The inclusion of transgender women in women's sports categories is a controversial decision. To compare body composition and physical fitness between transgender and cisgender women, a team from Brazil has conducted a meta-analysis encompassing 52 studies and 6,485 individuals, analysing these values before and after gender-affirming hormone therapy. Although trans women showed greater lean mass—an indicator of muscle mass—there were no significant differences in upper or lower body strength, nor in maximum oxygen consumption, compared to cis women one to three years after hormone therapy. ‘The current evidence is, for the most part, of low certainty and heterogeneous quality, but it does not support theories about the inherent athletic advantages of trans women over cis women,’ say the authors of the study, published in the British Journal of Sports Medicine.

The International Athletics Federation has decided to ban transgender athletes who have transitioned after puberty from participating in international women's competitions. Although there are currently no trans athletes competing on the international circuit, the Federation "decided to prioritise the fairness and integrity of women's competition before inclusion", according to the statement issued. At a press conference, its president, Sebastian Coe, said: "We will be guided by the science that will inevitably develop in the coming years around physical performance and male advantage. As more evidence becomes available, we will review our position.