DESCRIPTION: Current U.S. Veteran demographics reveal an aging population with significant cardiovascular dysfunction. This ultimately manifests as mobility limitation, inactivity, and a subsequent worsening of cardiovascular disease (CVD) that often leads to death. However, despite this clear negative cycle of events, there is not a single clinically accepted, and therefore routinely utilized, method of assessing vascular health. As nitric oxide (NO) is anti- atherogenic and cardioprotective, identifying an in vivo bioassay of NO bioavailability has significant worth in ths arena. Passive leg movement (PLM) and the subsequent blood flow increase, measured non-invasively by ultrasound Doppler in the common femoral artery, is emerging as a method by which vascular endothelial function and therefore NO bioavailability can be determined, however, this method is still in its infancy. Here, we propose the validation and characterization of PLM, as a novel, clinically relevant, method to determine vascular health and guide rehabilitation. With the growing interest in personalized medicine, the development of tools, such as PLM, that allow individualized assessments to guide the physician, the patient, and the rehabilitative team, are essential. Therefore two specific aims are proposed that will address the Central Hypothesis that PLM is an NO-dependent, reproducible, and clinically relevant tool to assess vascular health across the human lifespan. The ultimate goal of the proposed studies will be to assist in catalyzing the transition of the assessment of endothelial function by PLM from research to clinical practice.