Gender and Sport

Sports competitions have historically been divided into two categories — men and women — for one simple reason: the body that has gone through male puberty is, in most athletic domains, considerably stronger, faster and larger than the body that has gone through female puberty. The women’s category does not exist as a matter of courtesy, but because fair competition and the safety of female athletes could not otherwise be guaranteed. The question of whether transgender women — biological males who identify as women — should be allowed to compete in the women’s category goes directly to the foundation of this distinction.

More on this site: World Aquatics, World Athletics and Riley Gaines — Swimming Against the Current.

Related topics can be found under Sport and transgender youth.

Male puberty: a physiological legacy that remains

The advantages conferred by male puberty are substantial and largely permanent. Under the influence of testosterone during puberty, males develop on average:

• considerably greater muscle mass and strength (in the order of 30–50% in the upper body);
• larger bones, a larger skeletal frame and greater bone density;
• greater heart and lung capacity;
• a more advantageous lever structure (longer limbs, narrower hips);
• higher haemoglobin levels and therefore greater oxygen-carrying capacity.

One or two years of oestrogen therapy — as required by some sports federations — does not reverse these changes. Skeletal structure, heart size and lever proportions are permanent. Muscle mass and strength do decrease somewhat, but studies (including Hilton & Lundberg, 2021; Roberts et al., 2021) show that a substantial proportion of the strength gap compared with women remains even after several years of hormone treatment. Hilton and Lundberg’s review is explained on gendersport.nl.

Unfair competition

Allowing transgender women to compete in the women’s category means in practice that biological males — often carrying a lifelong legacy of male puberty — compete against women. In disciplines where strength, speed and power are decisive (athletics, swimming, cycling, weightlifting, MMA, rugby), this results in demonstrable performance advantages. For elite female athletes, this means losing podium places, scholarships, record opportunities and selection spots. This is not an abstract problem but a direct undermining of the women’s category itself.

Risk of injury to women

Safety is also a factor, alongside fairness. In contact and collision sports — rugby, football, judo, MMA — greater body mass, strength and bone density in biological males result in a demonstrably higher risk of injury for female opponents. In 2020, World Rugby concluded on the basis of its own research that allowing transgender women to compete in the women’s category increases the risk of serious injury by tens of percentage points. Similar considerations apply to other collision sports.

The policy of international sports federations

Under pressure from scientific evidence and female athletes, several international federations have revised their policies. World Aquatics (swimming, since 2022) and World Athletics (athletics, since 2023) exclude transgender women who have gone through male puberty from the women’s elite category. The UCI (cycling), World Rugby and USA Powerlifting follow similar lines. Since 2021, the IOC has left the decision to individual federations, but has now adopted its own guideline: from the 2028 Los Angeles Games onward, the women’s category will be reserved for female athletes without an SRY gene, determined through genetic testing (see IOC restores the women’s category). In the United States, the Supreme Court confirmed in 2026 that states may exclude trans women from girls’ and women’s sports. The sensitivity of the subject in American newsrooms became clear in August 2026, when a sports columnist at The Seattle Times resigned after his editors blocked a column about women’s sports.

Intersex athletes

A separate discussion concerns intersex athletes with a DSD condition (Differences of Sex Development) who were raised as girls but have XY chromosomes and endogenous testosterone levels in the male range (for example, 46,XY 5-alpha-reductase deficiency). Well-known cases such as Caster Semenya show that, in practical terms, these athletes have the same physiological advantages as other biological males. Sports federations have — rightly — established eligibility rules for this situation. This is not a “transgender” debate, but a debate about biological sex. See also Intersex.

Recreational sport

In recreational sport, performance and injury risk generally play a smaller role. Many clubs opt for pragmatic local solutions. This does not, however, relieve elite and competitive sport of its duty to protect the women’s category as a sex-based category, precisely because national and international titles, prize money and careers are at stake there.

What is at stake?

The women’s category in sport is an achievement of decades of women’s emancipation. It is based on biological sex, not on a feeling. Eliminating or hollowing it out entirely in the name of inclusion means, in practice, excluding women from their own category. That is too high a price to pay — and more and more sports federations, athletes and scientists are reaching the same conclusion.