Time-of-Day-Dependent Effects of Aerobic Exercise on Carotid Hemodynamics in Sedentary Adults

Aerobic exercise (AE) modulates vascular function through hemodynamic responses, thereby influencing cardiovascular health and risk, with the circadian rhythm system playing a crucial role. This chronobiological study investigated diurnal variations in exercise-induced hemodynamic changes in the common carotid artery. In a randomized crossover trial, twenty-two sedentary adults completed eight AE interventions (one per laboratory visit day), with each session performed at one of eight evenly distributed time points (from 06:00 to 20:00). Vascular ultrasound imaging and hemodynamic parameter calculations were performed both pre- and post-exercise. Compared to other time points, AE at 06:00 and 18:00 induced a greater and more sustained increase in mean flow rate and wall shear stress (WSS). Moreover, AE at 06:00 was associated with a smaller increase in oscillatory shear index and a larger decrease in peripheral resistance compared to other time points. Exercise-induced hemodynamic responses exhibited significant temporal variations. These findings emphasize the importance of exercise timing in optimizing vascular benefits for sedentary individuals.