Continuing the Conversation: Reply to the Letter to the Editor: Equity360: Gender, Race, and Ethnicity: Sex and Fairness in Sports

To the Editor,

I appreciate the ongoing conversation with the Board of Pride Ortho [16] regarding the question of whether transgender women should compete in women’s sports.

First, let’s discuss the facts that are indisputable. Human bodies compete in sports. Males and females are biologically different. Males have physiologic competitive advantages over females in sports. Women’s (female) sports were created to provide women with the opportunity to engage in fair competition by competing against other women (females). Males do not become females with gender-affirming therapy and treatment.

My position that integrity in competition requires a female-only category is based on these indisputable facts and the best science to date, which shows that the male advantage remains, despite testosterone suppression [1, 4]. Respectfully, Pride Ortho does not address these indisputable facts or science in a straightforward manner. Rather, I interpret this letter from Pride Ortho [16] as an attempt to justify the inclusion of transgender women in female sports with several arguments that I will respectfully rebut.

First, the authors argue that the research studies I cited are flawed because they did not control for variables such as lean body mass or cardiovascular capacity. Although it is established that relative physiology and performance metrics are important in sports that are weight-sensitive, it is reductionist thinking to assume that relative metrics are solely responsible for performance. It is well-known that both absolute and relative physiologic characteristics determine performance. This is why, for instance, the compound score in cycling, which accounts for absolute and relative (to body mass) power output, predicts performance better than a relative power output metric [7].

Furthermore, it is critical to acknowledge that those variables the authors opine should be controlled for are, in fact, strongly influenced by sex. Females have lower lean body mass and cardiovascular capacity than males—two systems that are clearly influenced by androgens during development. The biological role of sex creates these differences, and to argue that studies should normalize or adjust for sex-determined variables means that such research is no longer a study on differences between males and females. Instead, it becomes a statistical deception, one that attempts to remove key elements of male advantage by adjusting for it so that it no longer exists. In reality, neither statistics nor testosterone suppression can achieve this removal of male advantage.

I will elaborate further on this critical point because it has become a flawed argument to claim that testosterone suppression in male athletes makes it fair for them to compete against females. If only 6’2” male and female athletes who have identical height, weight, bone density and dimensions, cardiovascular capacity, lean body mass, and strength are compared with each other, then sex becomes irrelevant as a determinant of performance because you would have forcibly matched all the sex-determined characteristics between two individuals. Note that such a study is only possible if one very purposefully finds and matches a female with exceptional physiology (high percentile for variables such as height, mass, cardiovascular capacity, lean body mass, and strength) to a male who within the male population would be physiologically rated considerably lower than an exceptional male. That is, it would require the comparison of an elite, highly trained female athlete to a comparatively mediocre performance male athlete. This concept is illustrated for the one-dimensional outcome of hand grip strength by Leyk et al. [8], where the strongest female athlete had hand grip strength equal to the 58th percentile among untrained males. The same is true for nearly every other physiologic characteristic and the combination of those characteristics for the purpose of sport. Testosterone suppression and estrogen supplementation do not change a male body into a female body.

Second, the authors write, “The scientific community has already established that transgender women’s bodies are inherently different than those of cisgender males” [16], perhaps as a position to advance that transgender women should be embraced in the women’s category because transgender women are somehow not male. My understanding, based on their letter, is that the authors base this statement on evidence from relatively small studies showing lower bone density, lean muscle mass, and muscle strength in transgender women before beginning gender-affirming hormone therapy than in males [20, 21]. However, lower vitamin D and higher parathyroid levels were also found at baseline in these transgender women, with the researchers concluding that the differences identified may be related to the less active lifestyles of transgender women. Furthermore, any male who falls above or below the male average on any measurement is still a male. Regarding potential overlap of testosterone levels in the nonpathologic male and female athlete, the study by Healy et al. [5] remains fatally flawed, irrespective of the debate regarding accuracy of the hormone assay, because the athletes’ sex was not determined. There is no evidence to support the statement that the bodies of transgender women are inherently different from those of men. Human bodies are either male or female, with a very small percentage having a disorder of sexual development (which is not a different sex).

Third, Pride Ortho contends some of my references do not rise to the appropriate level of evidence, yet they do not refute the evidence. The YouTube video I referenced [18] was created by Ross Tucker PhD, a world-renowned sports scientist. In this video, Dr. Tucker shares and discusses the state of the science on sex differences in athletics. This excellent video, which I highly recommend to all, states that at any matched level, many men outperform all women (a fact I will highlight further in the next paragraph). I also cited evidence to this effect in the legal testimony by Coleman [3].

Fourth, Rahman et al. [16] challenge my statement that sex is the dominant factor in athletic performance. The authors provide no evidence to dispute that statement, because that evidence does not exist. There simply is no other factor as predictive as sex for athletic capability. There are no female athletes who outperform the likes of Michael Phelps, Novak Djokovic, LeBron James, or Usain Bolt. The authors claim that my position “vastly oversimplifies the complexity of athleticism.” They note that “muscle mass alone does not translate into the type of skills needed to beat Serena Williams (23-time tennis Grand Slam winner).” I call to the authors’ attention that in 1998, Serena Williams posted a challenge that she could beat any professional male tennis player with a world ranking below 200. She did not even challenge the top males. She was taken up on that offer by Karsten Braasch, ranked the 203rd man in world tennis at that time, and he beat Serena 6-1 at an exhibition match at the 1998 Australian Open [6]. Thus, one of the best female tennis players could not beat the 203rd-ranked male tennis player.

Serena Williams herself has repeatedly expressed her opinion on the differences between women’s and men’s tennis: “If I were to play Andy Murray, I would lose 6-0, 6-0, in five to six minutes, maybe 10 minutes. No, it’s true. It’s a completely different sport. The men are a lot faster and they serve harder, they hit harder, it’s just a different game” [9, 23]. In my own sport of rowing, 21 Olympic male single scullers would have beaten the 2021 Olympic Champion women’s single sculler, the amazing New Zealander Emma Twigg [22]. Her time would have put her in the fourth-level final in the men’s category (the D final). I will not detail such findings in other sports; they are comparable. Of course, other factors such as skill, training, and dedication impact athletic performance. But between male and female athletes, there is no controversy that sex is the dominant factor in athletic performance.

Fifth, the authors criticized references I cited regarding the evolution of more-restrictive hormonal and surgical treatment for pediatric gender dysphoria as being written by an “anti-trans think tank,” the Society for Evidence-Based Gender Medicine, or news agencies rather than peer-reviewed publications. I did not read, however, that the accuracy of the information stated was in dispute. To dispel any doubt that professional medical opinions in some countries have evolved to support more-restrictive hormonal and surgical treatment for pediatric gender dysphoria, I cite the official Swedish government document [17], which states that “At group level (i.e. for the group of adolescents with gender dysphoria, as a whole), the National Board of Health and Welfare currently assesses that the risks of puberty blockers and gender-affirming treatment are likely to outweigh the expected benefits of these treatments.” Likewise, the official documents of the United Kingdom [10] and Finland [15] are referenced. The official document of Norway is online [19], but because I was unable to find an English-language version, I refer the reader to a review by Block [2].

Finally, the authors argue that there are so few transgender women athletes, and they are not taking Olympic medals away from females, so what is the big deal? They note that transgender women do not always win, and this is certainly true, because competition may not be at the same matched level. However, transgender women who make a team or victory podium at any level have taken those opportunities and honors away from deserving female athletes. The evidence that I have cited in this letter, and prior letters [12-14], makes it clear that being born male provides a performance advantage that is not erased with testosterone suppression. Females have the right to fair competition, just as males have.

I want to emphasize that my position is not a political one; it is a scientific one. Pride Ortho expressed disappointment in my column [11] and my responses. I express disappointment that the reality of sex-based performance differences in sports seems challenging for some to acknowledge, and some may perceive my position as “anti-diversity.” As I have repeatedly stated, I have advocated for diversity in our profession over my entire career and will continue to do so. However, the reality that transgender women athletes have a biological sports performance advantage compared with female athletes cannot be ignored. Until science proves that the male physiologic advantage can be erased, females need female-only competition to ensure their right to a level playing field. Inclusion of transgender athletes must be accomplished without discriminating against female athletes, and I welcome creative solutions from my Pride Ortho colleagues.