Within-Session Responses to High-Intensity Interval Training in Chronic Stroke

Poststroke hemiparesis often leads to a vicious cycle of limited activity, deconditioning, and poor cardiovascular health. Accumulating evidence suggests that exercise intensity is a critical factor determining gains in aerobic capacity, cardiovascular protection, and functional recovery after stroke. High-intensity interval training (HIT) is a strategy that augments exercise intensity using bursts of concentrated effort alternated with recovery periods. However, there was previously no stroke-specific evidence to guide HIT protocol selection. Purpose: This study aimed to compare within-session exercise responses among three different HIT protocols for persons with chronic (96 months after) stroke. Methods: Nineteen ambulatory persons with chronic stroke performed three different 1-d HIT sessions in a randomized order, approximately 1 wk apart. HIT involved repeated 30-s bursts of treadmill walking at maximum tolerated speed, alternated with rest periods. The three HIT protocols were different on the basis of the length of the rest periods, as follows: 30 s (P30), 60 s (P60), or 120 s (P120). Exercise tolerance, oxygen uptake ((v) over dotO(2)), HR, peak treadmill speed, and step count were measured. Results: P30 achieved the highest mean (v) over dotO(2), HR, and step count but with reduced exercise tolerance and lower treadmill speed than P60 or P120 (P30: 70.9% (v)over dotO(2peak), 76.1% HR reserve (HRR), 1619 steps, 1.03 mIs(-1); P60: 63.3% (v) over dotO(2peak), 63.1% HRR, 1370 steps, 1.13 mIs(-1); P120: 47.5% (v) over dotO(2peak), 46.3% HRR, 1091 steps, 1.10 mIs(-1)). P60 achieved treadmill speed and exercise tolerance similar to those in P120, with higher mean (v) over dotO(2), HR, and step count. Conclusions: For treadmill HIT in chronic stroke, a combination of P30 and P60 may optimize aerobic intensity, treadmill speed, and stepping repetition, potentially leading to greater improvements in aerobic capacity and gait outcomes in future studies.