Femoral Doppler Blood Flow. Contrast-enhanced Ultrasound. Immunoassay of Serum and Muscle Inflammatory Biomarkers. For both experimental groups, the investigators will assess various serum and muscle cytokines including TNF-a, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, GM-CSF, and IFN-γ. Samples will be measured by immunoassay using the Millipore high sensitivity Human Cytokine-13plex kit (Millipore, Billerica, MA). TGF-β will be determined using the Millipore Single Plex kit.