Cerebrovascular Response to an Acute Bout of Low-Volume High Intensity Interval Exercise and Recovery in Young Healthy Adults
Introduction: High intensity interval exercise (HIIT) is performed widely. However, there is a gap in knowledge regarding the acute cerebrovascular response to low-volume HIIT. Our objective was to characterize the middle cerebral artery blood velocity (MCAv) response during an acute bout of low-volume HIIT in young healthy adults. We hypothesized MCAv would decrease below baseline (BL) 1) during HIIT, 2) immediately following HIIT, 3) and 30-minutes after HIIT. As a secondary objective, we investigated sex differences in the MCAv response during HIIT. Methods: Twenty-four young healthy adults completed HIIT (12 male, age 25 (SD 2)). HIIT included 10-minutes of 1-minute high intensity (~70% estimated maximal watts) and active recovery (10% estimated maximal watts) intervals on a recumbent stepper. MCAv, mean arterial pressure (MAP), heart rate (HR), and end tidal carbon dioxide (PETCO2), were recorded at BL, during HIIT, immediately following HIIT, and 30-minutes after HIIT. Results: Contrary to our hypothesis, MCAv remained above BL during HIIT. MCAv peaked at minute 3 then decreased concomitantly with PETCO2. MCAv was lower than BL immediately following HIIT (p < 0.001). Thirty-minutes after HIIT, MCAv returned to BL (p = 0.47). Compared to men, women had a higher MCAv at BL (p = 0.001), during HIIT (p = 0.009), immediately following HIIT (p = 0.004) and 30-minutes after HIIT (p = 0.001). Conclusions: MCAv did not decrease below BL during low-volume HIIT. However, MCAv decreased below BL immediately following HIIT and returned to resting values 30-minutes after HIIT. MCAv also differed between sex.