Reasoned arguments are made on both sides. Going through puberty as a male provides physical advantages that persist even after testosterone levels are suppressed, such as broader shoulders, bigger hands, longer torsos, denser muscles and greater heart and lung capacity.
In January, the international and European federations of sports medicine issued a joint statement that said, in part, that high testosterone concentrations “confer a baseline advantage for athletes in certain sports” and that to uphold “the integrity and fairness of sport,” these advantages “must be recognized and mitigated.”
Yet there has been relatively little scientific research involving elite transgender athletes. And studies have not quantified testosterone’s precise impact on performance. The governing body of track and field, which has instituted stringent regulations on permitted levels of testosterone, last year corrected its own research. It acknowledged that it could not confirm a causal relationship between elevated testosterone levels and performance advantages for elite female athletes.
FINA left itself vulnerable to critics who charge that it acted hastily and recklessly, taking retribution against Thomas and trying to create a solution for a problem that doesn’t exist. The Human Rights Campaign, an L.G.B.T.Q. civil rights organization, blamed the swimming governing body for “caving to the avalanche of ill-informed, prejudiced attacks targeted at one particular transgender swimmer.”