The goal of this randomized, double-blind, sham-controlled clinical trial is to evaluate the benefits of home-based, leg heat therapy (HT) on lower-extremity functioning and quality of life in patients who suffer from lower-extremity peripheral artery disease (PAD). We will randomize 106 patients to one of two groups that either receive leg HT or a sham intervention. The primary study outcome is the change in 6-minute walk distance between baseline and the 12-week follow up. Secondary outcomes include changes in the short physical performance battery score, handgrip strength, quality of life (measured by the Walking Impairment Questionnaire and Short-Form (SF)-36 Questionnaire), calf muscle strength (measured using a calf ergometer), size (measured by magnetic resonance imaging) and bioenergetics (assessed using phosphorus-31 magnetic resonance spectroscopy), and physical activity (measured by accelerometer).

The lack of accessible therapies amenable for application in the home setting is a major obstacle for treating patients who suffer from lower-extremity peripheral artery disease (PAD). The investigators will determine whether unsupervised, home-based leg heat therapy (HT) improves walking performance compared to a sham intervention. Leg HT will be applied using water-circulating trousers coupled with a water pump and a water heater. Patients will be randomized into one of two groups: those receiving HT (n=53) or those receiving a sham treatment (n=53).The water heater and pump given to participants in the HT group will be adjusted to circulate water at 42ºC through the trousers. In the sham group, water at 33ºC will be circulated through the trousers. Participants will be asked to apply the therapy daily for 90 min for 3 consecutive months. Outcomes will be assessed at baseline, at the completion of the intervention (end of week 12) and at a follow-up visit, 12 weeks after the end of the intervention (week 24). The primary study outcome is the change in 6-minute walk distance between baseline and the 12-week follow up. Secondary outcomes include changes in the short physical performance battery score, which combines performance in walking speed, standing balance, and repeated chair rises, changes in handgrip strength, perceived quality of life (measured by the Walking Impairment Questionnaire and Short-Form (SF)-36 Questionnaire), calf muscle strength (measured using a calf ergometer), size (measured by magnetic resonance imaging) and bioenergetics (assessed using phosphorus-31 magnetic resonance spectroscopy), and physical activity (measured by accelerometer).

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.