Strength versus Function: New Review Finds Fitness Parity Between Transgender and Cisgender Women

As transgender women maintain a higher absolute muscle volume compared to cisgender women, the debate regarding transgender participation in sex-segregated sports focuses on whether male puberty creates irreversible physical advantages. To fill this evidence gap, Sofia Mendes Sieczkowska of the Applied Physiology and Nutrition Research Group at the Universidade de São Paulo and colleagues led the review to synthesize evidence on how gender-affirming hormone therapy (GAHT) influences body composition and fitness to determine if functional disparities persist post-intervention.

Following PRISMA guidelines, the authors analyzed data from 52 studies involving 6,485 participants. The review compared body composition and physical fitness outcomes in transgender individuals before and after GAHT, as well as against cisgender control groups. Body composition was primarily assessed using dual-energy X-ray absorptiometry, while functional outcomes included upper- and lower-body strength and maximal oxygen consumption. Certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation framework.

Key Clinical Findings of the Study:

• Clinicians can inform patients and athletic organizations that after one to three years of gender-affirming hormone therapy (GAHT), transgender women reach physical fitness parity with cisgender women, demonstrating no significant differences in upper-body strength (standardized mean difference [SMD] 0.54), lower-body strength (SMD 0.05), or maximal oxygen consumption (VO₂ max) (SMD -0.28).
• Healthcare providers should recognize that although transgender women retain significantly higher absolute lean mass (SMD 1.92) than cisgender women, this does not confer a functional advantage, as their relative lean mass percentage (SMD 0.19) remains statistically comparable to cisgender female controls.
• Clinical evidence indicates that transgender women on GAHT possess markedly lower upper-body strength (SMD -1.25), lower-body strength (SMD -2.36), and aerobic capacity (SMD -1.50) than cisgender men, reflecting the effectiveness of testosterone suppression in reducing male-typical physiological markers.
• For transgender men, one year of testosterone therapy facilitates significant physiological improvements, including an increase in absolute lean mass (SMD 0.52) and a mean difference (MD) of 3.81 kgf in upper-body strength, though their relative lean mass (SMD -6.42) remains lower than that of cisgender men.
• Practitioners monitoring hormonal transition in transgender women should anticipate a distinct shift in body composition within the first year, typically involving an MD increase in fat mass of 2.68 kg and a concurrent MD decrease in absolute lean mass of 2.03 kg.

The authors concluded that, based on the current evidence, transgender women do not demonstrate inherent athletic advantages over cisgender women in measured fitness outcomes. However, they emphasized that the overall certainty of evidence remains low, and results should be interpreted cautiously.

The review highlights the need for longer-term, sport-specific studies in trained athletic populations to better understand how hormone therapy, training status, and competitive context interact to influence performance.

Reference

Mendes Sieczkowska S, Caruso Mazzolani B, Reis Coimbra D, et al. Body composition and physical fitness in transgender versus cisgender individuals: a systematic review with meta-analysis. Br J Sports Med. 2026; doi:10.1136/bjsports-2025-110239.