Franklin published a heartfelt "thank you" and explanation on ESPN.com.
Missy Franklin was the golden girl of the 2012 London Olympics. Four years later she lost every one of her individual races in Rio.
Three Coloradans will compete on the U.S. Paralympic swim team, including Brickelle Bro, who was born without feet.
Franklin won four gold medals at the 2012 Summer Olympics. She wants to become the most decorated female swimmer ever.