The incendiary issue of transgender participation in sports returned to the fore this week after a high school girls’ team won a state championship with help from a trans girl.

Olympic medalists were among critics who joined the backlash to Chloe Barnes’ role in Brookline High School’s victory in Massachusetts. Barnes is a junior who competed under rules that allow students to ‘participate in a manner consistent with their gender identity’.

It’s the latest flashpoint in the debate at state legislatures across America and in Congress, where Republicans propose banning trans women and girls from women’s team sports. The issue was thrust into the mainstream when trans swimmer Lia Thomas became an NCAA champion in March 2022.

Supporters of inclusion claim fairness can be maintained when trans women assigned male at birth compete against women, while opponents that argue women’s sports must be protected face accusations of transphobia.

But cut through the often toxic political mudslinging that dominates the debate and, according to researchers and elite athletes, the science speaks for itself: Trans women have a physical advantage over biological females – and no treatment exists which can unravel that.

Current and former athletes say trans athletes like Lia Thomas (left), the swimmer who enjoyed modest success in male categories before becoming a national champion in women’s events after she transitioned, highlight the physical advantages of trans women

Lia Thomas, right, and teammate Hannah Kannan stand on the pool deck at the Ivy League Women’s Swimming and Diving Championships at Harvard University, February 18, 2022

Transgender cyclist Veronica Ivy, formerly known as Rachel McKinnon (left) defended her right to compete in women’s sport despite accepting trans athletes may retain a physical advantage over their rivals

Veronica Ivy won the UCI Women’s Masters Track World Championship for the women’s 35–44 age bracket in 2018, while competing as Rachel McKinnon, becoming the first transgender track cycling champion

Tommy Lundberg, a lecturer in physiology at Sweden’s Karolinska Institute and leading researcher on the subject, told DailyMail.com: ‘The most important thing is whether or not you have benefited from male development and male puberty and if you’ve done that, you’re going to have advantages you cannot undo later.’

Supporters of inclusion for trans women argue that a sustained course of gender-affirming care to suppress testosterone levels eliminates the advantage.

But Lundberg’s landmark 2021 study with Emma Hilton, a developmental biologist at the University of Manchester in the UK, disputes that.

The research found that men typically have a 10-50 percent performance edge over women. After a trans woman has completed 12 months of testosterone suppression, the loss of ‘lean body mass, muscle area and strength typically amounts to approximately 5%’, according to the paper.

‘The muscular advantage enjoyed by transgender women is only minimally reduced when testosterone is suppressed,’ the study said.

Other studies have recorded similar findings. A paper published in the International Journal of Environmental Research and Public Health last year said ‘the former male physiology of trans woman athletes provides them with a physiological advantage over the cis-female athlete.’

Nancy Hogshead, a former pro swimmer who won three gold medals and one silver at the 1984 Olympics, told DailyMail.com: ‘Trans women have an undeniable physical advantage.

World Rugby’s policy states trans women who transitioned after puberty cannot compete in women’s rugby. French rugby player Alexia Cerenys (center), who transitioned at age 25, is still able to compete in France after its rugby federation voted in favor of trans participation

Alexia Cerenys became the first openly trans women to play at the top level of amateur rugby in France after the country’s governing body went against World Rugby’s guidance on the participation of trans women in the women’s game

Cerenys had already been playing unofficially as a flanker for the Lons Women’s Rugby team in the French Pyrenees for several years before France’s national federation officially endorsed the participation of trans women in women’s rugby

‘Their bodies do what male bodies do when they go through puberty and is the reason why we segregate sports ubiquitously around the world… Unless we’re talking about just playing, just recreational sports. All competitive sports is sex-segregated.’

Hogshead founded Champion Women in 2014 and became one of the first elite athletes to campaign for protected female categories in sport. She’s now joined by a growing number of current and former professionals, including other Olympians, who oppose transgender inclusion.

British Olympic silver medalist Sharron Davies, who also campaigns on the issue, accused Brookline High School of ‘cheating’ after its championship victory.

Caitlyn Jenner, who won gold in the male decathlon at the 1976 Olympics before becoming one of the world’s best-known trans women, has called Thomas’s success ‘anathema to what sports represents and the spirit of competition’.

Hogshead added that ‘Lia Thomas showed us all [the physical difference]’ between trans women and biological females.

Thomas enjoyed modest success in male categories before becoming a champion in women’s swimming after she transitioned. Her story is the standout in a growing list of high-profile and controversial cases of trans participation.

Cece Telfer became the first openly trans woman to win an NCAA title when she placed first in the 400m hurdles at the Division II National Championships in 2019.

The following year, Laurel Hubbard, from New Zealand, became the first openly transgender woman to compete at the Olympics when she took part in weightlifting at the Tokyo games.

Veronica Ivy won the UCI Women’s Masters Track World Championship for the women’s 35–44 age bracket in 2018, while competing as Rachel McKinnon, becoming the first transgender track cycling champion.

Cece Telfer became the first openly trans woman to win an NCAA title when she placed first in the 400m hurdles at the Division II National Championships in 2019 (pictured)

Telfer, right, has denied she has a physical advantage and previously suggested that hormone suppression treatment made her the ‘weakest female’ at the championship event

Telfer competed in her university’s men’s track and field team before she transitioned, but did not enjoy the same level of success

Laurel Hubbard, from New Zealand, became the first openly transgender woman to compete at the Olympics when she took part in weightlifting at the Tokyo games in 2020

Hubbard, the first openly transgender woman to compete at the Olympics, placed last in her group

After the games, Hubbard (left) thanked the International Olympic Committee for ‘establishing that sport is something for all people. It is inclusive. It is accessible’

The issue also exists in amateur sports. In February, Tiffany Newell, 50, placed first in the W50 1,500m, which is open to women aged 50 to 54, at the Canadian Masters Indoor Championships in Toronto.

Newell, who enjoyed several victories and even set national records in women’s events after her transition in 2017, retired from competing ‘indefinitely’ days later due to the backlash.

Many trans athletes compete under rules set by sports governing bodies like World Athletics that allow those who have undergone gender-affirming treatment and can demonstrate testosterone levels below a certain threshold.

Some of these international organizations have tightened their rules in the wake of recent controversies. Months after Thomas’s win, FINA, the governing body for competitive swimming, announced athletes who transition after age 12 would no longer be allowed to compete in female events.

But other governing bodies have tilted the other way. Alexia Cerenys became the first openly trans women to play at the top level of amateur rugby in France after the country’s governing body went against World Rugby’s guidance to the contrary.

World Rugby says letting trans women play can potentially increase the risk of serious injuries to biological female players in what is already a rough-and-tumble game.  

The clash is also playing out in state legislatures across America as politicians battle over the inclusion of trans girls in competitive sport at the youth level and in schools and colleges.

The debate around trans women competing in women’s events has also been highlighted in amateur sports. Tiffany Newell, 50, has set several records at Masters events in Canada since transitioning in 2017

Newell (left) placed first in the W50 1,500m, which is open to women aged 50 to 54, at the Canadian Masters Indoor Championships in Toronto, which took place in February

In 2022, Newell set a new Canadian record in the 5,000m in the women’s 45-49 age category with a time of 18:02:30. Canadian Masters Athletics ratified the time under the World Athletics policy for trans athletes. Pictured: Newell with her friend Paul James (right)

Legislators in Wyoming approved a bill on February 28 that prevents athletes assigned male at birth from competing in women’s sports teams. The bill follows similar ones in states including Florida, Oklahoma, Ohio and Mississippi.

Republicans in Congress are also pursuing similar legislation. These discussions are often divided along party lines: Democrats typically back inclusion while Republicans support protected categories.

President Joe Biden’s administration has proposed updates to Title IX, which prohibits sex-based discrimination in schools, to include protections around gender identity and sexual orientation.

But for researchers like Lundberg, the science speaks for itself.

‘The bottom line right now that I am arguing is that you can’t have both right now – we can’t have inclusion and fair competition at the same time in the female category,’ he added.

‘Sports organizations basically need to choose between those two. Either you uphold the integrity of women’s sports, but that’s not compatible with the inclusion of transgender women in female sports. That’s just a reality.’