Acute Vascular Responses to All‐Extremity Aerobic Exercise

Abstract

Endothelial function and central arterial stiffness are independent predictors of future cardiovascular events. High‐intensity interval training (HIIT) is a popular and oftentimes superior exercise strategy for decreasing cardiovascular disease risk than moderate‐intensity continuous training (MICT). We have recently adapted HIIT on a non‐weight‐bearing all‐extremity ergometer to reduce impact on the joints and involve muscles in the whole body to activate a larger amount of muscle mass than in lower‐extremity HIIT. However, the acute vascular responses to all‐extremity HIIT and MICT remain unexplored and may be important for optimizing exercise prescription. Therefore, the purpose of this study was to investigate the acute effects of all‐extremity HIIT and MICT on endothelial function, central arterial stiffness and hemodynamics. Sixteen young men (21±1 years of age, means±SE) who were free of clinical disease and did not use tobacco products or medications participated in this study. Vascular measures were assessed at pre‐exercise, at the end of a single session of HIIT and MICT and following recovery. HIIT and MICT were matched for caloric expenditure and were performed on an all‐extremity non‐weight‐bearing ergometer, at least one week apart. HIIT consisted of 4×4‐min intervals at 90% peak heart rate (HRpeak) interspersed by 3‐min intervals at 70% HRpeak for a total of 40 min. MICT consisted of 47 min at 70% HRpeak. Endothelial function was assessed using brachial artery flow‐mediated dilation (FMD) via high resolution ultrasonography in response to 5 min forearm blood flow occlusion. Arterial stiffness (carotid to femoral pulse wave velocity; cfPWV), aortic wave reflection (augmentation index normalized at heart rate 75; AIx75) and aortic systolic and diastolic blood pressure (aoSBP and aoDBP) were assessed using a validated cuff‐based device. HIIT did not result in significant changes in FMD (P=0.08), cfPWV (P=0.3), aoSBP (P=0.1) or aoDBP (P=0.2) within one hour from exercise cessation. AIx75 and heart rate were increased at the end of HIIT and remained elevated following recovery (P≤0.002 vs. pre‐exercise). In response to MICT, FMD remained unchanged (P=0.1). However, cfPWV decreased at the end of MICT (P=0.003) and returned to the pre‐exercise level following recovery (P=0.5). AIx75 increased at the end of MICT (P<0.0001) and returned to the pre‐exercise level following recovery (P=0.3). aoSBP decreased following recovery compared with end of MICT (P=0.04), but was not different than the pre‐exercise level (P=0.3). aoDBP did not significantly change in response to MICT (P=0.09). In conclusion, all‐extremity HIIT and MICT did not attenuate endothelial function or result in adverse changes in aortic blood pressure. MICT, but not HIIT, slightly reduced central arterial stiffness. These findings may have important implications for exercise prescription.