Background: Dynamic cerebral autoregulation (dCA) maintains stable cerebral blood flow despite transient fluctuations in arterial blood pressure. While acute exercise is a potent stimulus for cerebrovascular adaptation, it also imposes substantial haemodynamic stress on the cerebral circulation. High-intensity interval exercise (HIIE) elicits cardiovascular and metabolic adaptations comparable to, or greater than, those achieved with moderate-intensity continuous exercise (MICE); however, its acute effects on cerebrovascular regulation remain poorly understood. Therefore, this study compared the acute effects of HIIE and MICE on dCA in inactive adults.
Methods: Twelve inactive adults (5 females, age: 50.3 ± 9.3 years, BMI: 27.2 ± 4.7 kg/m2, V̇O₂max: 27.9 ± 9.3 mL/kg/min) completed four laboratory visits. During the initial visit, participants performed a ramp incremental cycling test to volitional exhaustion to determine maximal oxygen uptake (V̇O₂max) and establish individualised exercise intensities. Participants subsequently completed three randomised, time-matched (30 min) experimental conditions: moderate-intensity continuous exercise (MICE; 90% gas exchange threshold), high-intensity interval exercise (HIIE; 10 x 1-min intervals at 70% Δ), and a seated control condition (CON). dCA was assessed before, and 10 and 60 min following each condition using a 5-min repeated sit-to-stand manoeuvre performed at 0.05 Hz. Middle cerebral artery blood velocity (MCAv) and arterial blood pressure (ABP) were continuously measured using transcranial Doppler ultrasonography and finger photoplethysmography, respectively. dCA was quantified using transfer function analysis (TFA), from which gain, normalised gain, phase, and coherence were determined, and subsequently analysed using a two-way repeated-measures ANOVA (time x condition).
Results: No significant main effects of condition or time, nor condition x time interactions, were observed for TFA gain (all P ≥ 0.40, ηp² ≤ 0.08), normalised gain (all P ≥ 0.58, ηp² ≤ 0.045), phase (all P ≥ 0.27, ηp² ≤ 0.11), or coherence (all P ≥ 0.31, ηp² ≤ 0.10).
Conclusion: This study provides novel evidence that a single bout of HIIE and MICE do not alter dCA in inactive adults, suggesting that cerebral pressure-flow regulation is preserved despite the challenging haemodynamic demands of HIIE.