Each time University of Pennsylvania swimmer Lia Thomas dives off the race block, she’s swimming against more than just the women next to her.

The 22-year-old transgender woman holds the fastest swim times in the country among NCAA women in two events.

But Thomas’ success has placed her at the center of a heated national debate on transgender athletes’ — especially trans women’s — rights to play sports, and even led the NCAA and national swimming league to change their eligibility policies.

Thomas’ detractors say that her male-at-birth assignment gives her an unfair biological advantage, while supporters say that because Thomas has followed all eligibility protocols, she has a right to compete.

National attention is unlikely to waver anytime soon. At the Ivy League Championship, Thomas was crowned a champion in three events, and broke three Harvard University Blodgett Pool records and two Ivy League meet records.

And in March, all eyes will be on Thomas as she joins the nation’s other top swimmers at the NCAA championships.

So, what is the controversy? Do trans women retain physical advantages? And what are the NCAA’s rules?

In the words of a top researcher: “It’s a complicated thing.”

Here’s what you need to know about Thomas, the debate, and the science behind hormone therapy.

Who is Lia Thomas?

Lia Thomas is a 22-year-old senior on the Penn women’s swim team. She swims freestyle.

Thomas, who hails from Austin, Texas, is a transgender woman, meaning she was assigned male at birth and is a woman.

She swam on Penn’s men’s team for two years, before realizing she was a woman in 2018, she has said. She was worried about how coming out would affect her swimming career, she said in a previous interview, and waited a year to begin medically transitioning.

“I was struggling, my mental health was not very good. It was a lot of unease, basically just feeling trapped in my body. It didn’t align,” she said.

“I decided it was time to come out and start my transition.”

She started taking testosterone suppressants and estrogen supplements in May 2019 and came out to her teammates that fall. She continued competing on the men’s team that season while taking the suppressants.

Thomas began submitting medical proof and paperwork to the NCAA in summer 2020 and was approved for eligibility. She did not compete at all last year as the season was canceled by the pandemic. This is her first season on the women’s team.

Thomas has shattered school records and holds this year’s fastest time in the 200- and 500-yard freestyle. She’s an NCAA championship favorite.

Thomas burst into the spotlight in early December after a record-breaking meet in Akron, Ohio.

She swam the 200y free in 1 minute, 41.93 seconds, marking the fastest time in the nation among college women this year and setting school, pool, and program records — edging out the previous top women’s time by just six-tenths of a second.

Thomas also posted the nation’s best 500y freestyle time at 4:34.06 seconds — besting the previous top time by seven-tenths of a second.

At the Ohio meet, Thomas finished the 1,650y race nearly 38 seconds before the second-place finisher. A clip of the race went viral, with critics using it as “evidence” that Thomas held an unfair biological advantage.

She hasn’t set any national records.

Earlier this month, 16 members of the Penn women’s swim team sent a letter to the university and Ivy League, speaking out against Thomas’ participation in the championship meets, claiming she has an unfair advantage and is taking “competitive opportunities” away from other women on the team.

“When it comes to sports competition, ... the biology of sex is a separate issue from someone’s gender identity,” they wrote. “Biologically, Lia holds an unfair advantage over competition in the women’s category.”

They said that because Thomas went through male puberty, her body will always have advantages, such as height, larger lungs, and more strength.

Others, such as former Olympic swimmer and lawyer Nancy Hogshead-Makar, have said the percent change in Thomas’ race times hasn’t lowered enough after taking hormones to be what she believes is fair. She said that in swimming, women’s race times are typically 7% to 13% slower than men’s, depending on the event.

Compared with her times before starting hormone therapy, Thomas’ top times in the 200y freestyle have dropped by about 3%, and her 500-free time dropped about 6%. Her 1,650-free time dropped the most, by just over 7%.

She has also pointed to Thomas’ jumps in the rankings, noting she went from being ranked average in the men’s league to being the top swimmer on the women’s league.

“You can say that’s not fair,” said Hogshead-Makar, CEO of Champion Women.

She also said the NCAA rushed into its original trans inclusion policy in 2011 before much research was available, and failed to make any updates until this year amid the controversy. She said sports organizations should “let science be the guide.”

Some argue that because Thomas has fulfilled all eligibility requirements, she should be allowed to compete. They say that she’s not successful because she’s trans but because she is a hardworking athlete racing in a sport she loves as her authentic self.

“Lia is a woman,” Schuyler Bailar, the first openly trans Division I male swimmer, previously told The Inquirer. “Sports require people to beat other people. That’s how they work. Any woman beating any other woman is not stealing a spot but earning a spot.”

Bailar sent a letter of support for Thomas to the NCAA last week, signed by 310 current and former collegiate swimmers, including five of Thomas’ teammates.

“Protecting women’s sports means protecting all women,” Penn law students wrote in a Daily Pennsylvanian column.

Thomas has fulfilled all eligibility requirements, and after undergoing hormone therapy for nearly 33 months, experts have said, Thomas’ testosterone levels have likely lowered to that of the average cis-woman’s — or a woman whose gender identity matches what they were assigned at birth.

Many trans athletes often take time off or step away from sports entirely once they begin their transition, experts said, due to discomfort or public scrutiny. Thomas hasn’t.

“Her visibility has already and will save lives,” Bailar said.

Brooke Forde, a Stanford swimmer and Olympian who won the NCAA championship in the 500y free in 2019, said she welcomes Thomas’ competition and has great respect for her. Thomas will likely be one of Forde’s key competitors in March.

“I believe that treating people with respect and dignity is more important than any trophy or record will ever be, which is why I will not have a problem racing against Lia at NCAAs this year,” Forde wrote in a statement.

Source: Swim Cloud (Rankings are not exclusive to that year but are overall rankings among college swimmers of previous years, too.)

In January, the NCAA revised its policy on transgender athletes’ eligibility, effective immediately.

The previous policy from 2011 allowed trans athletes to compete on the teams that aligned with their gender identity, as long as trans women completed one year of testosterone-suppression treatment.

Now, instead of a uniform policy across all sports, the NCAA will use the policy of each sport’s national governing body, meaning that eligibility requirements will vary by sport. If a sport’s national governing body does not have a policy, it defers to the international body. If there is no international policy, the International Olympic Committee’s policy will be followed.

The NCAA will also now require testosterone testing in championship windows, and at designated points throughout the year starting in 2022-23.

Earlier this month, USA Swimming — the national governing body — announced a new policy that will require trans women athletes to submit an application to compete to a three-member panel of “independent medical experts,” who will determine whether “prior physical development of the athlete as a male” gives the athlete “a competitive advantage over the athlete’s cisgender female competitors.”

The swimmer must also show that their testosterone levels have been less than 5 nanomoles per liter continuously for at least 36 months, which experts have said is excessive.

The NCAA announced Thursday that it will not adopt USA Swimming’s policy ahead of the national championship, clearing the way for Thomas to compete. The NCAA may adopt the policy for competition after next month’s championship.

To remain eligible, Thomas just must show that her testosterone levels are below 10 nmol/L, four weeks before the championship.

Not all trans and nonbinary people undergo hormone therapy. Medical transition is not the benchmark of gender identity, and neither are hormones.

In certain sports leagues, hormone therapy is required, but there are so few elite trans athletes, and even fewer participating in medical studies, so there’s not much research on the subject.

There are a few studies to draw from, though.

How quickly a person’s body changes depends on the hormone therapy regimen, said Joanna Harper, who is researching transgender athletic performance at Loughborough University in England.

In 2015, Harper analyzed 200 long-distance race times from eight trans women over seven years, including times before and after beginning hormone therapy.

Testosterone is a hormone that exists in everyone, but cis-men produce it at much higher levels, and during puberty, it contributes to such body changes as increased strength, bone density, and height. The continuous presence of testosterone also contributes to higher hemoglobin levels, which often give men stronger endurance capabilities, and explosiveness in sports.

According to Harper’s research, within one month of taking testosterone-suppressing drugs and estrogen, a trans woman’s testosterone levels can drop to that of the average cis-woman’s.

Her study also found that within four months, a trans woman’s hemoglobin levels will drop to that of the average cis-woman’s. Within one year of taking hormone therapy, the trans women ran 12% slower — the average time difference between elite male and female distance runners.

“The biggest strength [loss] changes occur within the first year,” Harper said.

Christina Marie Roberts, a pediatric physician at Children’s Mercy Hospital in Kansas City, Mo., published a study in 2020 examining the fitness test scores of transgender members of the Air Force before and after beginning hormone therapy.

The research showed that trans women’s physical fitness started to significantly decline between the first and second year on hormone therapy, Roberts said, and by the end of the second year, the number of push-ups and sit-ups performed by a trans woman was equal to the average cis-woman’s. Trans women’s run times remained slightly faster.

It depends when they begin hormone therapy and how long they’ve been on it, Harper and Roberts said.

Trans youth who begin hormone therapy before puberty or early into puberty will have little to no physical advantages over their cis-gender competitors, Roberts said.

Trans women who begin their medical transition after puberty will always retain some physical advantages, Harper said, such as height and limb length. Their overall strength levels will also never fully reduce to that of the average cis-woman’s, Harper said.

“It’s a complicated thing,” she said. She said each sport requires its own analysis, especially those that are more physical and where safety concerns could come into play.

“Their bigger frames are now going to be powered by reduced muscle mass, reduced aerobic capacity,” Harper said. “It’s a lot more complex than people would think.”

Pressure and chronic stress caused by public scrutiny can also affect an athlete’s performance and mental health, and make the person feel ostracized, Roberts said.

“The idea of a level playing field is illusory,” Harper said, whether it be physical advantages, such as Michael Phelps’ high-functioning lungs, or socioeconomic status.

“We celebrate athletes who have advantages,” she said. “Anyone who’s ever guarded LeBron James can tell you that he has advantages, right?”

The more accurate phrase to use is “meaningful competition” — such as dividing sports and athletes by age, weight, and/or gender so there’s equal opportunity to win.

“So the question is ‘In women’s sports, can we have meaningful competition between trans women and cis women?’” she said. “Definitive numbers are still maybe 20 years away. But I think that in most sports, we can have meaningful competition.

“Lia’s advantages haven’t entirely gone away, let’s be clear on that,” she said. Harper said the entire advantage may “go away eventually” in some sports, but “there’s no definitive research at this point.”

No. And no trans person transitions just to get an “edge” in sports.

Harper said groups seeking to ban trans athletes altogether often use fearmongering to claim that “trans women are taking over women’s sports.” She said that if trans women make up about 1% of the population, and there are more than 200,000 women competing in NCAA sports, there should be about 2,000 trans women in college sports. But there aren’t, and Thomas is the first to be so successful.

“Trans women haven’t taken over NCAA sports. They’re still hugely underrepresented,” she said.

Hogshead-Makar said that elite trans women athletes should be able to be part of the team but not fully compete.

Some still say that’s exclusive and harmful.

“People talk about, ‘Oh, yeah, we should have a third division where we’ll put all the trans people.’ And I’m like, there aren’t that many of them,” said Roberts, the physician. “The whole point of inclusion is you’re including them.”

No. She has won some races but lost others. Her showing at the Ivy League Championship was the closest she’s come to replicating her success at the Ohio meet, but she still remained a few seconds off.

Yes. Thomas is not the first trans swimmer to begin transitioning during college, but she is one of the first to near championship-level competition post-transition.

There are also other highly successful trans women athletes, such as CeCé Telfer, who won an NCAA Division II title in the hurdles in 2019. There are many more trans athletes who — like everyone — are just average.