High altitude acclimatization produces a suite of physiological changes that might support an improved athletic performance at low altitude and thus lead to the strategy of athletic training at high altitude. Although there is substantial literature on high altitude physiology in humans, there are few studies on horses. Our interest in the physiological responses to high altitude in equids has been driven by the concerns of how athletic performance is altered at altitude and how conditioning at altitude may improve performance subsequently at low altitude. This review serves to illustrate what is currently know about the physiological changes of horses to altitude, at rest and during exercise, and to highlight how performance is impacted both at high altitude and subsequent return to low altitude.
