Cerebrovascular responses to graded exercise in young healthy males and females

Abstract

Although systemic sex-specific differences in cardiovascular responses to exercise are well established, the comparison of sex-specific cerebrovascular responses to exercise has gone under-investigated especially, during high intensity exercise. Therefore, our purpose was to compare cerebrovascular responses in males and females throughout a graded exercise test (GXT). Twenty-six participants (13 Females and 13 Males, 24 ± 4 yrs.) completed a GXT on a recumbent cycle ergometer consisting of 3-min stages. Each sex completed 50W, 75W, 100W stages. Thereafter, power output increased 30W/stage for females and 40W/stage for males until participants were unable to maintain 60-80 RPM. The final stage completed by the participant was considered maximum workload(W_max ). Respiratory gases (End-tidal CO₂ , EtCO₂ ), middle cerebral artery blood velocity (MCAv), heart rate (HR), non-invasive mean arterial pressure (MAP), cardiac output (CO), and stroke volume (SV) were continuously recorded on a breath-by-breath or beat-by-beat basis. Cerebral perfusion pressure, CPP = MAP (0. 7,355 distance from heart-level to doppler probe) and cerebral vascular conductance index, CVCi = MCAv/CPP 100mmHg were calculated. The change from baseline (Δ) in MCAv was similar between the sexes during the GXT (p = .091, ω_p² = 0.05). However, ΔCPP (p < .001, ω_p² = 0.25) was greater in males at intensities ≥ 80% W_max and ΔCVCi (p = .005, ω_p² = 0.15) was greater in females at 100% W_max . Δ End-tidal CO₂ (ΔEtCO₂ ) was not different between the sexes during exercise (p = .606, ω_p² = -0.03). These data suggest there are sex-specific differences in cerebrovascular control, and these differences may only be identifiable at high and severe intensity exercise.

Keywords: brain blood flow; cerebrovascular control; high-intensity exercise; sex differences; transcranial doppler.