|The recent Tokyo Olympic Games present an opportunity for a number of intriguing discussions in a physiology classroom. Typical discussion topics around the Olympic Games involve muscle strength, muscle power, aerobic fitness, bioenergetics, and a number of other physiological factors that determine athletic performance. Coronavirus, immunity, disease transmission, and similar topics may be unique areas of discussion related to the Tokyo Olympic Games. Another topic that has been prevalent in the news for the Tokyo Olympic Games is the role of sex and gender in athletic competition.
Before and during the Tokyo Olympic Games several athletes were featured in news headlines due to either gender identity or differences of sexual development (DSD, also sometimes called disorders of sexual development). Male-to-female transgender athletes competing in women’s sports in the Tokyo Olympic Games include weightlifter Laurel Hubbard, archer Stephanie Barrett, cyclist Chelsea Wolfe, soccer player Quinn, and volleyball player Tifanny Abreu, (1, 2). There have also been news stories about Caster Semenya, Christine Mboma, and Beatrice Masilingi being ineligible to participate in the Olympics due to their DSD causing their serum testosterone concentrations to be above the allowed limits for female athletes (3, 4). In addition to physiology sex and gender are interwoven with culture, religion, and politics, so how to discuss sex and gender in the physiology classroom needs to be carefully considered by each instructor depending on the campus climate, policies, and individual comfort level with walking into these potential minefields. However, sex and gender in sports are very appropriate topics to discuss from a physiological perspective.
Although sex and gender have been used interchangeably in common conversation and in the scientific literature, the American Psychological Association defines sex as “physical and biological traits that distinguish between males and females” (5) whereas gender “implies the psychological, behavioral, social, and cultural aspects of being male or female (i.e., masculinity or femininity)” (6). Using these definitions can be helpful to draw a clear distinction between gender (and/or gender identity) as a social construct and sex as a biological variable, which can help focus the discussion on physiology.
As reviewed by Mazure and Jones (7) since 1993 the NIH puts a priority on funding research that includes women as well as men in clinical studies and includes an analysis of the results by sex or gender. Mazure and Jones (7) also summarized a comprehensive 2001 Institute of Medicine sponsored evaluation that concluded that every cell has a sex. A 2021 Endocrine Society scientific statement provides considerable information on the biological basis of human sexual dimorphism, disorders of sexual development, and lack of a known biological underpinning for gender identity (8). On August 12, 2021 a PubMed search using the term “Sex Matters” (in quotation marks) returned 179 results, with many of the linked papers demonstrating the importance of sex for health, disease, and overall biological function (without quotation marks there were 10,979 results). Given that there have been various discussions in the news media and across social media blurring the distinction between sex and gender, it is very important that students in physiology understand that sex in humans is an important biologically dimorphic trait of male or female.
Relevant to a discussion of the Olympic Games, the differences in performance between male and female running has been analyzed for world’s best and world’s 100th best (9), annual world’s best performance (10), world record performance (11-13), Olympic and elite performance (13-16), High School performance in CA, FL, MN, NY, and WA (17), and 100 all-time best Norwegian youth performance (18). Hilton and Lundberg (19) also provided an excellent review of the large differences in athletic performance between men and women in numerous sports. Overall, by mid-puberty males outperform comparably aged and trained females by 10-60%, depending on the sport (see figure 1 of Hilton and Lundberg, reproduced here with no changes under the Creative Commons license https://creativecommons.org/licenses/by/4.0/).
Hilton and Lundberg (19) also reviewed the present state of research regarding the effects of male-to-female hormone treatment on muscle strength and body composition and concluded that men typically have 45% more muscle mass than women, and male-to-female hormone treatment reduces muscle mass by ~5%. These authors also concluded that men typically have 30-60% higher muscle strength than women, and male-to-female hormone treatment reduces muscle strength by 0-9%. Overall, Hilton and Lundberg (19) conclude that transwomen retain considerable advantages over cisgender women even after 1-3 years of male-to-female hormone treatment. Harper at al. (20) also reviewed the research regarding the effects of male-to-female hormone treatment on muscle strength and body composition and came to the same conclusions as Hilton and Lundberg. Harper et al. (20) further concluded that male-to-female hormone treatment eliminates the difference in hemoglobin concentrations between cisgender men and women. In a single research project, Roberts et al. (21) observed that before transition male-to-female members in the US Air Force completed a 1.5 mile running fitness test 21% faster than comparably aged cisgender women. After 2.5 years of male-to-female hormone treatment the transwomen completed the 1.5 mile running fitness test 12% faster than comparably aged cisgender women. (Figure 1 Hilton and Lundberg)
All of the previously mentioned information is important to consider when asking if transwomen can be fairly and safely included in women’s sports. It is also important to note that the effects of male-to-female hormone treatment on important determinants of athletic performance remain largely unknown. Measurements of VO2max in transwomen using direct or indirect calorimetry are not available. Measurements of muscle strength in standard lifts (e.g. bench press, leg press, squat, deadlift, etc.) in transwomen are not available. Nor have there been evaluations of the effects of male-to-female hormone therapy on agility, flexibility, or reaction time. There has been no controlled research evaluating how male-to-female hormone treatment influences the adaptations to aerobic or resistance training. And there are only anecdotal reports of the competitive athletic performance of transwomen before and after using male-to-female hormone treatment.
The safe and fair inclusion of transgender athletes and athletes with DSD in women’s sports is a topic being debated in many states and countries, and by many sporting organizations including the International Olympic Committee. In the end, whether it is safe and fair to include transgender athletes and athletes with DSD in women’s sports comes down a few facts that can be extrapolated, lots of opinions, and an interesting but complicated discussion. This is a worthwhile discussion in a physiology classroom because it allows a good review of the biologically dimorphic nature of human sex. However, the safe and fair inclusion of transgender athletes and athletes with DSD in women’s sports is also a discussion that should be approached with caution due to the many opinions this topic entails that reside outside of physiology.
1. The Economist explains: Why are transgender Olympians proving so controversial? The Economist. https://www.economist.com/the-economist-explains/2021/07/16/why-are-transgender-olympians-proving-so-controversial. [Accessed: August 12, 2021, 2021].
2. Pruitt-Young S. Live Updates: The Tokyo Olympics Canadian Soccer Player Quinn Becomes The First Out Trans And Nonbinary Gold Medalist NPR. https://www.npr.org/2021/08/06/1025442511/canadian-soccer-player-quinn-becomes-first-trans-and-nonbinary-olympic-gold-meda. [Accessed: August 12, 2021, 2021].
3. The Clock Ticks on Caster Semenya’s Olympic Career https://www.nytimes.com/2021/06/28/sports/olympics/caster-semenya-olympics-gender.html. [Accessed: August 12, 2021, 2021].
4. Tokyo 2020: Two Namibian Olympic medal contenders ruled ineligible for women’s 400m due to naturally high testosterone levels CNN. https://www.cbs58.com/news/tokyo-2020-two-namibian-olympic-medal-contenders-ruled-ineligible-for-womens-400m-due-to-naturally-high-testosterone-levels. [Accessed: August 21, 2021, 2021].
5. APA Dictionary of Psychology: sex. American Psychological Association. https://dictionary.apa.org/sex. [Accessed: August 12, 2021, 2021].
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