Purpose: To determine the walking economy before and after the onset of claudication pain in patients with peripheral arterial disease (PAD), and to identify predictors of the change in walking economy following the onset of claudication pain.
Methods: A total of 39 patients with PAD were studied, in which 29 experienced claudication (Pain group) during a constant load, walking economy treadmill test (speed = 2.0 mph, grade = 0%) and 10 were pain-free during this test (Pain-Free group). Patients were characterized on walking economy (ie, oxygen uptake during ambulation), as well as on demographic characteristics, cardiovascular risk factors, baseline exercise performance measures, and the ischemic window calculated from the decrease in ankle systolic blood pressure following exercise.
Results: During the constant load treadmill test, the Pain group experienced onset of claudication pain at 323 +/- 195 seconds (mean +/- standard deviation) and continued to walk until maximal pain was attained at 759 +/- 332 seconds. Walking economy during pain-free ambulation (9.54 +/- 1.42 ml x kg(-1) x min(-1)) changed (P < .001) after the onset of pain (10.18 +/- 1.56 ml x kg(-1) x min(-1)). The change in walking economy after the onset of pain was associated with ischemic window (P < .001), hypertension (P < .001), diabetes (P = .002), and height (P = .003). In contrast, the Pain-Free group walked pain-free for the entire 20-minute test duration without a change in walking economy (P = .36) from the second minute of exercise (9.20 +/- 1.62 ml x kg(-1) x min(-1)) to the nineteenth minute of exercise (9.07 +/- 1.54 ml x kg(-1) x min(-1)).
Conclusion: Painful ambulation at a constant speed is associated with impaired walking economy, as measured by an increase in oxygen uptake in patients limited by intermittent claudication, and the change in walking economy is explained, in part, by severity of PAD, diabetes, and hypertension.