"When it comes to the female trans athlete, I'm confused," the lesbian swimmer said in a commentary on National Public Radio.

Diana Nyad, the long-distance swimmer who made history three years ago by swimming from Cuba to Key West at the age of 66, is one of the nation's most prominent out sports figures. So it's only natural that she has opinions on the current state of LGBT athletics.

In an NPR commentary aired Wednesday, Nyad discussed trans athletes. For the first time ever, trans men are being welcomed without restriction at the Olympics and trans women are being allowed to compete without having gender-affirming surgery (though no opently trans athletes are known to be competing in Rio). Nyad expressed personal conflict over female trans athletes, saying they may have a physical advantage over cisgender female athletes.

"If a male has gone through one year of hormone therapy and tests within the accepted range of estrogen-testosterone levels as female, even without undergoing sex-change surgery, she is now female, fair and square, in the world of sports. But is she?" Nyad said.

Nyad referenced trans tennis champ Renee Richards, who transitioned in the 1970s.

"Some of the women [tennis players] at the time, although respectful of Renee's personal life decisions, deemed it unfair to face a 6-foot-1-inch athlete who was not long before male, with bigger-than-normal hands, a smaller-than-normal hip girdle," the swimmer said.

Nyad ended her commentary by expressing support for the gender binary evolving in sports, but admitted, "When it comes to the female trans athlete, I'm confused."

Ultimate Fighting Championship champ and Olympic medalist Ronda Rousey raised eyebrows with similar comments in 2014. Roussey said she wouldn't fight a transgender woman because of a perceived advantage. Transgender fighter Fallon Fox disputed Rousey's assertion, saying, "I'm quite sure that there are quite a few female [mixed martial arts] fighters who have the guts to fight another skilled woman without peeing their panties. ... I think they may be a little more mentally tough and say, 'I'll fight a trans woman, just like I'll fight a lesbian woman or a black woman.'"

Meanwhile, medical professionals have said that trans women may actually be at a disadvantage because of hormone therapy, which can lead to decreased bone strength and muscle density. Others say that a trans woman who's a few years into her transition has musculature and bone structure very similar that of to her cisgender peers.