All participants will have PAD. PAD will be defined as follows. First, an ABI <= 0.90 at the baseline study visit is an inclusion criterion for PAD. Second, potential participants who have an ABI > 0.90 but ≤ 1.00 and experience a 20% or higher drop in ABI after heel-rise exercise will be eligible. Third, potential participants with an ABI > 0.90 who have vascular lab evidence of PAD or angiographic evidence of PAD will be eligible. Finally, potential participants with a history of lower extremity revascularization who do not meet the criterion above and have an ABI > 0.90 with a 20% or higher drop in ABI after heel-rise exercise will be eligible.