Influence of high-intensity interval training to exhaustion on the directional sensitivity of the cerebral pressure-flow relationship in young endurance-trained men

We previously reported subtle dynamic cerebral autoregulation (dCA) alterations following 6 weeks of high-intensity interval training (HIIT) to exhaustion using transfer function analysis (TFA) on forced mean arterial pressure (MAP) oscillations in young endurance-trained men. However, accumulating evidence suggests the cerebrovasculature better buffers cerebral blood flow changes when MAP acutely increases compared to when MAP acutely decreases. Whether HIIT affects the directional sensitivity of the cerebral pressure-flow relationship in these athletes is unknown. In 18 endurance-trained men (age: 27 ± 6 years, VO₂ max: 55.5 ± 4.7 ml·kg^-1 ·min^-1 ), we evaluated the impact of 6 weeks of HIIT to exhaustion on dCA directionality using induced MAP oscillations during 5-min 0.05 and 0.10 Hz repeated squat-stands. We calculated time-adjusted changes in middle cerebral artery mean blood velocity (MCAv) per change in MAP (ΔMCAv_T /ΔMAP_T ) for each squat transition. Then, we compared averaged ΔMCAv_T /ΔMAP_T during MAP increases and decreases. Before HIIT, ΔMCAv_T /ΔMAP_T was comparable between MAP increases and decreases during 0.05 Hz repeated squat-stands (p = 0.518). During 0.10 Hz repeated squat-stands, ΔMCAv_T /ΔMAP_T was lower during MAP increases versus decreases (0.87 ± 0.17 vs. 0.99 ± 0.23 cm·s^-1 ·mmHg^-1 , p = 0.030). Following HIIT, ΔMCAv_T /ΔMAP_T was superior during MAP increases over decreases during 0.05 Hz repeated squat-stands (0.97 ± 0.38 vs. 0.77 ± 0.35 cm·s^-1 ·mmHg^-1 , p = 0.002). During 0.10 Hz repeated squat-stands, dCA directional sensitivity disappeared (p = 0.359). These results suggest the potential for HIIT to influence the directional sensitivity of the cerebral pressure-flow relationship in young endurance-trained men.