Research shows that hormone therapy produces significant changes to athletic performance in trans women, with most physiological advantages substantially reduced or eliminated over time. Evidence indicates that the body undergoes measurable adaptations that bring performance metrics closer to those of cisgender women.
Guidelines from sports medicine research demonstrate specific timelines for these changes. Haemoglobin levels, which carry oxygen around the blood during exercise, drop to female levels after approximately one year of hormone treatment. After two years of hormone therapy, studies show no significant difference in aerobic fitness, endurance, and running speed between trans women and cisgender women. Muscle mass decreases and strength reduces progressively over time, with most gender-related measures falling into the female range by two to three years of treatment.
People often ask whether any advantages remain after hormone therapy. The evidence suggests that these physiological changes mean many of the physical advantages that might have existed before hormone treatment are substantially reduced or eliminated. After sufficient time on hormone therapy, remaining performance differences typically come down to individual factors such as skill, practice, and natural talent rather than the effects of having gone through male puberty. This research helps inform evidence-based policies in competitive sport.