PURPOSE: The purpose of this study was to demonstrate differences in cardiovascular and autonomic nerve function among physical activity levels and associations between physical activity level and cardiovascular and autonomic nerve function.METHODS: Sixty-six healthy young adults voluntarily participated in this cross-sectional study. Physical activity levels were assessed using triaxial accelerometers for 7 consecutive days. Central hemodynamics and arterial stiffness were measured using the Sphygomo-Cor Xcel system. Autonomic nerve function was assessed by heart rate variability.RESULTS: The highest tertile group of the total quantity of physical activity had higher lnRMSSD than did the lowest tertile group (<i>p</i>=0.047). The augmentation index adjusted for heart rate at 75 beats per min (AIx@75) was lower in the highest tertile group of vigorous-intensity physical activity than in the lowest tertile group (<i>p</i>=0.012). Moreover, AIx@75 was negatively associated with vigorousintensity physical activity (r=-0.27, <i>p</i>=0.028).CONCLUSIONS: High levels of physical activity contribute to the dominance of parasympathetic nerve activity at rest. Increased engagement in vigorous-intensity physical activity can help reduce arterial pulse wave reflection, an independent risk factor for cardiovascular diseases, even in healthy young adults.