Ransgender women don’t have as much muscle mass as cisgender men, but have higher levels than cisgender women, according to a small new study.
Researchers said their new research could help inform policymakers about decisions about transgender women’s participation in sporting events.
The study, published in the British Journal of Sports Medicine, examined muscle strength as well as heart and lung capacity in transgender women who had received long-term gender-affirming hormone therapy.
This was compared to men and women who are cisgender – meaning their gender identity matches their biological sex at birth.
These findings add new insights to the scant information available on a highly controversial topic about transgender women’s participation in physical activity.
Experts, led by a team in So Paulo, Brazilwanted to assess the impact of long-term estrogen therapy and prior testosterone exposure during puberty on performance.
They did an analysis of 15 transgender women with an average age of 32 years, who received an average of 14 years of hormone therapy.
They also examined 13 cisgender men and 14 cisgender women.
No of the participants were athletes and all had similar levels of physical activity.
Researchers examined cardiopulmonary — heart and lung function — when participants used a treadmill.
They also assessed strength through hand grip tests and assessed body fat and muscle mass.
Total body fat was lower in the transgender women than in the cisgender women, but higher than in the cisgender men.
Similarly, the muscle mass in the transgender women was higher than in the cisgender women, but lower than in the cisgender men.
Grip strength was also greater in the transgender women than in the cisgender women, as was cardiopulmonary function.
“These findings add new insights to the scant information available on a highly controversial topic regarding transgender women’s participation in physical activity,” the authors wrote.
They added: “These findings can inform policy and help decisions about transgender women’s participation in sports activities.
“Future studies with transgender athletes explaining and quantifying variable exposure times to pubertal development and assessing muscle cell metabolism are needed to elucidate the effects of long-term gender-affirming hormone therapy on the sports performance of transgender women.”
This new evidence does not support trans women’s eligibility for the female categories of most sports
Commenting on the study, Dr. Channa Jayasena, clinical associate professor and consultant reproductive endocrinology and andrology at Imperial College Londonsaid: “This small but well-designed study compared many measures related to physical performance in trans women, cisgender women and cisgender men.
“They found differences in muscle development, strength and oxygen consumption between the trans women and cisgender women.
“This suggests that there are likely minor differences in how the muscles work between trans and cisgender women.
“However, none of the participants were athletes. And it is possible that similar differences in muscle function are found in cis-gender athletes.”
Alun Williams, professor of sports and exercise genomics at Manchester Metropolitan Universityadded: “This new evidence does not support the eligibility of trans women for the female categories of most sports.
“Studies of well-trained athletes before and during their treatment, using tests that are more accurate and relevant to competitive sport, are needed to better inform sport fitness policy.”