Biological sex is a primary determinant of athletic performance because of fundamental sex differences in anatomy and physiology dictated by sex chromosomes and sex hormones. Adult men are typically stronger, more powerful, and faster than women of similar age and training status. Thus, for athletic events and sports relying on endurance, muscle strength, speed, and power, males typically outperform females by 10%–30% depending on the requirements of the event. These sex differences in performance emerge with the onset of puberty and coincide with the increase in endogenous sex steroid hormones, in particular testosterone in males, which increases 30-fold by adulthood, but remains low in females. The primary goal of this consensus statement is to provide the latest scientific knowledge and mechanisms for the sex differences in athletic performance.
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Several longitudinal studies in transgender women show a reduction in hemoglobin/hematocrit (the latter equivalent to cisgender women after ~4 months), and lean body mass, muscle cross-sectional area, and muscle strength, but are typically stronger than cisgender women (387) even 14 yr after initiation of GAHT (388). For example, nonathletic transgender women who underwent estrogen treatment for 12 months decreased muscle volume by 5% but maintained muscle strength (384).
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Individuals with 46,XY DSD who are born with female or ambiguous genitalia and functioning testes, such as in the case of 5-alpha reductase deficiency, will produce testosterone concentrations in the typical male range (9,325) (Fig. 2). Except in cases of androgen resistance (CAIS), the individual will respond to testosterone made during puberty and adult life with increased virilization and muscle development (9,325). The prevalence of 46,XY DSD is estimated to be ~140 times greater (7.1/1000 vs 0.05/1000) among elite women athletes than the general population (18,404). These findings, together with an increased occurrence of mild forms of hyperandrogenism (PCOS) among elite female athletes (393), support an advantageous role of endogenous hyperandrogenism for athletic performance in women.