Do transgender women have a physical advantage over cisgender women in athletic competitions?

From the Guidelines

Transgender women may have some physical advantages over cisgender women in athletic competitions, but these advantages diminish substantially with hormone therapy, and many performance metrics move closer to female ranges after 1-2 years of treatment. The primary advantage stems from developmental effects of testosterone during male puberty, which can result in greater height, bone density, muscle mass, and cardiovascular capacity 1. However, hormone therapy, typically consisting of estradiol and testosterone blockers like spironolactone, leads to significant reductions in muscle mass, strength, and hemoglobin levels after 1-2 years of treatment 1.

Some key points to consider include:

• Thigh muscle volume decreases by 5% and quadriceps CSA decreases by 4% in trans women on hormone therapy 1
• Lean body mass decreases by 3.0% to 5.0% in trans women on hormone therapy 1
• Hemoglobin levels decrease significantly in trans women on hormone therapy 1
• Breast development is sustained during the first three years of hormone therapy, but may not be a significant factor in athletic performance 1

The timing of transition is also important, as those who transition before or during early puberty using puberty blockers typically develop physical characteristics more aligned with cisgender women. Athletic governing bodies continue to evaluate policies based on emerging research, with some implementing testosterone level requirements and minimum duration of hormone therapy before competition eligibility. Overall, while some physical advantages may persist, the extent of these advantages varies significantly based on individual factors, and hormone therapy substantially reduces the differences in physical characteristics between transgender women and cisgender women.

From the Research

Physical Advantage of Transgender Women over Cisgender Women

• The question of whether transgender women have a physical advantage over cisgender women in athletic competitions is complex and has been studied in various research papers 2, 3, 4, 5, 6.
• Studies have shown that transgender women undergo significant changes in body composition, bone mineral density, and muscle strength during cross-sex hormone therapy 2, 3, 4.
• Prior to hormone therapy, transgender women tend to have lower bone mineral density and muscle mass compared to cisgender men, but these differences decrease over time as they undergo hormone therapy 2.
• Research has found that after 1-2 years of hormone therapy, transgender women experience a decrease in muscle mass and strength, and an increase in fat mass, which can lead to a more "female" body fat distribution 3, 4.
• A study found that after 12 months of gender-affirming treatment, transgender women showed a general increase in fat mass and a decrease in overall lean body mass and handgrip strength 4.
• Another study found that after 2 years of gender-affirming hormone therapy, no advantage was observed for physical performance measured by running time or in trans women, and by 4 years, there was no advantage in sit-ups 5.
• The existing literature suggests that physical performance of nonathletic trans people who have undergone hormone therapy for at least 2 years approaches that of cisgender controls 5.

Muscle Strength and Body Composition

• Transgender women tend to have higher absolute lean mass compared to cisgender women, but relative percentage lean mass and fat mass, as well as muscle strength corrected for lean mass, are similar to those of cisgender women 5.
• A study found that thigh muscle volume decreased by 5% in transgender women after 12 months of hormone therapy, while quadriceps cross-sectional area decreased by 4% 4.
• The rate of change in body composition during hormone therapy can vary greatly among individuals, with some transgender women experiencing little to no change in body composition 6.

Implications for Athletic Competitions

• The research suggests that transgender women may not have a significant physical advantage over cisgender women in athletic competitions after undergoing hormone therapy for a certain period of time 5.
• However, more research is needed to fully understand the effects of hormone therapy on physical performance and to inform policies on the participation of transgender athletes in competitive sports 5.