EIPH often occurs in horses that race at high speeds, with the number of affected race horses increasing in proportion to the speed and intensity of the exercise. It may occur in racing Thoroughbreds (flat racing, steeplechasing or jump racing), American Quarter Horses (incidence of 50–75%), Standardbreds (incidence of 40–60%), Arabians, and Appaloosas. EIPH also occurs in eventers, jumpers, polo ponies, endurance horses, draft horses that pull competitively,[1] and horses taking part in Western speed events such as barrel racing,[2] reining and cutting.