Home Body Building Supplements Transgender Women In Competitive Sports – T NATION+ – COMMUNITY

Transgender Women In Competitive Sports – T NATION+ – COMMUNITY

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Transgender Women In Competitive Sports – T NATION+ – COMMUNITY


No Politics, Just Science

Are trans women and biological women really suitable athletic competitors? Here’s the actual science.


Various factors, including genetics, training, nutrition, and psychological factors, influence athletic performance. However, one key factor to have a significant impact on athletic performance is sex.

Men and women have physiological differences that affect their athletic abilities, such as muscle mass, bone density, and hormone levels. These differences have led to a performance gap between male and female athletes in most sports and have also raised questions about the performance advantages of transgender women over biological women.

I was prompted to write this article by the recent legal battle between USA Powerlifting and a transgender athlete, as outlined in this excerpt:

“USA Powerlifting lost a two-year court battle after a judge ruled that it had discriminated against transgender athlete JayCee Cooper by banning her from competing in women’s competitions.” (1)

The court ruled that the federation must revise its policy and allow transgender women (biological males) to compete against biological women.

What frustrates me is the widespread reluctance to discuss uncomfortable subjects. And make no mistake, this is an uncomfortable subject. I’m certainly not setting out to be malicious or hurt anyone’s feelings. But meaningful and necessary discussions inherently have the potential to offend someone. This is a contentious issue that isn’t going anywhere, and the best way to proceed is to promote more open dialog, not prevent it. Without public discourse, there can be no understanding and, by extension, no resolution.

Therefore, I want to clarify what this article is and what it is not. This is not a discussion about politics or social issues. My objective is simply to convey the available evidence regarding differences in athletic performance between biological and transgender women and how this affects fairness in competition.

I will not touch on transgender men in competitive sports since, outside of the use of banned substances (which admittedly does go against WADA regulations and is an issue in and of itself), the data does not currently support that through pharmacology they could close this gap in most sporting events.

At the time of this writing, the evidence shows that transgender women maintain a significant physiological advantage over biological women. This advantage is not removed through the IOC guidelines of one year of HRT and testosterone levels of no more than 10 nmol/L.

International Olympic Committee Guidelines

Because the IOC is the organization many other organizations look to for guidance, it’s important to first review their standards to contextualize subsequent information. In the 2021 Olympic Charter, it states that the mission and role of the IOC are…

“…to encourage and support the promotion of ethics and good governance in sport as well as education of youth through sport and to dedicate its efforts to ensuring that, in sport, the spirit of fair play prevails and violence is banned…” (2).

In the “IOC Framework Fairness Inclusion Non-Discrimination 2021,” they highlight the following:

Let’s focus on declaration 5.2. In most instances, this is sound criteria since it puts the burden of evidence on the organization in an attempt to thwart discrimination. However, in this context, it fails to acknowledge a few key points.

First, the IOC already separates male and female categories due to universally acknowledged physiological advantages enjoyed by males. The assumption that this physiological gap would disappear through HRT lacks scientific and intellectual rigor.

Since we know that a physiological performance gap exists between male and female competitors, the prudent thing to do would be to wait until we have better evidence prior to making sweeping decisions about competition against biological females.

This would not preclude them from competition and instead would permit the establishment of a transgender category to promote inclusivity in sport.

The International Olympic Committee established criteria by which transgender women are allowed to compete in sporting events against biological women. I want to highlight a few key points below from the consensus meeting:

“Those who transition from male to female are eligible to compete in the female category under the following conditions:

2.1. The athlete has declared that her gender identity is female. The declaration cannot be changed, for sporting purposes, for a minimum of four years.

2.2. The athlete must demonstrate that her total testosterone level in serum has been below 10 nmol/L for at least 12 months prior to her first competition (with the requirement for any longer period to be based on a confidential case-by-case evaluation, considering whether or not 12 months is a sufficient length of time to minimize any advantage in women’s competition).

2.3. The athlete’s total testosterone level in serum must remain below 10 nmol/L throughout the period of desired eligibility to compete in the female category.

2.4. Compliance with these conditions may be monitored by testing. In the event of non-compliance, the athlete’s eligibility for female competition will be suspended for 12 months.” (3)

At this time, the IOC has failed to put forth a scientific rationale to justify the guideline of testosterone remaining below 10 nmol/L, and the 12-month timeline assigned. The common assumption is that suppressed testosterone removes the performance advantage sufficiently to ensure fairness.

However, this is overly reductionist, and, as we’ll discuss later, it’s largely incorrect. Additionally, under Section 1. Transgender Guidelines, it states:

“Nothing in these guidelines is intended to undermine in any way the requirement to comply with the World Anti-Doping Code and the WADA International Standards.”

But this initiative isn’t possible since transgender women are required to take exogenous substances currently banned by WADA (4). Therefore, within the IOC’s own criteria, competition between transgender women and biological women goes against their prerequisites for inclusion. That being said, there’s no reason why a separate division cannot be made to promote inclusivity.

Sexual Dimorphism in Male and Female Athletes

Sexual dimorphism refers to the differences in physical characteristics between males and females, which arise due to the different roles that males and females play in reproduction. These differences are seen in a wide range of traits, including body size, muscle mass, and bone density. (5). Regarding athletic performance, sexual dimorphism is a major factor in the performance gap between male and female athletes.

Men, on average, have larger muscle mass and greater bone density than women, which gives them an advantage in sports that require strength and power, such as powerlifting and weightlifting. Men also have higher testosterone levels, a key hormone for muscle growth and repair.

A paper by Haizlip et al. found “a prevalence of slower type-I and -IIA fibers in females compared with males that parallels the lower contractile velocity in females compared with males. The prevalence of the slower-twitch fibers is also a benefit to female performance in that the slower oxidative fibers and higher oxidative capacity allow for increased endurance and recovery, highlighting the sex-based differences in response to fatigue or muscle tetanus.” (26)

Research also shows that male powerlifters have significantly greater muscle mass and bone density than female powerlifters, which translates to greater strength and power output. Similarly, male weightlifters have higher levels of testosterone and greater muscle cross-sectional area than female weightlifters, which leads to more weight lifted in competitions.

Note that strength and power requirements may vary between sporting events, and, in some sports, the performance gap between male and female athletes is smaller or non-existent. For example, in endurance sports such as distance running and swimming, women may outperform men due to their greater aerobic capacity and lower body mass.

Interestingly enough, prior to puberty in age-matched sporting events, it’s often claimed there isn’t a meaningful difference in physical performance. But pre-puberty performance differences are not negligible across the board and have various influences, such as genetic factors or activation of the hypothalamic-pituitary-gonadal axis or other sex-specific differences in muscle (33) (34). After puberty, we see a clear and substantial male advantage in physical performance (6). One such difference is that, after puberty, men produce 20 times the testosterone compared to women and have roughly 15 times the circulating testosterone concentration compared to women of all ages (7) (8) (9) (10).

Previously I mentioned that HRT did not sufficiently reduce the physiological advantage, yet here I’m saying hormones have a monumental impact. This sounds like a contradiction to some, so here’s a parallel example.

Imagine a natural athlete decides to start using performance-enhancing drugs. After twenty years of consistent use, this individual decides to stop, wait the predetermined time specified by the federation, and compete as a natural lifter.

At the time of the competition, this athlete is technically natural and has hormone values within the specified normal range. However, the athlete has enjoyed two decades of training, recovering, and adapting as an enhanced athlete. Most, if not all, of the physiological adaptations have already been realized and now offer a significant advantage over the athletes who are competing as lifetime naturals.

Similarly, during and after puberty, males experience chronic adaptations such as larger and stronger bones, increased muscle mass, increased strength, higher circulating hemoglobin, and even potential behavioral differences, which confer a substantial performance advantage over female athletes. Below is a data set summarizing testosterone levels using mass spectrometry-based methods to measure serum testosterone in healthy men and women. The healthy reference range for men ages 18-40 is 7.7-29.4 nmol/L (11).

The healthy reference range for menstruating women under 40 is 0-1.7 nmol/L. If we refer back to the IOC guidelines for an upper limit of testosterone set at 10 nmol/L, this is nearly six times the upper limit for the average healthy woman. I want to highlight this to again point out the seemingly arbitrary nature of this standard established by the IOC.

Note that only when circulating testosterone is consistently elevated well beyond the normal female range, the effects would mimic puberty in young boys. As you can see in the table above, most women never reach that level chronically to enjoy these additional physiological benefits.

These biological sex differences lead to increased muscle fiber size, number of muscle fibers, increased satellite cell proliferation and myonuclei, as well as increased motor neuron size.

A paper by Handlesman et al. reported:

“There is experimental evidence that testosterone increases skeletal muscle myostatin expression, mitochondrial biogenesis, myoglobin expression, and IGF- content, which may augment energetic and power generation of skeletal muscular activity.” (11) (12) (13) (14) (15) (16).

These physiological adaptations contribute substantially to increased power output, strength, and speed – critical in various sports.

Hemoglobin is the protein in red blood cells responsible for delivering oxygen to the tissues (17). Increased hemoglobin concentration improves oxygen transport and enhances aerobic energy expenditure. Research shows a strong relationship between hemoglobin concentrations and aerobic capacity (18). Thus, increased hemoglobin concentration can increase time to exhaustion and enhance recovery between bouts of physical exertion.

Bone size and density can also vary significantly between males and females. A 2018 paper noted:

“Bone grows in length due to epiphyseal chondral growth plates that provide cartilage, forming the matrix for lengthening of long bone, which is terminated by an estrogen-dependent mechanism that depends on aromatization of testosterone to estradiol.”(11).

These androgenic effects on bone are likely irreversible, which further demonstrates why HRT is insufficient to eliminate the performance gap between males and females.

From a 2018 paper, Nature Versus Nurture: Have Performance Gaps Between Men and Women Reached an Asymptote?:

“One might assume performance gaps would be greatest in events requiring explosive muscular power/sprinting ability, but we found this only in swimming, not running. The greater gap in sprint swimming (13%) vs. running (10-11%) suggests anthropometric advantages associated with the start and/or upper body power in swimming contribute an additional ~2% beyond advantages for men assumed during sprint running.” (19).

As mentioned previously, HRT cannot reverse the anthropometric advantages male athletes maintain over female competitors in certain sports. By extension, post-pubertal advantages would persist for transgender females, such as stature and lever length.

A 2010 paper by Thibault et al. described the performance gap that exists between male and female competitors, as seen below (20):

  1. Sex is a major factor influencing best performances and world records.
  2. A stabilization of the gender gap in world records is observed after 1983, at a mean difference of 10.0% ± 2.94 between men and women for all events.
  3. The gender gap ranges from 5.5% (800-m freestyle, swimming) to 36.8% (weightlifting).
  4. The top ten performers’ analysis reveals a similar gender gap trend, with a stabilization in 1982 at 11.7%.
  5. Results suggest that women will not run, jump, swim, or ride as fast as men.

These findings are mirrored by the larger body of evidence which demonstrates the physiological differences in performance between male and female athletes post-puberty.

Biological Basis for Performance Advantages in Transgender Females

The performance differences between male and female athletes are seen in various sports, including swimming, sprinting, powerlifting, and weightlifting. There’s a long history of sex-based segregation in sporting events to preserve fairness and protect female competitors.

According to World Athletics (personal communication, July 2019), roughly 10,000 males have personal best times faster than the current Olympic 100m female champion. This is just one of the many examples of performance disparities between male and female competitors (21).

Here’s a graph from a 2021 research paper depicting the male advantage in sporting events:

On average, men maintain a 30-50% performance advantage over female competitors. In some instances, such as punching, this difference may be as high as 162% (36).

In this particular study, note that the male who generated the least power produced greater power than the female with the highest power output. Although the performance differences in prepubescent children don’t appear to be the deciding factor in winning, the research found male youth athletes ages 9-17 performed better in most athletic events such as sprinting, jumping, strength, endurance, and grip strength (21).

A 2005 paper by Eiberg et al. looked at maximum oxygen uptake (Vo(2)max) and physical activity in children 6-7 years of age and found “Vo(2)max is higher in boys than girls (+11%), even when related to body mass (+8%) and LBM (+2%).” (22)

A 1997 study by Bohannon found high degrees of sexual dimorphism, leading to significant differences in upper-body musculoskeletal performance and characteristics (23).

Physiological characteristics such as increased total blood volume, contractility, capillary density, mitochondrial content, etc. play a role in oxygen uptake (42). These adaptations are not eliminated through HRT, which can confer a performance advantage to a transgender female over a biological female, depending on the demands of the sport.

A 2009 paper by Lassek et al. found, on average, men have roughly 61% more muscle mass than women associated with elevated levels of testosterone (24). Researchers also found that males have 41% greater fat-free body mass, 75% more muscle mass in the arms, roughly 90% greater upper-body strength than females, and 65% more strength in the legs (24).

According to a paper by Morris et al., “Males also have 20-25% greater bone mineral content in the bones of the forelimbs, a trait required for larger muscle attachment areas and greater ability to withstand larger forces produced by larger muscles.” (25)

This difference in muscle mass distribution can also present a distinct advantage to male athletes in sports that rely heavily on upper-body strength and power. Evidence also suggests sexual dimorphism in muscle mass and performance has a long evolutionary basis in humans.

A 2020 paper by Hilton et al. found:

“The smallest performance gaps were seen in rowing, swimming, and running (11-13%), with low variation across individual events within each of those categories. The performance gap increases to an average of 16% in track cycling, with higher variation across events (from 9% in the 4000 m team pursuit to 24% in the flying 500 m time trial).

The average performance gap is 18% in jumping events (long jump, high jump, and triple jump). Performance differences larger than 20% are generally present when considering sports and activities that involve extensive upper-body contributions.

The gap between the fastest recorded tennis serve is 20%, while the gaps between the fastest recorded baseball pitches and field hockey drag flicks exceed 50%.

Sports performance relies to some degree on the magnitude, speed, and repeatability of force application and, with respect to the speed of force production (power), vertical jump performance is, on average, 33% greater in elite men than women, with differences ranging from 27.8% for endurance sports to more than 40% for precision and combat sports”(21) (35).

We see a similar performance disparity in Olympic weightlifting data between equivalent male-female and top/open weight categories. As you can see in the table below, when weight categories and experience are matched, male athletes maintain a significant performance advantage against female competitors.

Between 1998 and 2018, the 69kg weight class was part of male and female competitions. According to the available data, the performance gap between men and women in Olympic weightlifting is 31-37%.

This gap increases when looking at the top male and female powerlifters. Open Powerlifting is an independent organization that accurately archives the world’s powerlifting data. At the time of this writing, Dan Bell is the number one open powerlifter on the planet. His combined total between the squat, bench press, and deadlift is 2606.9 pounds (27). April Mathis is the number one open female powerlifter in the world. Her combined total between the squat, bench press, and deadlift is 1703 pounds (28).

The disparity in performance between their total is 903.9 pounds or roughly 65%. These are the best open powerlifters, which means their weight isn’t matched. However, if we were to compare John Hack, who competes in the 198 class with a total of 2270.7 pounds, to April Mathis, who competes in the +198 class, we still see a significant discrepancy of 567.7 pounds or 33.33% (29).

Females also have lower bone density than males, which may make them more susceptible to stress fractures and other bone-related injuries (30) (31). Due to the physiological differences between males and females, they’re also at different risks of injury.

Females are more prone to ACL injuries, possibly due to their wider pelvis and increased Q-angle, which may lead to greater valgus stress on the knee joint during athletic movements. On the other hand, males are more prone to injuries such as groin pulls and hernias due to their larger inguinal canal. These differences and more can confer a competitive advantage depending on the sporting activity (33).

A 2006 paper found:

“In general, females experienced increased frontal plane moments and decreased sagittal plane moments during early deceleration. These differences are suggestive of an at-risk pattern in that frontal plane support of the knee is afforded primarily by passive structures (including the anterior cruciate ligament). Furthermore, increased quadriceps activity and smaller net flexor moments may suggest less sagittal plane protection (i.e., increased tendency towards anterior tibial translation).” (38)

Anthropometric measurements such as height, weight, and body fat percentage also differ significantly between males and females. Males are generally taller and heavier than females and have a lower percentage of body fat. These differences can have a significant impact on athletic performance.

For example, taller athletes tend to have a longer stride length, which can be beneficial in sports such as sprinting and jumping. Muscle cross-sectional area is another area where males have an advantage over females. Studies show that males have a greater muscle cross-sectional area, particularly in the upper body, which can lead to increased strength and power output (32).

As highlighted by Lundberg and colleagues:

“This Olympic weightlifting analysis reveals, even after adjustment for mass, biological males are significantly stronger (30%) than females, and that females who are 60% heavier than males do not overcome these strength deficits.” (21)

Transgender women appear to retain most, if not all, of their bone mineral density even after 24 months of testosterone suppression (34). A paper by Ruetsche and colleagues found:

“We conclude that in M-F transsexuals, BMD (bone mineral density) is preserved over a median of 12.5 years under antiandrogen and estrogen combination therapy, while in F-M transsexuals BMD is preserved or, at sites rich in cortical bone, is increased to normal male levels under a median of 7.6 years of androgen treatment in this cross-sectional study. IGF-1 could play a role in the mediation of the effect of androgens on bone in F-M transsexuals.” (35)

These findings were supported by a 2017 paper by Singh-Ospina et al., which found no increase in bone fracture rate over 12 months of testosterone suppression therapy (36).

A paper titled “Bone Safety During the First Ten Years of Gender-Affirming Hormonal Treatment in Transwomen and Transmen” found that hormone therapy did not have a negative effect on bone mineral density and monitoring wasn’t necessary unless they presented with risk factors before beginning treatment (37).

Estrogen improves muscle proteostasis and increases sinew collagen content, which can have a positive effect on muscle mass (44). The training status of a transgender woman is also important because a higher training age is associated with better retention of muscle mass and, therefore, will maintain a greater advantage over untrained transgender athletes.

A 2020 paper found:

“Given the maintenance of BMD and the lack of a plausible biological mechanism by which testosterone suppression might affect skeletal measurements such as bone length and hip width, we conclude that height and skeletal parameters remain unaltered in transgender women, and that sporting advantage conferred by skeletal size and bone density would be retained despite testosterone reductions compliant with the IOC’s current guidelines.” (21)

Additionally, a reduction in muscle mass does not necessarily result in an equivocal loss of muscular strength (39). Also, athletes undergoing testosterone suppression can continue to gain muscle and strength when engaged in resistance training (40).

One paper found:

“Despite low levels of serum testosterone, the goserelin group demonstrated a significant increase in lean body mass, and two subjects showed extreme increases in lean body mass compared with their fellow subjects. The respective subjects gained 3.9 and 2.8 kg of lean body mass compared with the mean gain of 1.3 ± 1.2 kg for the goserelin group. Several mechanisms may be responsible for this observation. First, the adrenal glands secrete ∼10% of the total testosterone production and are not suppressed by GnRH analogs. The very low level of endogenous testosterone in the goserelin group, however, may still have an effect on the adaptation to strength training. Second, recent studies have revealed that several other mediators may be involved in the adaptation to strength training: the androgen receptors, IGF-IEa, IGF-IEb, IGF-IEc, myogenin, myoD, myostatin, etc. These mechanisms may not be influenced by suppression of endogenous testosterone.” (40)

Essentially, the subjects had testosterone levels suppressed to female levels of 2 nmol/L and still saw increases in total lean body mass by +2% and lean mass in the legs by +4% accompanied by a significant increase in strength in the 10RM leg press and bench press by +32% and 17%. This demonstrates that effective resistance training during HRT can mitigate muscle loss and actually enhance muscle and strength beyond baseline.

A paper by Hanson et al. looked at androgen deprivation therapy in relationship to resistance training. Researchers found:

“Strength training significantly increased total body muscle mass (2.7%), thigh muscle volume (6.4%), power (17%), and strength (28%). There were significant increases in functional performance (20%), muscle endurance (110%), and QoL scores (7%) and decreases in fatigue perception (38%). Improved muscle function was associated with higher functional performance (R (2) = 0.54) and lower fatigue perception (R (2) = 0.37), and both were associated with improved QoL (R (2) = 0.45), whereas fatigue perception tended to be associated with muscle endurance (R (2) = 0.37).” (42)

This demonstrates the impact of proper training on enhancing athletic performance during androgen deprivation.

Many claim testosterone suppression will eliminate the performance advantage of biological males. However, this data demonstrates that transgender athletes may retain most of their physical performance and may actually continue to see performance enhancement beyond baseline despite undergoing HRT.

To summarize the aggregate body of literature, here’s an excerpt from a 2021 paper by Hilton et al.:

“These data overwhelmingly confirm that testosterone-driven puberty, as the driving force of development of male secondary sex characteristics, underpins sporting advantages that are so large no female could reasonably hope to succeed without sex segregation in most sporting competitions.” (21)

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