 The investigators will test the hypothesis that PAD patients using an AFO during a graded exercise test will demonstrate a greater PWT compared to PWT assessed without the use of an AFO. Secondary hypotheses include evaluation of the effect of an AFO on: 1 calf muscle function, 2 claudication onset time, 3 functional ability, 4 peak oxygen consumption, and 5 patient-reported outcomes. We will also examine the effects of the AFO on outcomes following 12 weeks of community walking. 