Known changes of the hypothalamic-pituitary-adrenal (HPA) axis, as well as other neurotransmitter systems, lead to alteration of peripheral and central nociception during acute and chronic stress. Exercise is one example of such physiologic stress. Exercise, in various forms, has been shown to exert effects on pain attenuation. Several studies have demonstrated post-exercise reduction in pain ratings, increased pain threshold as well as attenuation of pain-related increases in motor evoked potentials. This phenomenon is referred to as exercise-induced analgesia (EIA) or, perhaps more accurately, exercise-induced hypoalgesia (EIH).