Transwomen and elite sport

With little scientific evidence available on the effects of gender affirming hormone therapy (GAHT) on athletic performance in trans athletes, sports governing bodies remain uncertain on the fairness and inclusiveness of transwomen competing in the women’s category.

To provide scientific data to help address this issue, researchers at Loughborough University are working on three studies investigating the physiological effects of GAHT on athletic performance in trans athletes.

The biological impact of short term (1-2 years) GAHT and its association with athletic performance

The first study is a longitudinal study, assessing the physiological and performance changes in a small cohort of transwomen athletes, both before and during GAHT, for a period of up to two years. Outcome measures are being assessed at baseline, every three months during the first year, with subsequent measures taken every 6 months.

Measures include: blood analyses (estrogen, testosterone, haemoglobin), skeletal muscle biopsy (to examine fibre type, capillary -to-fibre ratio), body composition (bioelectrical impedance), strength measures (bench press, knee extensor, handgrip), aerobic and anaerobic power (maximal oxygen uptake test and Wingate test, respectively), arterial stiffness (applanation tonometry), regional blood flow (strain-gauge plethysmography) and vascular function (ultrasound).

The aim of this study is to better understand the physiological changes that occur in transwomen athletes in response to GAHT, and to examine whether these changes relate to changes in athletic performance. 

The performance impact of longer-term (1-5 years) GAHT

The second study is both retrospective and prospective, gathering data – via an online survey – of historic and current athletic performance in trans athletes competing in sports where results are measured in centimetres (distance), grams (weight), or seconds (time).

Retrospective performance data, both before and after GAHT initiation, are being collected. Prospective data are also being collected for a further 12 months. Participant clinical reports of testosterone levels are also being documented. To be part of this study participants must be at least one-year into starting GAHT and returning to competition: i) in their identified gender (versus in their birth sex category), and i) in the same sport.

The aim of this study is to examine changes in athletic performance over time in transgender athletes using long-term GAHT.

Comparing the athletic performance of transwomen athletes with that of female athletes

The third study is a cross-sectional study comparing the athletic performance of transwomen athletes who have medically transitioned for at least three years, with that of age-, sport- and competition level-matched female athletes.

Measures include: blood analyses (estrogen, testosterone, haemoglobin), strength measures (bench press, handgrip, knee extensor), aerobic and anaerobic power (maximal oxygen uptake test and Wingate test, respectively), and sport-specific testing (eg, for cyclists, determination of critical power).

This study aims to examine how long-term (>3 years) suppression of testosterone due to GAHT influences the physiological and sporting attributes of transwomen athletes, and how this compares with female athletes. 

Research Ethics

All of the studies have been approved by the Loughborough University ethics committee. 

All the studies are being led by a team of researchers from Loughborough University’s School of Sport, Exercise and Health Sciences and will run for several years. Their combined findings will provide evidence-based data that are much needed to further our understanding how hormone therapy in transwomen athletes impacts their athletic performance and physiology.

However, due to the challenges faced in this area of research – namely, very few transgender athletes to assess – it is recognised that it will be many more years before a large enough body of evidence will be available to meaningfully support sporting bodies to develop informed guidelines regarding transwomen athletes in elite sport.