Thread by @KirstiMiller30

The Hilton & Lundberg article is an argumentative essay, but it has been incorrectly interpreted by the deer's in the headlights as a scientific review, with severe impacts on trans women’s participation in elite sport @RogerPielkeJr @DrRyanStorr

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https://twitter.com/KirstiMiller30/status/1494079886545551362

Methodological Concerns Regarding Hilton & Lundberg (2020) Transgender Women in the Female Category of Sport: Perspectives on Testosterone Suppression and Performance Advantage.

This is a condensed detailed analysis of the methodology and integrity of Hilton & Lundberg (2020), especially important because of the impact of this single paper on sport policies regarding trans women.

The paper has several notable weaknesses which are never addressed, which are categorized and listed below. It is a reasonable conclusion that this paper draws from a prior ideological position seeking to discredit and exclude transgender athletes and misuses the available

literature to justify this position. In other words, this is an argumentative paper presented as a scientifically rigorous review.

Author bias:
The primary author, Dr. Emma Hilton, does not have a background of sports medicine, and none of her prior publication credits are on topic with sports performance, transgender health or any kind of exercise.

Co-author Dr. Tommy Lundberg does have a background in sports science. Unfamiliarity with trans women as a population: Use of terminology ‘Biological Males’
Use of cis-men population comparators
Drawing false conclusions:

Hilton & Lundberg do not appropriately review the available literature and draw false comparisons between men and women athletes. As a specific example, the authors state “This Olympic weightlifting analysis reveals key differences between male and female strength capacity.

It shows that, even after adjustment for mass, biological males are significantly stronger (30%) than females”. This is a disingenuous statement as:

1. Sport (historical and cultural context aside) is segregated by gender because men produce higher strength in terms of total mass. Because women have a higher percentage of body fat mass in comparison with lean body mass,

we segregate some sports in respect to both total mass and gender because it allows for an approximate comparison of total lean body mass.

2. In sports without weight categories, height and weight do not meet the threshold to be considered characteristics involved with “intolerable unfairness.” Advantages due to being taller or heavier in these sports (e.g., basketball, volleyball, rugby)

are not currently considered “unfair”. The average NBA player, for example, is nearly 10 inches taller than the average man and 40 pounds heavier.

3. Male and female muscle is the same strength when comparing equivalent cross section/size (Costill et al., 1976; Schantz et al., 1983).

4. Much of the increased strength of cis-men compared to cis-women can be explained by height differences. When adjusting for height and fat free mass, this relative difference disappears (Castro et al., 1995; Harms, Cooper, & Tanaka, 2011).

5. Lean body mass increases with height for both men and women (Forbes, 1974).

6. It is unsafe for cis-women to attempt to achieve cis-male levels of fat (Nazem &
Akcerman, 2012). This affects speed and endurance activities due to having excess non- performant mass.

The assumptions employed and conclusion posed by the authors is therefore not supported by evidence found in the literature. The authors systematically use adjustment for mass instead of fat-free mass which leads to significant errors when comparing population groups.

This argument is of key importance as trans women athletes undergoing HRT increase their estradiol, affecting total body fat percentage, and also significantly reduces testosterone, reducing muscle mass, red blood cell count and other factors important for athletic performance.

(The authors appear to be aware of the distinction between total mass and fat free mass as shortly after they state, “even when expressed relative to fat-free weight, VO2(max) is 12-15% higher in males than in females”.)

What is needed to have effective comparisons is:

1. Comparing trained athlete cohorts.

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

3. Height-matched control groups. Omissions and errors in Table 4:
In Table 4 of their article, Hilton & Lundberg (2020) summarize their findings from available literature, categorizing differences between men’s and women’s athletic performance.

This table has many errors, some of which demonstrate the authors’ disregard for scientific objectivity. In addition, there were omissions of contradictory data from this table. These errors and omissions are listed below.

1. For their reference group the authors employed compares“average cis women”to cis-men, without adjustment for height or weight. This is significant since cis men are, as a population, taller than cis women, and we would expect to see similar results in comparing any taller

group to a shorter group (for example, comparing five foot four inches tall cis women to five foot ten inches tall cis women).

2.Authors state that“grip a trength provides an excellent proxy measurement general strength in a broad population”. However, this is distinctly incorrect (Yeung et al., 2018).

Grip strength is largely correlated with hand size rather than strength due to gripping testing device easier (Alahmari et al., 2019).

3.The authors cite a study whereby testosterone-suppressed untrained transgender women see an increase of lean mass (4% leg and 2% overall) after an intense 8 week training cycle. However, in doing so, they omit Roberts, Nuckols, & Krieger’s (2020) findings

that untrained females also show high capacity to build muscle mass especially in upper body strength. The authors also do not show the relative strength compared to trained female competitors - a more appropriate comparison group - nor do they include that their control group

without testosterone suppression gained significantly more mass and a 400% greater increase to isometric strength. The authors additionally omit that trans women participants failed to gain any noticeable gains to isometric strength.

Yet despite these observations, the authors conclude “endogenous testosterone is of paramount importance for the muscular adaptation to strength training.”

4.They claim the 12months hormone suppression as determined by the IOC (2015 policy) insufficient by using data where hormone suppression was present for less than two months.

5.Pelvic width comparison is used as a measure,but studies show that pelvic width difference, including q angle, does not have any benefit for athletic ability (such as moving or jumping); gait differences, lift ability and risk to injury also are not meaningful as a result of

q angle (Bruton, O’Dwyer & Adams, 2013; Hertel, Dorfman & Braham, 2004; Kernozek & Greer, 1993; Thomas, Corcos & Hasan, 1998; Nguyen et al., 2009; Sigawrd & Powers, 2006).

This includes a study by Sigward & Powers which was referenced by the authors as leading to increased injury in athletics, but the original paper states “No differences in kinematics were found.”

6. Bone density was used extensively as evidence of the advantage trans women retain. The claims were unsubstantiated, with no citations to demonstrate bone density as a performance enhancer.

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…

7. The authors argue that larger lung size is a retained advantage .However, they do not adjust for height and ignore studies which have demonstrated that lung size is not a good predictor for sport performance.

The differences are due to respiratory muscles enhancement, not lung size (Degens et al., 2019; Hopkins et al., 2018).

These findings are misrepresented in the table with the conclusion that “Respiratory function, pulmonary ventilation (maximal)” are significant, when they are not.

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, Segizbaeva, & Isaev, 2000).

Or that it is not a limiter for exercise “After differences in lung volume are acconted for there is no intrinsic sex difference in the DLco, Vc, or Dm response to exercise” and “together, these data suggest that the pulmonary capillary blood volume response is

proportional to lung size and is adequate to meet individual oxygen demand during exercise” (Bouwsema, Tedjasaputra & Stickland, 2017).

The limiting factor in endurance sport however is oxygen carrying capacity of blood (red blood cell count which is affected by hormones dramatically) and heart muscle (Fomin et al., 2012; Åstrand et al., 1964).

8.Haemoglobin (red blood cell count)is drastically affected by HRT,falling im cis women’s range after 3-4 months Loughborough 2020 & 6 months (SoRelle et al., 2019). This is largely ignored by Hilton & Lundberg.

bjsm.bmj.com/content/55/15/…

9.Hilton & Lundberg misrepresent lean body mass of trans-women throughout Table 4 by assuming baseline strength levels are comparable to cis-men.

But Van Caenegem et al. (2015) - whom they cite elsewhere in the paper - show that trans women as a population start with far lower muscle mass.

This means that the reductions recorded in Table 4 are mostly “on top of” the already reduced population level in comparison to cis-men.

10. Table 4 reports absolute values for Wiik et al (2020) instead of the published height adjusted levels.

11. Hilton & Lundberg exclude the female reference values from Fighera et al (2018) in Table 4, presumably as Fighera et al.’s (2018) conclusion was that appendicular lean mass was similar among trans and reference women, and lower in trans women

when compared to cis men - a point which contradicts Hilton & Lundberg’s argument.

The authors do not report on advantages that women have over men, which are salient to their argument and conclusion:

1Endurance is higher and recovery is a quicker in women than in men(due to higher proportion of type 1 muscle fibers; Haizlip, Harrison & Leinwand, 2015).

This performance advantage is important, since individual variation is higher than the variation between genders, and individuals with high level of type 1 muscle fibers gravitate towards endurance sport.

2.The authors suggest that men outperform women on items such as flexibility, which is not supported in literature (Rene’, 1984).

3.Women have increased glycogen sparing fat oxidation during endurance exercise (Tarnopolsky, 2008).

4.Women experience higher perfusion,ECV and MBV at stress(Nickanderetal., 2020).

5. At a population level untrained ciswomen outperform men with balance(Torres, Reis & Abreu, 2014).

Each of these pieces supports the claim that the Hilton & Lundberg article is an argumentative essay, but it has been incorrectly interpreted as a scientific review, with severe impacts on trans women’s participation in elite sport.
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