Dynamic cerebral autoregulation across the cardiac cycle during 8 hr of recovery from acute exercise

Current protocols examining cerebral autoregulation (CA) parameters require participants to refrain from exercise for 12-24 hr, however there is sparse objective evidence examining the recovery trajectory of these measures following exercise across the cardiac cycle (diastole, mean, and systole). Therefore, this study sought to determine the duration acute exercise impacts CA and the within-day reproducibility of these measures. Nine participants performed squat-stand maneuvers at 0.05 and 0.10 Hz at baseline before three interventions: 45-min moderate-continuous exercise (at 50% heart-rate reserve), 30-min high-intensity intervals (ten, 1-min at 85% heart-rate reserve), and a control day (30-min quiet rest). Squat-stands were repeated at hours zero, one, two, four, six, and eight after each condition. Transcranial doppler ultrasound of the middle cerebral artery (MCA) and the posterior cerebral artery (PCA) was used to characterize CA parameters across the cardiac cycle. At baseline, the systolic CA parameters were different than mean and diastolic components (ps < 0.015), however following both exercise protocols in both frequencies this disappeared until hour four within the MCA (ps > 0.079). In the PCA, phase values were affected only following high-intensity intervals until hour four (ps > 0.055). Normalized gain in all cardiac cycle domains remained different following both exercise protocols (ps < 0.005) and across the control day (p < .050). All systolic differences returned by hour six across all measures (ps < 0.034). Future CA studies may use squat-stand maneuvers to assess the cerebral pressure-flow relationship 6 hr after exercise. Finally, CA measures under this paradigm appear to have negligible within-day variation, allowing for reproducible interpretations to be drawn.