The decision by the International Olympic Committee (IOC) to exclude transgender women and most athletes with differences of sex development (DSD) from women’s Olympic sport has won praise from most major sports bodies but criticism from some activist groups.
It also closes the door on a period where often well-intentioned inclusivity came at the expense of sportswomen, and those who pointed out that the rules were not fair.
In the melee of relief and bitter disappointment, misconceptions and confusion have been able to flourish. So why has the IOC changed its rules on elite sport leading up to the 2028 Olympics?
Central to the new policy on the protection of the female category is that male physical advantage is real. Men hold a performance advantage over women of 10-12% in most running and swimming events and at least 20% in most throwing and jumping events. The advantage can be more than 100% in explosive events such as boxing or weightlifting. The IOC document says: “Males have larger and stronger skeletal muscle and bone, larger and stronger hearts, larger lung size, more red blood cells, and lower body fat than females trained to the equivalent level. Together these attributes afford males individual sex-based performance advantages in sports and events that rely on strength, power and/or endurance.”
These physical advantages mean that the fastest 14-year-old boys run the 100m more quickly than the women’s world record; the No 1 women’s tennis player, Aryna Sabalenka, lost last December’s battle of the sexes game to an out-of-shape Nick Kyrgios, then ranked at No 671 in the world; and if there were no category for women at the Olympics, there would be no female medallists – except in equestrian events, and possibly static shooting. This does not mean that women’s sport is lesser, it just means the two sexes are different.
The science on this is not contested, except by those undertaking the wildest mental gymnastics. The fact that some athletes are “unfairly” perfect for a particularly discipline – such as the swimmer Michael Phelps and his incredible wingspan – does not mean we should embed unfairness into a category. Phelps’s advantage over his closest male rivals was less than 0.5%, and his individual world records have all since been broken. If he had raced against women, the difference would be 10-12%. As the developmental biologist Emma Hilton has written: “The single biggest genetic advantage Phelps has is a Y chromosome.”
The IOC stresses that it has become clearer and better understood over the past few years that both those trans women who reduce their testosterone levels, and nearly all athletes with XY-DSD who have been required to reduce their testosterone, still have a significant advantage over their female counterparts due to male puberty.
It is this evidence that has caused the IOC to change its mind. Where it once thought it could balance its previous policy of inclusivity with safety and fairness, the science now overwhelmingly says it cannot.
The second big IOC decision is to rule that anyone who competes in the female category must have a screening for the SRY gene, to be taken once in their lifetime and described as “a segment of DNA that is almost always on the Y chromosome, initiates male sex development in utero and indicates the presence of testes/testicles”.
This would take the form of a cheek swab, or a blood or saliva test, no more difficult than ancestry DNA tests. It is nowhere near as intrusive as the regular doping rigmarole that all Olympic athletes regularly have to endure, including having to urinate in front of doping control officers.
And it is far preferable to the alternatives – either a whispering campaign based on what athletes look like, or the pre-2021 IOC position that demanded trans women athletes and those with XY-DSD reduce their testosterone levels.
There have been claims that sex screening targets black athletes from the global south, such as South Africa’s Caster Semenya, Kenya’s Margaret Wambui and Burundi’s Francine Niyonsaba, who all won medals in the 800m at the 2016 Olympics, fairly under the IOC rules of the time. But that is not accurate. The SRY screening will be applied to anyone who wants to compete in the female category at the 2028 Olympics, regardless of where they are from. As XY-DSD athletes, Semenya, Wambui and Niyonsaba were reported female at birth but have the SRY gene and male-level testosterone to which their bodies typically respond, and this confers physical advantage. They would therefore now be excluded. Their previous inclusion meant there were female runners from South Africa, Kenya and Burundi who didn’t get a chance to go the Olympics.
Now the IOC has made its decision, it must ensure that these screening procedures are watertight and discreet, that the promise to prioritise athletes’ “dignity, physical and psychological health” is kept and that there is a duty of care for those athletes whose dreams have been upended.
Overwhelmingly, the IOC decision is what female athletes want. The last time there was a large survey of female athletes was after the Atlanta Games in 1996. Out of a cohort of 928, 82% of women wanted to continue with sex screening, which was mandated at the Olympics from 1968 to 1998. The authorities then did the opposite. The IOC has said that athlete feedback into the 2026 decision, including 1,100 responses to an online survey, revealed a “strong consensus” that fairness and safety in the female category “requires clear, science-based eligibility rules”.
With this decision should come an extra drive to ensure sport is possible for all. Trans athletes and those with DSD must be welcomed with open arms, whatever their gender identity and however they present, but unfortunately we can’t wave a magic wand. The science shows if you have gone through male puberty, you must compete in the male cohort. Sport only works if you hold a category space. The IOC’s decision, rightly, gives dignity back to the female class.