Exertional rhabdomyolysis (tying-up) is a painful muscle condition in horses that causes muscle breakdown during or after exercise, requiring careful management to prevent recurrence.
Tying-up causes acute, severe suffering: affected horses seize up mid-exercise, unable to continue, with muscles in agonizing spasm. The condition frequently occurs during or immediately after exertion, meaning affected horses often cannot return to their stable under their own power. The severity ranges from mild stiffness to complete inability to stand, muscle necrosis, and life-threatening kidney damage from myoglobin overwhelming renal filtration. Horses with chronic recurrent ER live under ongoing risk of painful episodes, and their management requires substantial modification of feeding and exercise that may conflict with performance demands. The welfare concern extends to horses in work pressure environments where signs of tying-up are minimized or the horse is pushed through episodes. Prevention is significantly more welfare-friendly than repeated treatment, and genetic testing now allows identification of horses with heritable forms before they enter work.