While many Americans will be tuning into the Super Bowl on Sunday, there's another big sports competition this weekend: the Cyclo-Cross World Championships. This weekend's event, in Louisville, Ky., marks the first time in its 60-year history that the world championships will be held outside of Europe. Cyclo-cross, a grueling sport requiring riders to traverse mud, sand and other obstacles, is growing rapidly in the U.S. And the fans can be a bit crazy. At the 2012 Louisville Derby City Cup, hundreds of people — some in costumes — packed onto the course to cheer the riders on.