This work will: a) identify whether vascular stiffness and indices of NO action are impaired throughout the arterial tree in DM1; b) identify the impact of fitness, MCR blockade or the combination to improve vascular function; and c) introduce a rational paradigm for early, proof-of-concept testing of interventions that may improve vascular health in DM1. While multiple endpoints are measured in the proposed studies, the investigators designate one primary conduit vessel endpoint (augmentation index) and one primary microvascular endpoint (microvascular blood volume by CEU); the studies are powered on these measures. The investigators believe that their laboratories are in a unique position with respect to their demonstrated scientific expertise to deliver this fundamental information.