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Jan 21 23 tweets 4 min read
I want to try to explain something about testosterone and performance, since it has become the ‘fixation’ and the ‘the fix’ for inclusion policies for both DSD and trans athletes. So here’s a thread to ‘debunk’ and explain why T level, per se, is not quite the right place to look
First, testosterone is clearly a significant driver of the biological, and hence performance, differences between M and F. Nobody should dispute that (yet they do - more on this later). What sport has done, understandably, is to try to capitalise on this “cause-effect” concept to
…resolve the tension that exists between self ID and entry into the closed women’s category. Recall that women’s sport exists to exclude people who do not experience androgenisation during puberty and development. So sport said “If we can reverse the T levels, we can achieve...
…a balance of priorities”. As we now know, this is untrue - there is too much asymmetry, and once androgenisation has occurred, some changes are irreversible (skeleton), some only partly reversible, and only a few can be “undone”. The result is retained advantage, which is why
…simply lowering T does not allow a balance between fairness, safety & inclusion (despite persistent claims that it can, including in the recent FIMS and IF position statement). However, the preoccupation with T persists, and even in the absence of the above, is still misplaced
The reason is that a snapshot of T levels (which is what we do when we sample every athlete at the World Champs) is not actually the thing that is responsible for the problem. The T has already done the work - it happens in the womb, primarily at puberty, and into adulthood, but
…it is not in and of itself, the problem. That’s why it is a red herring to get sucked into debates about overlap in T levels between men and women. It’s irrelevant to look at the level of T on Day X and compare athletes and try to deduce which has the performance advantage.
All that matters is the “movie” up to that point, not a “snapshot” at that point, if this makes sense? A “snapshot” approach also invites disingenuous and dishonest portrayals of the actual importance of T, where people will say stupid things like “T has no performance effects"
They say this because when you look at a sample of elite males, or elite females, and try to correlate T with performance, you get very weak relationships. The Olympic 100m final finishing positions are in no way predicted by the who has highest T and lowest T. For many reasons
You’ll also hear things like “Usain Bolt has higher T levels than teen-age girls, but many of them run 800m faster than him. Therefore, T is not that important for performance” (yep, this one actually happened). The point is this - it’s not the level of T, it’s the job done by it
So the key is whether androgenisation occurred, and T levels at any time at life are an excellent guide to whether this binary outcome exists. It’s a “yes, it has” or “no, it hasn’t”, predicted remarkably well by whether T is high or low, but not by the actual level.
The same is true for things like VO2max in marathon runners, or height in the NBA. Nobody in their right minds would dispute that these characteristics matter for performance. But if you only looked at NBA players, height would be a poor predictor of NBA success, and if you only
…measured VO2max in elite marathon runners, you’d be led to believe there is no predictive power. So what’s going on? Well, the simplest way to put it is that “Everyone in that group already has it, so of course it makes less of a difference”. It’s like this: You need that thing
…to get through the door, but once you’re inside, a host of other factors are what makes the difference. The attribute is your “ticket to the dance”, but it doesn’t determine your ability to dance. There’a room for tall, there’s a room for high VO2 maxes, a room for Fast-twitch
…and of course, there’s an adjacent room for people who don’t have that attribute. Think of mass - there’s a room for heavyweights, a room for middleweights etc. And OK, in the case of mass, we can change rooms (within reason, anyway). A room for disability level. A room for age
Now run this same hypothetical, but for biological sex, male & female. What’s the “ticket” to get in? It’s not the level of testosterone. That’s the fallacy. It’s the presence (binary) of testosterone during life PLUS the ability to use it, such that androgenisation has occurred
So that gets you through the door, into the appropriate ‘dance’. But once there, everyone has the ticket - they’re either androgenised (male room) or not (female room). And the door between them must remain locked. Trying now to measure T levels, and lower them, is irrelevant
Anyway, hope the analogy works. We create “spaces” for sport, into which we allow only certain people, and then recognise that once in that space, all the other things make the difference. That’s the whole point! It’s why teenage girls can beat Bolt in an 800m. It’s not the T!
This is also why it’s so stupid to keep saying “But TW are not winning everything”. Point is there’s a group in one room (male, androgenised) & a group in another (female, unandrogenized), and then everything else plays out. Some people in the male room are very unathletic
…and so if they climb through the window to enter the female room, they’ll still be outperform by exceptional women who have all those attributes that are meant to determine the result. That says as much about the women’s exceptionalism as it does the man’s relative mediocrity!
Which is the same phenomenon in play when a heavyweight sneaks into a middleweight dance and loses, or able-bodied athletes race the paralympics and failsto win. That failure doesn’t invalidate the essential difference between rooms. You have to compare “like” vs “like” for that
That “like” for “like” matchup is where we see thousands, possibly hundreds of 1000s, of males, with performance capabilities greater than the best female. That specific corner of the room (elite athlete, scholarship-seeking athletes) reveals how significant M vs F biology is
Anyway, enough of the room analogy. We can enjoy the dance, but we have to sure people have the right tickets to the right place! (end)

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More from @Scienceofsport

Jan 20
Michael Phelps, whose biological traits fall within norms for the men he swam against, recognises advantages of trans swimmers who retain many biological male traits

Remember. Advantages DO matter if they cross category boundaries. Sport does not exist to celebrate testosterone
Just like boxing does not exist to reward size/mass Paralympics do not exist to reward the absence of disability, and youth sport does not exist to reward maturation. We separate groups into categories/classes so that we can reward what is meaningful, unconfounded by what is not
This is, of course, the reason that we can celebrate Phelps for exceptional performances. And why we celebrate Ledecky for the same reason, even though if directly matched, only one would be rewarded. Hence, we ‘remove’ the effect of testosterone with a category that excludes it
Read 4 tweets
Dec 28, 2021
Interesting thing about this argument (which tries to turn the desire to protect women’s sport into some kind of disparagement of women) is the irony that it’s only a CLEAR separation of the sexes that allows us to celebrate athletic achievements of women. It’s only when we (1/
…blur the lines and try to deny biological realities that we invite direct comparisons between male and female performance (which, in a further irony, is the premise for the necessary separation!) that women’s sport is undermined. For instance, nobody should have an issue (2/)
…celebrating a Wimbledon title for Williams as equal to that or Federer, or the 100m gold to Thompson as equal to that of Bolt. They exist so distinct from one another that they carry the same weight, one is not lesser. So categories in fact PROTECT the merits of a performance
Read 4 tweets
Nov 19, 2021
Our latest podcast is out, and in it, we discuss the IOC’s transgender guidelines. Here’s a short video segment, “First reactions”. You can listen to the full episode here (or wherever you get your pods!)…
The missing truth: aside from the deception of saying “no presumed advantage”, the missing piece is a simple statement of biological fact that trans women retain advantages even after T suppression (let alone without it). This omission can only be due to political influence.
This omission is compounded by two poor errors. First is framing it as an “individual athlete” assessment. That we can treat a group or person as a subset of the group from which they arise, and assess fairness based on their ability/characteristics. This unravels sport’s meaning
Read 6 tweets
Oct 1, 2021
Rather than write a long thread, here’s a podcast or an instagram video with my thoughts on yesterday’s Sports Council transgender guidelines, what they say, imply, confirm, and mean for the future:…

Or the insta, if preferred:…
One thing I discuss in the podcast is the appalling issue raised by the report, which is fear of recrimination that has been created for those (particularly women) who speak out with concerns about fairness & safety. That they’re backed by scientific evidence has been irrelevant.
The report makes clear how threatened people have felt, how lacking confidence to express legitimate thoughts on this issue. So when people say “We consulted widely”, I’d urge caution, because unless people are protected, they’re not being honest, because they’re scared. And with
Read 11 tweets
Sep 23, 2021
So, @WorldRugby has released guidelines for contact load during training in elite rugby. You can read the full document and a summary infographic here:… I wanted to share brief thoughts on the process & principles behind the guidelines, so here goes...
@WorldRugby First, the need. Research has found that training injury risk (in terms of incidence, or injury risk per 1000 hours) is relatively low, BUT…because training volume is so high, a large number of injuries happen in training. And full contact training has the highest risk. So the
@WorldRugby …need is created by the risk. Plus, cumulative load (including training) is clearly important. Therefore load management principles, just like you’d apply to any training programme, are crucial to reduce injury risk. That’s summarised in the first of the infographics:
Read 18 tweets
Aug 18, 2021
@SUE_K47 Yes I saw it. And it’s important that the research be recognised as flawed (in some respects, faulty) & limited. But I don’t see this as the bombshell Roger is claiming. the DSD policy has two components - the evidence around specific events (which is what the paper did so badly
@SUE_K47 …and second, the principle regarding androgenisation in males, not females, that necessitates a separate competition. I think everyone at CAS already knew this about the research - it was discussed at great length there. From the flaws to the theoretical problems. The IAAF even
@SUE_K47 …conceded, at CAS, that there were issues with the research, and nobody claimed it was “conclusive proof” of advantage. So this correction doesn’t actually change much about what was heard by CAS - both sides debated the paper pretty intensely. So I don’t think it’s a ‘bombshell
Read 10 tweets

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