USCA11 Case: 18-13592 Document: 304-1 Date Filed: 12/30/2022 Page: 55 of 150
unequivocally negligible” between males and females, measurable physical differences between males and females develop during puberty that significantly impact athletic performance. Emma N. Hilton & Tommy R. Lundberg, Transgender Women in The Female Category of Sport: Perspectives on Testosterone Suppression and Performance Advantage, 51 Sports Medicine 200–01 (2021). Indeed, during puberty, “testosterone levels increase 20-fold in males, but remain low in females, resulting in circulating testosterone concentrations at least 15 times higher in males than in females of any age.” Id. at 201. And “the biological effects of elevated pubertal testosterone are primarily responsible for driving the divergence of athletic performances between males and females.” Id.
For example, in comparison to biological females, biological males have: “greater lean body mass,” i.e., “more skeletal muscle and less fat”; “larger hearts,” “both in absolute terms and scaled to lean body mass”; “higher cardiac outputs”; “larger hemoglobin mass”; larger maximal oxygen consumption (VO2 max), “both in absolute terms and scaled to lean body mass”; “greater glycogen utilization”; “higher anaerobic capacity”; and “different economy of motion.” The Role of Testosterone in Athletic Performance, Duke Ctr. for Sports L. & Pol’y 1 (Jan. 2019). These physical differences cut directly to the “main physical attributes that contribute to elite athletic performance,” as recognized by sports science and sports medicine experts. Id. In tangible performance terms, studies have shown that these physical differences allow post-pubescent males to “jump (25%) higher than females, throw (25%) further
