How a Flawed Meta-Analysis Misled the Public on Transgender Athletes

A deeply flawed meta-analysis on transgender fitness reveals a troubling breakdown in the British Journal of Sports Medicine’s peer-review process.

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About the Author

James L. Nuzzo, PhD, is an exercise scientist and men’s health researcher. Dr. Nuzzo has published over 80 research articles in peer-reviewed journals. He writes regularly about exercise, men’s health, and academia at The Nuzzo Letter, with additional writings appearing at Reality’s Last Stand and Australians for Science & Freedom. In 2025, Dr. Nuzzo documented his academic cancellation using a freedom of information request. He is active on X @JamesLNuzzo.

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Earlier this year, a meta-analysis on physical fitness in transgender individuals was published in the British Journal of Sports Medicine, one of the most historically important journals in sports medicine and exercise science. The paper’s eight authors, led by Sofia Mendes Sieczkowska, concluded that “transgender women do not exhibit significant differences in upper-body strength, lower-body strength, or maximal oxygen consumption relative to cisgender women after 1–3 years of [gender-affirming hormone therapy].” Based on this conclusion, the authors expressed support for “nuanced, sport-specific policies rather than blanket bans” regarding the inclusion of transgender individuals in sports.

The paper caused an initial stir online—and rightly so. Below, I show how the authors misled the public by concluding that their meta-analysis provided evidence of no difference in muscle strength between women and transgender women (i.e., biological males) after “1–3 years” of cross-sex hormones. More specifically, the authors did not even follow their own inclusion criteria. In some cases, they included data that should have been excluded; in others, they excluded data that should have been included. Underlying all of this is the fact that the muscle-strength meta-analysis was underpowered from the start, with only a few studies contributing to the analysis.

Let us now take a closer look at the data and the claims.