The argument that sports categories be divided according to current testosterone completely misunderstands the biological function of testosterone.
It assumes symmetry - that is, if T causes X, removing T will remove X.

That is intuitive and sometimes true, but not necessarily so. Any developmental biologist will tell you that the effects of a molecule on a target system are not always reversible.
Target tissues can be induced to develop in ways that are irreversible or heavily resistant to change.

Once such a developmental change is set, removing the trigger makes no difference.
Some targets of T *are* dependent on current levels of T. For example, the amount of hemoglobin (Hb; oxygen-carrying cells) in the blood is very sensitive to T, and reduction of T very quickly and reliably leads to reduction in Hb.
Some targets of T will, once triggered and set, will be insensitive to future loss of T, most obviously skeletal shape.

And some targets of T may be somewhat sensitive to loss of T, notably muscle mass.
But even within muscles, some effects of T are likely irreversible and some may be very sensitive. There’s no evidence that T changes alter fibre type (broadly, explosive v endurance types) but it seems to alter the size of fibres.
But some of these and other findings will come from studies adding T to a low T environment, and to go back to the start, we cannot assume symmetry of effect.

In terms of % change, females who supplement T gain more muscle than males suppressing T lose.
And I haven’t touched on long term effects of T on capacity to train, resistance to injury etc. ‘Muscle memory’ needs greater study.

If anyone has insight here, feel free to add thoughts!
These concepts are often referred to as a ‘legacy effect’, and that’s a phrase one often comes across in discussions of sporting policies regarding transwomen.

In short, the effects of T are, in many physiological contexts, likely to be enduring and/or permanent.
I should credit @jasonkoop for shared ponderings on assumed symmetry.
Another dev bio angle to understanding mechanisms of activity.

A molecule can induce different effects at different concentrations, but not always in an immediately understandable pattern. That is, one might observe increasing Effect X with increasing T *to a point*.
Over a threshold T, we might then see Effect X plateau (become less responsive to increasing T).

Alternatively, we might see no Effect X until a threshold of T is reached, and a 100% response thereafter. Essentially, a certain amount of T acts as switch.
Testosterone acts through receptors, and receptor availability will be a ‘limiting step’ to how much T one can process.

To grossly simplify, if you have enough T to trigger all your receptors, extra T won’t make a difference.
But we know that T receptor numbers are themselves responsive to amount of T (your body adapts) and we know that doping works in males (although is it more effective in those with lower T?). It’s complicated.

The above simplification was only to illustrate a principle.
Regardless, I have a vague idea that a linear/plateau T mechanism might underpin the premise that male performance doesn’t appear to be linked to T once a threshold has been reached but females perhaps do see improved performance with elevated T (weightlifting/PCOS).

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More from @FondOfBeetles

19 Feb
@GaryLineker Hi Gary. People have tried to get me sacked/suspended for questioning the fairness of inclusion of transwomen in female sports (see pinned academic review for more info).
@GaryLineker Fortunately, my institute has been supportive of my voice.

The same institute whose students no platformed tireless feminist activist and advocate Julie Bindel @bindelj from a debate, ironically, about free speech.

I’ve been lucky. Many other women less so.
@GaryLineker @bindelj In the course of my research, I’ve met some fantastic national and international female athletes, current and retired, who are terrified of even raising questions about current sports policies.
Read 6 tweets
19 Feb
Add the NBA to that list.

If, as we are told, sporting ability is a random mix of innate talent and acquired skills mapped onto a continuum of bodies, it’s deeply puzzling that very few females have ever possessed a winning combination.
If, as we are told, sporting success can hinge on a favourable socioeconomic climate, why have privileged females never made the grade?
If, as we are told, sporting success can hinge on a favourable cultural environment (or outright nepotism), why have privileged females never made the grade?
Read 4 tweets
18 Feb
@RobynRyle 1. Socioeconomic and similar barriers are not ‘unfair’, they are examples of an ‘unjust society’. We can try to address that in sports as a general good. So broadening access by providing programmes, funding for equipment and coaching, and so on.
@RobynRyle 2. You say: it's deemed unfair for a 126 pound featherweight to compete against a 200-plus pound heavyweight.

Does use of ‘deemed’ mean you don’t actually agree such a match would be unfair?
@RobynRyle 3. On genetic advantages, you cite cyclists/runners with extraordinary muscular metabolism, basketballers/swimmers with skeletal syndromes and baseballers with superior vision.
Read 13 tweets
15 Feb
Will the @ONS please confirm that if trans people mark their legal/selfID sex (Q3) and state a corresponding gender identity (Q27), they have no way of ascertaining which people are trans.

And thus, no way of:
1. Estimating true numbers within the population.
2. Understanding population patterns of trans identity.
3. Understanding whether trans people are in stable relationships, and/or are parents.
4. Knowing whether trans people have stable jobs, and whether they earn similarly to peers.
5. Knowing whether they live in stable accommodation.
6. Knowing how educational attainment maps to peers.
7. Understanding rates of health issues in trans people.
8. Knowing whether they can afford and/or manage to heat their house.
Read 5 tweets
11 Feb
Emma Hilton: "Sex denialists have captured existing journals. We are dealing with a new religion"…
What do Creationists and Sex Denialists have in common?

1. The framing of human classifications, whether it’s species or sex, as “arbitrary”.

2. The distortion of science and the development of sciencey language to create a veneer of academic rigour.
3. The Gish Gallop: throw any old argument, regardless of its validity, in quick succession at your opponent, force frustrated submission.

‘What about intersex? What about this article? What about an XY person with a uterus? What about the fa’afafine? But clownfish.’
Read 4 tweets
2 Feb
@Hogshead3Au @BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 OK.

Fitness data from over 85k AUS children aged 9–17 yrs showed that, compared with 9 yr females, 9 yr males were 9.8% faster in sprints, 16.6% faster over 1 mile, could jump 9.5% further, could complete 33% more push-ups in 30 s and had 13.8% stronger grip.
@Hogshead3Au @BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 Here is my full description of that data.


1.6km timed run (CV endurance)

The *best* 17 yr old girls are matched by *average* 17 yr old boys, and beaten, by some measure, by the best 9 yr old boys.

@Hogshead3Au @BARBARABULL11 @boysvswomen @cbrennansports @Martina @devarona64 Male advantage of a similar magnitude was detected in a study of Greek children, where, compared with 6-year-old females, 6-year-old males completed 16.6% more shuttle runs in a given time and could jump 9.7% further from a standing position.
Read 25 tweets

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