>Only 16 studies incorporated any form of physical activity assessment. Among these, two exclusively recruited amateur athletes, and another reported that they included only sedentary individuals
>Methods for assessing physical activity levels varied: three studies used weekly METs (metabolic equivalents); three applied the Baecke questionnaire (mean scores); two reported the percentage or number of ‘active’ participants; two documented weekly exercise frequency; two measured weekly exercise duration; one used the Sport Index (mean scores); one used Saltin-Grimby scale (categorising their activity as sedentary, some physical activity or regular physical); one simply noted ‘regular physical activity’ without further detail, and one reported including only sedentary individuals.
>Only a minority of studies (n=7) applied statistical adjustments for confounders in the outcome analyses. The most frequently adjusted variables were body composition (eg, lean or fat mass), age, hormone levels (eg, testosterone) and nutrient intake (eg, protein, vitamin D). Additionally, one study adjusted for cardiovascular variables, such as stroke volume, in analyses of maximal oxygen consumption (VO₂ max).
>20 studies lacked dropout data, 11 reported none and 4 had significant attrition (≥20 participants) and 1 had minimal dropouts (n=2).
>Regarding outcomes and measurement methods, studies assessed body composition (n=52), muscular strength (n=21) and aerobic capacity (n=8) (online supplemental table S5). DXA was the most used tool for assessing body composition (n=38), followed by bioelectrical impedance analysis (BIA) (n=7). Upper-body strength was primarily evaluated using handgrip dynamometry (n=19), with either hydraulic or electronic devices. A smaller number of studies assessed lower-body strength, assessed mainly through countermovement jump (n=5) and aerobic capacity assessed through cardiopulmonary exercise testing (n=5) or 1.5 mile run time (n=2).
>Transgender women demonstrated higher absolute lean mass (kg) compared with cisgender women
>No significant differences were observed between transgender women and cisgender women in absolute fat mass (kg)
A lot of this is just comparing body composition which is not necessarily the most relevant metric to consider here re: elite athlete performance.
>Transgender women had a lower upper-body strength than cisgender men
>Transgender women exhibited lower lower-body strength than cisgender men
>Transgender men exhibited lower upper-body strength compared with cisgender men
>No significant differences were observed between transgender men and cisgender women in absolute fat mass
>Longitudinal analysis of cross-sex hormone therapy in transgender women: baseline to 1 year.No significant change was observed for relative lean mass.These results remained consistent across all categories. The same applies for the three year period studied
Quality scores ranged from 10 to 19, with most studies rated as high (70.6%; n=12) or fair (17.6%; n=3), and 11.8% as low quality (n=2) for cross-sectional studies. Using AXIS, the most common weaknesses identified in the articles were the lack of justification of the sample size (n=13) and the use of a convenience sample (n=15).
Among cohort and quasi-experimental studies, 65.6% exhibited moderate ROB, with limitations concerning confounding (15/32 studies, 46.8%, moderate risk) and selective reporting (22/32 studies, 68.8%, moderate risk). Bias in participant selection, intervention classification and deviations from intended interventions were predominantly low risk (24/32, 75%; 25/32, 78.1%; 30/32, 93.8%, respectively).
All RCTs were classified as some concerns. Methodological concerns primarily stemmed from selection of the reported result (3/3 studies, 100%, some concerns); deviation from intended interventions (3/3 studies, 100%, some concerns); and randomisation process (2/3 studies, 66.6%, some concerns).
>The primary findings indicate that transgender women exhibit body composition distinct from both cisgender men and cisgender women. Specifically, transgender women possess significantly higher fat mass than cisgender men but levels comparable to cisgender women. Regarding lean mass, transgender women show values significantly higher than cisgender women but significantly lower than cisgender men. Of relevance, despite differences in lean mass, no significant differences were found in upper-body or lower-body strength between transgender women and cisgender women
>Because the lean mass and performance data were not necessarily derived from the same cohorts or study designs, direct correlations between muscle mass and functional strength cannot be inferred
>This systematic review aligns with previous ones in highlighting critical research limitations. This includes the typically short study durations (<3 years) and a lack of data on elite athletes.
>The limitations of this review are related to the identified gaps in literature and include.....the reliance on lean mass and strength as proxies for performance, rather than sport-specific outcomes (eg, race times, power output), which limits practical importance to real-world sport scenarios....studies with small sample sizes and unmeasured confounding were included, potentially leading to overestimated results due to heterogeneity, sampling error and/or publication bias.
Yes it is very cool and important that this is being studied! I'm open to whatever findings are made! But can people not act like this is some grand study that establishes trans women are on even ground with cis women in all sports and competing together is fair and that they have absolutely no advantages. The reporting on this is extremely biased.