Trans women hold physical edge 14 years after hormone therapy

TRANSGENDER women are stronger and have better heart and lung capacity than women, even 14 years after taking hormone therapy, a study suggests.

The research, from Brazilian scientists, may raise pressure for trans women to be excluded from female sports after they found transgender women were about 20 per cent stronger and their ability to use oxygen during exercise was 20 per cent greater.

Writing in the British Journal of Sports Medicine, Prof Leonardo Alvares, of the University of Sao Paulo Hospital Clinics, said the findings add insights to the “sparse information available” on the participation of transgender women in physical activities.

“It could inform policy and help in decisions about the participation of transgender women in sporting activities,” he added.

The team assessed the heart-lung capacity and strength in 15 transgender women, 13 cis-gender men and 14 cisgender women. The trans women had been on hormone therapy for an average of 14 years.

Testosterone exposure changes muscle mass, strength, body fat and red blood cell capacity. Researchers wanted to find out if the effect was long-lasting after suppressing the hormone.

The scientists measured how efficiently the body transports and uses oxygen, known as VO2, which can be 50 per cent higher in men than women. VO2 is believed to be the best indicator of aerobic capacity. They found that in transgender women, the VO2 peak was about 2,606 and in women it was 2,167. Men scored 3,358.

When grip strength was measured – a proxy for muscle condition and overall strength – transgender women achieved about 35kg (77lbs) compared with women, who managed about 29kg. Commenting on the research, Alun Williams, professor of sport and exercise genomics at Manchester Metropolitan University, said: “This new evidence doesn’t support the eligibility of trans women for the female categories of most sports.”

However, Prof Williams warned that the research had not been carried out on athletes. “Studies of well-trained athletes before and during their treatment, using tests that are more accurate and more relevant to competitive sport, are required to better inform sport eligibility policies,” he said.

Dr Channa Jayasena, a clinical senior lecturer and consultant in reproductive endocrinology and andrology at Imperial College London, said: “This suggests that there are likely to be small differences in how the muscles work between trans and cis-gender women.

“However, none of the participants were athletes. It is possible that there are similar differences in muscle function found among cis-gender athletes.”

‘There are likely to be small differences in how the muscles work between trans and cis-gender women’