Iowa State University Veterinarian

Document Type



Exercise related myopathies of horses have been recognized by horse owners and veterinarians for more than 100 years. Symptoms ranging from mild alterations in gait and attitude to severe muscle spasm, immobility, and myoglobinuria are common. Exertional myopathy has had many names: azoturia, Monday morning disease, tying-up, cording-up, paralytic myoglobinuria, paralytic hemoglobinuria, exertional rhabdomyolysis, and simply myositis, have been used to describe it in the literature. Many clinicians feel that azoturia and tying-up represent two different diseases with different etiologies. Most, however, have come to believe that there is one disease process, more appropriately termed exertional myopathy, with a wide range in severity of clinical signs.