The issue of integrating transgender athletes into sport is becoming more prominent with the rising numbers of those identifying as transgender in society. Whether it is fair for transgender athletes to be included in their affirmed gender category across all levels of sport from grassroots to elite is the crux of the debate. Previous studies have shown muscle mass loss in transwomen and muscle mass and strength gain in transmen after 1 year of gender-affirming treatment (GAT). Wiik et al., 2020 found that transmen retain a strength disadvantage over cisgender men and transwomen retain muscle mass and strength advantages over cisgender women after 1 year of GAT. Roberts et al., 2020 also found that running performance in transwomen was maintained but not baseline muscular strength. However, very little data on sports performance measures outside muscular strength and running times exist, nor has any of the previous data been compared with a comparative control group. Aim: To investigate the effect of “muscle memory” in transgender athletes and investigate changes in physiology after 2 years of GAT such as bone mineral density, lean muscle mass, and fat mass, coupled with sports performance measures in transwomen and transmen athletes and compare them with a cisgender female athletic cohort. This will elucidate what advantages/disadvantages transgender athletes gain/retain after 2 years of GAT over their cisgender counterparts and this will better inform policymakers who control their integration into their affirmed gender category in sport.