Thread by @Scienceofsport

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)