USA Swimming, the national governing body for competitive swimming in the United States, released a new policy Feb. 1 regarding male-to-female transgender athletes.

The Athlete Inclusion, Competitive Equity and Eligibility Policy requires a trans-identifying male to have a testosterone level of “less than 5 nmol/L” continuously for at least three years before competing in elite female swimming competitions. Additionally, a three-person panel of independent medical experts will determine if the transgender athlete has a “competitive advantage” over biological women based on “prior physical development of the athlete as a male.”

In a press release, USA Swimming acknowledged “a competitive difference in the male and female categories and the disadvantages this presents in elite head-to-head competition.”

The organization cited statistical data that shows that “the top-ranked female in 2021, on average, would be ranked 536th across all short course yards (25 yards) male events in the country and 326th across all long course meters (50 meters) male events in the country, among USA Swimming members.

“The [new] policy therefore supports the need for competitive equity at the most elite levels of competition,” it concluded.

The rules change comes on the heels of the NCAA’s announcement Jan. 19 that transgender participation for each sport will now be determined by the policy for the sport’s national governing body.

A transgender swimmer, known as Lia Thomas, has been at the center of the controversy concerning transgender athletes. Thomas, a biological male, has been shattering records during his first year as a member of the University of Pennsylvania women’s swimming team. But not all of his teammates welcome his participation.

According to SwimSwam, 16 members of the UPenn women’s swimming and diving team issued an open letter Feb. 3 to the school and the Ivy League asking them to submit to USA Swimming’s new guidelines. 

“Lia’s inclusion with unfair biological advantages means that we have lost competitive opportunities,” the letter reads. “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.”

USA Swimming said its policy will remain in place until swimming’s worldwide governing body FINA (Fédération Internationale De Natation) issues one of its own.