The impact of topical capsaicin application on the muscle metaboreflex and microvascular responsiveness

Topical capsaicin reduces metaboreflex responses during post-exercise circulatory arrest (PECA) in males, but its effects in females and on microvascular responsiveness in either sex remain unclear. This study hypothesized that capsaicin would reduce blood pressure during PECA in males but not females, and enhance microvascular responsiveness in both sexes. Healthy males (n = 9) and females (n = 11) were randomly assigned to one of three conditions: capsaicin applied to the exercising arm, capsaicin applied to the non-exercising arm, or no capsaicin (control). Blood pressure was measured via the brachial artery during a handgrip exercise at 30% maximal voluntary contraction, followed by PECA using a rapid inflation cuff. Microvascular responsiveness was assessed with near-infrared spectroscopy (NIRS) during a post-occlusive reactive hyperemia test, conducted before and twice after capsaicin application. Capsaicin did not significantly alter blood pressure during PECA (p > 0.05), but a significant interaction was observed for microvascular responsiveness (p = 0.01). Although topical capsaicin did not attenuate metaboreflex-induced blood pressure changes, it enhanced microvascular responsiveness in the exercising arm compared to the systemic control. These findings suggest localized vascular benefits of capsaicin, but no clear impact on the metaboreflex. Further research is needed to clarify sex-specific responses to topical capsaicin.