 Specific Aim 2. Determine how baseline and exercise-induced changes in the vascular parameters measured in specific aim 1 are related to LV systolic and diastolic functional reserve, cardiac output response, metabolic exercise performance, and changes in pulmonary capillary blood volume. LV systolic and diastolic function will be assessed by echo-Doppler and TDE parameters at rest and immediately after peak exercise. Cardiac output response will be determined by the product of echo-Doppler stroke volume and heart rate. Exercise performance will quantified by expired gas analysis. Pulmonary blood volume will be estimated based upon the ratio of diffusion capacity of nitric oxide and carbon monoxide, obtained both at rest and immediately post exercise. Regression analyses will then be performed using the measured components of afterload and vascular stiffness as the independent variable and each of the above parameters as dependent output variables to delineate the role of vascular stiffening on exercise performance, reserve and ventricular-vascular coupling. 