Comparative effects of different types of exercise on endothelial function, arterial stiffness, and executive function in sedentary young individuals: a randomized controlled trial

Purpose : Prior research has demonstrated the significant benefits of regular exercise for vascular and cognitive function. However, it remains unclear whether different types of exercise have varying effects. The present study aims to determine the differential impacts of high-intensity interval training (HIIT), moderate-intensity continuous training (MICT), and resistance exercise (RE) on endothelial function, arterial stiffness, and executive function in sedentary young individuals, as well as explore the underlying mechanisms. Methods : Sixty-three sedentary participants were randomly divided into HIIT, MICT, RE, and control groups. Macrovascular and microvascular endothelial function were assessed using brachial artery flow-mediated dilation (FMD) and fingertip reactive hyperemia index (RHI), respectively. Arterial stiffness was evaluated through carotid-femoral pulse wave velocity (cfPWV), ankle-brachial index (ABI), and augmentation index (AIx). Executive functon(EF) performance was evaluated using the Stroop and N-back tasks. Functional near-infrared spectroscopy (fNIRS) was employed to measure cortical activation and real-time oxyhemoglobin concentration (Oxy-Hb) changes in different cerebral regions. Key biomarkers for vascular and cognitive function, including BDNF, irisin, VEGF, IGF-1, and TNF-α, were measured using enzyme-linked immunosorbent assays. Results : Compared to the baseline values, significant increases in mean shear rate, FMD, and RHI, as well as a decrease in cfPWV, were observed in all three intervention groups but not in the control group after 8 weeks of intervention. Moreover, 8 weeks of HIIT and MICT but not RE significantly reduced AIx, while significant differences in FMD and peak diameter were noted only in the HIIT and MICT groups compared to the control group. In addition, a significant difference in the change of RHI was observed only between the control and HIIT groups. Compared to the baseline values, the reaction times for the incongruent Stroop task and the 3-back task significantly decreased after 8 weeks of HIIT and MICT. However, reduced reaction times for the Stroop interference task and the 2-back task were observed for only the HIIT group. During the Stroop task, a significant increase in Oxy-Hb in the frontopolar area (FPA) was noted after 8 weeks of both HIIT and MICT. Additionally, a significant increase in Oxy-Hb in the orbitofrontal area was observed solely in the RE group, while significant increases in Oxy-Hb under both the left and right of dorsolateral prefrontal cortex (L-DLPFC and R-DLPFC) were observed only in the HIIT group. During the N-back tasks, Oxy-Hb in the FPA region significantly increased after 8 weeks of both HIIT and MICT. Furthermore, significant increases in Oxy-Hb under the L-DLPFC region were observed solely in the HIIT group. Compared to the baseline values, the circulating IGF-1 levels increased significantly in all three intervention groups, but not in the control group, after 8 weeks of intervention. Additionally, only HIIT and MICT interventions led to a significant increase in circulating BDNF levels. Futhermore, circulating irisin levels increased significantly after 8 weeks of HIIT and RE, but not MICT. There were no significant differences in TNF-α and VEGF among all groups. Correlation analyses showed that an increased mean shear rate was positively correlated with improvements in both FMD and RHI. In addition, changes in circulating BDNF levels were positively correlated with changes in FMD, while changes in circulating IGF-1 levels were positively correlated with changes in RHI and negatively correlated with changes in AIx following the 8-week intervention. Increased circulating BDNF levels were associated with elevated Oxy-Hb levels in the right DLPFC region and improvements in EF performance. Importantly, the observed enhancements in vascular functon(evidenced by improved FMD and reduced cfPWV) were significantly associated with increases in EF (evidenced by elevated Oxy-Hb levels and reduced reaction times) after 8 weeks of exercise intervention. Conclusion : Eight weeks of HIIT, MICT, and RE effectively improved macrovascular and microvascular endothelial function while reducing arterial stiffness in sedentary young individuals. Notably, both HIIT and MICT, but not RE, efficiently activated certain brain regions, such as the FPA and DLPFC, leading to the improvement in EF performance. Among these exercise modalities, HIIT appeared to be the most potent in improving both vascular and cognitive function in this population. It is crucial to highlight that the exercise-induced enhancement of vascular function plays a pivotal role in cognitive improvement Mechanistically, increased blood flow shear stress and elevated circulating levels of biomarkers like BDNF and IGF-1, induced by exercise, are involved in the regulatory mechanisms.