Reacción a "A review finds no differences in physical performance between trans women and cis women, even though they have more muscle mass"

This article provides an updated summary of physical fitness and body composition in transgender individuals compared to cisgender individuals, integrating data from observational and longitudinal studies that analyse key variables such as fat and lean mass, muscle strength, and maximum oxygen consumption (VO₂max).

The results show that, in transgender women, relative fat mass (%), upper and lower body strength, and VO₂max are similar to those observed in cisgender women, although absolute lean mass (kg) is higher in some cases. However, this higher lean mass does not seem to translate into significant differences in overall physical fitness, underscoring the importance of distinguishing between body composition and functional performance. Analysis in transgender men shows higher fat mass (before or in the early stages), while muscle mass and strength data remain below those observed in cisgender men.

The article highlights the role of gender-affirming hormone therapy (GAHT) as a modulator of body composition and VO₂max. In transgender women, longitudinal evidence indicates that hormone therapy is associated, over the first three years, with an increase in fat mass and a reduction in lean mass and strength, especially in the upper body, progressively placing their physiological profiles within the ranges described for cisgender women. However, we must bear in mind that transgender women have also shown lower muscle mass and strength compared to cisgender men. In parallel, transgender men have been observed to have a physiological pattern consistent with the effects of GAHT, with a reduction in fat mass and an increase in lean mass and strength after its initiation.

The article contributes significantly to clarifying the current state of scientific evidence in a field that requires cautious, evidence-based and contextualised interpretations. We must therefore bear in mind that physical fitness is not a single or static variable, but is determined by the interaction of multiple factors: endocrine, nutritional, training, health, age, etc. Therefore, in order to reach more solid conclusions, further studies are needed that assess these factors together and not in isolation.

From a methodological point of view, the authors rigorously acknowledge the limitations of the available evidence, pointing out that most studies have low certainty and heterogeneous quality, with small sample sizes and considerable variability in designs, variables assessed and instruments used. This transparency strengthens the interpretative validity of the work and avoids overly generalised conclusions. With these conclusions, the data provided should be subject to review as more robust and methodologically homogeneous longitudinal studies become available.