Trans women in female sports: A sports scientist’s take

When Lia Thomas won the women’s 500-yard freestyle at the 2022 NCAA Division 1 swimming championships, the issue of trans women’s participation in female sports ignited national headlines.

This news organization interviewed Ross Tucker, PhD, an exercise physiologist from South Africa, who was involved in the World Rugby Transgender Guidelines, which prohibit trans women’s participation.

This interview has been edited for length and clarity.
 

Let’s start with the proinclusion argument that there are always advantages in sports.

That’s true. The whole point of sports is to recognize people who have advantages and reward them for it. By the time this argument comes out, people have already accepted that males have advantages, right?

Some do, some don’t.

If someone uses this argument to say that we should allow trans women, basically biological males, to compete in women’s sports, they’ve implicitly accepted that there are advantages. Otherwise, what advantage are you talking about?

They would say it’s like the advantage Michael Phelps has because of his wingspan.

To answer that, you have to start by asking why women’s sports exist.

Women’s sports exist because we recognize that male physiology has biological differences that create performance advantages. Women’s sports exist to ensure that male advantages are excluded. If you allow male advantage in, you’re allowing something to cross into a category that specifically tries to exclude it. That makes the advantage possessed by trans women conceptually and substantively different from an advantage that’s possessed by Michael Phelps because his advantage doesn’t cross a category boundary line.

If someone wants to allow natural advantages to be celebrated in sports, they’re arguing against the existence of any categories, because every single category in sports is trying to filter out certain advantages.

Weight categories in boxing exist to get rid of the advantage of being stronger, taller, with greater reach. Paralympic categories filter out the natural advantage that someone has if, for example, they are only mildly affected by cerebral palsy, compared with more severely affected.

If someone wants to allow natural advantages, they’re making an argument for all advantages to be eliminated from regulation, and we would end up with sports dominated by males between the ages of 20 and 28.
 

There are some people suggesting open categories by height and weight.

The problem is that for any height, males will be stronger, faster, more powerful than females. For any mass, and we know this because weightlifting has categories by mass, males lift about 30% heavier than females. They’ll be about 10%-15% faster at the same height and weight.

There’d be one or two sports where you might have some women, like gymnastics. Otherwise you would have to create categories that are so small – say, under 100 pounds. But in every other category, most sports would be completely dominated by males.

It’s not a viable solution for me unless we as a society are satisfied with filtering out women.
 

Another argument is that if trans women have an advantage, then they would be dominating.

That one misunderstands how you assess advantage. For a trans woman to win, she still has to be good enough at the base level without the advantage, in order to parlay that advantage into winning the women’s events.

If I was in the Tour de France and you gave me a bicycle with a 100-watt motor, I wouldn’t win the Tour de France. I’d do better than I would have done without it, but I wouldn’t win. Does my failure to win prove that motors don’t give an advantage? Of course not. My failure says more about my base level of performance than it does about the motor.

In terms of trans athletes, the retention of biological attributes creates the retention of performance advantages, which means that the person’s ranking relative to their peers’ will go up when they compare themselves to women rather than men. Someone who’s ranked 500 might improve to the 250s, but you still won’t see them on a podium.

It’s the change in performance that matters, not the final outcome.
 

Wasn’t Lia Thomas ranked in the 500s in the men’s division?

There’s some dispute as to whether it was 460 or 550 in the 200- and 65th in the 500-yard freestyle. But the concept is the same and we can use that case because we know the percentage performance change.

As Will Thomas, the performance was 4:18 in the 500-yard freestyle. As Lia Thomas, it’s 4:33. Ms. Thomas has slowed by 5.8% as a result of testosterone suppression. That’s fairly typical; most studies so far suggest performance impairments in that range.

The thing is that the male-female gap in swimming times is 10%-12% on average. That means that Ms. Thomas has retained about half the male advantage.

In strength events, for instance, weightlifting, where the gap is 30% or more, if you lost 10%, you’d still retain a 20% advantage and you’d jump more ranking places.

The retention of about half the male advantage is enough for No. 1 in the NCAA, but it’s not enough to move Ms. Thomas to No. 1 in the world.

The record set by Katie Ledecky in the 500 freestyle is 4:24. Thomas swam 4:18 as a man so could only afford to lose about 1% to be the record holder in women’s swimming.
 

When Ms. Thomas was beaten by cisgender women in other events, your point is that’s just because her baseline (pretransition) time wasn’t good enough.

Exactly. Are your performances in men’s sports close enough to the best woman such that you can turn that retained advantage into dominance, winning in women’s sports?

If the answer to that is yes, then you get Thomas in the 500. If the answer to that is not quite, then you get Thomas in the other distances.
 

On your podcast, you expressed frustration at having to keep debunking these arguments. Why do you think they persist?

There are a few things in play. There are nuances around the idea of advantage that people from outside sports don’t always appreciate.

But then the second thing comes into play and that’s the fact that this is an emotive issue. If you come to this debate wanting trans inclusion, then you reject the idea that it’s unfair. You will dismiss everything I’ve just said.

There’s a third thing. When people invoke the Phelps wingspan argument, they haven’t thought through the implications. If you could sit them down and say: “Okay. If you want to get rid of regulating natural advantages, then we would get rid of male and female categories,” what do you think would happen then?

They may still support inclusion because that’s their world view, but at least they’re honest now and understand the implications. But most people don’t go through that process.
 

 

I get that men are faster but I was shocked at how many are faster than elite women – for example, Allyson Felix.

There’s an amazing visual representation of that.

That’s a classic example where, if you’re immersed in sports, it becomes intuitive. If you’re not, you do a double-take and think, is that right? Position determines perspective.
 

Do you think some of it is because we’re constantly told that girls and women can do anything?

It’s a paradox that is difficult for people to get their minds around because in most walks of life, we can say that women can do anything. Of course, it’s arguably more difficult for women to become CEOs of Fortune 500 companies. This is a work in progress.

But sports are different. In sports, it’s not possible to directly compare male and female, and then tell girls they can be the best at whatever in the whole human race. That’s the uniqueness of sports and the reason categories exist in the first place. The biology does matter.
 

Speaking of biology, you’ve said that the focus on testosterone levels is a bit of a red herring.

Yes. The authorities were looking for a solution.

They grabbed onto the idea that lowering testosterone was the solution and perpetuated that as the mechanism by which we would ensure fairness. The problem is that my concentration of testosterone today is only a tiny part of the story.

I’ve been exposed to testosterone my whole life. My twin sister has not. There are many differences between us, but in terms of sports, the main biological difference is not that my testosterone is higher today; it’s that my testosterone has been higher my whole life. It’s the work done by that hormone over many years that makes a difference.

The key issue is, has this body, this physiology, been exposed to and benefited in the sports context, from male hormones – yes or no?

If your answer is yes, then that body belongs in male sports. With gender identity, we want to accommodate as far as possible, but we can’t take away that difference. That’s where we create this collision of rights between trans women and women.
 

Ultimately, your point is that we can’t have both fairness and inclusion.

When we sat down to do the World Rugby trans guidance, we had an epiphany: It doesn’t matter which way we go; we’re going to face hostility.

Once you accept that there are two parties that are affected and one of them will always be unhappy, then you start to see that fairness and inclusion can’t be balanced.
 

What about Joanna Harper’s proposal to make rules case by case and sport by sport?

First, it could be tricky legally because you’re effectively discriminating against some people within a subset of a subset. You’re going to end up saying to some trans women: “You can play because you don’t pose a safety or fairness issue.” But to another: “You can’t because you’re too strong.”

Then the problem is, how do you do that screening? It’s not like you can measure half a dozen variables and then have an algorithm spit out a performance level that tells you that this trans woman can compete here safely and fairly. It’s a theoretical solution that is practically impossible.

At a conference in Boston recently, Joanna said that when there are no medals, prize money, scholarships, or record times, we should allow inclusion. But just because a woman isn’t winning medals or going to the Olympics doesn’t mean there’s not considerable value for her if she were to make her school team, for instance.

There are only 11 places on the soccer field, eight lanes in a swimming pool. The moment you allow someone in, you potentially exclude someone else. And that happens everywhere, not only at the elite level.
 

Would you ever make a distinction between elite and subelite?

One of the beauties of sports is that it’s a meritocracy; it functions on a pathway system. I don’t think the level matters if you can track that this person’s presence denied a place on the team or a place at the competition to someone else.

With Lia Thomas, it’s not only denying the silver medalist gold or fourth place a bronze; it’s also the fact that there are only so many places at that meet. For some, that was their ambition and they weren’t able to realize it.

Now, a lot of sports are played outside that pathway. Say your local tennis club has a social league. There is little there to stand in the way of inclusion. Although I’m mindful that there may be a women’s league where it does matter to them.

We can try to accommodate trans women when the stakes are not high, provided that two requirements are met: One is that there’s no disruption to the selection/meritocracy pathway; and the second key point is that women must be okay with that inclusion, particularly if there are safety considerations, but even if it’s just a fairness consideration.

That’s where it gets tricky, because there are bigoted people in the world. Unfortunately, sometimes it’s difficult to tell whether people are using scientific arguments to prop up bigotry or whether they are genuine.
 

Joanna Harper has said that if you support inclusion, you have to be okay with trans women winning.

Winning the summer tennis league is not winning in the same sense as winning at the NCAA.

But the moment winning means selection and performance pathways, then I think we have to draw a line. The moment participation disrupts the natural order in sports, then it’s a problem.

In World Rugby, we proposed open competitions lower in contact to deal with the safety concerns. That was rejected by the trans community because they felt it was othering – that we were trying to squeeze them off to the side.

If you offered me one of two choices: no participation, or inclusion and they have to be able to win, I’d go for the former.
 

 

How did you get involved in this topic?

I got involved because I testified in the Caster Semenya case at the Court of Arbitration for Sport.

That is not a transgender issue; it’s a difference of sex development issue. What it has in common is the question of what to do with male-bodied biological advantage in sports.

When World Rugby joined the Olympic Games, we followed the IOC transgender policy. In 2019, it became apparent from the latest research that male advantage isn’t removed by testosterone suppression. We decided to delete the previous policy and make a new one.
 

The latest IOC policy is kind of no policy; it leaves it up to the governing bodies for each sport.

The one element of progress in what the IOC released, and it really is the only one, is that they’ve recognized that sports have to manage three imperatives: fairness, inclusion, and safety.

The 2015 IOC document says something like “sports should strive to be as inclusive as possible, but the overriding objective remains to guarantee a fair competition.” Basically, fair competition was nonnegotiable and must be guaranteed.

Of course, that policy allowed for testosterone suppression, and you’d have a difficult time convincing a physiologist that lowering testosterone guarantees fair competition.

Where there is merit in the current policy is that it’s clear that sports like rugby, boxing, taekwondo, and judo have a different equation with respect to safety, fairness, and inclusion than sports like equestrian, shooting, and archery. I think that’s wise to acknowledge.

However, the IOC policy doesn’t do anything to lead. In fact, what they said was extraordinary: There should be no presumption of advantage. If there’s no presumption of advantage for male-bodied athletes, then why do they persist with two categories? If there’s no presumption of advantage for trans women, are they saying that gender identity removes the advantage? We know that’s not true. We know that at the very least, you should presume that there is some advantage. How you manage it is up to you, but you can’t say that it’s not there.
 

This is a hostile debate. Have you ever thought: Maybe I’ll just shut up and stick to other sports topics?

Big time. The Lia Thomas case brought out a lot of vitriol. From about 2017, the situation we had with Ms. Thomas was predictable. The problem is that 95% of the world didn’t know this was happening and were taken by surprise.

The number of people who have opinions has exploded. A lot wade in without much thought. I’ve seen people question Lia Thomas’s motives. Presumably, Lia Thomas is trans, identifies as a woman, and therefore thinks she belongs in women’s sports. But I’ve seen people saying she only wants to swim in women’s sports because she knows she’ll win. And that’s not the worst of it. I’ve seen people saying Lia Thomas is only identifying as a woman so she can get into women’s changing rooms.

I don’t see how that helps the conversation. It just polarizes to the point that neither side is listening to the other. Before it was the trans community that wasn’t interested in talking about the idea of advantage, fairness, and safety. Their position is that trans women are women; how do you even have a discussion when they’ve got that dogma as their foundation?

Now, unfortunately, on the other side, we’re seeing unnecessary offensive tactics. For example, I’ve referred to Lia Thomas as “she.” I’ll have people shouting at me for using “she.” You’ve got to pick your battles, and that’s not the one you want to be fighting, in my opinion.

A version of this article first appeared on Medscape.com.

When Lia Thomas won the women’s 500-yard freestyle at the 2022 NCAA Division 1 swimming championships, the issue of trans women’s participation in female sports ignited national headlines.

This news organization interviewed Ross Tucker, PhD, an exercise physiologist from South Africa, who was involved in the World Rugby Transgender Guidelines, which prohibit trans women’s participation.

This interview has been edited for length and clarity.
 

Let’s start with the proinclusion argument that there are always advantages in sports.

That’s true. The whole point of sports is to recognize people who have advantages and reward them for it. By the time this argument comes out, people have already accepted that males have advantages, right?

Some do, some don’t.

If someone uses this argument to say that we should allow trans women, basically biological males, to compete in women’s sports, they’ve implicitly accepted that there are advantages. Otherwise, what advantage are you talking about?

They would say it’s like the advantage Michael Phelps has because of his wingspan.

To answer that, you have to start by asking why women’s sports exist.

Women’s sports exist because we recognize that male physiology has biological differences that create performance advantages. Women’s sports exist to ensure that male advantages are excluded. If you allow male advantage in, you’re allowing something to cross into a category that specifically tries to exclude it. That makes the advantage possessed by trans women conceptually and substantively different from an advantage that’s possessed by Michael Phelps because his advantage doesn’t cross a category boundary line.

If someone wants to allow natural advantages to be celebrated in sports, they’re arguing against the existence of any categories, because every single category in sports is trying to filter out certain advantages.

Weight categories in boxing exist to get rid of the advantage of being stronger, taller, with greater reach. Paralympic categories filter out the natural advantage that someone has if, for example, they are only mildly affected by cerebral palsy, compared with more severely affected.

If someone wants to allow natural advantages, they’re making an argument for all advantages to be eliminated from regulation, and we would end up with sports dominated by males between the ages of 20 and 28.
 

There are some people suggesting open categories by height and weight.

The problem is that for any height, males will be stronger, faster, more powerful than females. For any mass, and we know this because weightlifting has categories by mass, males lift about 30% heavier than females. They’ll be about 10%-15% faster at the same height and weight.

There’d be one or two sports where you might have some women, like gymnastics. Otherwise you would have to create categories that are so small – say, under 100 pounds. But in every other category, most sports would be completely dominated by males.

It’s not a viable solution for me unless we as a society are satisfied with filtering out women.
 

Another argument is that if trans women have an advantage, then they would be dominating.

That one misunderstands how you assess advantage. For a trans woman to win, she still has to be good enough at the base level without the advantage, in order to parlay that advantage into winning the women’s events.

If I was in the Tour de France and you gave me a bicycle with a 100-watt motor, I wouldn’t win the Tour de France. I’d do better than I would have done without it, but I wouldn’t win. Does my failure to win prove that motors don’t give an advantage? Of course not. My failure says more about my base level of performance than it does about the motor.

In terms of trans athletes, the retention of biological attributes creates the retention of performance advantages, which means that the person’s ranking relative to their peers’ will go up when they compare themselves to women rather than men. Someone who’s ranked 500 might improve to the 250s, but you still won’t see them on a podium.

It’s the change in performance that matters, not the final outcome.
 

Wasn’t Lia Thomas ranked in the 500s in the men’s division?

There’s some dispute as to whether it was 460 or 550 in the 200- and 65th in the 500-yard freestyle. But the concept is the same and we can use that case because we know the percentage performance change.

As Will Thomas, the performance was 4:18 in the 500-yard freestyle. As Lia Thomas, it’s 4:33. Ms. Thomas has slowed by 5.8% as a result of testosterone suppression. That’s fairly typical; most studies so far suggest performance impairments in that range.

The thing is that the male-female gap in swimming times is 10%-12% on average. That means that Ms. Thomas has retained about half the male advantage.

In strength events, for instance, weightlifting, where the gap is 30% or more, if you lost 10%, you’d still retain a 20% advantage and you’d jump more ranking places.

The retention of about half the male advantage is enough for No. 1 in the NCAA, but it’s not enough to move Ms. Thomas to No. 1 in the world.

The record set by Katie Ledecky in the 500 freestyle is 4:24. Thomas swam 4:18 as a man so could only afford to lose about 1% to be the record holder in women’s swimming.
 

When Ms. Thomas was beaten by cisgender women in other events, your point is that’s just because her baseline (pretransition) time wasn’t good enough.

Exactly. Are your performances in men’s sports close enough to the best woman such that you can turn that retained advantage into dominance, winning in women’s sports?

If the answer to that is yes, then you get Thomas in the 500. If the answer to that is not quite, then you get Thomas in the other distances.
 

On your podcast, you expressed frustration at having to keep debunking these arguments. Why do you think they persist?

There are a few things in play. There are nuances around the idea of advantage that people from outside sports don’t always appreciate.

But then the second thing comes into play and that’s the fact that this is an emotive issue. If you come to this debate wanting trans inclusion, then you reject the idea that it’s unfair. You will dismiss everything I’ve just said.

There’s a third thing. When people invoke the Phelps wingspan argument, they haven’t thought through the implications. If you could sit them down and say: “Okay. If you want to get rid of regulating natural advantages, then we would get rid of male and female categories,” what do you think would happen then?

They may still support inclusion because that’s their world view, but at least they’re honest now and understand the implications. But most people don’t go through that process.
 

 

I get that men are faster but I was shocked at how many are faster than elite women – for example, Allyson Felix.

There’s an amazing visual representation of that.

That’s a classic example where, if you’re immersed in sports, it becomes intuitive. If you’re not, you do a double-take and think, is that right? Position determines perspective.
 

Do you think some of it is because we’re constantly told that girls and women can do anything?

It’s a paradox that is difficult for people to get their minds around because in most walks of life, we can say that women can do anything. Of course, it’s arguably more difficult for women to become CEOs of Fortune 500 companies. This is a work in progress.

But sports are different. In sports, it’s not possible to directly compare male and female, and then tell girls they can be the best at whatever in the whole human race. That’s the uniqueness of sports and the reason categories exist in the first place. The biology does matter.
 

Speaking of biology, you’ve said that the focus on testosterone levels is a bit of a red herring.

Yes. The authorities were looking for a solution.

They grabbed onto the idea that lowering testosterone was the solution and perpetuated that as the mechanism by which we would ensure fairness. The problem is that my concentration of testosterone today is only a tiny part of the story.

I’ve been exposed to testosterone my whole life. My twin sister has not. There are many differences between us, but in terms of sports, the main biological difference is not that my testosterone is higher today; it’s that my testosterone has been higher my whole life. It’s the work done by that hormone over many years that makes a difference.

The key issue is, has this body, this physiology, been exposed to and benefited in the sports context, from male hormones – yes or no?

If your answer is yes, then that body belongs in male sports. With gender identity, we want to accommodate as far as possible, but we can’t take away that difference. That’s where we create this collision of rights between trans women and women.
 

Ultimately, your point is that we can’t have both fairness and inclusion.

When we sat down to do the World Rugby trans guidance, we had an epiphany: It doesn’t matter which way we go; we’re going to face hostility.

Once you accept that there are two parties that are affected and one of them will always be unhappy, then you start to see that fairness and inclusion can’t be balanced.
 

What about Joanna Harper’s proposal to make rules case by case and sport by sport?

First, it could be tricky legally because you’re effectively discriminating against some people within a subset of a subset. You’re going to end up saying to some trans women: “You can play because you don’t pose a safety or fairness issue.” But to another: “You can’t because you’re too strong.”

Then the problem is, how do you do that screening? It’s not like you can measure half a dozen variables and then have an algorithm spit out a performance level that tells you that this trans woman can compete here safely and fairly. It’s a theoretical solution that is practically impossible.

At a conference in Boston recently, Joanna said that when there are no medals, prize money, scholarships, or record times, we should allow inclusion. But just because a woman isn’t winning medals or going to the Olympics doesn’t mean there’s not considerable value for her if she were to make her school team, for instance.

There are only 11 places on the soccer field, eight lanes in a swimming pool. The moment you allow someone in, you potentially exclude someone else. And that happens everywhere, not only at the elite level.
 

Would you ever make a distinction between elite and subelite?

One of the beauties of sports is that it’s a meritocracy; it functions on a pathway system. I don’t think the level matters if you can track that this person’s presence denied a place on the team or a place at the competition to someone else.

With Lia Thomas, it’s not only denying the silver medalist gold or fourth place a bronze; it’s also the fact that there are only so many places at that meet. For some, that was their ambition and they weren’t able to realize it.

Now, a lot of sports are played outside that pathway. Say your local tennis club has a social league. There is little there to stand in the way of inclusion. Although I’m mindful that there may be a women’s league where it does matter to them.

We can try to accommodate trans women when the stakes are not high, provided that two requirements are met: One is that there’s no disruption to the selection/meritocracy pathway; and the second key point is that women must be okay with that inclusion, particularly if there are safety considerations, but even if it’s just a fairness consideration.

That’s where it gets tricky, because there are bigoted people in the world. Unfortunately, sometimes it’s difficult to tell whether people are using scientific arguments to prop up bigotry or whether they are genuine.
 

Joanna Harper has said that if you support inclusion, you have to be okay with trans women winning.

Winning the summer tennis league is not winning in the same sense as winning at the NCAA.

But the moment winning means selection and performance pathways, then I think we have to draw a line. The moment participation disrupts the natural order in sports, then it’s a problem.

In World Rugby, we proposed open competitions lower in contact to deal with the safety concerns. That was rejected by the trans community because they felt it was othering – that we were trying to squeeze them off to the side.

If you offered me one of two choices: no participation, or inclusion and they have to be able to win, I’d go for the former.
 

 

How did you get involved in this topic?

I got involved because I testified in the Caster Semenya case at the Court of Arbitration for Sport.

That is not a transgender issue; it’s a difference of sex development issue. What it has in common is the question of what to do with male-bodied biological advantage in sports.

When World Rugby joined the Olympic Games, we followed the IOC transgender policy. In 2019, it became apparent from the latest research that male advantage isn’t removed by testosterone suppression. We decided to delete the previous policy and make a new one.
 

The latest IOC policy is kind of no policy; it leaves it up to the governing bodies for each sport.

The one element of progress in what the IOC released, and it really is the only one, is that they’ve recognized that sports have to manage three imperatives: fairness, inclusion, and safety.

The 2015 IOC document says something like “sports should strive to be as inclusive as possible, but the overriding objective remains to guarantee a fair competition.” Basically, fair competition was nonnegotiable and must be guaranteed.

Of course, that policy allowed for testosterone suppression, and you’d have a difficult time convincing a physiologist that lowering testosterone guarantees fair competition.

Where there is merit in the current policy is that it’s clear that sports like rugby, boxing, taekwondo, and judo have a different equation with respect to safety, fairness, and inclusion than sports like equestrian, shooting, and archery. I think that’s wise to acknowledge.

However, the IOC policy doesn’t do anything to lead. In fact, what they said was extraordinary: There should be no presumption of advantage. If there’s no presumption of advantage for male-bodied athletes, then why do they persist with two categories? If there’s no presumption of advantage for trans women, are they saying that gender identity removes the advantage? We know that’s not true. We know that at the very least, you should presume that there is some advantage. How you manage it is up to you, but you can’t say that it’s not there.
 

This is a hostile debate. Have you ever thought: Maybe I’ll just shut up and stick to other sports topics?

Big time. The Lia Thomas case brought out a lot of vitriol. From about 2017, the situation we had with Ms. Thomas was predictable. The problem is that 95% of the world didn’t know this was happening and were taken by surprise.

The number of people who have opinions has exploded. A lot wade in without much thought. I’ve seen people question Lia Thomas’s motives. Presumably, Lia Thomas is trans, identifies as a woman, and therefore thinks she belongs in women’s sports. But I’ve seen people saying she only wants to swim in women’s sports because she knows she’ll win. And that’s not the worst of it. I’ve seen people saying Lia Thomas is only identifying as a woman so she can get into women’s changing rooms.

I don’t see how that helps the conversation. It just polarizes to the point that neither side is listening to the other. Before it was the trans community that wasn’t interested in talking about the idea of advantage, fairness, and safety. Their position is that trans women are women; how do you even have a discussion when they’ve got that dogma as their foundation?

Now, unfortunately, on the other side, we’re seeing unnecessary offensive tactics. For example, I’ve referred to Lia Thomas as “she.” I’ll have people shouting at me for using “she.” You’ve got to pick your battles, and that’s not the one you want to be fighting, in my opinion.

A version of this article first appeared on Medscape.com.

When Lia Thomas won the women’s 500-yard freestyle at the 2022 NCAA Division 1 swimming championships, the issue of trans women’s participation in female sports ignited national headlines.

This news organization interviewed Ross Tucker, PhD, an exercise physiologist from South Africa, who was involved in the World Rugby Transgender Guidelines, which prohibit trans women’s participation.

This interview has been edited for length and clarity.
 

Let’s start with the proinclusion argument that there are always advantages in sports.

That’s true. The whole point of sports is to recognize people who have advantages and reward them for it. By the time this argument comes out, people have already accepted that males have advantages, right?

Some do, some don’t.

If someone uses this argument to say that we should allow trans women, basically biological males, to compete in women’s sports, they’ve implicitly accepted that there are advantages. Otherwise, what advantage are you talking about?

They would say it’s like the advantage Michael Phelps has because of his wingspan.

To answer that, you have to start by asking why women’s sports exist.

Women’s sports exist because we recognize that male physiology has biological differences that create performance advantages. Women’s sports exist to ensure that male advantages are excluded. If you allow male advantage in, you’re allowing something to cross into a category that specifically tries to exclude it. That makes the advantage possessed by trans women conceptually and substantively different from an advantage that’s possessed by Michael Phelps because his advantage doesn’t cross a category boundary line.

If someone wants to allow natural advantages to be celebrated in sports, they’re arguing against the existence of any categories, because every single category in sports is trying to filter out certain advantages.

Weight categories in boxing exist to get rid of the advantage of being stronger, taller, with greater reach. Paralympic categories filter out the natural advantage that someone has if, for example, they are only mildly affected by cerebral palsy, compared with more severely affected.

If someone wants to allow natural advantages, they’re making an argument for all advantages to be eliminated from regulation, and we would end up with sports dominated by males between the ages of 20 and 28.
 

There are some people suggesting open categories by height and weight.

The problem is that for any height, males will be stronger, faster, more powerful than females. For any mass, and we know this because weightlifting has categories by mass, males lift about 30% heavier than females. They’ll be about 10%-15% faster at the same height and weight.

There’d be one or two sports where you might have some women, like gymnastics. Otherwise you would have to create categories that are so small – say, under 100 pounds. But in every other category, most sports would be completely dominated by males.

It’s not a viable solution for me unless we as a society are satisfied with filtering out women.
 

Another argument is that if trans women have an advantage, then they would be dominating.

That one misunderstands how you assess advantage. For a trans woman to win, she still has to be good enough at the base level without the advantage, in order to parlay that advantage into winning the women’s events.

If I was in the Tour de France and you gave me a bicycle with a 100-watt motor, I wouldn’t win the Tour de France. I’d do better than I would have done without it, but I wouldn’t win. Does my failure to win prove that motors don’t give an advantage? Of course not. My failure says more about my base level of performance than it does about the motor.

In terms of trans athletes, the retention of biological attributes creates the retention of performance advantages, which means that the person’s ranking relative to their peers’ will go up when they compare themselves to women rather than men. Someone who’s ranked 500 might improve to the 250s, but you still won’t see them on a podium.

It’s the change in performance that matters, not the final outcome.
 

Wasn’t Lia Thomas ranked in the 500s in the men’s division?

There’s some dispute as to whether it was 460 or 550 in the 200- and 65th in the 500-yard freestyle. But the concept is the same and we can use that case because we know the percentage performance change.

As Will Thomas, the performance was 4:18 in the 500-yard freestyle. As Lia Thomas, it’s 4:33. Ms. Thomas has slowed by 5.8% as a result of testosterone suppression. That’s fairly typical; most studies so far suggest performance impairments in that range.

The thing is that the male-female gap in swimming times is 10%-12% on average. That means that Ms. Thomas has retained about half the male advantage.

In strength events, for instance, weightlifting, where the gap is 30% or more, if you lost 10%, you’d still retain a 20% advantage and you’d jump more ranking places.

The retention of about half the male advantage is enough for No. 1 in the NCAA, but it’s not enough to move Ms. Thomas to No. 1 in the world.

The record set by Katie Ledecky in the 500 freestyle is 4:24. Thomas swam 4:18 as a man so could only afford to lose about 1% to be the record holder in women’s swimming.
 

When Ms. Thomas was beaten by cisgender women in other events, your point is that’s just because her baseline (pretransition) time wasn’t good enough.

Exactly. Are your performances in men’s sports close enough to the best woman such that you can turn that retained advantage into dominance, winning in women’s sports?

If the answer to that is yes, then you get Thomas in the 500. If the answer to that is not quite, then you get Thomas in the other distances.
 

On your podcast, you expressed frustration at having to keep debunking these arguments. Why do you think they persist?

There are a few things in play. There are nuances around the idea of advantage that people from outside sports don’t always appreciate.

But then the second thing comes into play and that’s the fact that this is an emotive issue. If you come to this debate wanting trans inclusion, then you reject the idea that it’s unfair. You will dismiss everything I’ve just said.

There’s a third thing. When people invoke the Phelps wingspan argument, they haven’t thought through the implications. If you could sit them down and say: “Okay. If you want to get rid of regulating natural advantages, then we would get rid of male and female categories,” what do you think would happen then?

They may still support inclusion because that’s their world view, but at least they’re honest now and understand the implications. But most people don’t go through that process.
 

 

I get that men are faster but I was shocked at how many are faster than elite women – for example, Allyson Felix.

There’s an amazing visual representation of that.

That’s a classic example where, if you’re immersed in sports, it becomes intuitive. If you’re not, you do a double-take and think, is that right? Position determines perspective.
 

Do you think some of it is because we’re constantly told that girls and women can do anything?

It’s a paradox that is difficult for people to get their minds around because in most walks of life, we can say that women can do anything. Of course, it’s arguably more difficult for women to become CEOs of Fortune 500 companies. This is a work in progress.

But sports are different. In sports, it’s not possible to directly compare male and female, and then tell girls they can be the best at whatever in the whole human race. That’s the uniqueness of sports and the reason categories exist in the first place. The biology does matter.
 

Speaking of biology, you’ve said that the focus on testosterone levels is a bit of a red herring.

Yes. The authorities were looking for a solution.

They grabbed onto the idea that lowering testosterone was the solution and perpetuated that as the mechanism by which we would ensure fairness. The problem is that my concentration of testosterone today is only a tiny part of the story.

I’ve been exposed to testosterone my whole life. My twin sister has not. There are many differences between us, but in terms of sports, the main biological difference is not that my testosterone is higher today; it’s that my testosterone has been higher my whole life. It’s the work done by that hormone over many years that makes a difference.

The key issue is, has this body, this physiology, been exposed to and benefited in the sports context, from male hormones – yes or no?

If your answer is yes, then that body belongs in male sports. With gender identity, we want to accommodate as far as possible, but we can’t take away that difference. That’s where we create this collision of rights between trans women and women.
 

Ultimately, your point is that we can’t have both fairness and inclusion.

When we sat down to do the World Rugby trans guidance, we had an epiphany: It doesn’t matter which way we go; we’re going to face hostility.

Once you accept that there are two parties that are affected and one of them will always be unhappy, then you start to see that fairness and inclusion can’t be balanced.
 

What about Joanna Harper’s proposal to make rules case by case and sport by sport?

First, it could be tricky legally because you’re effectively discriminating against some people within a subset of a subset. You’re going to end up saying to some trans women: “You can play because you don’t pose a safety or fairness issue.” But to another: “You can’t because you’re too strong.”

Then the problem is, how do you do that screening? It’s not like you can measure half a dozen variables and then have an algorithm spit out a performance level that tells you that this trans woman can compete here safely and fairly. It’s a theoretical solution that is practically impossible.

At a conference in Boston recently, Joanna said that when there are no medals, prize money, scholarships, or record times, we should allow inclusion. But just because a woman isn’t winning medals or going to the Olympics doesn’t mean there’s not considerable value for her if she were to make her school team, for instance.

There are only 11 places on the soccer field, eight lanes in a swimming pool. The moment you allow someone in, you potentially exclude someone else. And that happens everywhere, not only at the elite level.
 

Would you ever make a distinction between elite and subelite?

One of the beauties of sports is that it’s a meritocracy; it functions on a pathway system. I don’t think the level matters if you can track that this person’s presence denied a place on the team or a place at the competition to someone else.

With Lia Thomas, it’s not only denying the silver medalist gold or fourth place a bronze; it’s also the fact that there are only so many places at that meet. For some, that was their ambition and they weren’t able to realize it.

Now, a lot of sports are played outside that pathway. Say your local tennis club has a social league. There is little there to stand in the way of inclusion. Although I’m mindful that there may be a women’s league where it does matter to them.

We can try to accommodate trans women when the stakes are not high, provided that two requirements are met: One is that there’s no disruption to the selection/meritocracy pathway; and the second key point is that women must be okay with that inclusion, particularly if there are safety considerations, but even if it’s just a fairness consideration.

That’s where it gets tricky, because there are bigoted people in the world. Unfortunately, sometimes it’s difficult to tell whether people are using scientific arguments to prop up bigotry or whether they are genuine.
 

Joanna Harper has said that if you support inclusion, you have to be okay with trans women winning.

Winning the summer tennis league is not winning in the same sense as winning at the NCAA.

But the moment winning means selection and performance pathways, then I think we have to draw a line. The moment participation disrupts the natural order in sports, then it’s a problem.

In World Rugby, we proposed open competitions lower in contact to deal with the safety concerns. That was rejected by the trans community because they felt it was othering – that we were trying to squeeze them off to the side.

If you offered me one of two choices: no participation, or inclusion and they have to be able to win, I’d go for the former.
 

 

How did you get involved in this topic?

I got involved because I testified in the Caster Semenya case at the Court of Arbitration for Sport.

That is not a transgender issue; it’s a difference of sex development issue. What it has in common is the question of what to do with male-bodied biological advantage in sports.

When World Rugby joined the Olympic Games, we followed the IOC transgender policy. In 2019, it became apparent from the latest research that male advantage isn’t removed by testosterone suppression. We decided to delete the previous policy and make a new one.
 

The latest IOC policy is kind of no policy; it leaves it up to the governing bodies for each sport.

The one element of progress in what the IOC released, and it really is the only one, is that they’ve recognized that sports have to manage three imperatives: fairness, inclusion, and safety.

The 2015 IOC document says something like “sports should strive to be as inclusive as possible, but the overriding objective remains to guarantee a fair competition.” Basically, fair competition was nonnegotiable and must be guaranteed.

Of course, that policy allowed for testosterone suppression, and you’d have a difficult time convincing a physiologist that lowering testosterone guarantees fair competition.

Where there is merit in the current policy is that it’s clear that sports like rugby, boxing, taekwondo, and judo have a different equation with respect to safety, fairness, and inclusion than sports like equestrian, shooting, and archery. I think that’s wise to acknowledge.

However, the IOC policy doesn’t do anything to lead. In fact, what they said was extraordinary: There should be no presumption of advantage. If there’s no presumption of advantage for male-bodied athletes, then why do they persist with two categories? If there’s no presumption of advantage for trans women, are they saying that gender identity removes the advantage? We know that’s not true. We know that at the very least, you should presume that there is some advantage. How you manage it is up to you, but you can’t say that it’s not there.
 

This is a hostile debate. Have you ever thought: Maybe I’ll just shut up and stick to other sports topics?

Big time. The Lia Thomas case brought out a lot of vitriol. From about 2017, the situation we had with Ms. Thomas was predictable. The problem is that 95% of the world didn’t know this was happening and were taken by surprise.

The number of people who have opinions has exploded. A lot wade in without much thought. I’ve seen people question Lia Thomas’s motives. Presumably, Lia Thomas is trans, identifies as a woman, and therefore thinks she belongs in women’s sports. But I’ve seen people saying she only wants to swim in women’s sports because she knows she’ll win. And that’s not the worst of it. I’ve seen people saying Lia Thomas is only identifying as a woman so she can get into women’s changing rooms.

I don’t see how that helps the conversation. It just polarizes to the point that neither side is listening to the other. Before it was the trans community that wasn’t interested in talking about the idea of advantage, fairness, and safety. Their position is that trans women are women; how do you even have a discussion when they’ve got that dogma as their foundation?

Now, unfortunately, on the other side, we’re seeing unnecessary offensive tactics. For example, I’ve referred to Lia Thomas as “she.” I’ll have people shouting at me for using “she.” You’ve got to pick your battles, and that’s not the one you want to be fighting, in my opinion.

A version of this article first appeared on Medscape.com.