Sixteen members of the University of Pennsylvania women’s swimming team sent a letter to university and Ivy League officials asking them to prevent a transgender teammate from competing in women’s races because she has a competitive advantage, the Washington Post reports.

Lia Thomas is a transgender woman who has been undergoing hormone therapy for two years.  While a member of the men’s swimming team at Penn, Thomas was ranked 462nd among swimmers; swimming in the women’s competition has vaulted her to top in the nation.

“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 read. “However, we also recognize that when it comes to sports competition, that the biology of sex is a separate issue from someone’s gender identity. Biologically, Lia holds an unfair advantage over competition in the women’s category, as evidenced by her rankings that have bounced from #462 as a male to #1 as a female. If she were to be eligible to compete against us, she could now break Penn, Ivy, and NCAA Women’s Swimming records; feats she could never have done as a male athlete.”

The letter was composed by sixteen members of the team, but they did not sign the letter for fear of repercussions from coaches and school officials.  Instead, the swimmers sent the letter through a former Olympic swimmer who is now a lawyer handling issues in women’s sports.

The swimmers want Penn and the league to stand down from a proposed lawsuit against a recent NCAA ruling that allows the proper jurisdictional body for each sport to determine the ability for transgender athletes to compete.