A longtime exercise rider and the horse he was riding both died after a training accident early Saturday morning at Churchill Downs racetrack in Louisville. Odanis Acuna was “breezing,” or gently working out, 2-year-old colt New York Harbor just before 6 a.m., when the horse broke down about a sixteeth of a mile from the finish line. The horse broke either one or several bones in his leg and Acuna sustained fatal injuries to the head and neck during the fall, trainer Kenny McPeek told racing magazine Blood Horse.