CARDIOVASCULAR RESPONSE TO EXERCISE



The heart responds to exercise principally by adrenergic stimulation and vagal withdrawal, which increase heart rate and contractility, and by peripheral circulatory alterations . The increase in heart rate usually accounts for the majority of the increase in cardiac output. Increased contractility contributes to the increase in cardiac output by increasing the stroke volume.

Vessels supplying exercising muscles dilate, whereas the remaining vascular beds vasocon-strict. Isometric and isotonic exercises affect the cardiovascular system somewhat differently. The predominant response to isometric exercise (e.g., weight lifting) is an increase in peripheral vasoconstriction with a subsequent increase in arterial pressure. In contrast, isotonic exercise (e.g., jogging) reduces systemic vascular resistance primarily in exercising muscles, which improves cardiac output. Those who exercise regularly obtain a cardiac training effect, with a lower resting heart rate and a greater capacity to increase cardiac output during exercise.