Should Trans Woman Athletes be Allowed to Compete in Women’s Sports?

The answer to this clickbait headline is a simple one: yes. Duh. Why shouldn’t we be allowed? What are you – some kind of transphobe?

But people are seriously up in arms over this, so I guess we’re talking about it now. The main arguments appear to be that trans women are at an apparent advantage over cis women because of greater bone density, muscle mass, and differences in hormone levels. So let’s tackle each of these.

Bone Density

According to a study by the Department of Endocrinology at Ghent University Hospital, “Transsexual women before the start of hormonal therapy appear to have lower muscle mass and strength and lower bone mass compared with control men.”

Granted, the study does mention that these deviations may be “related to a less active lifestyle”, because trans women apparently tend to be more sedentary from a young age. But then again, might the reason that cis women tend to have lower bone density than men be because society tends to force them sit still and be pretty from an early age, whereas boys are encouraged to run around and do other high impact activities?

In order to promote bone osteogenesis (the calcification of soft tissues into bone mass), children must be physically active. Yet boys tend to be more involved in sports and allowed to run around acting crazy, climbing up trees and jumping out of them, while girls are told “don’t do somersaults, you’re in a dress!”, “that’s a boy sport!”, and in general dissuaded from physical activities.

In which case, one has to wonder how much of the differences in bone density between cis males and females has to do with social roles, as opposed to biology?

Furthermore though, how different from each other are female and male bones anyway? We tend to think that archaeologists and forensic scientists can just look at any bone and tell you what sex the person was. But that’s an outdated idea. In 1972, anthropology professor at Pennsylvania State University Kenneth Weiss observed a discrepancy between male and female bones at archaeology sites: there were 12% more male bones.

This didn’t make sense, since male and female populations tend to be fairly evenly dispersed. As it turned out, archaeologists were just more likely to put bones they couldn’t categorize because they blurred gender lines into the male pile because… well… patriarchy.

It appears that since Weiss called out the archaeology community, they began changing their acts, because in 1993, a masters student at the University of Tennessee named Karen Bone discovered that the ratio of male to female bones had evened out. This was because more bones were being labeled “indeterminate”.

After all, wide-hipped men exist, as do narrow hipped women. People come in all shapes and sizes, regardless of the configuration of their genitals.

Muscle Mass

Going back to the Department of Endocrinology study at Ghent University Hospital: “Transsexual women before the start of hormonal therapy appear to have lower muscle mass and strength and lower bone mass compared with control men.”

And again, this may have much to do with sedentary lifestyles, in which case we could bring up the same sociological nature-over-nurture questions as before.

Regardless, we know that muscle mass correlates with hormone levels, which is the primary biological reason we could point to for why males tend to have more muscle mass. So with transgender women already presenting pre-HRT with low testosterone levels, and the whole point of HRT being to drop their testosterone to normal female ranges, we can assume that twitch-muscle fibers (these contribute to explosive takeoffs in sprints) would be decreased and oxygen availability to the muscles via red blood cells would be reduced.

And in fact, we do find that trans women have lower Red Blood Cell (RBC), hemoglobin (which transports oxygen within the RBC’s), and hematocrit (the volume of RBC’s per whole blood) levels following HRT. Lower RBC and hemoglobin count means less oxygen supplied to the muscles, and with less oxygen available to help break down glucose into adenosine triphosphate (ATP) molecules for fuel, the less useful whatever muscle mass happens to be there actually is.

In terms of twitch muscle fibers, no studies appear to exist that analyze that in particular in trans women. A study published in the Journal of Clinical Endocrinology and Metabolism did show that, while overall muscle mass decreased (though not as significantly as expected) for trans women following HRT, strength did not appear to change (though keep in mind that trans women present with lower strength pre-HRT anyway).

Although estrogen replacement has been known to increase muscle mass and strength in post-menopausal women, so I suppose it’s always possible that the overabundance of estradiol in trans women could work to partially counteract some of the muscle and strength loss from the testosterone suppression, especially when trans women tend to present with lower muscle mass from the get-go.

Hormone Levels

A study in Biological Psychiatry showed that pre-HRT transgender women tend to have longer androgen receptor lengths, leading to reduced sensitivity to androgens in general, which may contribute to the above mentioned lesser muscle mass, strength, and bone density than control cisgender men.

On top of that, trans athletes are under strict hormone standards (where non-professional athletes are not, so maybe they’re not the ones to be testing when asking this particular question). The International Olympic Committee guidelines state that transgender woman competitors must be identifying continuously as their identified gender for four years and their testosterone levels must be below 10 nmol/L for at least one year prior to competition.

World Athletics guidelines require testosterone levels under 5 nmol/L for at least a year (this would match their intersex guidelines), and ICO is considering following suit.

So hormone levels aren’t even an issue now because trans women must be within normal female levels in order to compete. Now, is that necessary? A 2017 systemic review showed no evidence that transgender athletes had an advantage at any stage in transition.

Besides, ultimately such tight hormonal regulations only really impact intersex women who were assigned as female at birth (as trans female athletes are generally already on HRT). For instance, Caster Semenya, for instance, won multiple Olympic gold medals, but was barred from competing after she was subject to hormone testing and found to have naturally elevated testosterone and XY chromosomes (yes, those Assigned Female at Birth can have XY chromosomes too). She was eventually allowed to compete again, but only if she went on androgen suppressants.

Similar androgen level controversies occurred with other intersex athletes, including Dutee Chand, Maria José Martínez-Patiño, Stanisława Walasiewicz, and others.

But let’s get back to transgender athletes and ask the real question: how good are trans women at sports anyway?

Trans Women are Statistically Not that Great at Sports

There’s a very obvious selection bias when it comes to reporting on trans athletes – that is, you only hear about them when they win. But they frequently lose.

Rachael Mckinnon was a trans woman who was the center of controversy after breaking the record for the women’s 35-39 age bracket 200-meter time trial by a whopping 0.24 seconds (she notes in her New York Times op-ed that her time is still lower than the 40-44 and 45-49 age categories). But that was just for the Master’s Track Cycling championships. In elite races, her highest was a bronze medal in 2018 and her highest placing in 2019 was 8th. But of course no one talks about that because it wouldn’t be particularly interesting to read an article about a random trans woman placing 8th in a sprint. McKinnon lost 17 out of 22 events in 2019 (those aren’t exactly the best odds there). She also caught flack for beating athlete Dawn Orwick in a sprint event, except that Orwick had beat her in the 500-meter just prior.

Allayva Stier started training much harder after transitioning than before, training 5 days a week when pre-transition she only trained 2-3 times a week. And in 2019, that extra training paid off when she won a whole 2 races… out of 35. Stier started out placing among the fastest in boys competitions in her high school though, winning a number of competitions and making it to state. But her times dropped when she began medical transition and now she’s, needless to say, not that great.

Evelyn Sifton was a Canadian cyclist who placed 3rd out of 6 in a Montreal competition. Yet she still received transphobic comments by other competitors – after getting lapped by the 1st and 2nd place winners!

Athena Del Rosario is a trans soccer goalie who went from being one of the fastest runners in boys soccer to barely qualifying the mile runs in needed to place in girls soccer. Even still, she’s received her fair share of flack for apparently dominating against cisgender women. And while her stats are impressive, they’re hardly “dominating”.

Tara Seplavy is a cyclist. Unfortunately there’s really not much to say about her beyond that. She hasn’t received a single win in her three years of competing in women’s tournaments. In fact, she’s placed last place more than once. Did anyone tell her about her “biological advantage”? I don’t think she got the memo. She has no illusions about her performance though. Seplavy has professional coaches and works her ass off, but as she’s said, “I went from being a mediocre dude on a bike to being a mediocre woman on a bike. It’s not like I just changed my gender and my times stayed the same. I have to work that much harder for marginal gain.”

I could keep listing examples, but you get the point. At the end of the day, you can’t show me a single trans woman athlete who has won a competition, who hasn’t also lost. Sure, if you’re only focusing on wins, then trans athletes can seem intimidating. But if you actually compare their averages to the averages of cisgender competitors, then they’re actually quite comparable. Every. Singe. Time.

Male and Female Differences in Sports

Male and female times only differ by an average of 10-12% across events. Sure, this marginal difference likely stems from certain biological differences, such as those that we discussed above.

But trans women already tend to present with lower bone-density, muscle mass, strength, and testosterone levels pre-HRT (so maybe comparing us to cisgender men isn’t exactly the most accurate to begin with), and then we lose yet more bone density, muscle mass, and testosterone as a result of HRT.

So the question is, does HRT adequately reduce our physical abilities by roughly 10%? I think we’ve already proved that it does with our look at trans athlete averages and the fact that even those who get attention for beating cis women wind up losing, sometimes to those same cis women.


Are Men Actually More Physically Fit than Women Though?

Alright, let’s step away from trans rights and get into some general feminist analysis here and take a hard look at the apparent gender differences in sport. Sure, men tend to outperform women in traditional sports. But again, let’s consider the fact that boys are actively encouraged to be involved in physical pursuits while girls are genuinely dissuaded from such activities.

Let’s also for a moment consider that sports were invented for and by men (who also happen to be the ones most trained from an early age in them). So obviously men are going to have an advantage in activities that they themselves invented. After all, women weren’t allowed in the Olympics until 1900, and only then in certain more “feminine” activities, so it’s been an uphill battle.

So now comes the question: are there sports in which women have physiological advantages? Yes. Ultra-endurance races. Women regularly beat men in transcontinental cycling (Fiona Kolbinger cycled 2,485 miles and beat the 2nd place competitor by 6 hours – this race consisted of 224 men and 40 women), Pam Reed won the 135-mile Badwater Ultramarathons against male competitors, Lael Wilcox won the 4,300 mile Trans Am against men, Caroline Boller set a course record at the 50 mile Benzos Bend in Texas, and Diana Nyad set a record in the 110 mile swim from Cuba to Florida.

Women do so well in ultra-endurance possibly due to women having on average 6-11% more body fat than men, resulting in more energy storage over time.

The journal Nature has been theorizing that women will one day completely overtake men in even Olympic races, going off of data showing that women’s times have improved much more rapidly than men’s over the years. There is, of course, a very simple reason as to why female athletes might be improving so rapidly since the 80’s: there’s consistently been more of them entering into competitions since then.

This is yet another selection bias slowly being corrected. I mean it’s basic probability. If there are significantly more men competing, then they have better odds of getting better times. It’s telling that as more women have been competing in the Olympics, that gap between male and female times has gradually narrowed. Men only regularly outperform women because we live in a misogynistic world that holds women back, so maybe let’s check the ideas we have about male and female differences.

In Conclusion

So now that we have all that out of the way, let’s review what we’ve learned so far.

  • Male and Female times only differ by around 10%
  • That margin keeps narrowing as more female athletes enter competitions
  • Transgender women have lower bone density, muscle mass, strength, and testosterone than men to bein with
  • Trans women are required to be on HRT and have their testosterone in normal female ranges prior to competition
  • Is HRT enough to sufficiently narrow that 10% gap?
  • I can only assume so looking at our mediocre averages
  • Oh and also women are for more capable than we’re given credit, and that will be shown in due time
  • Any questions?



Van Caenegem E, Taes Y, Wierckx K, Vandewalle S, Toye K, Kaufman J-M, et al. Low bone mass is prevalent in male-to-female transsexual persons before the start of cross-sex hormonal therapy and gonadectomy. Bone. 2013 May;54(1):92-7

Weiss, Kenneth M. “On the systematic bias in skeletal sexing”. American Journal of Physical Anthropology. September 1972. Volume37, Issue2. P. 239-249

Bone, Karen Elizabeth, “A Bias in Skeletal Sexing. ” Master’s Thesis, University of Tennessee, 1993.

SoRelle JA, Jiao R, Gao E, et al. Impact of Hormone Therapy on Laboratory Values in Transgender Patients. Clin Chem. 2019;65(1):170-179. doi:10.1373/clinchem.2018.292730

Wiik, Anna, et al. “Muscle Strength, Size, and Composition Following 12 Months of Gender-affirming Treatment in Transgender Individuals”, The Journal of Clinical Endocrinology & Metabolism, Volume 105, Issue 3, March 2020, Pages e805–e813,

Hare, L., Bernard, P., Sánchez, F. J., Baird, P. N., Vilain, E., Kennedy, T., & Harley, V. R. (2009). Androgen receptor repeat length polymorphism associated with male-to-female transsexualism. Biological psychiatry65(1), 93–96.

Jones BA, Arcelus J, Bouman WP, Haycraft E. Sport and Transgender People: A Systematic Review of the Literature Relating to Sport Participation and Competitive Sport Policies. Sports Med. 2017;47(4):701-716. doi:10.1007/s40279-016-0621-y

Pearson, H. Will women outpace men in 2156?. Nature (2004).

10 responses to “Should Trans Woman Athletes be Allowed to Compete in Women’s Sports?”

  1. I’ve been keen on sport all my life even though, in the main, I’ve not been particularly good at most of the ones I’ve tried.
    I’m a keen viewer though, and since accepting the truth about myself have been trying to decide just where I stand with regard to the trans-athlete problem.
    This post has been very enlightening and certainly helps me to decide more in favour, which is where I would want to be.
    Thank you!

    • I’m so glad! All this unease over trans women in sports is just because people don’t understand who and what we are, and most don’t want to. To be fair, they’d rather us not be in men’s sports either (when I tried playing sports with boys before coming out, I got teased for “throwing like a girl” and being weak and called a sissy). They’d much prefer it if we just stopped existing altogether. But that’s tough luck for them because we’re here, and we’re making strides to change society. It’ll happen. Not too long ago, sports teams were criticized for desegregating and people used the argument that black people had “natural talent” and were “stronger and taller because only the strong could survive slavery” and whatever other kind of pseudo-Darwinian garbage they could come up with. In fact, I’ve heard these very arguments in my lifetime! Sometimes, shouting “that’s not fair!” is just another way of saying “I don’t understand and I don’t want to – make it go away!” They can dress it up with science all they want, but they always come up short in the end.

  2. That’s not what the recent SCOTUS ruling means at all! In the majority opinion, Justice Gorsuch states that when deciding to discriminate against transgender people, those decisions are necessarily based upon the person’s sex, which makes such decisions a violation of Title VII of the Civil Rights Act of 1964. It doesn’t say you can’t discriminate against members of either sex, just that the discrimination can’t be *because* they are transgender.

    And as Ariel pointed out, this is only applicable to employment.

    Your claim is little more than fearmongering.

  3. My first problem with this article is that all of the studies used are comparing transsexual women to cismen when the initial question is if “Trans women athletes be allowed to compete in women sports”. Trans women will obviously have lower muscle mass and hormone levels than men since they are talking treatments specifically to lower them. Second, the argument that since women apparently are forced or told to not do “boyish” activities when they are young; that’s why they aren’t as strong or physically capable as men. That argument has so many holes in it. Firstly, their numerous examples of women who were physically active and involved in sports from young ages and yet those same women aren’t as physically capable as their male counterparts. Essentially, you argue against basic biology with that point, since during puberty; the male body goes through specific changes that allow men to grow bigger muscles and be more athletic in general. Furthermore, you disproved your point that men’s and women’s bones weren’t distinguishable. I will say the part where they put the bones where they weren’t sure about in the pile with men was wrong; it still means that they were able to clearly determine male bones compared to female bones with a few outliers here and there. Also, I am a track and field athlete my events are 100m, long jump, 4x100m relay and 200m. You say a 10-12% difference in times is small or minimal in this article, THAT IS WRONG. A 10% difference in a race is huge, in 100m 10% means I finished the race and you’re still at the 90m mark and in 200m I would have finished the race and you’re at the 80m mark 20 whole meters behind me. THAT’S A LOT; Not to mention that if it was a 1200m race I would finish and you would be 120m behind me. Your probably not gonna see this anyway or if you do you’ll probably ignore it and call me another transphobic, misogynistic pig who’s afraid that the patriarchy will get destroyed. That’s not true, I’m an athletic black kid who doesn’t want possible misleading information to give people a somewhat skewed look at this issue. I won’t say that everything written in this article is wrong because it isn’t. The hormone section and certain parts of other sections were right or good enough for me (that’s why I didn’t mention them in this comment). I hope you see my points and where I’m coming from; I actually stumbled upon this article because I am doing research for a school assignment (I’m in high school btw if you hadn’t realized already) so I’m not trying to send hate or say that trans people are evil or none of that bull, I just wanted to point out certain problems I had with the article.

    • I can understand where my comparing of trans woman values to that of cis men when the issue in question is whether we belong in female categories could be confusing. Unfortunately, the dominant narrative is that we’re simply men trying to dominate women’s sports, in which case my strategy in the ongoing debate becomes juxtaposing trans women against cis men. Please note also that the studies showing that trans women have decreased muscle mass, strength, and testosterone levels are all based on pre-transition trans women. That is, the studies in question specifically sought out trans women who had never taken any form of HRT. If comparing trans woman values to cis woman values is important to you, I would direct you to the section in the article titled “Trans Women are Statistically not that Great at Sports”, where you’ll find trans female sports statistics pitted against cis female sports statistics, and the results are simply that we’re mediocre at best (and that’s just at the ameture level! No trans woman has ever even made it to the Olympics, though some have tried. Some have competed at the elite level in other areas but have never actually won anything. Only ever do they win at the ameture level, and even then it’s pretty scarce). I’ll just let the statistics speak for themselves, thanks.

      The issue of outliers in bones becomes relevant when you consider that trans women are outliers as it pertains to biology, as was discussed in the section prior. Although, to your credit, I never actually provided any kind of data to back up such an inference. However, I do find it amusing that in this case, 12% is a small deviation, whereas you claim that in athletics, 10% is a large margin. That said, let’s move on to that 10% margin in athletic performance. Yes, in a sprint, 10% absolutely makes or breaks the competition. The question here – and the question I’m more interested in asking – is 1) where trans women fall within that 10%, and 2) whether HRT is enough to further bridge that gap. As we already addressed, trans women present PRIOR TO INITIATING HRT with lower muscle mass, lower bone density, and lower testosterone. Meaning that trans women would already be expected to perform below that deviation to begin with. And then once HRT is initiated and their testosterone has been adequately suppressed below the typical cis female levels for at least one year, we can expect that that gap would further narrow. So I’m in no way here claiming that 10% isn’t significant as it pertains to sprinting. I’m claiming that 10% is a small gap to close when we account for all the differences in natal biology coupled with hormone usage. Just to give an anecdote (if it matters), when I was in the Navy (prior to HRT), I always got lapped by cis women on our PFT’s. And now that I’ve been on HRT for 3.5 years, I’m even slower and can’t lift things. I skate and play sports with women in my community and I’m always near last place (if not completely last place).

      In the bit about biological differences between women in men coming down – PARTIALLY – to social differences, we have to keep in mind that we’re talking about averages here. Women have only been allowed to compete in the Olympics and at many elite levels since the early to mid 1900s (depending on the competition). Because of this, there are fewer women even interested in sports than there are men who are. If women were socialized the same as men, we would see more women become interested in and engaged in sports. This is really a question of statistics and averages.

      All said and done, I wouldn’t call you a “transphobe” or what-have-you for simply poking holes in the data I presented and the way I chose to present it. You’re allowed to disagree with the way I present hand-picked data. Good luck on your school assignment.

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