USA Swimming announced Tuesday new rules regarding the participation of transgender women in "approved elite events."
Effective immediately, transgender women swimmers who are USA Swimming athletes must maintain a testosterone level below 5 nanomoles per liter continuously for at least 36 months before competition.
In addition to testosterone levels, transgender women must provide evidence that they do not have a competitive advantage from being assigned male at birth. The evidence will be reviewed by a panel of three independent medical experts.
Past rules that governed Olympic-level swimmers mandated testosterone levels below 10 nanomoles per liter for one year. USA Swimming said its new policy will not apply to non-elite athletes.
"USA Swimming has and will continue to champion gender equity and the inclusivity of all cisgender and transgender women and their rights to participate in sport, while also fervently supporting competitive equity at elite levels of competition," USA Swimming said in a statement. "While recognizing the need for the aforementioned guidelines in elite competition, sport is an important vehicle for positive physical and mental health, and, for this reason, USA Swimming remains steadfast in its continued commitment to greater inclusivity at the non-elite levels."
Swimming has become a focus of debate around transgender inclusion in sports because of the success of Penn swimmer Lia Thomas. Thomas previously swam for three seasons on the Penn men's team, and has posted some of the top times in the 200-yard, 500-yard and 1,650-yard freestyle events during her first season on the women's team.
On Jan. 19, the NCAA announced that, effective immediately, it would adopt, on a sport-by-sport basis, the policies of national governing bodies to determine eligibility for transgender athletes. Although USA Swimming is the national governing body for swimming, it is unclear whether the NCAA will enforce the new policy for the current season.
The NCAA has not responded to a request for comment, and Penn said it is working with its compliance office to determine Thomas' eligibility.
Last summer's Tokyo Olympics were the first to see publicly out transgender athletes compete. Laurel Hubbard, a weightlifter from New Zealand, and Chelsea Wolfe, an alternate on the United States BMX team, became the first transgender women to qualify for the Olympics. Canadian soccer player Quinn and American skateboarder Alana Smith became the first out non-binary athletes to compete at the Olympics.