The Pain Trajectory During Treadmill Testing in Peripheral Artery Disease

Background Ischemia-induced pain associated with walking (claudication) in peripheral artery disease limits mobility and diminishes quality of life. Self-reports of pain during standardized treadmill testing are used in clinical trials to assess the efficacy of interventions. Objectives The aim of this study was to model pain trajectories during a peak walking test after 12 weeks of treatment in participants in four randomly assigned treatment groups (treadmill, arm ergometry, combination, and usual care) compared with baseline pain trajectories. Methods Self-reports of pain obtained at baseline and after 12 weeks of supervised exercise training for 41 participants (71% male; age, M = 64 years, SD = 8.6 years) were used. Pain was measured every 30 seconds with a numeric rating scale that had ordinal response options ranging from 0 (no pain) to 5 (severe pain). The test was continued until the maximum level of pain was reached and the participant could no longer walk. Observed responses from individual cases were plotted and patterns of pain were identified. A hierarchical generalized linear model for ordinal data was fit to compare baseline and postintervention trajectories. Results : Patterns in observed data reflected variations in time to onset of mild pain, acceleration to severe pain, and total walking time. All groups improved at 12 weeks; arm ergometry trajectories showed slower onset of pain, whereas treadmill training produced slower rates of increase to the maximum toward the end of the test. Effects for individuals appear as offsets from personal models at baseline. Discussion Change in the experienced claudication trajectory varied by type of exercise. Findings can inform design of future trials and aid decision making about exercise interventions for claudication.