important longitudinal studies have tracked active duty military personnel who transitioned while maintaining rigorous fitness testing. Results show that aerobic performance in trans women declines over the first two to four years of hormone therapy. After approximately two years, trans women remain slightly faster than cisgender women in endurance running but significantly slower than cisgender men. After four years, the difference disappears, and 1.5 mile run times converge with cisgender female averages.
Strength-related performance shows a more complex pattern. Push up scores and grip strength decline substantially with testosterone suppression, although residual differences may remain even after several years. These differences are generally small, and their competitive relevance varies widely across sports. In many non-contact sports such as distance running, rowing, or swimming, endurance outcomes matter more than absolute power output. In some sports that require brief anaerobic bursts or maximum strength, such as sprinting or weightlifting, differences in fast twitch capacity may retain more importance.
C. What the Evidence Does Not Show
There are several claims frequently invoked in public debates that lack empirical support.
There is no evidence that trans women dominate women’s sports.
Participation data from national and collegiate associations show extremely low numbers of trans athletes. There is no documented pattern of competitive displacement.There is no proven sustained advantage from prior exposure to testosterone after long-term suppression.
Residual differences have been observed, but they are sport specific and usually modest. No study shows that trans women retain universal advantages.There is no injury-based evidence that trans women pose heightened danger in sport.
Safety concerns in combat sports are reasonable theoretical considerations, but there is no observed injury pattern attributable to transgender participation.
D. Where Research Remains Limited
The existing studies have limitations. Sample sizes are often small. Research on elite athletes is scarce, which means that conclusions for high performance contexts must be cautious. There is insufficient data on certain high power sports, and virtually no data on sports like wrestling, rugby, or martial arts competitions where both strength and technique interact dynamically.
However, gaps in the research cannot justify sweeping bans or assumptions of universal advantage. Instead, gaps should motivate further research and precise regulation.
The overall picture is clear. Transgender performance outcomes vary by sport, by physiology, and by transition stage. This heterogeneity demands sport-specific policy, not blanket exclusion.
The Myth of a Single Sports Advantage
A. Sports Are Not Physiologically Uniform
One of the fundamental errors in the current policy landscape is the assumption that all sports rely on the same physiological traits. In reality, sports vary dramatically in which attributes determine success. Some require precision and dexterity, others require explosive power, others value endurance, and many require a blend of attributes plus technical skill. Regulations for trans athletes that treat sport as a monolith ignore basic exercise physiology.
Endurance sports rely heavily on oxygen uptake capacity, lactate threshold, and efficiency. Strength sports rely on lean mass, force production, and neural activation patterns. Skill sports rely predominantly on training, strategy, and coordination. Motor learning and tactical planning matter far more in chess, shooting, golf, and archery than raw physical traits. Even within track and field, the physiological demands of sprinting differ from those of distance running.
Because the relevant performance factors differ so widely, a single overarching eligibility rule cannot fairly govern all sports.
B. Examples That Demonstrate the Variation
The best example of misguided policy is competitive chess. Chess performance does not depend on muscle mass, testosterone levels, bone structure, or any measurable sex-linked physical trait. Despite this, some federations have implemented restrictions on transgender competitors. This is a clear case where non-scientific reasoning has superseded objective evidence.
Conversely, in sports like shot put or powerlifting, muscular strength and limb leverage can influence performance. Hormone therapy reduces these factors in trans women but does not eliminate them entirely. The fairness question in these sports differs from endurance events or skill sports, so the regulatory approach should also differ.
C. Why Blanket Bans Fail
Blanket bans assume that all trans women have overwhelming advantages across all sports. The scientific record does not support this assumption. Performance outcomes depend on specific physiological systems, and hormone therapy affects these systems in specific ways.
A one size fits all ban ignores the complexity of sport. It oversimplifies physiology, disregards research on endurance convergence, and fails to account for training, coaching, access, socioeconomic factors, and technique. Sport is never only about biology. It is about development, opportunity, and skill acquisition.
Level of Play: Why Context Changes the Entire Conversation
A. Youth Sport
Youth sport prioritizes participation, development, and physical and mental health. Prepubertal children have no sex-linked athletic advantage. Therefore, restricting transgender children from participating in the category that matches their gender identity has no scientific justification.
Moreover, exclusion at young ages can cause significant psychological harm. Studies consistently show that youth who experience gender affirmation in social settings report lower rates of depression, anxiety, and suicidality. Youth sport settings play an important role in providing community and belonging. Policies that impose exclusion on children thus contradict both scientific evidence and best practices for youth wellbeing.
B. High School and Collegiate Sport
The landscape becomes more complex after puberty, when sex-linked physiological differences begin to manifest. At this level, fairness in competition and inclusion both matter. Many collegiate systems, including the NCAA until recent restructuring, required one year of testosterone suppression for trans women. This approach was originally designed to approximate the reductions in performance observed during the early stages of hormone therapy.
However, one year of suppression does not perfectly align with research on endurance convergence, which tends to occur closer to three or four years. Therefore, collegiate policy designers must consider whether a one year threshold is sufficient for specific sports and whether stronger sport-specific policies are appropriate.
C. Elite and Professional Sport
Elite sport requires precise physiological regulation because small differences can decide outcomes. Elite athletes train at extremely high levels, and even minor advantages can matter. For this reason, organizations such as the IOC and World Athletics have implemented testosterone thresholds for female category eligibility. These thresholds, however, have shifted over the past decade due to both scientific debates and legal pressures.
In elite contexts, there is a legitimate argument for stricter criteria, especially in sports where strength and power heavily determine performance. However, elite criteria cannot simply be transposed onto youth or recreational levels. Fairness and safety considerations differ by context and must be weighed accordingly.
D. The Need for Alignment
The lack of consistency across levels of play produces confusion and undermines trust. Athletes deserve policies that are coherent, transparent, and consistent with available evidence. A child playing soccer in a community league should not be subject to the same rules as a professional boxer, nor should a collegiate swimmer be governed by a policy written for competitive chess. Context matters.
Safety, Injury Risk, and the Combat Sports Question
A. Theoretical Concerns
Combat sports involve striking, grappling, and physical contact, which raises reasonable questions about safety. Some sports medicine groups argue that trans women may retain advantages related to bone geometry, muscle mass, or reaction speed that could elevate injury risks for cisgender female opponents. The Association of Ringside Physicians has recommended excluding trans women from combat sports on the basis of potential risks.
B. Lack of Empirical Evidence
However, these claims remain theoretical. There is no documented pattern of injuries caused by trans athletes in combat sports. There is also little recorded participation, which means safety predictions are based on modeling rather than data. Some combat sports researchers argue that without empirical injury evidence, bans lack sufficient justification. They recommend sport-specific evaluation and further study, not categorical exclusion.
C. How Safety Policies Can Respect Both Fairness and Dignity
Safety is a legitimate concern. It should be addressed through concrete measures such as:
Medical evaluations on a case-by-case basis
Strength and weight class considerations
Skill matching in sparring or competition
Development of trans-inclusive but safety-focused categories if necessary
Combat sports must find a balance between inclusion and safety. Science can guide this balance better than fear-driven legislation.
Performance, Equity, and the Fear of Dominance
A. The Myth of Transgender Dominance
One of the dominant narratives in public debate suggests that trans women will sweep podiums and displace cisgender women. There is no evidence to support this claim. Trans athletes represent a very small percentage of competitors in any sport. Participation is often limited by social barriers, financial barriers, and institutional restrictions.
Where trans women have competed in women’s categories, results show no pattern of disproportionate winning. Many compete at recreational or mid-level athletic tiers, not at elite national levels. Transition related physiological changes also reduce performance significantly compared to pre-transition baselines.
B. Outlier Cases and Misinterpretation
High profile outlier cases often shape public perception. When a trans woman wins a competition, headlines tend to sensationalize the result. Cases in which trans athletes compete without winning or perform below the level of cisgender peers rarely attract attention.
Public debate often fails to recognize that exceptional individuals exist in every demographic group. Dominance narratives ignore training histories, coaching access, socioeconomic factors, and simple individual variation.
C. Moral Panic and Sociological Context
The rapid spread of restrictive policies in the absence of data aligns with patterns of moral panic observed in other sociopolitical issues. Communities often respond to perceived threats that are symbolic rather than evidence based. Transgender athletes have become symbolic figures in larger cultural debates about gender, identity, and social norms. The emotional weight of these debates often obscures scientific reasoning.
Policy Disarray in 2025
A. International Inconsistency
The IOC, World Athletics, FIDE, and other international bodies have adopted divergent policies. Testosterone thresholds vary. Eligibility review periods differ. Some organizations require long-term documentation of hormone therapy while others impose categorical restrictions. These discrepancies create uncertainty, especially for athletes transitioning across competition levels.
B. The Consequences of Incoherence
When governing bodies fail to align their policies with scientific evidence or with each other, the result is an unstable system that undermines athlete trust. Trans athletes face inconsistent rules, sometimes changing within the same competitive season. Cisgender athletes are left uncertain about the fairness and transparency of the rules governing competition. Organizations risk legal challenges from both sides, and public confidence erodes.
C. The Role of Political Pressure
In some cases, policy shifts have occurred in response to political pressure rather than scientific findings. Legislators with little knowledge of sports physiology have enacted sweeping bans that override sport governing bodies. This politicization harms the integrity of sport and destabilizes regulatory authority.
A Science First Model: The Case for a Trans Sports Union
A. Purpose and Structure
One novel idea is the creation of a Trans Sports Union (TSU) that would serve as an independent, multidisciplinary review body. It would include experts in sports medicine, endocrinology, exercise physiology, biomechanics, legal ethics, and athlete representation. Its mission would be to review each sport individually, assess the physiological demands, and create evidence-based eligibility standards.
B. Sport Specific Assessment
The TSU would evaluate each sport by examining:
Primary performance determinants such as endurance, power, technique, or strategy
Injury and safety considerations
Hormone therapy effects on the relevant physiological systems
Age and development categories
Participation rates and competitive impact
This approach would ensure that the policies for each sport reflect its specific context.
C. Hormone Thresholds and Evidence Integration
The TSU would determine whether hormone thresholds are necessary for particular sports and what duration of hormone therapy should be required. The thresholds would be grounded in peer-reviewed research, not arbitrary tradition. The TSU would update guidelines as new studies emerge.
D. Fairness, Safety, and Inclusion Balanced Together
By applying a sport-specific approach, the TSU would preserve competitive integrity without resorting to discriminatory exclusion. Youth sports could emphasize inclusion, recreational sports could use simplified guidelines, and elite sports could adopt stricter criteria based on physiological evidence.
E. International Harmonization
An independent union could work alongside existing federations to harmonize global policy. International alignment would reduce confusion, improve athlete mobility, and create globally recognized standards. This would benefit both transgender athletes and cisgender female competitors by increasing transparency and predictability.
What We Need Moving Forward
A. Research Priorities
Future studies must focus on:
Long-term performance trajectories of transgender athletes in elite settings
Injury data in full contact sports
Strength versus endurance effects in different transition timelines
Sport-specific performance modeling
B. Standardizing Policy Across Levels
Policies must remain flexible across youth, collegiate, and elite contexts, but they should share a coherent scientific foundation. A standardized framework would reduce arbitrary variation and increase fairness.
C. Ensuring Policy Keeps Pace with Science
The landscape of gender affirming medicine will evolve. Physiological research will expand. Policies must be reviewed regularly rather than fixed indefinitely. A science first approach requires continuous reassessment.
Simply Put: Toward Precision and Fairness
The debate about transgender athletes has often been dominated by fear, political pressure, and misunderstanding. Yet the science in 2025 offers a clear path forward. Athletic performance depends on sport specific physiological demands. Endurance performance in trans women converges with cis women after several years of hormone therapy. Strength differences may remain but are generally modest and not universally decisive. Prepubertal youth have no sex-linked advantage. Safety concerns in combat sports deserve study but require empirical evidence, not assumptions.
Policies that treat all sports as identical ignore fundamental exercise science. Blanket bans undermine fairness and inclusion. A sport-specific, evidence-based approach implemented by an independent review body such as the proposed Trans Sports Union would align regulation with scientific understanding and human dignity. Only through such an approach can sport remain fair, inclusive, and grounded in reality.
A science first direction does not promise perfection, but it offers clarity. It respects athletes. It honors evidence. It moves the conversation beyond rhetoric and toward a better future for all who compete.
References
FIDE. (2023). Policy on transgender participation in chess.
HRC | Get the Facts on Sports Bans by Trans & Non-Binary Students
Strangio, C. (2020) Four Myths About Trans Athletes, Debunked | American Civil Liberties Union
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