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Effect of gender affirming hormones on athletic performance in transwomen and transmen: implications for sporting organisations and legislators
  1. Timothy A Roberts1,
  2. Joshua Smalley2,
  3. Dale Ahrendt2
  1. 1Pediatrics, Children's Mercy Division of Adolescent Medicine, Kansas City, Missouri, USA
  2. 2Pediatrics, San Antonio Military Medical Center, Fort Sam Houston, Texas, USA
  1. Correspondence to Dr Timothy A Roberts, Pediatrics, Children's Mercy Division of Adolescent Medicine, Kansas City, Missouri, USA; taroberts{at}


Objective To examine the effect of gender affirming hormones on athletic performance among transwomen and transmen.

Methods We reviewed fitness test results and medical records of 29 transmen and 46 transwomen who started gender affirming hormones while in the United States Air Force. We compared pre- and post-hormone fitness test results of the transwomen and transmen with the average performance of all women and men under the age of 30 in the Air Force between 2004 and 2014. We also measured the rate of hormone associated changes in body composition and athletic performance.

Results Participants were 26.2 years old (SD 5.5). Prior to gender affirming hormones, transwomen performed 31% more push-ups and 15% more sit-ups in 1 min and ran 1.5 miles 21% faster than their female counterparts. After 2 years of taking feminising hormones, the push-up and sit-up differences disappeared but transwomen were still 12% faster. Prior to gender affirming hormones, transmen performed 43% fewer push-ups and ran 1.5 miles 15% slower than their male counterparts. After 1 year of taking masculinising hormones, there was no longer a difference in push-ups or run times, and the number of sit-ups performed in 1 min by transmen exceeded the average performance of their male counterparts.

Summary The 15–31% athletic advantage that transwomen displayed over their female counterparts prior to starting gender affirming hormones declined with feminising therapy. However, transwomen still had a 9% faster mean run speed after the 1 year period of testosterone suppression that is recommended by World Athletics for inclusion in women’s events.

  • gender
  • steroids
  • body weight
  • physical fitness
  • treatment

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  • Contributors All authors listed on this manuscript have contributed to the following tasks: substantial contributions to the conception or design of the work, or the acquisition, analysis or interpretation of data; drafting the work or revising it critically for important intellectual content; final approval of the version published; and agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Disclaimer The views expressed are solely those of the authors and do not reflect the official policy or position of the US Army, US Navy, US Air Force, the Department of Defense or the US Government.

  • Competing interests TAR receives research funding for an unrelated project as part of the Merck Pharmaceuticals Investigator Directed Research Programme. JS is on active duty with the United States Air Force. DA is an employee of the United States Department of Defense.

  • Patient and public involvement Patients and/or the public were involved in the design, or conduct, or reporting, or dissemination plans of this research. Refer to the methods section for further details.

  • Patient consent for publication Not required.

  • Ethics approval This study was approved by the 59th Medical Wing institutional review board.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement A de-identified copy of the data is available from the corresponding author upon reasonable request.