Athletes on the University of Pennsylvania women's swimming and diving team have put out an open letter to UPenn and the Ivy League asking them to follow the new transgender guidelines issued by USA Swimming and to refrain from taking legal action against the NCAA.

Sixteen athletes, led by three-time Olympic gold medalist Nancy Hogshead-Makar, published the open letter Thursday morning asking the school and the Ivy League "to support us as biological women." According to Swimming World, the letter was written in response to a statement by several members of UPenn's swim team in support of Lia Thomas, a male who identifies as female.

Hogshead-Makar, a civil rights lawyer and CEO of Champion Women, is an advocate for women's rights and has fought for equal opportunity for women in sports. She has criticized policies pushing for the inclusion of transgender athletes in women's sports, noting that biological men have unfair advantages when competing against women.

The letter praised new "Athlete Inclusion Procedures" released by USA Swimming on Tuesday, guidelines for including transgender athletes in women's sports that acknowledge the "competitive difference in the male and female categories and the disadvantages this presents in elite head-to-head competition."

“Tuesday, USA Swimming released new ‘Athlete Inclusion Procedures’ shortly after the NCAA acknowledged that each sport should determine how fairness and inclusion were to be accomplished,” the letter states. “In particular, we appreciate USAS Guideline’s guiding purpose, to ensure that transgender women competing in the Female competition category 'do not have an unfair advantage over their cisgender Female competitors in Elite Events.'"

“We fully support Lia Thomas in her decision to affirm her gender identity and to transition from a man to a woman. Lia has every right to live her life authentically," the letter continues.

“However, we also recognize that when it comes to sports competition, the biology of sex is a separate issue from someone’s gender identity.”

The swim team members write that as a biological male, Thomas has an "unfair advantage" over female competitors and that some women have missed opportunities as a result.

“The Penn Women’s Swimming Team has over 40 women, but only 18 of us are chosen to compete in the end-of-year culmination of our work: the Ivy Championships,” they write.

“Most important to us is that Lia’s inclusion with unfair biological advantages means that we have lost competitive opportunities. Some of us have lost records. But even those that swim different events than Lia or were not in contention to make the Ivy Championships, we stand by our teammates who have lost out.

“It has often felt like Penn, our school, our league, and the NCAA did not support us.”

The letter says these athletes have been threatened with losing job offers or getting kicked off the team for speaking out.

"When media have tried to reach out to us, these journalists have been told that the coaches and athletes were prohibited from talking to them," the letter states. "We support Lia’s mental health, and we ask Penn and the Ivy League to support ours as well."

The women emphasized that Thomas is welcome to train with them and that they want to find a place for transgender athletes to compete against others fairly.

"However, sport is competitive by definition, and Lia’s wins, records, and honors should not come at our expense, the women who have worked their entire lives to earn a spot on the Penn Women’s Swimming Team," they write.

The debate over how to include transgender athletes in sports at both the high school and collegiate levels has ignited national controversy. Some states have taken action to prohibit gender dysphoric males from competing against women with "Fairness in Women's Sports" bills. South Dakota Gov. Kristi Noem (R) has been credited with proposing the strongest version of this legislation, which would prohibit any student at a state school from joining a sports team that does not match his or her biological sex.

Advocates for LGBT Americans say it is unfair and discriminatory to prohibit student athletes from expressing themselves by competing on the teams with which they identify.

But female athletes have pushed back, arguing that men have natural advantages that make them stronger and faster than women, advantages that do not go away with hormone therapy or because a male identifies as female.

For example, Ainsley Erzen, a high school athlete that won the girls 800-meter high school national championship in track, wrote in a recent op-ed that her record-breaking accomplishments for women would be a poor performance for a male athlete.

"My time of 2:06.52, the time that made me the fastest Iowa high school female 800 runner of all time, the time that earned me the title of national champion, was easily beat by 85 high school boys at the 2021 Iowa high school state track meet alone. Eighty-five. Just in our small state of Iowa.," Erzen wrote for the Des Moines Register.

"The results of the 2021 Drake Relays proved to be no different, as the last male runner came through the line in a time of 2:03. That same year, a time of 2:13 was enough to make me the 800-meter Drake champion. The slowest boy was easily 10 seconds faster than the first-place girl."

Erzen goes on to argue that the different standards set for male and female competitions are all the evidence needed to show that biological differences matter and that women need to be protected from unfair competition.

For the members of the UPenn swim team that wrote the letter, the proof is in Lia Thomas' dominant performance against female competitors.

The new USA Swimming transgender policy requires athletes to provide evidence "that the prior physical development of the athlete as a male, as mitigated by any medical intervention, does not give the athlete a competitive advantage over the athlete’s cisgender female competitors."

Transgender competitors must also show evidence "that the concentration of testosterone in the athlete’s serum has been less than 5 nmol/L (as measured by liquid chromatography coupled with mass spectrometry) continuously for a period of at least thirty-six (36) months before the date of application."

The policy is only applicable to athlete members of USA Swimming.

It was implemented after the NCAA announced last month that the governing bodies of each sport would be given the authority to determine athlete eligibility, including polices on the inclusion of transgender athletes.