Sex Differences in Athletic Performance: Perspectives on Transgender Athletes

Abstract

Sex hormone concentrations, particularly testosterone, are primary determinants of sex-based differences in athletic and sports performance, and this relationship may inform fair competition and participation for athletes. This article describes the sex-based dichotomy in testosterone and the implications for sex-based differences in individual sports performance, including factors that relate to athletic performance for transgender individuals, and areas of future investigation.

Figure 1.. Approximate mean total testosterone concentrations of males and females across the lifespan.

Line and scatter plot displaying total testosterone concentrations of individuals with a male sex (blue lines and symbols) and female sex (red lines and symbols) across the lifespan. The estimate of error represents a 95% confidence interval around the mean. This figure shows the non-overlapping and significant sex-related dimorphism in endogenous testosterone concentrations that emerge during adolescence and persist throughout adulthood. Note the drop in testosterone concentrations at birth and the transient “minipuberty” of infancy in early post-natal life. This figure is drawn using data from (60, 129).

Figure 2.. Number of adolescent boys <18 years who would beat the women’s world record time/distance.

This figure depicts the number of males under the age of 18 with a faster time or longer/higher distance than the female’s world record holder for each track and field event. Data retrieved from worldathletics.org.

Figure 3.. Sex differences in world record times/distances by sport.

This figure shows the percent difference between males and females (positive difference indicates males have better performance than females) in outdoor running (a), freestyle swimming (b), speed skating (c), and outdoor jumping (d) with males being faster or jumping longer/higher in all events. Records are as of November 1, 2022; data extracted from online publicly available databases.

Figure 4.. Key metrics of body size among male and female athletes competing in the 2012 London Olympic Games.

Bi-directional error scatter plots displaying height and weight of male (blue symbols) and female (red symbols) athletes competing in the 2012 London Olympic Games. This figure represents 272 athletes competing in Athletics throwing events (148 males, 124 females, triangles); 512 athletes competing in rowing events (330 males, 182 females, circles); 163 athletes competing in Athletics jumping events (81 males, 82 females, squares); 860 athletes competing in swimming events (445 males, 415 females, diamonds); and 1,344 athletes competing in Athletics running events (700 males, 644 females, hexagons). As determined using univariate analysis of variance, both height and weight are different between each sporting event (P < 0.001) and larger among males compared to females (P < 0.001). However, there are no interactions of sporting event and sex. This figure represents data from a public repository (130).

Figure 5.. Impact of exogenous hormone therapy on factors relevant to athletic performance.

This figure was created from the known information to date extracted from several articles, systematic reviews and meta-analyses showing the impact of gender affirming hormone therapy (testosterone or estradiol) among transgender individuals on various factors relevant to athletic performance (90, 101, 131, 132). Note that changes may vary by individual, and type and duration of gender affirming hormone therapy. Created with BioRender.com.