Testosterone & Beyond: The Male Advantage

Description

Does testosterone suppression remove the male sports performance advantage? Adapted from a literature review by developmental biologist Dr. Emma Hilton (@FondOfBeetles) and clinical physiologist Dr. Tommy Lundberg (@TLexercise), we present a review of sex differences in athletic ability and 11 long-term studies to evaluate whether testosterone suppression removes the male sports performance advantage achieved at puberty.

Sources

Main source:

[1] Hilton, E., Lundberg, T. (2020). Transgender women in the female category of sport--Perspectives on testosterone suppression and performance advantage. Sports Medicine.

Sex difference sources:

[2] Lee DH, Keum N, Hu FB et al. (2017). Development and validation of anthropometric prediction equations for lean body mass, fat mass and percent fat in adults using the National Health and Nutrition Examination Survey (NHANES) 1999-2006. Br J Nutr., 118(10):858–866.

[3] Janssen I, Heymsfield SB, Wang ZM, Ross R. (2000). Skeletal muscle mass and distribution in 468 men and women aged 18-88 yr. J Appl Physiol. 89(1):81–88.

[4] Bohannon RW, Wang YC, Yen SC, Grogan KA. (2019). Handgrip strength: A comparison of values obtained from the NHANES and NIH Toolbox studies. Am J Occup Ther. 73(2).

[5] Neder JA, Nery LE, Shinzato GT, Andrade MS, Peres C, Silva AC. (1999). Reference values for concentric knee isokinetic strength and power in nonathletic men and women from 20 to 80 years old. J Orthop Sports Phys Ther. 29(2):116–126.

[6] Jantz LM, Jantz RL. (1999). Secular change in long bone length and proportion in the United States, 1800-1970. Am J Phys Anthropol. 110(1):57–67.

[7] Lepley AS, Joseph MF, Daigle NR et al. (2018). Sex differences in mechanical properties of the achilles tendon: Longitudinal response to repetitive loading exercise. J Strength Cond Res. 32(11):3070–3079.

[8] Pate RR, Kriska A. (1984). Physiological Basis of the Sex Difference in Cardiorespiratory Endurance. Sport Med An Int J Appl Med Sci Sport Exerc. 1(2):87–89.

[9] Best SA, Okada Y, Galbreath MM et al. (2014). Age and sex differences in muscle sympathetic nerve activity in relation to haemodynamics, blood volume and left ventricular size. Exp Physiol. 99(6):839–848.

[10] Tong E, Murphy WG, Kinsella A et al. (2010). Capillary and venous haemoglobin levels in blood donors: a 42-month study of 36 258 paired samples. Vox Sang. 98(4):547–553.

Longitudinal studies:

[11] Gooren LJG, Bunck MCM. (2004). Transsexuals and competitive sports. Eur J Endocrinol. 151(4):425–9.

[12] Haraldsen IR, Haug E, Falch J, Egeland T, Opjordsmoen S. (2007). Cross-sex pattern of bone mineral density in early onset gender identity disorder. Horm Behav. 52(3):334– 343.

[13] Mueller A, Zollver H, Kronawitter D et al. (2011). Body composition and bone mineral density in male-to-female transsexuals during cross-sex hormone therapy using gonadotrophin-releasing hormone agonist. Exp Clin Endocrinol Diabetes. 119(2):95–100.

[14] Wierckx K, Van Caenegem E, Schreiner T et al. (2014). Cross-sex hormone therapy in trans persons is safe and effective at short-time follow-up: results from the European network for the investigation of gender incongruence. J Sex Med. 11(8):1999– 2011.

[15] Van Caenegem E, Wierckx K, Taes Y et al. (2015). Preservation of volumetric bone density and geometry in trans women during cross-sex hormonal therapy: a prospective observational study. Osteoporos Int. 26(1):35–47.

[16] Gava G, Cerpolini S, Martelli V, Battista G, Seracchioli R, Meriggiola MC. (2016). Cyproterone acetate vs leuprolide acetate in combination with transdermal oestradiol in transwomen: a comparison of safety and effectiveness. Clin Endocrinol (Oxf). 85(2):239–246.

[17] Auer MK, Ebert T, Pietzner M et al. (2018). Effects of Sex Hormone Treatment on the Metabolic Syndrome in Transgender Individuals: Focus on Metabolic Cytokines. J Clin Endocrinol Metab. 103(2):790–802.

[18] Klaver M, De Blok CJM, Wiepjes CM et al. (2018). Changes in regional body fat, lean body mass and body shape in trans persons using cross-sex hormonal therapy: Results from a multicenter prospective study. Eur J Endocrinol. 178(2):163–171.

[19] Fighera TM, da Silva E, Lindenau JDR, Spritzer PM. (2018). Impact of cross-sex hormone therapy on bone mineral density and body composition in transwomen. Clin Endocrinol (Oxf). 88(6):856-862.

[20] Scharff M, Wiepjes CM, Klaver M, Schreiner T, T’Sjoen G, Heijer M Den. (2019). Change in grip strength in trans people and its association with lean body mass and bone density. Endocr Connect. 8(7):1020–1028.

[21] Wiik A, Lundberg TR, Rullman E et al. (2020). Muscle Strength, Size, and Composition Following 12 Months of Gender-affirming Treatment in Transgender Individuals. J Clin Endocrinol Metab. 105(3):dgz247.

Transcript

The following video was adapted from a literature review by developmental biologist Dr. Emma Hilton and clinical physiologist Dr. Tommy Lundberg.

Competitive sport is divided on the basis of sex due to differences in male and female athletic ability. Such sex differences begin in the womb and develop further in response to hormones during puberty. As both sexes mature, males exhibit physical performance advantages over females. This is why we separate sports by sex. However, this separation has excluded transgender woman from female sports.

To solve this, the International Olympic Committee determined criteria by which a transgender woman could be eligible to compete in the female category. This criteria required testosterone levels to be suppressed to 10 nanomoles per litre for at least 12 months before competition. Despite the regulation, a major question remained unanswered: does this testosterone suppression remove the male performance advantage? We're going to answer that by exploring three questions:

What are the biological differences between males and females and how do they relate to sports performance?

How big is the sports performance gap between males and females?

How does testosterone suppression affect the answer to question 1, and thus, question 2?

We'll start with question 1: What are the biological differences between males and females?

Compared to untrained and moderately trained females, equivalent males exhibit 45% more lean body mass and 30% less fat. In muscle mass, 33% more lower body and 40% more upper body. In muscle strength, 57% more grip strength and 54% more knee extension peak torque. In anthropometry and bone geometry, 9.4% greater femur length, 12% greater humerus length, and 14.6% radius length. In tendon properties, 83% more force and 41% more stiffness. In terms of the amount of oxygen one can utilize during intense exercise, known as VO2 max, males are able to utilize between 25 and 50% more oxygen. In respiratory function, males exhibit 48% greater pulmonary ventilation, allowing more air into and out of the lungs. Finally, in cardiovascular function, males exhibit up to a 43% greater volume of blood ejected from each ventricle and an 11% higher hemoglobin concentration, allowing for a more efficient oxygenation of muscles.

In all, compared to females, males have higher lean mass, less fat, more muscle mass, higher strength, longer bones, a narrower pelvis, stronger tendons, higher lung capacity, and higher cardiovascular output. This means that males are better at sports. But, how much better?

This brings us to question 2: How big is the sports performance gap between males and females? If we set the female performance level at 100%, and compare to males, we can see that males have a competitive advantage starting at 10-13% in activities like rowing, swimming, and track running; 16-22% in field jumping, tennis serve, golf driver speed, handball shot, and pole vaulting; 29-34% in cricket, volleyball serve, golf long drive, and weightlifting; and a more than 50% advantage in baseball pitch and field hockey. The more upper body strength is required in a sport, the larger the male performance advantage.

Take weightlifting for example. Males lift 30% heavier than females, not in different weight categories, but in the same weight category. This means that even if you equalize male and female body weight, which often serves to make height approximately equal too, the males will be able to lift 30% more.

In all, the biological performance advantage for males in competitive sports ranges from 10-50% depending on the sport.

Now that we've answered questions 1 and 2, we can evaluate question 3: How does testosterone suppression affect biological differences, and therefore, the performance advantages? If the male performance advantage ranges from 10-50%, testosterone suppression must reduce this advantage by 10-50% as well. To answer this, we present 11 long term studies of muscle and strength changes in adult transgender women undergoing testosterone suppression.

Study 1 shows, after three years of testosterone being suppressed to female levels, a total muscle area loss of…12%. This was the first study to measure changes in muscle size, and no study since has seen the same amount of change. This loss of 12% is as high as it gets. Remember, at baseline, males have over 30% more muscle than females. A 12% loss isn't enough to equalize this baseline difference, and the authors of this study conclude that while males lose muscle size, they retain significantly more muscle than females. The conclusion can be visualized in this graph.

Study 2 shows, after a year of T suppression, barely detectable changes after 1 year.

Study 3: after two years, a loss of 7% muscle strength.

Study 4: a loss of 5%.

Study 5: a loss of 9%.

Study 6: a loss of 2%.

Study 7: a loss of 3%.

Study 8: a loss of 6%.

Study 9: a loss of 4%.

Study 10: a loss of 4%.

And finally, study 11: a total muscle strength loss of 5%.

What's left is the math. The male sports performance advantage ranges from 10-50%, and testosterone suppression reduces the muscle mass and strength that accounts for a majority of this sports advantage by only 2-12%. For a concrete example, consider the strength-based sport of weightlifting. If the original male advantage in weightlifting is 30%, then testosterone suppression reduces this advantage by 10% at the high end and 5-7% on the average. This leaves a more than 20% advantage in weightlifting even after testosterone suppression.

As Hilton and Lundberg write, "The data presented here demonstrates that the male physical performance advantage over females, attributed to superior anthropometric and muscle mass/strength parameters achieved at puberty, is not removed by the current regimen of testosterone suppression... Rather, it appears that the male performance advantage is largely retained by transgender women and thus remains substantial."

From the data presented, we recommend the International Olympic Committee review their policies for eligibility:

"If those policies are purported to promote fairness, inclusion and safety of biologically female athletes, this review compels sporting organizations to reassess their policies regarding inclusion of transgender women."

I'm Zach, for the Paradox Institute.

END

© 2020 Zachary A. Elliott, All Rights Reserved.