Trans women runners get slower over time after starting hormone therapy, especially in longer races — their race times go up by about 14-17%, while sprints are less affected.

Trans women athletes tend to slow down more in long races after hormone therapy than in short sprints—suggesting endurance is affected more than quick bursts of power.

Trans women who aren't athletes seem to run about as well as cis women after two years on hormone therapy — their endurance might become similar during that time.

For transgender women runners, boosting their training might help maintain their running performance after starting hormone therapy.

Trans women under 30 who've been on hormone therapy for a year are still 9% faster at running than cis women the same age, even though they've lost their edge in push-ups and sit-ups. This suggests that one year of hormone treatment might not completely level the playing field for endurance sports.

Trans guys on testosterone get just as good at running 1.5 miles as cis guys within a year — starting out about 15% slower but catching up completely thanks to hormone therapy.