Sympathetic vasomotor out flow during low-intensity leg cycling in healthy older females

Background: Aging associated with an increase in arterial blood pressure (ABP) in response to whole-body dynamic exercise. However, the mechanisms underlying the elevated ABP response to dynamic exercise with aging have not been fully elucidated. One possible factor is an impairment of the cardiopulmonary baroreflex with age, which may lead to unrestrained sympathoexcitation and a greater increase in ABP during dynamic exercise. It has been reported that, in females, the inhibition of sympathetic vasomotor outflow during cardiopulmonary baroreceptor loading is attenuated with age. Thus, it is plausible to hypothesize that the muscle pump-induced inhibition of the sympathetic vasomotor outflow via the cardiopulmonary baroreflex is attenuated with advancing age in females. Purpose: The purpose of the present study was to elucidate age-related differences in the sympathoinhibitory effect of the cardiopulmonary baroreflex during low-intensity dynamic exercise in females. Methods: Nine older females (71±2 yrs, mean±SD) and ten younger females (21±2 years) participated in the study. The participants performed two 4-minute leg cycling session at 10% of heart rate reserve in a semi-recumbent position [MSNA and estimated central venous pressure (eCVP) trials]. MSNA was recorded via microneurography of the left radial nerve. CVP was estimated based on peripheral venous pressure, which was monitored using a cannula placed in the right antecubital vein. Results: The change in mean ABP during exercise was larger in older females compared to young females. MSNA burst frequency (BF) decreased during exercise in both groups, but the magnitude of the decrease in MSNA BF was smaller (P=0.004) in older females (-5.6±1.8 bursts/min) than in young females (-9.1±2.5 bursts/min). The eCVP increased during exercise in both groups, with no significant differences in the changes in eCVP between the two groups. Conclusion: These results suggest that the cardiopulmonary baroreflex-mediated inhibition of sympathetic vasomotor outflow may be attenuated with advancing age in females. This study was supported by JSPS KAKENHI #23K10633, #23K24736. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.