Michael Phelps is just one Olympic athlete involved in horse racing. (Eclipse Sportswire) Olympic athletes love competition and horse racing is one outlet where many of them get their fix in the off-season (or year-round). Read up on some of the current and past Olympians involved in Thoroughbred racing and get ready for Rio's opening ceremonies this Friday. Michael Phelps With 22 Olympic medals, swimmer Michael Phelps is the most accomplished U.S. Olympian of all time. He’s