Cerebral blood velocity responses during and after sprint interval exercise in healthy young adults

This study investigated the middle (MCAv) and posterior (PCAv) cerebral artery blood velocity and end-tidal carbon dioxide (P_ETCO₂) responses during sprint interval exercise (SIE). We also examined the relationships between MCAv, PCAv and blood pressure during the 60 min post SIE. Fourteen healthy adults completed four 30 s maximal cycle sprints, each separated by 4 min of unloaded cycling. MCAv and PCAv demonstrated a rapid increase followed by a return towards the initial baseline values during each sprint. The increase during the first sprint (MCAv: +31.9% ± 19.9%, PCAv: +32.5% ± 30.6%) was always greater than subsequent sprints (p ≤ 0.039). Each sprint was followed by a transient increase in MCAv and PCAv, which mirrored P_ETCO₂. SIE was followed by 60 min of hypocapnia, and blood pressure was significantly lowered 10-20 and 40-55 min post SIE. However, resting MCAv was not altered, and PCAv was only lower 5 min post SIE. Resting MCAv phase and gain, and PCAv phase were largely unaltered apart from the first 5 min post SIE. The ability to buffer changes in blood pressure during repeated squat-stand maneuvers remained intact 60 min post SIE, although a greater fall in MCAv and PCAv was noted during a single sit-to-stand transition at this time.