Quantifying Exercise Intensity to Predict Changes in Walking Capacity in People with Chronic Stroke

Abstract: Objective: To examine if exercise intensity, quantified as heart rate or training speed, predicts walking outcomes in people with chronic stroke. Design: This is a secondary analysis from a larger randomized clinical trial (PROWALKS; NIH1R01HD086362). Setting: Four, outpatient rehabilitation clinics. Participants: Participants with chronic stroke with a walking speed of 0.3-1.0m/s and step-activity of <8000 steps-per-day. This analysis included participants (n = 169; age: 63.1 (+/- 12.5 years), 46% female) with complete pre- and post-intervention data. Interventions: Participants were randomized into (1) fast-walking training or (2) fast-walking training and step-activity monitoring group. Of importance, participants received up to 36-sessions of 30-minute high-intensity treadmill walking training across 12-weeks. Main Outcome Measure(s): The primary outcomes were a pre-to-post intervention change in six-minute walk test distance and fastest walking speed. Exercise intensity was quantified as either a percentage of heart rate reserve or self-selected walking speed. Results: Four, separate multiple linear regressions with robust errors analyzed the relationship of exercise intensity (predictor; % heart rate or training speed) on pre-to-post intervention changes in walking capacity outcomes (outcome; Six-Minute Walk Test, Fastest Walking Speed) after accounting for covariates. Training speed was a significant predictor of both a change in Six-Minute Walk Test distance (b = 0.364 (95% CI (0.108 - 0.621)), p = 0.006) and Fastest Walking Speed (b = 0.001 (95% CI (0.001-0.002)), p = 0.003). Heart rate was not a significant predictor of either outcome (both p > 0.096). Conclusions: Training speed significantly predicts changes in walking capacity outcomes in people with chronic stroke following. This suggests rehabilitation clinicians may use training speed as the metric of exercise intensity when prescribing walking interventions to people with chronic stroke.