Emma Hilton Profile picture
Dec 8, 2020 8 tweets 2 min read Read on X
I am delighted to announce that Hilton and Lundberg, 2020 is now published! @TLexercise

‘Transgender Women in the Female Category of Sport: Perspectives on Testosterone Suppression and Performance Advantage’

link.springer.com/article/10.100… Image
Anyone wishing to spot changes from our pre-print:

1. We included a section on pre-pubertal differences (that is, even young boys outperform young girls, thus the performance gap is not solely down to pubertal T).
2. We extended our analysis of CV capacity changes and potential impact on endurance performance (although we had acknowledged a likely effect, we have drilled deeper into mechanism).
3. We have *significantly* extended our discussion of impact on athlete transwomen and the mitigating effects of exercise (that is, moderate training can mitigate or even reverse muscle/strength loss during T suppression).
The remaining differences are minor, and represent no significant change from the pre-print.
👀 Image
Come on people, I want to break the 1000 mark. Image

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More from @FondOfBeetles

Feb 6
I am starting to pull out details of this "meta" review that says trans-identifying males don't have advantage over women in sports.

I need a sanity check, because I'm only at Figure 1 and already there's an issue.

bjsm.bmj.com/content/early/…
So this is Figure 1A: fat mass (kg).

Alvares 2025, n=7, fat mass is higher in females as both absolute and relative values. This is logged as "favours cisgender", which is kinda odd because high fat mass isn't usually considered favourable for sports, but whatever.

TIMS: 16.2 kg (24%). F: 19.5 kg (26%).Image
But Ceolin 2024 is also logged as "favours cisgender" when their values are:

TIM: 18.2 kg (24%). F: 15 kg (25%). Their n = 47.
Read 7 tweets
Feb 4
What an insane bunch of cherry-picked metrics, cobbled together to try and argue that trans-identifying males should be in female sport.

bjsm.bmj.com/content/early/…
There are little-to-no controls for physical fitness in the individual studies.

Yet they conclude: “transgender women do not exhibit significant differences in upper-body strength, lower-body strength or maximal oxygen consumption relative to cisgender women after 1–3 years of GAHT.”

You haven’t controlled for fitness!!!
Their "performance" data. Can you see one study that really sticks out as an outlier? Image
Read 10 tweets
Nov 4, 2025
The claim that won't die: trans-identifying males are "underpowered" and therefore "disadvantaged" in sport.

"One can imagine a large car with a small engine competing against a small car with a small engine, and that summarizes the playing field." Joanna Harper, Huff Post, 2016.

"You have a bigger body, and you have a smaller engine to move that vehicle around." Yannis Pitsiladis, BBC, 2019.

"giving trans women the disadvantage of having to power larger skeletal frames with reduced strength and aerobic capacity." Jamie Agapoff, 2025.
What happens when a trans-identifying male suppresses testosterone?

They lose a bit of muscle mass.
Their haemoglobin drops to female-typical levels.

The claim that won't die rests on the idea that trans-identifying males retain their skeletal frame and most of their muscle mass, but become unable to move it around a sports fields, rendering them "disadvantaged".
The words "underpowered" and therefore "disadvantaged" are carefully chosen, and typically leave the reader to infer that this means "underpowered" and therefore "disadvantaged" compared to females.

So it's fair to have them in female sport, right?

Wrong.
Read 10 tweets
Sep 26, 2025
Shocking from @nrarmour here.

“Most of the studies used to ban transgender women so far are based on the performances of cisgender men, which scientists have argued is not an appropriate comparison.”

That’s me, @TLexercise and others.

“Others” including the ones moaning about not having their say. You know, the say they took for granted. The one they didn’t tell @nrarmour about.

Ever read their archery paper?Image
Image
“Other studies have compared the performances of transgender women athletes with sedentary cisgender women, also argued as an inappropriate comparison.”

NGL, bit flummoxed here. Any ideas?

If you want inappropriate comparisons, try the Fat Bloke Study. Written by the scientists moaning about being excluded.

Nancy @nrarmour links to it. Fails to care that the reason why trans-identifying males can’t jump as high as the female comparators is that they are 20kg heavier, carrying way more fat, and are far less fit.
For disclosure, I have not been part of this IOC working group.
Read 4 tweets
Sep 22, 2025
So the actual paper is fine. I’ve only skimmed, but it looks at gene expression between male and female humans and mice, to answer questions about the evolution of genes associated (or not) with sex. Image
The authors - who admit in peer review that these graphs exaggerate overlap - suggest in discussion that if one were to look at gene expression in, say, the skin from an individual within the overlap, you could not identify whether that individual was male or female.
It’s a high-level take on a more simple principle in this debate: overlapping height, and is a 5’8” individual male or female?

The authors use the same analogy in the introduction.
Read 9 tweets
Sep 20, 2025
World Athletics reveals the scale of the issue of male athletes with DSDs competing in the female category in international track and field.

I am not surprised at the number (I suspect the true figure is higher).

Nobody working in this area will be surprised at the number.
Even the ones who said it was “just a few”. They knew the scale.

Even the ones who said “you’re racist” as they fervently argued that black women are fundamentally different to white women. They knew the scale.
Also a poorly kept “secret” is that the majority of this cohort are 5ARD, where males can appear to be female at birth but have male-pattern athletic advantage.

This is the DSD that Caster Semenya has.
Read 6 tweets

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