I. ABOUT SCIENCE AND SEX
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A1. Biological sex is the designation of an individual as male or female based on reproductive organs and associated primary and secondary sex characteristics. Biologically, they are either female with ovaries/eggs and an estrogenic endocrine system, or they are male with testes/sperm and an androgenic endocrine system.
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A2. Sex differences are anatomical and physiological differences that are determined by or related to biological sex. Males on the one hand and females on the other have distinct genetic and chromosomal, gonadal, endocrinological, and phenotypic (external secondary) characteristics. The field of sex differences in biomedical research specifically studies these distinctions, which have implications not only for reproduction and sport, but also for immunology and cardiovascular health, among other things. As the Institute of Medicine has explained, “basic biochemical differences” exist between males and females even “at the cellular and molecular levels.”
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A3. We have separate-sex sport and eligibility criteria based on biological sex because this is the only way we can assure that female athletes have the same opportunities as male athletes not only to participate but also to win in competitive sport. We also separate males and females in contact sports for reasons related to on-the-field playing-safety. From the onset of male puberty, male bodies develop such that they are as a group faster, stronger, and more powerful than female bodies as a group. The performance gap between male and female athletes that emerges from that point typically ranges from 8-20%, but up to 50% depending on the sport and event. If we did not separate athletes on the basis of biological sex – if we used any other physical criteria – we would never see females in finals and on podiums.
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A4. No. There are no other physical criteria that could be used to determine eligibility that would similarly assure sex equality in competitive sport. Based on those different criteria, e.g., matching leg length, wing span, height, weight, etc., males as a group would always outperform females as a group because their biological sex differences–primarily testosterone levels in the male range from the onset of puberty and throughout the athletic career. Team USA stars Missy Franklin and Ryan Lochte illustrate this point well. They are both multiple Olympic and world champions in swimming. Both had first class training, coaching, and support. Both are 6’2” with reported 6’4” wingspans. Both held the world record in the 200 meters backstroke. But had they raced each other on their best days, Lochte would have finished about a half lap ahead of Franklin. In 2012, the year Franklin set her world record, her time of 2:04.06 would have placed her in a tie for 50th in the U.S. men’s Olympic Trials.
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A5. No. Testosterone-driven sex differentiation at puberty results in males developing larger hearts and higher capacity for oxygen transport and carbohydrate processing, as well as different skeletal and muscular composition. All of these characteristics provide males with superior strength, speed, power, and endurance.
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A6. Experts estimate the male advantage is normally between 8 and 20% depending on the sport and event, and up to 50% in sports and events featuring explosive power. For example: Team USA’s best female high jumper is Vashti Cunningham, NFL star Randall Cunningham’s daughter. She is regularly ranked among the top ten best female high jumpers in the world. Her best jump as a professional (6’ 7 ½”) is regularly surpassed by dozens of U.S. high school boys.
As the chart immediately below – comparing California high school performances – shows, this isn’t a phenomenon exclusive to professionals. Because the performance gap emerges at the onset of male puberty, as a group, high school girls have no chance against high school boys as a group.
2019 CALIFORNIA REGIONAL HIGH JUMP RESULTS[1]
[1] This chart is based on data from Athletics.net, California High Jump Results, accessed on September 25, 2019.

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A7. No. It is a fact – not myth or outdated stereotype – that starting from the onset of male puberty, i.e., starting in middle school, there is an average 8-20% performance gap between males and females, which reaches to 50% in some sports and events. The proposition that better resources and support for female athletes can change biological imperatives and competitive results is false. Some individual females can and will outperform some individual males. But even the very best female athletes are routinely surpassed not only by the very best male athletes but also by second tier male athletes. For example, the world records in the men’s and women’s shot put are nearly identical – 74’4” for the men and 74’23/4” for the women. But the women’s shot put is 8.8 lbs. while the men’s is almost twice as heavy at 16 lbs. The same pattern holds for the women’s world records in all of the races on the track from 100 meters to 10,000 meters. Indeed, not only are those records surpassed by many men each year, they are also surpassed by many high school boys. The pattern also holds for high school athletes who aren’t yet superstars. With rare exceptions, from the onset of male puberty, even the best high school girls have no chance to succeed against high school boys.
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A8. Testosterone is an anabolic-androgenic steroid. Anabolic steroids build body tissue, including but not limited to bone and muscle tissue and red blood cells. Androgenic steroids are responsible for male sex differentiation, i.e., for the development of male primary sex characteristics (in utero), and male secondary sex characteristics (in puberty). Because of its body building and sex differentiation effects, testosterone produced endogenously (naturally within the human body) is the primary driver of the sex differences in athletic performance, i.e., of the performance gap between male and female athletes. Beginning at puberty, at approximately age 11, the male testes begin producing significantly more testosterone than they did earlier in childhood, and also significantly more than is ever produced by female ovaries. This increased production triggers the onset of male puberty, and thereafter builds and sustains the male body in the respects that matter for sports performance: speed, strength, power, and endurance. The exogenous use of testosterone (doping) is banned by all national and international sports organizations because of these anabolic effects.
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A9. Both males and females produce testosterone naturally in their bodies, males primarily in the testes and females primarily in the ovaries. Starting from the onset of male puberty, generally about age 11, testes begin to produce much more testosterone than ovaries. From that point forward, the normal female range is between 0.06 and 1.68 nanomoles per liter (nmol/L), and the normal male range is between 7.7 and 29.4 nmol/L. The gap between top of the female range and the bottom of the male range is 6.02 nmol/L. Converted to ng/dL – the metric typically used in medicine in the U.S. – the normal female range is from 1.73 to 48.45 ng/dL, the normal male range is from 222 to 848 ng/dL, and the gap between the top of the female range and the bottom of the male range is 173 ng/dL. The figure below was published in 2020 in the Journal of the American Medical Association (JAMA). It represents data from the U.S. National Health and Nutrition Examination Survey (NHANES). It shows the increase in testosterone concentration in male youth starting from age 11 onward, as well as the gap that emerges as a result between male and female testosterone levels.

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A10. No. Although females do produce testosterone, mainly in their ovaries, healthy post-pubertal females never produce testosterone levels as high as post-pubertal males. Throughout childhood, up until the onset of male puberty, male and female testosterone levels are about the same; but from the onset of male puberty, male testes produce significantly more testosterone than female ovaries. From that point forward, normal female testosterone levels fall in a narrow range between 0.06 and 1.68 nanomoles per liter (nmol/L), and male levels fall in a broader range between 7.7 and 29.4 nmol/L. The gap between the normal male range and the normal female range is wide. As the following figure indicates, there is no overlap. Some biological females have higher than normal female testosterone levels, for example if they have polycystic ovaries, but again, no healthy female has a testosterone level even close to the normal male range.

This figure shows the normal female testosterone range on the left and the normal male range on the right. It also shows the abnormal testosterone ranges that can be produced by people with certain differences of sex development (DSDs). Some people with DSD prefer to describe themselves as intersex. The conditions marked in red are among those that affect genetic (biological) females. Those marked in green are two that affect (genetic) biological males. Those conditions are described further in the answer to Question 27 below.
Some advocates for trans and intersex athletes claim that there is an overlap in the normal ranges. This claim is not supported by the data or the current peer-reviewed literature. Their argument depends on the existence of a small number of outlier (abnormal) readings, i.e., on a small number of higher-than-normal female T readings and a small number of lower-than-normal male T readings. These abnormal readings are used by advocates to construct a “spectrum” that appears to negate the normal bimodal distribution by “filling in” the gap between the two ranges.[1] The figure above shows one way this optical effect can be achieved. It requires ignoring that more than 99% of the population has readings in the normal ranges, and then “filling in” the gap between those ranges with readings from the less than 1% of the population that has an intersex condition.
As the leading experts in the field have established, however, the overlap argument is not supported by the data points themselves, which do not distinguish between (1) doped and non-doped females; (2) females and males with differences of sex development; and (3) male readings taken at rest and following strenuous exercise—the latter has been established to lower normal levels temporarily. Additionally, they measure testosterone by immunoassay – which is inaccurate at lower testosterone concentrations in women – rather than by state-of-the-art methodology, i.e., by mass spectrometry.[2] Once those errors are corrected, the overlap disappears.
[1] Advocates may refer to this older paper to support their claim: Healy ML, et al., Endocrine profiles in 693 elite athletes in the postcompetition setting. Clin Endocr. 2014; 81(2): 294-305. PMID: 24593684.
[2] Handelsman DJ, Hirschberg AL, Bermon S. Circulating Testosterone as the Hormonal Basis of Sex Differences in Athletic Performance. Endocr Rev. 2018;39(5):803-29. Epub 2018/07/17. Clark RV, Wald JA, Swerdloff RS, Wang C, Wu FCW, Bowers LD, Matsumoto AM 2019 Large divergence in testosterone concentrations between men and women: Frame of reference for elite athletes in sex-specific competition in sports, a narrative review. Clin Endocrinol (Oxf) 90:15-22.
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A11. No. Elite female athletes generally have testosterone levels within the normal female range, i.e., below 1.68 nmol/L. If they have the condition known as polycystic ovary syndrome (PCOS), they may have testosterone levels up to 3 nmol/L, or, in rare instances, up to 4.8 nmol/L. This is why some sports organizations, wishing to be inclusive of all possible healthy biological females, set their maximum testosterone level at 5 nmol/L.
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A12. Testosterone is an excellent proxy for biological sex and a valid basis for an eligibility rule for the women’s category for the following reasons:
- Testosterone is the primary driver of the sex differences in athletic performance;
- Sport already tests for and monitors testosterone levels as part of the normal anti-doping process; and
- Different sex testing protocols are more intrusive and, in some cases, less accurate.
No other single criterion so comprehensively addresses sport’s and society’s concerns about the testing protocol.
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A13. Some sports organizations have adopted the level of 5 nmol/L as the upper limit for inclusion in the female category because it represents the outermost bounds that a healthy biological female – regardless of her legal or gender identity – can reach naturally. Almost all females, including elite athletes, have testosterone levels well below 5 nmol/L. The normal female range is between 0.06 and 1.68 nmol/L. Even females with the condition known as polycystic ovary syndrome (PCOS) – which can dramatically raise testosterone levels – only very occasionally reach 3 nmol/L, with rare readings up to 4.8 nmol/L. Setting the level at 5 nmol/L assures that no otherwise healthy biological female could be excluded by the standard. Given that 5 nmol/L is already high, however, some international federations are considering the lower limit of 3 nmol/L.
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A14. The female category was carved out from open (mixed or co-ed) sport as a protected space where females could compete only against each other and not also against males. It was designed specifically to exclude males, i.e., people with male sex-linked performance advantages. Testosterone is the primary driver of these sex-linked advantages. The male category is not policed because it does not need protection from itself; it was not designed to exclude or regulate males with natural male testosterone levels. Elite sport does, however, monitor testosterone levels in all athletes, male and female, for exogenous use of (i.e., doping with) androgens, including testosterone.
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A15. No. They are wrong. Transgirls/women are biologically male. Consequently, unless they go on puberty blockers and then on gender-affirming hormones before the onset of male puberty, they benefit from normal male sex development and differentiation. There is overwhelming evidence that individuals who are biologically male – however they identify – have an athletic advantage over individuals who are biologically female—however they identify. Gender identity has nothing to do with athletic ability. Additionally, there is convincing evidence[1] that, depending on the task, skill, sport, or event, transwomen maintain male sex-linked (legacy) advantages even after multiple years on standard gender-affirming hormone treatment.
[1] (1) Roberts TA, Smalley J, Ahrendt D. Effect of gender affirming hormones on athletic performance in transwomen and transmen: implications for sporting organisations and legislators. Br J Sports Med. 2020. Epub 2020/12/09. (2) Hilton EN, Lundberg TR. Transgender Women in The Female Category of Sport: Perspectives on testosterone suppression and performance advantage. Sports Medicine. 2021;51:(in press) (PMID 33289906 and doi: 10.1007/s40279-020-01389-3). (3) Handelsman DJ, Hirschberg AL, Bermon S. Circulating Testosterone as the Hormonal Basis of Sex Differences in Athletic Performance. Endocr Rev. 2018;39(5):803-29. Epub 2018/07/17. See also (4) Gooren LJ, Bunck MC. Transsexuals and competitive sports. Eur J Endocrinol. 2004;151(4):425-9. (5) Wiik A, Lundberg TR, Rullman E, et al. Muscle Strength, Size, and Composition Following 12 Months of Gender-affirming Treatment in Transgender Individuals. J Clin Endocrinol Metab. 2020;105(3). Epub 2019/12/04.
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A16. No. They are wrong. Although stereotypes and opportunities can affect the degree of the performance gap between the best females and the best males, the data and science are clear that for almost all sports and events we know that the gap itself is biologically-based and immutable.
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A17. A transgender person is currently defined as someone whose identifies as other than their biological sex. For example, a transgirl/woman is someone who identifies as a girl/woman even though they are biologically male. A person does not need to take gender-affirming hormones or have surgery to be considered transgender. Some transgender people are not on hormones and have not had surgery. Some transgender people take hormones but do not have surgery. And some transgender people do both. Whether a transgender person takes hormones, the level at which they choose to set their hormones, and whether they have surgery, are all matters of personal choice, medical advice, and/or opportunity.
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A18. No. Those transgirls/women who never experience the onset of male puberty do not develop the secondary sex characteristics that are responsible for the performance gap between male and female athletes. Preventing male puberty involves taking puberty blockers before its onset, and thereafter transitioning to gender-affirming hormones that keep testosterone levels consistently within the female range. In contrast, transgirls/women who go on blockers and/or gender-affirming hormones and/or have a gonadectomy only after they experience some or all of male puberty retain a “legacy advantage” as a result of this experience. The degree of their legacy advantage depends on a combination of factors including: the extent to which they have experienced puberty; whether they had a gonadectomy (surgical removal of their testes); the levels at which they maintain their circulating testosterone; and the particular sport and event in which they compete.
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A19. Legacy advantages are the male sex-linked advantages that remain even after a transgirl/woman has gone on gender-affirming hormones and/or gender-affirming surgery. They are the benefits for sport of having gone through all or part of puberty as a male.
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A20. Doping is the exogenous use – the taking – of prohibited performance enhancing drugs (PEDs), including testosterone and other body building androgens. These are among the substances that propelled the East German women to victory in the Olympic Games and World Championships in the 1970s and 1980s, costing clean American women and Team USA (and others) to lose out on medals they would otherwise have won. Some American athletes have also doped with androgens, but not in the systematic and state-sponsored way as the East Germans, and more recently the Russians. Transgirls/women who want to be included in girls’/women’s events are not doping; that is, they aren’t taking PEDs to compete. But their natural testosterone levels build strength, speed, and power in the same way that doping does; and because their natural levels are much higher than even those of doped female athletes, the effect on competition is the same or more overwhelming for the clean females in the field.
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A21. Yes. The data that exists about transgirls with no medical intervention is consistent with the fact that they are biologically male. For example, based on its interpretation of the State of Connecticut’s Equality Act, the Connecticut Interscholastic Athletics Conference (CIAC) permits transgirls to compete in girls’ events even if they have not yet gone on puberty blockers or gender-affirming hormones. (The CIAC places no physical or physiological conditions on their inclusion in girls’ sports.) Two transgirls who used to compete on their schools’ boys’ track teams moved to the girls’ teams when they came out as trans. They immediately dominated their events at their conference, state, and regional competitions, even though their performances would have been insufficient to qualify them for post-season competition had they competed in the boys’ divisions. And although they started competing in girls’ events before they began taking gender-affirming hormones, they continued to be among the best girls in their events even after they publicly stated they had started on puberty blockers and hormones. All told, just these two transgirls took “15 women’s state championship titles (titles held in 2016 by nine different Connecticut female athletes) and . . . more than 85 opportunities to participate in higher level competitions from female track athletes in the 2017, 2018, and 2019 seasons.”[1]

T MILLER – SPRINTS – 55 meters indoors and 100 meters outdoors

Miller competed on the boys’ track team her freshman year and through the winter of her sophomore year. She came out publicly as transgender in the middle of 10th grade, and then switched to the girls’ team for her remaining two-and-a-half years of eligibility.
Her hormone status for each season is derived from publicly available information.[2] Because that information indicates she went on hormones for the first time only at the end of the 2019 outdoor season, i.e., sometime in May, and because her best time that year was run before then, she is listed here as “not on hormones” for the year.
The table shows rankings for the 55 meters indoors first, followed by the 100 meters outdoors. The rankings in blue font show the division she actually competed in, and the point at which she switched from the boys’ to the girls’ division. Simply by walking off of the track in the boys’ events and walking onto the track in the girls’ events, she went from barely being in the top 400 in the state to being #1 in the state.
The girls’ rankings for her 9th grade year are those she would have achieved based on her times as run in boys’ events. The boys’ rankings for her sophomore, junior, and senior years are those she would have achieved based on her times as run in girls’ events. There were no rankings for the 100 meters outdoors her 12th grade year (2020) because the season was cancelled due to COVID.
A YEARWOOD – SPRINTS – 55 meters indoors and 100 meters outdoors

Yearwood competed on the girls’ team all four years in high school. She came out publicly as transgender in the 9th grade. Her hormone status for each season is derived from publicly available information.[3] The table shows rankings for the 55 meters indoors first, followed by the 100 meters outdoors. The boys’ rankings listed on the table are those she would have achieved based on her times run in girls’ events. There were no rankings for the 100 meters outdoors her 12th grade year (2020), because the season was cancelled due to COVID.
We don’t have statistics on the number of transgirls who have competed in girls’ events in high school sports. However, it appears that, at least in the past, most were already on gender-affirming hormones by the time they sought to participate on girls’ teams; trans advocacy groups seems generally to assume that this is the case when they speak to the issue. However, we are at a juncture in history where transgirls who are not on hormones are just beginning to ask to be included in girls’ competitions. In part this is because the standard of care in trans medicine now recommends that transkids “come out” socially before they transition medically; and many physicians now require that kids wait until they are 16 to go on gender-affirming hormones. For a transgirl, going out for a girls’ school sports team is one way to come out socially. We are thus increasingly likely to face situations like that in Connecticut where transathletes seek to compete in girls’/women’s sport while not on hormones.
[1] Verified Complaint for Declaratory and Injunctive Relief and Damages, Seoule et al. v. CIAC, Case No. 3:20-cv-00201, paragraph #77, filed in the United States District Court for the District of Connecticut (Feb. 12, 2020). These results are limited to conference, state and regional championships. They do not include all of the regular season or invitational events at which opportunities to move on through competitions to finals and/or wins and podium spots were affected.
[2] See, e.g., Beyond the Labels: Meet Terry Miller, Runner’s Space.com, May 26, 2019, available at https://www.runnerspace.com/gprofile.php?mgroup_id=44531&do=news&news_id=576791 (implying that Miller attended NSAF Nationals as a spectator not a competitor in her junior year, 2019, because she was not eligible to compete there due to the NSAF’s eligibility policy, which mirrored that of USATF, the NGB, not the CIAC, and Miller herself suggesting that she began taking hormones only in the latter part of that same year).
[3] See, e.g., Jeff Jacobs, As We Rightfully Applaud Yearwood, We Must Acknowledge Many Questions Remain, Hartford Current, June 17, 2017, available at https://www.courant.com/sports/hc-jacobs-column-yearwood-transgender-0531-20170530-column.html (reporting that Yearwood’s father “said his daughter will begin consultations in June [2017] about hormonal treatment”). That was at the end of 9th grade. The fact that she competed at NSAF Nationals in 11th grade (March 2019) means that she was on hormones in 10th grade since their eligibility policy requires that transgender athletes be on gender-affirming hormones with their level below 5 nmol/L for 12 months before being eligible to compete in their events and then throughout their competitive seasons.
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A22. Yes. The medical community now recommends that transkids “come out” socially before they transition medically. While some transgirls have opted to go out for a girls’ school sports team as one way to come out socially, this option is not so easily available to transboys who, because they are biologically female, are unlikely to be able to make a boys’ team. As a result, some transboys have chosen to come out socially while remaining on the girls’ team. This has allowed them to continue to participate and to remain competitive in high school sport. Some transgirls have chosen this same path, coming out socially while remaining on the boys’ team.
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A23. Going on gender-affirming hormones causes a decline in circulating levels of testosterone which, if consistently maintained over time, has some effect on athletic performance. This effect seems to be primarily on endurance, not on strength and power. The effect on speed seems to be dependent on the extent to which the event is endurance – as opposed to strength – and power-based. Thus, the nature and extent of the decline in male performance advantage, also known as the “legacy advantage”, appears to depend on the sport and the event. It also depends on the extent to which the individual experienced male puberty before they began their physical transition, and on how high they choose to maintain their testosterone levels once they do go on gender-affirming hormones. Regardless, as we explain in our answer to Question 15, the current state of the peer reviewed literature is that legacy advantages remain significant.
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A24. The NCAA, the IOC, and many international federations (IFs) and national governing bodies (NGBs), initially adopted eligibility rules that required transgirls/women to reduce their testosterone levels for at least a year before they would become eligible to compete in girls’/women’s events. This accommodation was a policy compromise, based in the hypothesis that if a transgirl/woman reduced her testosterone levels into the female range and kept her levels consistently within that range for at least a year, her male-linked advantages would decline to the point that it would be fair to include her in girls’/women’s competition. The hypothesis itself was based on the fact that transgirls/women are biologically male and that testosterone was the primary driver of the performance gap between male and female athletes. Just how much gender-affirming hormones reduces her male sex-linked advantages and what “legacy advantages” remain is the subject of ongoing scientific investigation. However, we now know more. Research over the last couple of years has demonstrated that one year of hormone therapy is insufficient and legacy advantage is greater than originally hypothesized.
In 2021, the IOC withdrew from its transgender eligibility governance responsibility and placed that responsibility into “the remit of each sport and its governing body to determine how an athlete may be at a disproportionate advantage against their peers, taking into consider the nature of each sport,” issuing vague guidance, the IOC Framework on Fairness, Inclusion and Non-Discrimination on the Basis of Gender Identity and Sex Variations. The Framework fails to clearly state that the rights of that subset of transgender women who have male sex-linked advantages will not be prioritized over the rights of females and transgender women who do not have such advantages or to require that IFs adopt evidence-based inclusion that does not defeat the female physiological category. Notwithstanding this deficient IOC guidance, IFs now have the real authority under the Olympic Charter to establish eligibility standards for their sports, a process that should be completed by the end of 2022. It is expected that they will develop standards for including transgender women in female sport that are based in the best available scientific evidence about how sex differences impact safety and performance and that under such rules, transgender women will be included in female sport in ways that are not category defeating. It is expected that NGBs, the USOPC, and other sports governing organizations like high school federations and the NCAA will adopt these rules consistent with science.
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A25. Yes. As our answer to Question 15 details, several peer-reviewed studies, including one based on data from the U.S. military, have confirmed that transwomen retain their male sex-linked advantages even after a year on gender-affirming hormones. This is especially the case for sports and events that are not endurance-based. Because of these retained advantages, USA Powerlifting and World Rugby have recently concluded that it isn’t possible to fairly and safely include transwomen in women’s competition. Other international sports federations have rejected the International Olympic Committee’s 2015 guidance suggesting that transwomen be included in women’s competition so long as they reduce their testosterone levels to the bottom of the male range (under 10 nmol/L). Many federations have reduced the required testosterone level to within the female range and/or precluded post-puberty transgender athletes from competing in the female category.
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A26.
No. In January of 2022, the NCAA withdrew its 2010 outdated transgender eligibility rule that lacked both rigor and detail. The old rule provided only that transwomen athletes be on gender-affirming hormones for at least a year, did not specify that they needed to bring their testosterone levels into the female range; did not require them to keep their levels consistently within that range; and the NCAA did not monitor their compliance. The updated NCAA policy calls for transgender participation in each sport to be determined by the policy for the national governing body of that sport, subject to ongoing review and recommendation by the NCAA Committee on Competitive Safeguards and Medical Aspects of Sports. If there is no NGB policy for a sport, that sport’s international federation policy would be followed. If there is no international federation policy, previously established IOC policy criteria would be followed.
Portions of the new policy were effective starting with the 2022 winter NCAA championships but full implementation does not begin until the 2023-24 academic year. Transgender student-athletes competing in until then will need to document sport-specific testosterone levels beginning four weeks before their sport’s championship selections. Starting with the 2022-23 academic year, transgender student-athletes need documented levels at the beginning of their season and a second documentation six months after the first. They will also need documented testosterone levels four weeks before championship selections. Effectively, the NCAA phase in process tells biological females to wait three years for fair competition.
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A27. Intersex conditions result from differences in biological sex development. They are also known as differences of sex development or DSDs. There are many different intersex conditions, but those that are relevant for sport all involve biological males – individuals with an XY karyotype, testes, and testosterone levels in the male range – whose sex development was atypical in some respect. For example, their external genitalia might not be fully formed or their androgen receptors may be less than typically sensitive. Athletes with such intersex conditions may be raised as male or female. People who are transgender do not generally consider themselves to be intersex. The two are related in sport to the extent that they may both involve biological males with full or partial male advantage who seek eligibility to compete in girls’/women’s sport.
The following table is illustrative. It is from an exhibit in the case brought by South African runner Caster Semenya against her international federation (the IAAF now World Athletics) at the Court of Arbitration for Sport (CAS) in Switzerland. Semenya is sometimes described as intersex. In 2019, CAS upheld the federation’s eligibility rules for the women’s category. Those rules require affected athletes to verifiably reduce their testosterone levels to within the normal female range for a 12-month period before they can compete in that category. Switzerland’s Supreme Court affirmed the CAS decision in 2020.
COMPARING BIOLOGICAL SEX TRAITS FOR PURPOSES OF GIRLS’ AND WOMEN’S SPORT (from IAAF Exhibit in Semenya and ASA v. IAAF)

Note: MTF = Male to Female
II. ABOUT CURRENT LAW ON SEX AND SPORTS
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A28. Separate-sex sport is regulated by a combination of statutes, regulations, and caselaw. This includes the Ted Stevens Olympic and Amateur Sports Act, Title IX and its regulations, the Equity in Athletics Disclosure Act, and court decisions interpreting their terms.
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A29. No. They are wrong. The point of the laws that create and regulate separate-sex sport is to ensure that females have the same opportunities as males not only to participate, but also to succeed. In addition to competing, this includes the fair ability to win and set records in regional, national, and international competitions. No male or female has an individual legal right to win or set records in their respective divisions, but as a class, females have the legal right to win and set records in girls’ and women’s sport, just as males that have that right in boys’ and men’s sport.
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A30. The re-definition of “sex” to include “gender identity” in a law that prohibits discrimination “on the basis of sex” would mean that programs receiving federal funds and operating in interstate commerce could not lawfully distinguish a biological female from a transgirl/woman. This would make it prima facie unlawful to do what is currently permitted, i.e., to have teams and events that are separated on the basis of biological sex. It would also make it prima facie unlawful to use testosterone — a sex-linked trait — as an eligibility criterion for inclusion in girls’ and women’s elite sport, e.g., as is currently required by the NCAA, the USOPC, the IOC, and the national and international sports federations. Both separate-sex sport itself and eligibility criteria based on biological sex and sex-linked traits like testosterone, are currently lawful exceptions to general prohibitions on sex discrimination. For this to remain the case, the Equality Act, as currently proposed, would need to be amended to provide for an express exception for competitive sport.
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We don’t know. Many of the EA’s advocates argue that the proposed EA Act won’t affect Title IX, without explaining why. Alternatively, others argue that, even if it does, Congress could restore separate-sex sport after the EA’s enactment, through additional legislation or regulations addressing sport. However, we believe that restoring separate-sex sport after the EA’s enactment is highly unlikely as a matter of standard legal analysis, legislative history, and politics.
The EA is designed to amend the Civil Rights Act of 1964. The definitions in that statute have been and will continue to be the basis for interpreting or defining the same words as used in all other civil rights legislation. That is, Congress cannot re-define “sex” in the principal statute and not have that definition apply directly or indirectly to the use of that term in other legislation. In fact, many of the EA proponents intend precisely this—make the change to the definition in the principal legislation, and this will automatically change the definition in related legislation.
Moreover, as a matter of standard legal analysis, absent a legislative carve-out for sport — i.e., an explicit acknowledgement of an exception — any newly enacted, categorical prohibition on discrimination between biological females and transgirls/women would be presumed to supersede any earlier legislation to the contrary, including Title IX.
The legislative history of the EA makes clear that its proponents intend for it to apply to sport with no conditions or exceptions and thus, to prohibit any distinctions between biological females and transgirls/women. At the House Judiciary Committee Hearings, both the witnesses and Democrats on the Committee insisted that transgirls/women be included in girls’ and women’s sport without any conditions because “transgirls are girls, transwomen are women, period.” And on the floor of the House, a bill was rejected by a vote of 181 to 228 that would have retained the longstanding exception in Title IX for separate-sex sport based on biology. (Specifically, Congressman Steube proposed legislation providing that, “Nothing in this Act or any amendment made by this Act may be construed to diminish any protection under Title IX of the Education Amendments of 1972.”) The Equality Act then passed the House by a vote of 236 to 173. If not amended, this legislative history would dictate the answer to whether Congress intended to permit or preclude distinctions on the basis of biological sex.
The natural experiment with state versions of the EA also make it clear that an explicit exception is necessary to maintain sex-segregated sports and spaces. In those contexts, trans advocates argue that under the state EAs, it is impermissible to separate or in any way differently to treat transgirls within girls’ sport. They make these arguments even though state legislatures did not consider sports as they were enacting their EA legislation.
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In Bostock, the Supreme Court ruled that “sex” in Title VII means “biological sex.” Contrary to what many proponents of the EA argue, Bostock did not define (or re-define) “sex” to include “gender identity.” Rather, it held that Title VII’s general prohibition of discrimination “on the basis of sex” precludes discrimination that takes into account a transgender employee’s sex and gender identity. Firing a person because they are transgender — i.e., because their gender identity is nonconforming — requires taking their sex into account, and this is prohibited by Title VII. Because the case involved Title VII’s general non-discrimination provision, not an existing exception that allows taking sex into account, the Court wrote that it was leaving the lawfulness of exceptions — including in bathrooms, locker rooms, and sport — for another day. Bostock explicitly did not rule on the lawfulness of the current scheme under Title IX and the other sport statutes.
Proponents of the EA nevertheless assert that Bostock applies to sport, completely ignoring the Court’s express pronouncement to the contrary. Specifically, in cases pending in the lower courts, they argue that Bostock supports the redefinition of “sex” to include “gender identity”, and that the decision requires the inclusion of transgirls/women in girls’ and women’s Title IX sport. Notably, however, they are inconsistent in their application of Bostock to the question whether administrators can lawfully distinguish biological females from transwomen/girls. For example, in pending federal cases in Connecticut and Idaho, advocates for transgender athletes argue that their inclusion in girls’ high school sports must be full and unconditional, without regard to whether they are on gender-affirming hormones. However, in the Idaho matter, in which college sports are also at issue, they don’t challenge the NCAA rule, which distinguishes female athletes from transgender athletes by requiring transwomen to undergo a year of gender-affirming hormone treatments before they can compete in women’s sport. They support the position that in college, conditions on transgender inclusion are permissible. This distinction between high school and college may make good policy sense; but it is an acknowledgement of the continued lawfulness not only of the NCAA rule, but also more generally of what that rule represents, i.e., the lawfulness of distinctions on the basis of sex in sport. It is also a tacit acknowledgment of the fact that — as the Supreme Court itself announced — Bostock is not dispositive in this area.
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A33. Formal sex-segregation in sport is the exception to general nondiscrimination law, requiring the exclusion of biological males from most girls’ and women’s sport. There is no case yet that finally resolves the question whether an exception to this general rule should be made for biological males who identify as women and girls. It is standard practice, however, for the courts to permit (and sometimes even to require) accommodations when there are good reasons for doing so, and when this is possible without imposing an undue burden. Thus, accommodations that would allow transgirls/women to compete in girls’/women’s sport should be permissible so long as they meet these standard criteria.
III. ABOUT POLICY AND SOCIETY
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A34. The principles that guided the Working Group in the development of its approach to trans-inclusion in girls’/women’s sport are the following:
1. Women’s sport is designed to provide a space where biological females – whatever their gender identity – can compete only against each other and not also against biological males—whatever their gender identity. The design is based in compelling data and scientific evidence on the immutable performance gap between male athletes and female athletes. This separate-sex space should be preserved and affirmed. Girls’ and women’s participation in competitive sport nurtures individual health and development, contributes to the welfare of the community, and powers society’s perception of the strength and value of women and girls.
2. Transgirls/women are biologically male and so per the design would normally be excluded. However, because their inclusion could also produce real value both for the individuals concerned and for society, we should work to avoid unnecessary distinctions and exclusions. Therefore, post-puberty advantaged transgender athletes should be fully included within the social construct of girls’ and women’s sports and provided with safe and fair competition accommodations, as long as it doesn’t impact on the fairness and safety of females’ competition.
3. Physical sex-linked differences between males and females are largely determined from the onset of male puberty. It is these differences that justify separate-sex sport, and thus, they must be taken into account in developing responsible policy for girls’ and women’s sport.
4. Protocols for co-ed sports are instructive, as is the related tradition in law and policy of looking for ways to include rather than to exclude when this is possible without doing harm to an otherwise valuable institutional design. Being transgender does not change the fact of one’s biological sex. Where it is recognized in existing co-ed sports policy that sex is relevant to fairness and safety, it cannot be ignored simply because an individual identifies as transgender. Similarly, where existing co-ed sports policy recognizes that sex is not relevant to fairness and safety, the goal should be unconditional inclusion.
5. Specifically rejected as guiding principles are the unscientific, politically-driven mantras that claim that:
- “sex-linked differences including testosterone levels are indistinguishable from other differences like height, weight, wingspan, and foot shape”;
- “the performance gap between male and female athletes is based in myth, stereotype, and cultural inequities”;
- “the physical legacy advantages associated with developing as a biological male don’t exist or matter to sports performance”;
- “there is no evidence that transwomen and transgirls have a competitive advantage over females”; and
- “females only have the right to participate not to win”.
These patently false claims have no place in a serious discussion of the policy question whether and how to include transgender athletes in girls’ and women’s sport.
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A35: Yes. We have publicly opposed these efforts and sought to work with like-minded state legislators of both parties toward law that would assure the inclusion of transgirls in girls’ sport in ways that are not female category defeating. Also, we want to be sure opportunities for transboys are similarly accommodated. Part of our work in this area has included the development of the following model statute that would accomplish these objectives.
A36: Access to female athletes’ locker rooms should remain restricted to female athletes. See rationale here
A37: They’re already competing in almost every imaginable sport. Here is a partial list of male winners in women’s sports.