Equine exertional rhabdomyolysis, known historically as Monday morning disease, causes painful muscle breakdown. Dietary and management changes largely prevent recurrence.
Equine rhabdomyolysis is intensely painful, causing muscle cramping and spasm comparable to severe muscle injuries in humans. Horses that continue working through an episode risk catastrophic muscle damage and organ failure. The welfare impact extends beyond the acute episode — chronically susceptible horses may experience repeated painful episodes if management changes are not made. The condition is largely preventable through appropriate dietary management: reducing non-structural carbohydrates on rest days, maintaining consistent low-level exercise rather than boom-bust patterns, and identifying underlying metabolic causes in horses with recurrent episodes.