Thread by @KirstiMiller30

Research finds trans women that undergo HRT their hemoglobin levels reduce to the normal F range within just 3–4 months & their Vo2 Max in 4-6 months & their muscle reduces mass 9.4 % in just the first 12ms of T deprivation.

https://twitter.com/kirstimiller30/status/1469204724180160512?s=21

Men are stronger than women due to the relative % of muscle vs. fat, and to power that extra muscle they have more oxygenating cells in the blood... both of which are controlled by hormones - not set during puberty.

There is ZERO research evidence of any biological advantages that would IMPEDE the fairness of trans women competing in any elite women’s sport not even Q angle, lung size, bone density & height, muscle mass, strength, endurance or testosterone levels!

Many studies in this area often use cis men as a reference group to trans women. This is highly flawed, as the typical pre-medical transition woman does not exhibit a body that is comparable to that of a cis man.

These flawed assumptions lead to an under reporting of the effect of testosterone suppression in individuals who were assigned male (none athletes) at birth due to a lower starting muscle mass pre-suppression.

Table 1 below illustrates the average height and weight of trans women participants.

Table 2 Height and weight among cis men and cis women (as presented by Harper, 2020).

The data in Tables 1 and 2 show that pre-testosterone suppression trans women cannot be compared to cis men (while closer to cis men for height, weight is lower and seemingly closer to cis women’s).

Trans women as a population have lower BMI than cis women, and therefore lower height adjusted muscle mass than cis women.

Research finds trans women have bone density lower than natal males, natal females, and FtMs, as a group, BEFORE hormone therapy even begins (sample=711, FAR larger than any of the studies Hilton uses)

asbmr.onlinelibrary.wiley.com/doi/full/10.10…

This is important to note as the majority of studies including. Wiik et al and @WorldRugby examining the effect of testosterone suppression in trans women assume that their starting muscle mass is equivalent to cis men. @RogerPielkeJr @DrAdaCheungAU @DrRyanStorr @seaningle

This finding is also supported by cross section studies measuring the baseline differences between pre-testosterone suppression trans women and cis men. These data clearly show that it is erroneous to assume trans women and cis men are synonymous.

Therefore, in order to examine if any adv exists, we must compare the observed reduction in LBM, CSA and strength with height adjusted cis women and not cis men. This is largely not done in the available literature and leads to misleading conclusions of any retained advantage.

An equivalent facetious argument using height would be that the average child grows 70cm by the age of 18 but the average adolescent only grows 30cm at the age of 18, therefore children who have turned 18 have an unfair advantage due to a 40cm height gap.

Table 3 below shows the relative change between pre-suppression non athlete transwomen and post-suppression transwomen, both of whom have lower LBM, CSA and strength than cis-men.

Neither of these options provides a robust framework by which trans athletes’ performance should be assessed.

Without making appropriate adjustments in height and LBM, and without consideration of other performance advantages or disadvantages, the standard set for fairness would require trans women to underperform or be at a demonstratable disadvantage compared to cis women.

There must therefore be critical examination of the few existing studies that examine the direct impact on trans athlete’s performance as a result of testosterone suppression through either Hormone Replacement Therapy (HRT) or surgical gonad removal.

Most studies including Wiik et al, Hilton et al 2020 & @WorldRugby use Erroneous Information and Flawed Measurement Techniques.

These studies allude to performance advantages which are derived from testosterone exposure during key periods of development (i.e. puberty).

However, while these advantages - such as Q angle, lung size and bone density - are commonly thought to confer a performance advantage, there is no support in the literature that these factors confer any such advantage.

The Q angle - defined as the angle between a line drawn from the anterior superior iliac spine (ASIS) to the center of the Patella & a 2nd line from the Patella to the Tibial Tubercle & has often been assumed to play a role in generating power during acceleration &

efficiency of a running stride. However, under investigation there appears to be no performance advantage conferred in sport as a result of Q angle, further increased risk of injury attributed to Q angle can be entirely removed with training (Bruton et al., 2013;

Kernozek & Greer, 1993; Thomas et al., 1998; Nguyen et al., 2009; Sigward & Powers, 2006; Hertel & Braham, 2004).

Arguments based on bone density derive from systematically racist arguments first introduced in the 1920’s while attempting to ignore this background, black women and women of color have higher bone density than white men (Leslie, 2012).

Additionally as discussed above Research finds trans women have bone density lower than natal males, natal females, and FtMs, as a group, BEFORE hormone therapy even begins (sample=711, FAR larger than any of the studies Hilton uses)

asbmr.onlinelibrary.wiley.com/doi/full/10.10…

This clearly removes any potential for bone density to be considered a factor for unfairness in trans athletes. @RogerPielkeJr @seaningle @CydZeigler @TraceyLeeHolmes

Lung size is also commonly attributed as performance enhancing; however, it is never adjusted for height (taller individuals naturally have larger lungs on average) nor is it a good predictor of sport performance (Hopkins et al., 2018; Degens et al., 2019; Åstrand et al., 1964).

To clarify, on the topic of Maximum Breathing Capacity (MBC) “MBC is not likely to be an adequate physiological measure of the competence of the respiratory system in strenuous work and should be regarded rather as the biomechanical limit of the possibilities of the

ventilatory apparatus” (Breslav et al., 2000, pp. 485) and “After differences in lung volume are accounted for there is no intrinsic sex difference in the DLco, Vc, or Dm response to exercise ...

together, these data suggest that the pulmonary capillary blood volume response is proportional to lung size & is adequate to meet individual oxygen demand during exercise” (Bouwsema et al., 2017).

As such, lung size should not be used as a proxy for an individual's endurance capacity.

The latest research from Loughborough University in the U.K, published recently in the British Journal of Sports Medicine, looks at how the protein in our red blood cells that helps oxygen flow to our muscles for aerobic activity is affected by hormone replacement therapy.

Loughborough University’s findings show the hemoglobin level in transgender women falls to levels in line with cisgender women in the space just three to four months on average.

That is a huge change and it affects all endurance sports, and, in fact, any sport where you were being active for more than a few minutes. The hemoglobin level in your blood is important for taking up and using oxygen in your muscle.

It's the single most important reason that men outperform women in endurance events, because of the higher hemoglobin level.

It has been long noted that hemoglobin levels are closely tied to testosterone levels. When trans women lower their T levels to female levels, which happens almost universally when trans women under undergo medical transition, trans women move from

male levels of hemoglobin to female levels of hemoglobin. All that a together clearly removes any potential for bone lung capacity to be considered a factor for unfairness in trans athletes.

Beyond using misleading physiological traits, studies often use measurement techniques with poor accuracy and generalizability. Hand grip strength, for example, is often used for broad population level analysis, however handgrip strength should not be used as a proxy

for overall muscle strength (Yeung et al., 2018). In fact, due to ease of gripping the testing device, grip strength is largely correlated with hand size and therefore height (Alahmari et al., 2019).

Additionally, some studies do not include cis female control groups, which leads to poor accuracy and confounding attributions.

One example of this can be found in Wiik et al., (2020)’s study, in which the authors’ results ignore that cis women are also able to maintain or increase muscle mass while undergoing intense training cycles and that untrained females have a high capacity to build muscle mass,

particularly upper body strength (Roberts et al., 2020). Without a cis women comparison group, the results are massively misleading.

Moreover, many strength studies ignore that untrained individuals can quickly gain strength independent of muscle gain due to neural mechanisms (Chilibeck et al., 1997).

Moreover, many strength studies ignore that untrained individuals can quickly gain strength independent of muscle gain due to neural mechanisms (Chilibeck et al., 1997).

This ability to quickly gain muscle is in addition to higher performance on strength tests that can be attributed to comfort and familiarity with testing devices after repeated use.

As such, sedentary adults should not be used as a proxy for elite athletes when determining the ability to gain or retain muscle mass. Additional studies need to be made which appropriately control for these factors.

This requires studies to use appropriate control groups of height adjusted elite athletes & measure muscle and strength from appropriate tests which can be used as a proxy for overall strength & adequately control for artifacts such as training familiarity &

neural adaptations which give inaccurate measurement results.

Testosterone Effects on the Body. The general effects of testosterone on the body presented below must be further explored and ought be taken as guideposts rather than definitive.

Many methodologies in these research projects relied on treating serum testosterone levels and doping as similar functions, but current science demonstrates that doping is not the same as serum testosterone levels.

Inpresent these effects below, however, to share a sense of the possible guideposts to explore and on which additional research is based.

Table 4 summarizes the evidence on the generalized effects of testosterone on
the body.

It is important to note that for some of these traits there is that effectively and directly links them to athletic performance, and some of these references are notably older. Many of these claims come as a result of directly comparing

male and female sports performance, which has many notable flaws (as previously discussed).

Many of the claims about the benefits of testosterone in athletics have gone unchecked since they are often taken for granted in biological research papers and do not include citations.

Many researchers have taken for granted without sufficient evidence - that there are links to performance to explore, despite the ‘taken-for-granted', unsubstantiated, and refuted natures of this claim.

Effects of Testosterone Suppression for Trans Women.

As we are examining elite athletes & the maximum potential of the human body, we must examine the extreme test case someone like myself a former dual international male athlete.

I was an individual whose body was indistinguishable from an elite male athlete prior to testosterone suppression/estradiol supplementation and hypothesize what performance effects an elite individual would undergo as a result of HRT.

I and @CarolineLayt and Hannah Mouncey are the type of case scenario that policy is considering, as many trans women have lower muscular mass & strength than elite female athletes.

In order to make this determination, we must look at the available evidence while considering if the research is making effective comparisons through:

1.Comparing trained athlete cohorts.

2.Including body composition (fat-free mass %)–affected by testosterone.

3. Using height-matched controlgroups.

4.Comparing participation rates between populations.

Athletes should be looked at holistically, that they are a sum of all their advantages and disadvantages which result in performance. Additional possible metrics of performance could include direct LBM (Lean Body Mass) measurement through a dexa MRI scan.

It is important to note that no one metric can be used to predict performance. Further, the metrics reported do not account for the population level-differences that exist between trans women and cis men.

Therefore, we must look at the absolute height adjusted values and compare these values with values produced by cis women. In this, athletes should be looked at holistically, that they are a sum of all their advantages and disadvantages which results in performance.

Existing studies often do not continuously measure muscle mass during the 12 months of testosterone suppression, nor do they continue after the 12 months suppression to see if any persisting trend exists.

This is significant for policy creation as a 12-month testosterone suppression requirement may be excessive to achieve practical performance equivalence.

This also holds true for studies examining hemoglobin and red blood cell count where levels normalize within 4 months. As a result, it is impossible to say exactly when any potential individual athletes

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