Author(s): CURTIN, E., WESTON, M., BUYS, P., EGAÑA, M., GILDEA, N. , Institution: TRINITY COLLEGE DUBLIN, Country: IRELAND, Abstract-ID: 2699

INTRODUCTION:
Dynamic cerebral autoregulation (dCA) reflects the capacity of the cerebrovasculature to buffer transient fluctuations in arterial blood pressure, thereby maintaining cerebral perfusion stability. Although findings are equivocal, considerable sex- and fitness-related variability in dCA exists, being shown to be impaired in endurance trained athletes compared to inactive and moderately active controls (Labrecque et al., 2017), as well as being impaired (Johnson et al., 2025; Labrecque et al., 2019) or enhanced (Favre & Serrador, 2019) in healthy young females compared to males. However, these findings are largely derived from single-metric assessments, including phase and gain, which may incompletely characterise the complexity of dCA regulation. Increasingly, multi-metric approaches are advocated, as no single metric sufficiently captures dCA (Brassard et al., 2024). Therefore, this study employed a novel multi-metric approach, including transfer function analysis (TFA) and directional sensitivity, to provide a more complete characterisation of dCA in healthy young males and females.
METHODS:
60 young adults (32 females; 22.6±2.7 years; V̇O₂max 44.4±8.8 ml/kg/min) volunteered to participate in this study, which involved two study visits. On visit one, participants completed a ramp incremental cycling test to exhaustion, followed by a supramaximal verification of maximal oxygen uptake (V̇O₂max). On visit two, dCA was assessed using a 5-minute repeated sit-to-stand manoeuvre completed at 0.05 Hz. Middle cerebral artery blood velocity (MCAv) and mean arterial pressure (MAP) was measured via transcranial Doppler ultrasonography and finger photoplethysmography, respectively. dCA was quantified using TFA and a novel directional sensitivity metric, expressing the average time-adjusted change in MCAv relative to MAP (ΔMCAvT/ΔMAPT), calculated separately for MAP increases and decreases. Independent t-tests were used to assess sex differences, and Pearson correlations examined associations between V̇O₂max and dCA metrics overall and by sex.
RESULTS:
No sex differences were observed in TFA metrics, (phase: p = 0.67; gain p = 0.40; normalised gain p = 0.99). V̇O₂max was significantly associated with phase in females (r = −0.42, p = 0.019) but not in males (r = −0.22, p = 0.29). V̇O₂max was not associated with gain or normalised gain, either overall or by sex (all p > 0.33). No directional sensitivity was observed, and ΔMCAvₜ/ΔMAPₜ during MAP increases and decreases showed no sex differences, and was unrelated to V̇O₂max, overall or by sex (all p > 0.35).
CONCLUSION:
These findings suggest that while dCA is not different between sexes, cardiorespiratory fitness may differentially influence specific components of dCA in females, highlighting the importance of sex-specific analyses and multi-metric approaches when investigating cerebral haemodynamic regulation.