Low InTensity Exercise Intervention in PAD

We will randomize 305 PAD participants to one of three parallel arms: Group 1: Low-intensity, self-paced walking exercise; Group 2: Standard high intensity, ischemic pain-inducing walking exercise; Group 3: Non-exercising attention control group. The low and high intensity exercise groups will attend center-based exercise sessions once per week for four weeks followed by transition to an entirely home-based exercise program for an additional 48 weeks (52 weeks total). Coaches will contact participants weekly by telephone after the first four weeks of the intervention. The low and high intensity exercise interventions will use identical self-regulatory and support strategies. However, the low intensity exercise group will be instructed to exercise with minimal to no ischemic leg discomfort and the high intensity group will be instructed to exercise to maximal ischemic leg pain. These two distinct exercise prescriptions will be reinforced during 48 weeks of home-based exercise, using a well-validated behavioral coaching model that can be delivered by telephone once weekly. Our primary outcome is change in six-minute walk distance at 52-week follow-up. If our hypotheses are correct, millions of people with PAD will benefit from this alternative exercise regimen which will be accessible to most of the 8 million people in the U.S. who suffer from PAD.

Inclusion criteria

All participants will have PAD. PAD will be defined as follows. First, an ABI < or = 0.90 at the baseline study visit is a well-accepted standard for the diagnosis of PAD and will be an inclusion criterion. Second, people with an ABI of >0.90 and < or = 1.00 who experience a 20% ankle systolic pressure drop after the heel-rise test will also be included. Third, potential participants with an ABI > 0.90 who have vascular lab evidence of PAD or angiographic evidence of PAD who have ischemic symptoms during the six-minute walk and/or treadmill exercise stress test will be eligible. In addition to meeting a criterion for PAD, all participants must be symptomatic, defined by one of the following criteria:; a) ischemic leg symptoms (primarily assessed with the San Diego Claudication Questionnaire); b) report ischemic leg symptoms at the end of the six-minute walk; c) report ischemic leg symptoms at the end of the baseline treadmill stress test; d) walking impairment questionnaire results, e) interview with the potential participant about the presence and nature of leg symptoms during walking activity.

Exclusion criteria

• Above or below knee amputation, critical limb ischemia, wheelchair confinement, or foot ulcer.
• Individuals whose walking is limited by a condition other than PAD.
• > Class II NYHA heart failure or angina. Increase in angina, angina at rest, or abnormal baseline treadmill stress test.
• Major surgery including lower extremity revascularization or orthopedic surgery during the prior three months or anticipated in the next twelve months.
• Major medical illness including renal disease requiring dialysis, lung disease requiring oxygen other than at night, or cancer (other than non-melanoma skin cancer) requiring treatment in the prior three years. Potential participants may still qualify if they have had treatment for early stage cancer in the previous three years and the prognosis is excellent.
• Mini-mental status examination score <23, dementia, or psychiatric illness including severe depression or anxiety. Investigator discretion may be used to allow some people with an MMSE below 23 to participate if the investigator determines there is another reason for their lower score, including lack of sufficient familiarity with the English language or lack of sufficient education to achieve a score of 23 or higher.
• Currently walking regularly for exercise at a level comparable to the amount of exercise prescribed in the intervention.
• Current or recent (within 3 months) participation in another clinical trial or cardiac rehabilitation. For a clinical trial of a stem cell or gene therapy intervention, potential participants will be potentially eligible immediately after the final study visit for the clinical trial, so long as long as at least six months has passed since the participant received their final treatment in the stem cell or gene therapy intervention. For a clinical trial involving open-label therapy in which the treatment is not related to functional performance and will not change during the LITE Trial, participants may still qualify for the LITE Trial based on investigator discretion.
• Individuals with PAD who have a history of lower extremity revascularization and have a normal ABI.
• Individuals who are not able to walk for exercise at a sufficiently slow pace to avoid ischemic leg symptoms.