Transgender women outpace cisgender women in athletic tests after 1 year on hormones
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Pretreatment differences in athletic performance for transgender women in the U.S. Air Force vs. cisgender women continue more than 1 year after starting feminizing therapy, according to findings published in the British Journal of Sports Medicine.
“Transgender women retain an advantage in upper body strength (push-ups and sit-ups) over female controls for 1 to 2 years after starting gender-affirming hormones,” Timothy Roberts, MD, MPH, in the division of adolescent medicine at Children's Mercy Kansas City, Missouri, told Healio. “Transgender women retain an advantage in endurance (1.5-mile run) over female controls for over 2 years after starting gender-affirming hormones. Athletic performance among transgender men matches or exceeds athletic performance for male controls after 1 year on testosterone.”
Roberts and colleagues conducted a retrospective review of medical records and fitness tests for transgender men and women who filed a request to begin gender transition or continue testosterone or estrogen while serving in the U.S. Air Force. Each individual’s age, service branch, military rank, gender assigned at birth, date testosterone or estrogen started, type of testosterone or estrogen used, and days between starting testosterone or estrogen and the first serum hormone level in the adult range were obtained.
Researchers evaluated data from the Air Force’s annual physical fitness assessment, which includes number of push-ups performed in 1 minute, number of sit-ups performed in 1 minute, and time required to run 1.5 miles. Pretreatment fitness was assessed using each participant’s most recent score from each event before starting testosterone or estrogen. For posttreatment fitness, researchers compiled all fitness test scores occurring in the first 30 months after testosterone or estrogen began for each individual. The time elapsed between starting treatment and the occurrence of each event was also recorded. Data from the study population were compared with the average performance among cisgender men and women younger than 30 years in the Air Force from 2004 to 2014.
Athletic advantage after 1 year
The study included 29 transgender men and 46 transgender women (mean age, 26.2 years). Pretreatment fitness scores were collected a mean 144.4 days before starting testosterone or estrogen, and the mean follow-up time was 394 days.
Compared with cisgender women, transgender women performed more push-ups (mean difference, 14.8 push-ups; 95% CI, 12.1-17.4) and more sit-ups (mean difference, 7.9 sit-ups; 95% CI, 5.7-10) prior to hormones. The transgender group continued to outperform the cisgender cohort until 2 years on treatment. For the 1.5-mile run, transgender women were faster than the cisgender women before treatment (mean difference, –147 seconds; 95% CI, –173 to –121). Times in the run worsened for transgender women after starting hormones, but the group remained faster than the cisgender cohort 2 years after treatment began (mean difference, –90 seconds; 95% CI, –169 to –10).
“Transwomen are currently mandated by World Athletics and the International Olympic Committee to have 1 year of testosterone suppression before being permitted to compete at the elite level,” Roberts said. “This may be too short if the aim is a level playing field.”
As Healio previously reported, the international governing body for track and field sports released new eligibility regulations in 2018 that required women with certain forms of hyperandrogenism to lower their natural testosterone level for at least 6 months prior to competing in races ranging from 400 meters to 1 mile. The requirements state that any woman who is “androgen-sensitive” with a circulating testosterone level of at least 5 nmol/L must reduce her testosterone level to less than 5 nmol/L with the use of hormonal contraceptives, and maintain that testosterone level continuously for as long as she wishes to remain eligible to compete in restricted events, including the 400-meter, 800-meter, 1,500-meter and 1-mile races, hurdles races and combined events over the same distances.
Transgender vs. cisgender men
Transgender men performed fewer push-ups compared with cisgender men prior to testosterone (mean difference, –16.1 push-ups; 95% CI, –20.3 to –12), but the difference disappeared 1 year after the testosterone began. Transgender men and cisgender men performed similarly in sit-ups prior to testosterone, and transgender men exceeded cisgender men after 1 year of testosterone (mean difference, 5.7 sit-ups; 95% CI, 1.7-9.8). The transgender group was also slower than the cisgender cohort in the 1.5-mile run at baseline (mean difference, 131 seconds; 95% CI, 83-178), but the difference disappeared 1 year after starting testosterone.
Before starting testosterone, the transgender male group performed more push-ups and sit-ups than cisgender women, with the difference growing after testosterone began. There was no difference at baseline between transgender men and cisgender women in the 1.5-mile run, but the transgender men were faster than cisgender women 1 year after testosterone started.
“Transgender male athletes develop a competitive advantage over female athletes after starting testosterone,” Roberts said. “Transgender males should be allowed to compete in men’s athletics after starting testosterone to ensure a level playing field for female athletes.”
Roberts said the findings reveal that inadequate evidence supports the World Athletics and International Olympic Committee’s current guidelines for transgender athletes.
“We need longer-term studies of the effect of testosterone suppression on athletic performance overall and in sport-specific activities (explosive strength, endurance and cardiovascular fitness) to inform guidelines for transgender inclusion in sport,” Roberts said.
For more information:
Timothy Roberts, MD, MPH, can be reached at taroberts@cmh.edu.
Perspective
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David J. Handelsman, MBBS, PhD
This study adds to growing evidence beyond the proven male physical advantage of 10% to 15% in sports requiring power or endurance and up to 50% where explosive power or complex movement skills are pivotal (Handelsman DJ, et al. Endocr Rev. 2018;doi:10.1210/er.2018-00020). These sex-based benefits in muscle, bone, cardiorespiratory function and blood hemoglobin originate with male puberty, which increases testosterone production 20-fold in men compared with children and women. Barring disease or suppressive drugs, adult male circulating testosterone concentrations maintain a cumulative androgenic advantage. These testosterone-mediated physiologic advantages form the basis for exclusion of male-bodied athletes from most female events other than before puberty or in sports not requiring intense physical demands, such as chess where open competition is logical, inclusive and fair.
A major question remains whether gender-affirming hormone treatment overcomes sex-based physical advantages sufficiently to maintain fairness so that an exception can be made for transwomen (natal males) treated with estrogens. The Roberts study based on prospective analysis of the U.S. military’s compulsory annual physical performance database shows convincingly that transmen (natal females) caught up with average male performance within 12 months of standard testosterone treatment as adults. By contrast, transwomen treated with estrogens after completing male puberty experienced only minimal declines in physical performance over 12 months, substantially surpassing average female performance for up to 8 years. Sporting federations should incorporate these findings into strategies for including transwomen in elite female competitions while maintaining fairness and safety for other women.
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