For nearly 40 years, Martha Karolyi has dominated the world of gymnastics. Together with her husband, Bela, they’ve coached generations of U.S. gymnasts. Now Karolyi is set to retire from her official role as national team coordinator for USA Gymnastics after the Summer Olympics. NPR’s Audie Cornish talks to Dvora Meyers, author of The End of the Perfect 10: The Making and Breaking of Gymnastics’ Top Score from Nadia to Now, about her legacy.