Longitudinal Performance Changes in Transgender Women Athletes Pre and Post Gender Affirming Hormone Therapy

The aim of this study was to evaluate athletic performance and training in transgender women (TW) athletes competing in running and swimming both pre and post gender affirming hormone therapy (GAHT). Using survey methods, 9 TW runners and 1 TW swimmer provided independently verified retrospective data for race times, training volume, height, body mass, and testosterone, oestrogen and haemoglobin concentrations and pre-GAHT and post-GAHT. Prospective data were collected for a further 12 months. Changes in performance and age-grade scores (AGs) for runners and FINA scores for the swimmer were calculated. For runners, pre-GAHT and post-GAHT differences in AGs were adjusted based on training differences over time. Post-GAHT, testosterone concentrations in TW (1.10 ± 0.52 nmol·L^-1) were female typical. Average race time for the runners increased by 14.6 ± 5.6% after 31 ± 23 months (range 5-86 months) of GAHT. Changes in training were positively associated with changes in AGs (p = 0.008). Pre-GAHT and post-GAHT average AGs of the runners did not differ with or without adjustment (p = 0.304) for training differences. Average race times for the swimmer increased by 5.2 ± 2.3% and FINA score increased by 65 points after 34 months of GAHT. In our sample of TW athletes taking GAHT, longer distance events were associated with larger decrements in performance compared with shorter distance events, with exercise training helping attenuate these decrements. Event demands and exercise training may be important considerations in understanding the effects of GAHT on athletic performance in TW athletes.