Impact of aerobic fitness on cerebral blood flow and cerebral vascular responsiveness to CO₂ in young and older men

Abstract

We sought to test the hypothesis that brain blood flow and cerebral vascular responsiveness to carbon dioxide (CVR ) are greater in aerobically trained young and old individuals compared to their untrained counterparts. In 11 young trained {[23 (20-26) years] [mean (95% confidence interval)]}, 10 young untrained [25 (22-28) years], 8 older trained [65 (61-69) years], and 9 older untrained [67 (64-71) years] healthy individuals, Doppler ultrasound of the internal carotid (ICA) and vertebral (VA) artery blood flow were determined, along with middle cerebral artery mean flow velocity (MCA V ). Bilateral ICA blood flow was higher in trained individuals when compared to untrained (≈31%, P < 0.05), but was not influenced by age. VA blood flow was not affected by age or cardiorespiratory fitness. MCA V was reduced with age [59.5 (55.0-64.1) cm/s young vs 43.6 (38.4-48.9) cm/s old, P < 0.05] with no significant effect of training observed. MCA CVR were not significantly affected by either age or training status, while ICA CVR tended to be elevated in the old trained group. These findings indicate that endurance training enhances bilateral ICA but not VA blood flow in both young and older individuals.

Six weeks of high‐intensity interval training to exhaustion attenuates dynamic cerebral autoregulation without influencing resting cerebral blood velocity in young fit men

“…For instance, aerobic exercise training alters favorably cerebrovascular health in varying clinical conditions ranging from chronic obstructive pulmonary disease (Lewis et al, ), cognitive impairments (Alfini et al, ), stroke (Ivey et al, ) and following cancer (Northey et al, ). Evidence show that life‐long aerobic training individuals with elevated CRF have higher resting intracranial blood velocity in the anterior circulation (as indexed by transcranial Doppler sonography of mean blood velocity in middle cerebral artery (MCAv mean ) (Ainslie et al, ; Bailey et al, ), and in the posterior circulation (as indexed by arterial spin labeling in posterior cingular cortex/precuneus) (Thomas et al, ) and higher extracranial blood flow (as indexed by carotid Doppler) (Braz et al, ) than their sedentary counterparts. In inactive individuals, short‐term aerobic training (12 weeks) longitudinally elevates CRF and cerebrovascular reactivity to carbon dioxide, whereas it induces equivocal MCAv mean responses at rest (Murrell et al, ).…”

Enhanced fitness relates to reduced cerebrovascular reactivity and perfusion in a sample of very healthy older adults

“…In the Thomas et al study, Master athletes were found to have a significantly reduced BOLD CVR compared to their sedentary counterparts over most of cerebral cortex. While most studies into these effects have identified a positive relationship between CVR and fitness [35][36][37][38] , these studies used transcranial Doppler (TCD) to measure effects.…”

“…If CVR is taken to be a marker of vascular health, it can be posited that those with higher fitness levels would have greater CVR, as their vascular system would be more compliant and have an increased ability to respond to a vasodilatory stimulus. Yet, the literature has found conflicting results, where some have observed increased CVR in relation to higher fitness levels [35][36][37][38] , others have found decreased CVR is related to increased fitness 19 , while others have found no difference [39][40][41] in aging. It is unclear however if this is due to differences in measurement method, spatial localization of the measurement or an interesting physiological interplay between multiple hemodynamic aspects of brain health.…”

Integrative cardiovascular control in women: Regulation of blood pressure, body temperature, and cerebrovascular responsiveness

“…99 In the cerebral circulation, there is conflicting evidence regarding the role of cardiorespiratory fitness. Some studies report that endurance-trained individuals have greater cerebrovascular reactivity 100 or no differences in cerebrovascular reactivity 101 or that cerebrovascular reactivity is positively associated with VO 2 max. 102,103 In addition, trained men have greater MCA blood velocity throughout the life span compared to sedentary men.…”