Recurrent exertional rhabdomyolysis (RER) develops in 5-10% of Thoroughbred racehorses. High-stress environments, nervous temperament, and diet influence the presentation of RER. RER-susceptibility is associated with alterations in intramuscular Ca2+ regulation with detrimental effects on mitochondria. Our study aims to determine underlying molecular drivers influencing RER-susceptibility by comparing the muscle proteome of control, RER-susceptible, and RER horses treated with dantrolene. Animals used in this study were Thoroughbred mares in race training between episodes of RER.