Unpacking the Science: Transgender Women in Female Sports – What Does the Evidence Say?

May 11
3 min read

By: Cassandra Williamson

11 May 2025, Sunday

The participation of transgender women in female sports categories is one of today's most hotly debated topics, sparking passionate discussions about fairness, inclusion, and the very nature of competitive sport. At the heart of this debate lies a critical question: Do transgender women retain a significant athletic advantage over cisgender women, even after undergoing gender-affirming hormone therapy (GAHT)?

Our comprehensive new report, "An Evidence-Based Analysis of Transgender

Women's Participation in Female Sports Categories: Evaluating the Null Hypothesis of Significant Athletic Advantage," dives deep into the current scientific literature to explore this complex issue. We've sifted through studies on physiological changes, athletic performance metrics, and the long-term effects of GAHT to provide an evidence-based perspective.

What did we find? The picture is far from simple.

● Physiological Shifts: GAHT brings about significant changes. For instance, hemoglobin levels, crucial for endurance, typically align with cisgender female ranges relatively quickly. However, the impact on muscle mass and strength is more nuanced. While GAHT leads to reductions, some research suggests that differences in lean body mass and certain strength measures may persist compared to cisgender women, even after several years of therapy.

● Performance Puzzles: When it comes to on-field performance, the data presents a mixed and sometimes contradictory picture. Some studies, like one involving U.S. Air Force personnel, indicated a retained advantage in running speed for transgender women after two years of GAHT. Yet, other research, often involving non-athletic populations, found no such difference. Similarly, while some strength advantages appear to diminish or disappear (especially when adjusted for body size), others, like absolute handgrip strength in one athlete study, remained higher.

● The Irreversible and the Unknown: Certain effects of male puberty, such as skeletal structure (height, bone size), are not reversed by adult hormone therapy and can offer biomechanical advantages in specific sports. The intriguing "muscle memory" hypothesis – suggesting that muscle cells might retain an enhanced capacity due to prior testosterone exposure – is also an area of ongoing scientific exploration.

● Gaps in the Science: It's crucial to acknowledge that the research landscape has limitations. Many studies involve non-athletic individuals, have small sample sizes, or lack long-term follow-up, especially with elite athletes. More research is desperately needed, particularly on athletes who began medical transition before or during early puberty.

So, is there a definitive "yes" or "no" to the question of retained advantage?

Based on the current body of evidence, a universal, blanket conclusion is scientifically elusive. The data suggests that any potential advantage is not uniform across all physiological systems or all sports. It appears to be highly dependent on the specific physical attribute in question (e.g., absolute strength vs. aerobic capacity), the demands of the particular sport, the duration of hormone therapy, and individual variability.

The debate often boils down to defining "significant advantage" – a concept that itself is complex, intertwining statistical findings with real-world sporting implications and ethical considerations of fairness and inclusion.

Want to understand the full picture?

This summary only scratches the surface. To truly grasp the nuances, explore the conflicting findings, and understand the critical questions that still need answers, we encourage you to read the full report. It provides a detailed examination of the studies, the methodologies, and the ongoing scientific discourse, offering a comprehensive foundation for anyone seeking an evidence-based understanding of this important and evolving issue.

Dive deeper into the science – read the full report [Link to where the full report would be].

Click HERE

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