Long-term Exercise Confers Equivalent Neuroprotection in Females Despite Lower Cardiorespiratory Fitness

Abstract

Females are more prone to cognitive decline, stroke and neurodegenerative disease, possibly due to more marked reductions in cerebral blood flow and cerebrovascular reactivity to CO2 (CVRCO2HYPER) in later life. To what extent regular exercise confers selective neuroprotection in females remains unestablished. To examine this, 73 adults were prospectively assigned to 1 of 4 groups based on sex (male, ♂ vs. female, ♀) and physical activity status (trained, ≥150 min of moderate-vigorous intensity aerobic exercise/week; n = 18♂ vs. 18♀ vs. untrained, no formal exercise; n = 18♂ vs. 19♀). Middle cerebral artery velocity (MCAv, transcranial Doppler ultrasound), mean arterial pressure (MAP, finger photoplethysmography) and end-tidal CO2 (capnography) were assessed at rest during normocapnea and hypercapnea (5% CO2) enabling CVRCO2HYPER to be assessed. Cerebrovascular resistance/conductance indices (CVRi/CVCi) were calculated as MAP/MCAv and MCAv/MAP. Maximal oxygen uptake (VO2MAX) was determined during incremental semi-recumbent cycling ergometry to volitional exhaustion. Despite having a lower VO2MAX, females were characterized by selective elevations in MCAv, CVRCO2HYPER and lower CVRi (P < 0.05), but the training responses were similar across sexes. Linear relationships were observed between VO2MAX and CVRCO2HYPER (pooled untrained and trained data; ♂ r = 0.70, ♀ r = 0.51; both P < 0.05) with a consistent elevation in the latter equivalent to ∼1.50%.mmHg−1 compared to males across the spectrum of cardiorespiratory fitness. These findings indicate that despite having comparatively lower levels of cardiorespiratory fitness, the neuroprotective benefits of regular exercise translate into females and may help combat cerebrovascular disease in later life.