Felix, the most decorated U.S. track and field athlete in history, announced her decision on Instagram. The 36-year-old has won 11 Olympic medals over the course of her career.

It started when Moustapha Sané lost his wallet in Dakar. He created the Facebook page "Trouvés ou Perdus" (French for found or lost). It often leads to a reunion, though some pigeons are still M.I.A.

David Brown already has one Paralympic medal under his belt. He and sighted guide Moray Steward hope to sprint their way to another in Tokyo.

"You're running against grown men, so you've got to do everything you can to beat them," Erriyon Knighton said. He's had a dramatic rise in track, beating a long-standing record set by Usain Bolt.

This weekend, Mary Louise Kelly continues a family tradition — running the Peachtree Road Race. It won't be in person, but it will bring her a chance to run with her father's spirit in her heart.