Reduced Middle Cerebral Artery Blood Velocity Response during Low-Volume High-Intensity Interval Exercise in Chronic Stroke

Abstract Background High-intensity interval exercise (HIIT) is currently being implemented in stroke rehabilitation to improve walking function. HIIT alternates between high-intensity and recovery bouts, which causes rapid increases and decreases in blood pressure, which may impact cerebrovascular function in people post-stroke. To date, there is no information on the acute cerebrovascular response in people post-stroke. To address this gap in knowledge, we tested whether the cerebrovascular response was reduced when compared to sedentary age- and sex-matched adults (CON) at the following timepoints: 1) baseline (BL), 2) during a single 10-minute bout of low-volume HIIT, 3) immediately following HIIT, and 4) 30 minutes after HIIT. Methods Middle cerebral artery blood velocity (MCAv), mean arterial pressure (MAP), heart rate (HR), and end tidal carbon dioxide (P ET CO 2 ) were recorded at all timepoints. A submaximal exercise test was used to determine the estimated maximal workload. The low-volume HIIT bout was performed on a recumbent stepper and consisted of 1-minute high-intensity bouts (70% estimated maximal watts) separated by 1-minute active recovery (10% estimated maximal watts). Statistical analysis used linear mixed models and ANCOVA. Results Individuals post-stroke demonstrated a reduced MCAv response during HIIT compared to CON (p = 0.03) and MCAv remained lower immediately following HIIT and 30-minutes after HIIT. MCAv decreased below BL immediately following HIIT in both groups (p ≤ 0.04) and returned to BL at 30-minutes after HIIT. No between differences were found for MAP, HR, and P ET CO 2 . Conclusions The key finding from this study suggests a reduced MCAv response during low-volume HIIT in individuals post-stroke compared to age and sex-matched sedentary adults and these differences remained up to 30 minutes following HIIT. Future work is needed to better understand the reduced MCAv response during HIIT despite increased metabolic demand. Clinicaltrials.gov # NCT04673994 .