This is fresh air, I'm Terry Gross. My guest, Champion Distance Runner, Lauren Fleshman,

is now a coach and activist working to reform the sports world to recognize the differences in

male and female bodies. She wants to stop framing female puberty as a threat to performance,

which results in practices that lead girls to become anorexic and stop menstruating,

disrupting the hormonal function essential to building healthy bones and a healthy body.

She says a surprising number of girls who enter sports programs aren't sticking around.

For those who do, physical and mental health problems occur at surprising rates,

and abuse is all too common. Many girls learn to hate their bodies. As a professional runner,

Fleshman says the only way to make a sustainable living is to get commercial endorsements.

For years, she was under contract to Nike. She has ideas about how that kind of contract needs

to be reformed too. She's now under contract with Wazel, a fitness apparel company for women

runners where she's a partner. Her new book, Good for a Girl, is a memoir and a critique of how the

sports world treats female athletes. Fleshman broke the American junior record in the 5,000 meters

race the first time she ran it, which qualified her for the Olympic trials. She is a graduate of

Stanford University, was a five time NCAA champion and won two national championships as a professional.

She retired from professional racing in 2016.

Lauren Fleshman, welcome to Fresh Air. In middle school, you were famous not only for winning races,

but for beating the boys in school. And then one day, you lost to a boy and you were crushed.

In retrospect, you attribute that to your body changing with puberty.

What changes did you experience personally as an athlete as you went through puberty?

Well, I had the benefit, I guess, in our current system. You'd call it that, of being a late bloomer.

So when I first got beat by one of my male peers in middle school in the mile, it was because he

...