Coronary heart disease(CHD) is the chief cause of death in postmenopausal women, and (1) reduced heart-rate (HR) variability, (2) increased blood pressure (BP) variability, (3) increased plasma concentrations of fibrogen and (4) plasminogen activator inhibitor-1 (PAI-1), (5) endothelial dysfunction,(6) plasma LDL-cholesterol greater than 160 mg/dl, (7) elevated plasma triglycerides, (8) increased fasting plasma and glucose, (9) obesity and (10) inactivity, are some of the CHD risk factors. Exercise is known to reduce risk factors (1) through (9) to a variable extent, but The possibility that different training intensities may alter the of these changes has not been adequately examined. We have recently observed that increased training intensity attenuates increases in insulin sensitivity in posmenopausal women. This attenuation of expected training effect could be mediated by catecholamine antagonism of insulin action. Increased training intensity could be increasing the sympathetic tone during the interval between daily walking bouts. As the effects of changes in sympathetic vagal control can be noninvasively monitored through changes in cardiovascular function, this study tests the hypothesis that increasing training intensity may adversely affect CHD risk factors (1) through (9) by increasing sympathetic relative to parasympathetic tone to the cardiovascular system during the interval between daily walking bouts. Forty healthy postmenopausal women will be used to study changes in CHD risk factors (1) through (9) as the function of training intensity, and a subset of 20 will be used for determination of urinary catecholamines (as an independent measure of sympathetic activation). Measurements will be taken at the start, after 15 weeks of training in the form of walking 24 km/week at either low exercise intensity set at individual's anaerobic threshold (AT) or at 25 % above the AT. The results will add to the understanding of the mechanism through which variable intensity of exercise training affects the physiology of postmenopausal women, and provide guidelines for setting the parameters of exercise training for optimal reduction of CHD risks.
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