Carotid artery wall mechanics in young males with high cardiorespiratory fitness.

Abstract

What is the central question of this study? Common carotid artery (CCA) two-dimensional strain imaging detects intrinsic arterial wall properties beyond conventional measures of arterial stiffness, but the effect of cardiorespiratory fitness on two-dimensional strain-derived indices of CCA stiffness is unknown. What is the main finding and its importance? Two-dimensional strain imaging of the CCA revealed greater peak circumferential strain and systolic strain rate in highly fit men compared with their less fit counterparts. Altered CCA wall mechanics might reflect intrinsic training-induced adaptations that help to buffer the increase in pulse pressure and stroke volume during exercise. The influence of cardiorespiratory fitness on arterial stiffness in young adults remains equivocal. Beyond conventional measures of arterial stiffness, two-dimensional strain imaging of the common carotid artery (CCA) provides new information related to the intrinsic properties of the arterial wall. Therefore, the aim of this study was to assess the effect of cardiorespiratory fitness on both conventional indices of CCA stiffness and two-dimensional strain parameters, at rest and after a bout of aerobic exercise in young, healthy men. Short-axis ultrasound images of the CCA were recorded in 34 healthy men {22years old [95% confidence interval (CI), 19, 22]} before and immediately after 5min of aerobic exercise (40% of maximal oxygen consumption). Images were analysed for arterial diameter, peak circumferential strain (PCS) and peak systolic and diastolic strain rates (S-SR and D-SR). Heart rate, systolic and diastolic blood pressure were simultaneously assessed, and Peterson's elastic modulus (Ep ) and β-stiffness (β1 ) were calculated. Participants were separated post hoc into moderate- and high-fitness groups [maximal oxygen consumption, 48.9 (95% CI, 44.7, 53.2) versus 65.6mlkg-1 min-1 (95% CI, 63.1, 68.1), respectively; P<0.001]. The Ep and β1 were similar between groups at baseline (P>0.13) but were elevated in the moderate-fitness group postexercise (P<0.04). The PCS and S-SR were elevated in the high-fitness group at both time points [3.0% (95% CI,1.2, 4.9), P=0.002, and 0.401s-1 (95% CI,0.085, 0.72), P=0.02, respectively]. No group differences were observed in CCA heart rate, systolic or diastolic blood pressure or D-SR throughout the protocol (P>0.05). Highly fit individuals exhibit elevated CCA, PCS and S-SR, which might reflect training-induced adaptations that help to buffer the increase in pulse pressure and stroke volume during exercise.