Intracranial vasomotor and blood flow responses to light intensity aerobic exercise in young adults: a 4D flow MRI study

Aerobic exercise elicits an increase in cerebral blood flow. This finding is evidenced by augmented internal carotid artery (ICA) and vertebral artery (VA) blood flow measured extracranially and supported by an increase in intracranial blood velocity (e.g., middle cerebral artery [MCA]). To date, no studies have quantified intracranial blood flow or vessel cross-sectional area (CSA) during exercise given challenges in combining aerobic exercise with magnetic resonance imaging (MRI) approaches. The present study leveraged an MRI-compatible exercise device and novel 4D flow MRI sequences that are less sensitive to motion artifacts to evaluate vasomotor and blood flow responses during aerobic exercise, and to explore the influence of biological sex. Thirty-four young adults (18 females, 31±5 years of age) completed supine exercise at 30% V̇O _2max in the MRI bore and CSA and blood flow were quantified in multiple intracranial arteries. Light intensity exercise elicited an increase in blood flow within the large intracranial arteries including the left ICA (∆18±17mL/min, P<0.001), right ICA (∆23±18mL/min, P<0.001), and basilar artery (∆15±14mL/min, P<0.001). Overall, global cerebral blood flow increased 58 ± 40 mL/min ( P<0.001). Further, light intensity exercise elicited vasodilation in the large intracranial arteries including the left ICA (∆0.8±1.2mm ² , P=0.001), right ICA (∆0.9±1.1mm ² , P<0.001), and basilar artery (∆0.5±0.7mm ² , P<0.001). Biological sex influenced blood flow responses in the left ACA ( P=0.048) but did not impact CSA responses (all P>0.08). This study provides novel insights to intracranial blood flow and vasomotor responses during aerobic exercise in young adults and the influence of biological sex.