ABSTRACT
Exercise intolerance, as a clinical sign, can have variable meaning depending on the observer's perspective. The use and expected performance level of the animal influence how easily exercise intolerance is perceived. Cardiovascular (CV) disease, as well as abnormalities in many other body systems, can underlie exercise intolerance. Several mechanisms, alone or in combination, can interfere with the animal's ability to sustain an optimal activity level. Cardiac disease often limits exercise capacity when the heart is unable to increase forward cardiac output (CO) sufficiently. Abnormal peripheral circulation contributes to inadequate skeletal muscle perfusion and fatigue during exercise. A weak or absent arterial pulse, coolness, pallor, pain, lack of sweating and venous return (horses), muscle contracture, or even paresis might be evident in the pelvic limbs. Ambulatory electrocardiography could uncover contributory arrhythmias, especially during exercise.
