Trans women have no biological advantage to cis women in sports

1. What the data actually show — slice by slice

Laboratory and field studies report a mixed picture: an IOC‑funded Brighton/UK study and related analyses found trans women had greater handgrip strength than cis women but lower lung function, jump height and relative VO2max after at least a year of hormone therapy ^{[2] [3] [6]}, while a running cohort in multiple reviews showed trans women still outperformed cis women at the 1.5‑mile test even after hormone therapy in one dataset (765 s. vs. 855 s.) ^{[1] [4]}. Other work finds hormone therapy reduces hemoglobin and aerobic capacity toward female ranges, and in some small samples trans women perform similarly to cis women on certain tasks after transition ^{[1] [7] [8]}.

2. Why results disagree — methods, samples and sports matter

The literature is constrained by low numbers of participants, heterogeneous cohorts and differing outcome measures: many studies recruit military personnel or recreational athletes rather than elite competitors, sample sizes are often in the dozens, and sports stress different physiological traits (strength vs. endurance vs. power), so a finding in one metric or sport does not generalize to all ^{[1] [5] [9]}. Researchers explicitly warn against extrapolating from cis male–female averages to predict trans athlete performance without direct comparisons ^[4].

3. The role of testosterone, puberty timing and residual advantages

Testosterone exposure during male puberty creates differences in stature, bone geometry and baseline muscle mass that some reviews argue are not fully reversed by estrogen and testosterone‑lowering therapy, producing potential residual advantages in some contexts ^{[10] [11]}. Other studies stress that lowering testosterone reduces hemoglobin and muscle mass and can move physiological metrics closer to cis female ranges — but which metrics and how much they matter for competitive advantage varies by sport ^{[1] [2] [4]}.

4. What governing bodies and experts say — uncertainty shapes policy

Because evidence is mixed and sport‑specific, policy decisions have split: some experts and federations insist on testosterone thresholds or time‑on‑therapy rules as a precaution, while others point to studies showing parity on many measures and call for inclusion and case‑by‑case assessment; commentators note the need for more elite‑level longitudinal data before firm, blanket rules can be justified ^{[5] [6] [8]}.

5. Hidden agendas, rhetoric and the limits of current reporting

Public debate is amplified by political and advocacy agendas on both sides: some outlets emphasize retained advantage to justify exclusionary policies, while advocacy groups highlight studies finding minimal differences to argue for inclusion ^{[12] [13]}. Journalistic and policy narratives sometimes overreach the underlying data — the strongest honest claim available from current research is uncertainty plus sport‑dependent nuance, not categorical equivalence or categorical advantage ^{[9] [11]}.

6. Bottom line

The best summary of the evidence is that trans women can retain advantages in some physiological measures after transition and lose ground in others; whether those differences translate into an unfair competitive edge depends on the sport, the athlete’s history (including puberty timing) and the specifics of hormone treatment, and the literature currently lacks the large, sport‑specific, elite‑level longitudinal studies required to declare a universal biological advantage or lack thereof ^{[2] [1] [5]}.