If a boy chemically prevents puberty, is it fair for him to compete in women's sports?

Even the few sports that have protected the elite female category leave the door open to males who have sidestepped puberty

The parents of two New Hampshire trans-identified boys filed a federal lawsuit challenging a state law that bars males from competing on girls’ teams. These paragraphs in the Boston Globe’s report stuck out to me:

The lawsuit contends, however, that being transgender “is not an accurate proxy for athletic performance or ability.” Tirrell and Turmell are taking puberty-blocking medication and hormone therapy, so they won’t experience the muscular development and other physical changes that’s typical for testosterone-driven male puberty, their lawsuit says.

Tirrell said she has entertained hopes of one day winning an athletic scholarship, but the notion that she has an unfair advantage or poses a physical risk to her teammates doesn’t match the reality: She stands 5 feet 6 inches tall and has less muscle mass than some of her female peers — not exactly the imposing presence that policy makers seem to have in mind.

There’s a lot to take in in these two paragraphs, much of it false or misleading. The ACLU, who is representing the families of Tirrell and Turmell, falsely claims that being transgender is not a proxy for athletic ability. No one has ever said that being transgender is a proxy for athletic performance; being male is.

In the second sentence, it’s important, in fact, shocking to note that Tirrell is only 15 and Turmell, 14, and already they have flooded their male bodies with puberty blockers, which have been banned for minors in six European countries, and opposite sex hormones. Not sure where the writer got the information about those drugs erasing male development, because that’s just not true, and the observation that Tirrell is 5’6” and has “less muscle mass than some of her female peers” is not only speculation, but utterly meaningless—some boys are shorter and less muscular than some girls but they still have a physical advantage by being male. A teenage boy who is in the 20^th percentile for height and weight is going to be taller and more muscular than a girl who is in the 20^th percentile.

This incident, and others like it, made me think about the use of puberty as a point of differentiation—before it we’re just interchangeable beings, and after, fully formed males and females. Imagining that sex differences don’t really exist before puberty propels gender doctors, parents, and trans advocates to think that dosing with puberty blockers early enough will turn an undifferentiated body into the sex of choice, thereby completely erasing male advantage. However, puberty is the phase that magnifies sex differences that already exist long before puberty, differences that account for the mountain of evidence from school fitness testing that boys run faster, jump higher, throw farther, and are stronger than girls from at least age eight. This is Greg Brown’s domain. His research found plenty of data showing that males have at least 3% to 5% advantage in competition over females long before puberty.

I spoke with Brown about his research and using male puberty as an eligibility line for participation in girls’ sports.

The Female Category: When I read World Athletic’s trans policy that said anyone who had been through male puberty was banned from competing in elite women’s track and field, I immediately wondered if this would incentivize some parents to start puberty blockers and cross sex hormones early. In fact, it seems like this is playing out.

Greg Brown: I agree. It’s one more reason for a child and parent to say we’ve got to get you started on puberty blockers. Then you’ll still be eligible for elite sports if the opportunity comes up.

TFC: If the goal of sports organizations like World Athletics is to keep males out of female sports, why don’t they ban those born male instead of leaving the door open to males who have not gone through male puberty? That seems to support the idea that a boy who has chemically avoided puberty is not really male.

Greg Brown: I agree that simply separating sports into categories for males and females based on sex is the best way to preserve safety and fairness in female sports, as a number of sports scientists just indicated. The notion that there are not sex-based differences in sports performance before puberty may be cultural. Scandinavian countries don’t offer competitive sports until puberty. Here in the U.S., most sports for children are developmental leagues, designed to get children out, learn basic sports skills,  and have fun. It may be an issue with resources, that there are not enough resources or numbers of kids to have a girls’ and a boys’ t-ball team. Another factor driving the idea that there are not sex-based differences in athletic performance before puberty comes from a paper published by David Handelsman in 2017 titled something like Sex-based Differences Start at Puberty. But his data shows boys swim faster by 1-2%, run faster by 3%, and jump higher or further by 6% before puberty. At puberty, those sex differences are magnified. So, I’m not sure why having gone through male puberty is considered a dividing line for eligibility in girls’ or women’s sports. Maybe it’s one of convenience.

TFC: Your research shows male advantage even before puberty. Can you talk about where prepubertal male advantage comes from? 

Greg Brown: Two thoughts: right after birth boys go through a mini puberty for 5-6 months, so have higher levels of testosterone than girls. This gives infant boys the advantage of more lean body mass, which is one of the major drivers of better sports performance. The second thought is that the Y chromosome inherently effects subtle differences like size and placement of lungs, more alveoli and more oxygenation of the blood and other small differences between boys and girls. It [Y chromosome] affects muscle fiber type. Skeletally, it’s been postulated there is a difference in shoulder structure because by two years old, boys throw farther, faster, and more accurately than girls. By eight years old, girls have a wider pelvis than boys, so boys have a straighter, more efficient hip-to-knee Q angle. It’s mostly postulating because there are problems with experimenting on young children of course, and really, people haven’t paid much attention [to prepubertal sex differences] until the last couple years.

TFC: That’s true. I wrote previously about the state of California abandoning fitness testing in schools, in part, because Cooper Institute, that designs the tests, would not develop a nonbinary score. Cooper Institute was aware of sex differences in physical ability because, from the start, they have had male and female scores for the various tests.

TFC: How do puberty blockers and female hormones given to an adolescent boy affect physical performance in the short run? 

Greg Brown: That’s a big unknown. This is one of the things the Cass review pointed out—we don’t know the many ways puberty blockers and cross sex hormones affect kids. There is no research on [how they affect] any type of physical fitness. We do know that there are changes in body composition—a reduction in normal male amount of lean body mass, but still more than average females, and an increase in body fat, closer to female levels. So, a male on puberty blockers and cross sex hormones would have body composition somewhere between normal male and female range. Puberty blockers slow increase in height, and the child stays shorter until he or she starts cross sex hormones. Then there’s a growth spurt and he or she ends up being the same height as he or she would have been without puberty blockers and hormones.

TFC: So, do those body composition and height changes erase the 3% to 5% sports advantage in boys you found?

Greg Brown: We can’t say for certain whether the fact that boys on puberty blockers and cross sex hormones retain more lean body mass and eventually grow taller than girls translates into sports advantage because there has not been any research. What we know is that overall, both before and after puberty, males have documented sports advantage and a good amount of that advantage is due to having more lean body mass (i.e. muscle mass) than females. It’s also abundantly clear that being taller gives advantages in some sport, like basketball, volleyball, and even swimming. The argument for including males who have used puberty blockers and cross sex hormones in girls’ and women’s sports is that there is no evidence that male advantage is not erased. But there’s no evidence that male advantage is erased, either, so we can’t say with confidence that it’s fair for a boy on puberty blockers and cross sex hormones to be in girls sports. Essentially, the argument to include males who have used puberty blockers and cross sex hormones in girls’ and women’s sports is that a smaller, less muscular, untrained, unathletic boy does not have advantage over girls, so he could fairly play on the girls’ team.

TFC: One of the incentives for starting puberty blockers and cross sex hormones with boys is to avoid male puberty, and thus still be eligible for women’s sports at the elite level. Elite level sports demand a lot of even the healthiest body. Over the long run, might osteoporosis and other side effects of puberty blockers preclude a career in top level sports? 

Greg Brown: Those are valid concerns. Research hasn’t shown more injuries in those who take puberty blockers, but as we know from the Cass review, this area is under-researched on all sorts of things. We just don’t know. It’s a logical concern that a person who has affected their fundamental development at puberty with puberty blockers and cross sex hormones will have side effects that prevent high level sports later.

TFC: Sports scientists talk about keeping male advantage out of female sports, but male advantage seems really hard to prove, particularly if the individual hasn’t gone through male puberty. Why not exclude males instead of “male advantage?”

Greg Brown: Jon Pike had something good to say about this at the ICONS conference. He said sports have categories, male and female, and those categories exist to make sports fair. Being male is a category advantage, which means that because you are male, you have an advantage. And he used the metaphor of a motorcycle race and a bicycle race. Even if you have a crappy motorcycle, you have a category advantage, you have a motorcycle, and can’t be in the bicycle race.

TFC: As it stands now, sports that have banned people who have gone through male puberty from elite women’s competition—World Athletics, World Aquatics, cycling, World Rugby—are leaving the door open to males who have chemically avoided male puberty. Yet your research shows males are faster and stronger even before puberty. Will that childhood advantage remain into adulthood?

Greg Brown: It’s hard to say because there’s no research on this. We know cross sex hormones reduce but do not remove male advantage, the advantage might be small. But looking at the last Olympics, races were won by 1/100th, 1/1000th of a second. A small advantage can make a big difference.