Acute Post-Exercise Internal Carotid Artery Hemodynamics Are Intensity Dependent in Young Adults

This research aimed to examine the impact of aerobic exercise intensity on acute post-exercise internal carotid artery (ICA) hemodynamics. This research tested the hypothesis that acute exercise would elicit intensity-dependent effects on ICA cross-sectional area (CSA), shear stress, and blood flow. Ten young, healthy adults (27 ± 4 years of age, 3 males, 7 females) completed a maximal oxygen uptake (VO2max) treadmill test followed by two randomized study visits that involved 30 minutes of treadmill exercise at 30% of VO2max or 70% of VO2max. At each study visit, a venous blood draw and ultrasound imaging of the ICA were completed before and 4 ± 1 min following exercise. During ultrasound imaging, beat-by-beat systemic blood pressure was measured. Vessel diameter and blood velocity were determined using automated edge detection software. ICA blood flow was calculated as: mean blood velocity x CSA x 60. Using measures of blood viscosity from the blood draw, shear stress was calculated as: (4 x viscosity x mean blood velocity)/mean vessel diameter. Mean arterial pressure and blood viscosity were not altered following exercise. ICA CSA was increased following exercise (Time: P = 0.03, Intensity: P = 0.24, Interaction: P = 0.38), but the magnitude of dilation did not differ following exercise at 30% VO2max (Δ0.01 ± 0.03 cm2) and 70% VO2max (Δ0.02 ± 0.04 cm2; P = 0.54). The impact of exercise on ICA shear stress was intensity dependent (Time: P = 0.02, Intensity: P = 0.03, Interaction: P = 0.03), such that shear stress was unaltered following exercise at 30% VO2max (Pre: 10 ± 2 dynes/cm2 vs. Post: 11 ± 3 dynes/cm2; Ppost-hoc = 0.13) but increased following exercise at 70% VO2max (Pre: 12 ± 4 dynes/cm2 vs. Post: 16 ± 4 dynes/cm2; Ppost-hoc = 0.04). ICA blood flow was increased following both exercise intensities (Time: P < 0.01, Intensity: P = 0.02, Interaction: P = 0.03), but a larger increase was observed following exercise at 70% VO2max (Δ257 ± 151 mL/min) compared with 30% VO2max (Δ109 ± 129 mL/min; P = 0.03). Therefore, aerobic exercise produced intensity dependent effects on acute post-exercise ICA hemodynamics. Vigorous intensity exercise increased shear-stress and provoked a larger increase in ICA blood flow compared to light intensity exercise. However, increases in ICA CSA following exercise did not differ between the two exercise intensities. Therefore, the greater increase in ICA blood flow following vigorous intensity exercise may be related to downstream effects in addition to shear-mediated dilation of the ICA. Supported by the Wisconsin Alumni Research Foundation (JNB) and the National Institutes of Health (NS117746; JNB). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.