Abstract
Sympathetic regulation of blood pressure (BP) and cerebral blood flow (CBF) is essential for maintaining cerebral perfusion during physiological stress. BP provides a driving force for CBF, and its beat-to-beat regulation is critical for cerebrovascular regulation. Sympathetic-BP transduction is the acute process by which sympathetic nerve activity (SNA) alters mean arterial pressure (MAP). Although age-related differences in BP and CBF control have been reported, it remains unclear whether dysregulation of SNA (i.e., sympathetic transduction) contributes to age-related impairments in cerebral hemodynamics, and if these responses are associated with maximal aerobic capacity (VO2max). To reduce confounding from sedentary behavior, which affects autonomic and vascular function, we restricted our sample to physically active adults. Therefore, the purpose of this study was to examine age-related differences in peak SNA-MAP and SNA-middle cerebral artery velocity (MCAv; an index of CBF) transduction under resting conditions in physically active adults. We hypothesized that older adults would exhibit reduced transduction compared with younger adults. Healthy young (20-35 years; n=17, 9F) and older (55-68 years; n=16, 6F) adults who regularly engaged in physical activity underwent continuous 5-minute recordings of SNA (peroneal microneurography), beat-by-beat MAP (finger photoplethysmography), MCAv (transcranial Doppler ultrasound), and heart rate (HR; 3-lead ECG). Resting muscle SNA was quantified as burst incidence (BI; bursts/100 heartbeats). On a separate visit, VO2max was measured via an incremental cycle ergometer test. Sympathetic transduction was assessed as the maximal change in SNA-MAP and SNA-MCAv, and group differences were analyzed with independent t-tests. Given that cardiac activity and aerobic capacity may influence pressure and flow responses, HR and VO2max were included and analyzed alongside transduction measures using Pearson correlations. Older adults exhibited lower peak SNA-MAP transduction (p< 0.05) and a trend toward lower SNA-MCAv transduction (p=0.07) compared with younger adults. Baseline BI was higher in older adults (p< 0.05), whereas HR and VO2max were higher in younger adults (both p< 0.05). In the combined sample, HR was not related to peak SNA-MAP transduction (r=0.05, p=0.78) but was positively associated with peak SNA-MCAv transduction (r=0.39, p< 0.05). VO2max was not associated with SNA-MAP (r=0.07, p=0.72) or SNA-MCAv transduction (r=0.03, p=0.87). Aging in habitually active adults is therefore associated with reduced sympathetic transduction, reflected by lower translation of muscle SNA into arterial pressure at rest. Despite age-related differences in HR and VO2max, these variables were not meaningfully related to SNA-MAP or SNA-MCAv transduction, suggesting that regular physical activity and higher cardiorespiratory fitness alone may not fully preserve resting sympathetic regulation of BP and cerebral perfusion in older adults. Funding: NIH R00 HL118154; Virginia Horn Henry Research Grant This abstract was presented at the American Physiology Summit 2026 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.