From HelpWiki

HS stands for hunt seat. Hunt Seat classes judge the horse and how well it responds to the hidden cues of the rider.  Hunt Seat Over Fences is a competition to jump over a course of fences, or obstacles.  A hunt seat show is judged based on precision and control of the horse, as well as how well the horse moves and approaches the jump. A normal hunt seat class judges the horse. On the other hand, a hunt seat equitation class judges the horse and rider together. You'll know your WOSE horse is best suited to hunt seat shows if it gets excellent odds on the show entries page.

On WOSE, the Hunt Seat event includes the classes:
Hunt Seat
Hunt Seat Equitation
Hunt Seat Under Saddle
Hunt Seat Over Fences
Hunt Seat, Short Stirrup

Do not confuse Hunter Equitation with the regular Equitation (or EQ) class. A horse with excellent odds in Hunt Seat Equitation will not have excellent odds in regular Equitation.  If your horse has excellent odds in this event, it can go into any class and still have excellent odds.

History of Hunt Seat

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Hunt Seat in Real Life

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