There are two main types of long distance riding, Endurance and Competitive trail riding. In an Endurance ride the winning horse is the first one to cross the finish line while stopping periodicaly to pass a veterinary check that deems the animal in good health and "fit to continue." In the US, most endurance rides are either 50 or 100 miles long, though shorter rides are organized for beginner and a few longer, usually multi-day rides exist. In the US, the American Endurance RIde Conference (AERC) sanctions endurance rides. Winning riders complete 100 mile rides in 10-12 hours.

Any breed con compete, but the Arabian generally dominated the top level because of the breed's stamina and natural endurance abilities.

Competitive trail rides are shorter, and factor other than speed are considered, horses may not com in under or over certain time, and veterinary checks, rider behavior and other elements play a role in the placings. 

Worldwide, rules vary. Endurance rides and  races can be any distance, though rarely over 160 km for a one-day competition.

For further information please check the web site of the THAI EQUESTRIAN FEDERATION: www.tefcenter.com