Many sports federations now have more exclusions for the women's category to limit the participation of transgender athletes. The question of what is fair and what is not is a hot topic in the sports world.The debate about transgender women athletes in competitive sports has been going on for years. In the United States, President Donald Trump recently signed a decree banning trans women athletes from women's sports nationally.

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Many federations have adjusted participation rules and made the female category more exclusionary. Many federations have tightened their participation rules. At the World Athletics Association, for example, no one who has gone through male puberty has been allowed to participate in women's competitions since 2023. And even stricter and exclusionary criteria could soon follow. The results of internal consultations on this could soon become known.

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With the new IOC presidency, changes could also be in the offing for the Olympic Games. On March 20, it will be announced who will succeed Thomas Bach in that role.

DW Fact check looked at the latest studies and talked to experts.

What are the differences in physical performance?

Men and women are assessed separately in most sports. This is because, according to a 2023 joint statement by scientists, "in athletic events and sports relying on endurance, muscle strength, speed, and power, men typically outperform women because of fundamental sex differences dictated by their sex chromosomes and sex hormones at puberty, in particular, testosterone."

Trans women — who were assigned to the male sex at birth but identify as female — also have these advantages. If they undergo hormone therapy as part of gender reassignment surgery, the differences to cisgender women are reduced. But even then, there are still advantages.

Incidentally, trans identity is often confused with intersexuality in the public debate. But intersex people — unlike trans people — have both male and female sexual characteristics from birth.

For example, in a study from 2024, published in the British Journal of Sports Medicine, the absolute hand grip strength of the 23 participating trans athletes (after at least one year of hormone therapy) was lower than that of the 19 participating cis men but higher than that of the 21 participating cis women. Hand grip strength is considered an indicator of overall muscle strength.

The trans women who took part also had an advantage in parameters such as absolute maximum oxygen uptake and the fat-free mass index. In some respects, however, they performed worse than the cis women, for example in the vertical jump with lunge. According to the study authors, this shows how complex the physiology of trans athletes is; they warn against a precautionary exclusion.

Joanna Harper, medical physicist at Loughborough University in the UK, also explains: "Trans women as a population group are taller, bigger, and in an absolute sense stronger than CIScis women, however after going through hormone therapy, trans women are now moving their bodies with reduced aerobic capacity, reduced muscle mass."

This can lead to disadvantages in terms of speed, recovery and endurance.

The expert also points out that trans people often struggle with poorer mental health due to prejudice and discrimination. This should not be underestimated as a component of athletic performance.

Greater effect after two years of hormone therapy

A 2020 study by Timothy Roberts and colleagues at the University of Missouri-Kansas City examined US military personnel who underwent gender-affirming surgery.

After one year of hormone therapy, trans women performed better in sports than cis women. After two years, their performance was largely equalized. According to the authors of the study, this is an indication that the one year of hormone therapy prescribed by some sports associations as a prerequisite for participation is too short.

In 2021, Alun Williams and other researchers from the British Association of Sport and Exercise Sciences came to the conclusion that, according to the available scientific evidence, hormone therapy only eliminates a fraction of the male advantage even after two years. Overall, the results are therefore quite different.

What role does puberty play?

Before puberty, boys and girls are physiologically much more equal when it comes to athletic performance. The differences become particularly clear when the testosterone level multiplies in boys, around the age of eleven.

However, some studies from younger years suggest that the differences before puberty are greater than previously assumed.

In a study published in 2024, sports scientist Gregory Brown from the University of Nebraska and researchers from the University of Essex in the UK analyzed the performance of 8 and under 8-year-olds and 9 and 10-year-olds in the 100 m, 200 m, 400 m, 800 m and 1500 m running events as well as in the shot put, javelin throw and long jump.

"The boys were running faster than the girls, the boys were throwing faster than the girls, the boys were jumping faster than the girls," Brown explains. "And of course, we calculated a percent difference and came up for running, it was anywhere from about 3 to 6% difference depending on the event. For long jump, it was about a little right around 5% difference. For the throwing events, it was close to 20 to 30% difference."

According to Brown, differences before puberty may also have to do with the so-called mini puberty of boys in the first months of life as well as with the Y chromosome or the SRY gene. The Y chromosome is one of the two sex chromosomes. Women usually have two X chromosomes (XX) and men have one X and one Y chromosome (XY). The Y chromosome carries many genes associated with male development and reproduction. The SRY gene is particularly important for male sexual development.

"Consistent male advantage even before puberty"

And what do these results say about the question of whether there can be fair competition between trans and cis women in sport?

For Brown, the finding of a continued advantage even before puberty casts even more doubt on whether hormone therapy could sufficiently offset the physical advantages of trans athletes and level the playing field. He explains the male advantage goes beyond hormones and puberty.

The results also cast doubt on whether it would be enough not to have had male puberty.

As already mentioned, the World Athletics Association has been relying on this requirement for participation in female competitions since 2023. This is de facto tantamount to excluding trans athletes, as the vast majority of them do not take gender reassignment measures before puberty.

In many places, puberty blockers and gender reassignment surgery before puberty are controversial and access is restricted.

Is the advantage of trans women over cis women in sports unfair?

Opinions differ on the extent to which fair competition between trans and cis female athletes is possible. But experts agree on one thing: There is a great need for further studies on the athletic performance of trans people in elite sports.

Harper explains — unlike Brown and Williams, for example — that in her opinion, science does not suggest that trans women should be banned from female competitions. Hormone therapy makes "meaningful competition" possible.

There is no such thing as 100% fairness in sport anyway, says Harper: "There are athletes who are gifted by nature and you know, is it fair for less gifted athletes to have to face those?"

"So, sports are inherently unfair. But when we subdivide sports into categories, we do so with the purpose that biological differences don't overwhelm what we seek in sports. So, for instance, big boxers have such a huge advantage over small boxers that we segregate that sport by weight categories so that small boxers can win something."

The boxing example shows that the search for competition categories that are not too differentiated, but sufficiently so, can be complex. The male advantage also plays a different role depending on the sport. While it creates major differences in strength sports, such as weightlifting, the situation is different in shooting or dance sports.

Last but not least, the issue of fairness must also be weighed against that of inclusion. The IOC also states: "Every person has the right to practice sport without discrimination and in a way that respects their health, safety and dignity. At the same time, the credibility of competitive sport — and particularly high-level organized sporting competitions — relies on a level playing field."

This article was first published on July 24, 2021, and was substantially revised on March 19, 2025, to reflect the latest discussions and studies on the athletic performance of trans women.

Rayna Breuer contributed to this Fact check.

Edited by: Astrid Prange de Oliveira, Carla Bleiker, Chiponda Chimbelu and Rachel Baig

(The above story first appeared on LatestLY on Mar 19, 2025 10:30 PM IST. For more news and updates on politics, world, sports, entertainment and lifestyle, log on to our website latestly.com).