Effects of Topical Capsaicin on the Metaboreflex and Microvascular Responsiveness in Aging

Background: Exaggerated blood pressure responses to physical activity with aging increase cardiovascular event risk. These responses are strongly driven by afferent feedback known as the exercise pressor reflex (EPR). Moreover, aging is linked to endothelial dysfunction which may reduce vasodilatory capacity and regional blood flow. Topical capsaicin applied to active skeletal muscle attenuates the metabolic arm of the EPR in young males, and increases vasodilation in skeletal muscle feed arterioles. However, these findings have not been translated to an aged population. The aim of the present study was to investigate the impact of topical capsaicin cream on EPR and microvascular responses in young and aged healthy males and females. HYPOTHESES: 1) topical capsaicin application would reduce mean arterial pressure (MAP) responses during post exercise circulatory arrest (PECA) in aged and young; 2) capsaicin application would increase microvascular responsiveness in young but not aged participants. Methods: In a randomized crossover design using 0.1% capsaicin topical pain-relief cream, 19 participants (13 Young, 6 Aged) had MAP and microvascular responses to exercise and PECA recorded 30- (T30) and 60-minutes (T60) post treatment. Briefly, rhythmic handgrip exercise of 20% maximal voluntary contraction was performed for 2-minutes on a custom-built pulley device prior to 3-minutes of blood flow restriction. Participants either received capsaicin on the exercising arm (CAP-EX) or the non-exercising arm (CONTROL). MAP was measured with beat-to-beat and centrally adjusted photoplethysmography and forearm microvascular responses were measured with near-infrared spectroscopy. Results: Preliminary data indicates that Δ MAP during PECA were not attenuated in young (Baseline, 14±6.5; T30, 14±6.5; T60 13±6.3; p>0.05) nor aged (Baseline, 9±6; T30, 9±5.8; T60 9±5.7; p>0.05). Microvascular reperfusion slopes were significantly increased when capsaicin was applied to the exercising arm similarly in young at T60 compared to capsaicin applied to the non-exercising arm (CONTROL, 2.34±0.77 %/sec; CAP-EX, 2.84±0.82 %/sec; P=0.032). No significant difference was shown in aged (P>0.05). Conclusions: These results show no attenuation of the metaboreflex during PECA, but an increase in microvascular reperfusion 60 minutes following capsaicin treatment in young, but not aged participants. These data show topical capsaicin may improve tissue reperfusion without attenuating blood pressure responses to physical activity. This research was supported by the University of Wisconsin-La Crosse College of Science & Health. 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.