 The goal is to test the ability to detect improved calf muscle perfusion and energetics in PAD patients in a randomized controlled trial of home exercise therapy. Eighty patients will be randomized to a 12 week home exercise program or no program control. Patients will be studied before and after program completion with MRIMRS, calf muscle biopsy for capillary density, and exercise performance measures. Arterial spin labeling peak exercise calf muscle perfusion will be used as the primary endpoint in the most symptomatic leg. All will undergo ASL, peak exercise PCr recovery kinetics, calf muscle biopsy, and functional measures including treadmill exercise, VO2 testing, and 6-minute walk. Correlations will be examined between changes in perfusion and energetics with changes in capillary density, peak VO2, and functional capacity from before to after completion of home exercise therapy. 