Lia Thomas after winning the 500 yard freestyle in March. The runners-up posed together.
In an interview with The New York Times on Monday, a Mayo Clinic doctor and an international physiologist who consults on the sports both confirmed Thomas's advantage is inescapable.
'There are social aspects to sport, but physiology and biology underpin it. Testosterone is the 800-pound gorilla,' Michael J. Joyner, the Mayo Clinic doctor, said.
Even though Thomas took testosterone suppressants - which are required by the N.C.A.A. - she still has an unfair advantage over the biological females she swims against.
'Lia Thomas is the manifestation of the scientific evidence. The reduction in testosterone did not remove her biological advantage,' Dr. Ross Tucker, a sports physiologist added.
Their comments confirm the fears of Lia's competitors, who were literally blown out of the water after she started transitioning from male to female when she was 19.
She has since soared to the top of the women's league tables, whereas she was unheard of as a male athlete.
The swimmer's teammates at Princeton have anonymously fought to have her excluded from the category.
They are too frightened to speak publicly about the issue for fear of being kicked off he team or lampooned by LGBTQ activism.
Lia, 22, has rarely spoken about the row but in a recent interview with Sports Illustrated, she defended her position saying: 'I am a woman, just like anybody else on the team. I've always viewed myself as just a swimmer.
'It's what I've done for so long; it's what I love.
'I get into the water every day and do my best,' she said.
In the Times article, one of the teammates revealed she had been rejected from a social eating club at Princeton because she had branded 'transphobic' for questioning Lia's place in the sport.
Her place has divided the world of sport.
Some say she should be allowed to compete in the category she identifies with whereas others, including tennis legend Martina Navratilova - who is gay - say it's unfair.
Navratilova was admonished for tweeting about Lia's situation and suggesting that she should compete with an asterisk next to her name.
She told the Times: 'I played against taller women, I played against stronger women, and I beat them all.
'But if I faced the male equivalent of Lia in tennis, that's biology. I would have had no shot. And I would have been livid.'
Trans tennis player Renee Richards transitioned from female to male in her 40s.
She said in an interview in 2012 that she had changed her position to acknowledge that male biology gives trans female athletes an advantage.
'Having lived for the past 30 years, I know if I'd had surgery at the age of 22, and then at 24 went on the tour, no genetic woman in the world would have been able to come close to me. And so I've reconsidered my opinion.
'There is one thing that a transsexual woman unfortunately cannot expect to be allowed to do, and that is to play professional sports in her chosen field. She can get married, live as woman, do all of those other things, and no one should ever be allowed to take them away from her.
'But this limitation — that's just life. I know because I lived it,' she told Slate in 2012, years before Lia transitioned.
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