In the United States, most endurance rides are either 50 or long. Shorter rides, called Limited Distance rides (LD), are organized for new riders to the sport or young horses being trained. However, LD's have evolved into a competition of their own, in which more experienced riders and horses also participate. There are also longer, usually multi-day, rides as well. In the US, the American Endurance Ride Conference (AERC) sanctions endurance rides. In the UK, Endurance GB is the governing body. Winning riders can complete rides in 14 to 15 hours.