There have been two academic reviews of musculoskeletal changes in transwomen suppressing testosterone.

Both conclude that loss of muscle mass and strength is small, and that strength advantage over females is retained.

Citations to follow.
The first review is Hilton and Lundberg, 2020, published in Sports Medicine.

The second review is Harper et al., 2021, published in the British Journal of Sports Medicine.…
Both of these academic reviews are peer-reviewed and published in high-quality, high-impact sports medicine journals.
The conclusions are here.

Hilton and Lundberg (first screenshot)

Harper et al. (second screenshot)
I am the first author of Hilton and Lundberg, and I have spent a lot of time researching the fairness issues arising from inclusion of transwomen in female sports.

Joanna Harper is the first author of Harper et al. She is a transwomen athlete who focuses on inclusion.
That scientists coming to the issue from two different angles reach the same conclusions about a given dataset should foster confidence in the scientific process and the conclusions reached by both groups.

Please make sure to use both citations when disseminating.
Note: this citation has been updated to 2021, presumably to reflect appearance in print, rather than online access.

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More from @FondOfBeetles

6 Mar
Full contact ‘collision’ sports are those where deliberate, forceful contact against an opponent are an integral part of gameplay.

The aim of contact play may be to defend or retrieve possession of, say, a ball (e.g. rugby) or to win by disabling your opponent (e.g. boxing).
Sports federations regulating full contact sports, where contact cannot be eliminated without changing the face of the sport, have a *special duty* to minimise the potential for injury during gameplay.

See Jon Pike @runthinkwrite on this.…
This is evident in policies to, for example, limit contact to specific moves or regions of the body, to regulate how contact is enacted, and the wearing of protective gear to minimise injury potential during contact.
Read 18 tweets
3 Mar
Systematic review from Joanna Harper on muscular changes in transwomen.

‘These findings suggest that strength may be well preserved in transwomen during the first 3 years of hormone therapy.’…
Her conclusions mirror those of a recent review by me and Tommy Lundberg @tlexercise

‘These longitudinal data comprise a clear pattern of very modest to negligible changes in muscle mass and strength in transgender women suppressing testosterone for at least 12 months.’
Link to our review here:…
Read 6 tweets
27 Feb
Over the past month or so, I have been testing the hypothesis ‘Doing X causes Y to happen’.

So I have been ‘Doing X’ a repeated number of times and scoring how often it ‘causes Y to happen’.
If I don’t do X, Y rarely happens, but there is a background rate of Y happening in the absence of X.

If I do X, Y almost always happens, but there have been a few times where it didn’t happen.
Not doing X = Y happens in 4/60 tests.

Doing X = Y happens in 57/60 tests.

It’s clear to me (and statistically) that ‘Doing X’ does indeed correlate with ‘Y happening’, and I have a well-known mechanism to assert not just correlation but cause.
Read 8 tweets
23 Feb
Excellent piece here from Jon Pike @runthinkwrite

I’ve often struggled to articulate the fallacious ‘Range Argument’. Jon makes a good job of it.
‘According to the range argument, however, lots of male-born people, including transwomen, are in the range of females. This means they are not necessarily faster or stronger than the fastest or strongest female athletes just because they were born male.’
‘So, if transwomen are “in the range” of female athletes, then their inclusion in sport is still fair, right?
Read 4 tweets
21 Feb
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.
Read 15 tweets
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

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