Objectives: To describe gait alterations associated with impaired walking endurance in patients with and without lower-extremity peripheral arterial disease (PAD) and determine whether the Caltrac accelerometer provides a valid measure of physical activity in PAD.
Design: Cross-sectional.
Setting: Academic medical center.
Participants: PAD (n = 40) and non-PAD patients (n = 22) from two Chicago hospitals.
Measurements: Participants underwent measurement of the ankle brachial index (ABI), leg length, and 6-minute walk. Steps per minute and step length were measured during the first and last 100 feet of the 6-minute walk. Participants wore a Caltrac accelerometer, sensitive to vertical acceleration, during the 6-minute walk and for 7 continuous days.
Results: Five PAD participants (13%) and one non-PAD participant (5%) ceased walking before the end of 6 minutes. Among the remaining participants, distance walked in 6 minutes was more highly related to walking velocity during the last 100 feet of the walk than walking velocity during the first 100 feet. ABI was associated significantly with cadence (20.77 steps/minute per unit ABI, P <.001) but not step length (10.12 centimeters/unit ABI, P =.08). ABI was associated significantly with 6-minute walk distance (493 feet/unit ABI, P =.018), but this association disappeared completely after adjustment for step length and cadence. We found no difference in accelerometer scores between PAD and non-PAD participants over a fixed distance of 800 feet (7.34 vs 7.17 activity units, P =.789). However, scores were significantly different after 7 days (730.8 vs 1,485.0 activity units, P =.003).
Conclusion: Walking performance in PAD patients who completed 6 minutes of walking was largely determined by a decline in walking velocity rather than slower initial walking velocity. ABI was more closely associated with cadence than step length. Future studies should assess the effect of exercise programs and revascularization on cadence and step length in PAD.