A decrease in systemic arterial compliance (SAC) increases left ventricular load along with the demand for excessive myocardial oxygen consumption when the age-related reduction of SAC reaches a marked level, and consequently may depress left ventricular pump function. Reduced left ventricular pump function decreases aerobic capacity, and some study groups have shown that SAC and/or central arterial distensibility is correlated with maximal aerobic capacity in humans. We thus hypothesize that, once the age-related reduction of SAC reaches a marked level, the participation of SAC in aerobic capacity will be significant even during sub-maximal exercise. Thirty young humans and 46 elderly humans participated in this study. SAC, oxygen uptake at the ventilatory threshold (VO2VT), and the ratio of increase in oxygen uptake, in cardiac output, and in effective arterial elastance to increase in work rate (deltaVO2/deltaWR, deltaCO/deltaWR and deltaEa/deltaWR) were measured. SAC was significantly higher in young subjects compared with elderly subjects, and was significantly related to VO2VT in elderly subjects. SAC also significantly correlated with deltaVO2/deltaWR, deltaCO/deltaWR and deltaEa/deltaWR in elderly subjects. When total subjects were divided by the value of SAC into 6 groups, the VO2VT values in the 3 groups with lower SAC were significantly lower than those in the 3 groups with higher SAC, and gradually decreased with the reduction of SAC. There were no changes in VO2VT among the 3 groups with higher SAC. These results suggest that the participation of SAC in aerobic capacity is significant even during sub-maximal exercise in individuals who show a pronounced age-related reduction of SAC.