The Effects of Exercise Training on Cardiac Autonomic Nervous Activity

Autonomic nervous system plays an important role in the regulation of the cardiovascular system both in ensuring optimal function during various activities in healthy individuals and also in mediating several of the manifestations of cardiac diseases [Task Force, 1996]. This system is responsible for rapid regulation of cardiac rhythm and function in order to match cardiac output with the body need during various exogenic stimuli, as exercise. Therefore, sympathetic outflow to the heart and withdrawal of the parasympathetic system activity underlie the cardiovascular system's first response to exercise, an increase in heart rate. In the short term, activation of the sympathetic nervous system is a compensatory protective mechanism. However, chronic activation of sympathetic nervous system has been shown to produce adverse effects on the myocardium and the peripheral circulation, and these effects are believed to contribute to cardiac and vascular structural alterations, that may advance disease progression [Makikallio et al., 2001].