AIM 3: To determine the acute and chronic L-citrulline supplementation on endothelial function by measuring flow-mediated vasodilation, vasoactive substances, and Endothelial Progenitor Cells (EPCs). This aim will examine the working hypothesis L-citrulline will result in greater circulating levels of vasodilatory substances including nitric oxide, prostacyclin, and EPCs whereas vasoconstrictor substances endothelin-I (ET-1) will decrease. This aim will be tested by measuring serum levels of these substances before and immediately after the session at baseline and 7 days after the intervention.