Leg Heat Therapy in Peripheral Artery Disease

Inclusion Criteria: * Men and women older than 50 years * Resting ankle-brachial index (ABI) of 0.9 or less in at least one leg. Individuals with a resting ABI between 0.91 and 1.00 at baseline will be eligible if their ABI drops by 20% or greater following a heel-rise test. Exclusion Criteria: * Critical limb ischemia (ischemic rest pain or ischemia-related, non-healing wounds or tissue loss) * Prior foot or leg amputation * Exercise tolerance limited by factors other than leg pain (e.g. angina, arthritis, severe lung disease, etc). * Recent (\<3 months) lower-extremity revascularization or orthopedic surgery * Use of walking aid other than a cane * Active cancer * Chronic kidney disease (eGFR \<30 by MDRD or Mayo or Cockcroft-Gault formula) * Class 2 or 3 obesity (BMI ≥ 35 kg/m2) * Unable to fit into water-circulating trousers * A Mini-Mental Status Examination score \<23 * Impaired thermal sensation in the leg As this study involves MR imaging, patients that have contraindications to MRI will be included in the study but will not be allowed to participate in the MRI experiment. Information about biomedical devices that may pose a risk to patients undergoing MRI is available on the Internet at www.MRIsafety.com. These exclusions include: cardiac pacemaker, implanted cardiac defibrillator, aneurysm clips, carotid artery vascular clamp, neurostimulator, insulin or infusion pump, implanted drug infusion device, bone growth/fusion stimulator, cochlear, otologic, or ear implant and history of claustrophobia or who are unable to lie flat or who do not fit inside the bore of the scanner.