“…Exercise is a naturally a stressor per se and induces a biologic response that can be either an enhancer or a limiting factor for an athlete’s sporting ability [ 11 ]. Yet, in competitions, equine athletes face a mixture of other stressors including transportation [ 12 ], veterinary examinations [ 13 ], rider’s ability [ 14 ], a new and a noisy environment [ 15 ], separation from stablemates [ 16 ] and, specifically in endurance, exposure to large conglomerations of unfamiliar horses in large starts, and musculoskeletal pain from an injury that might arise [ 17 ] that can also elicit a stress response. Moreover, individual intrinsic factors such as age, gender, breed, inherited temperament, experience, and previous training [ 11 ] are known to impact stress biomarkers.…”