Muscle Metaboreflex Modulates Dynamic Cardiovascular and Cerebrovascular Responses to Acute Hypotension in Humans

We aimed to investigate whether the muscle metaboreflex modulates arterial baroreflex-mediated cardiovascular responses as well as cerebrovascular responses to acute hypotension in humans. Acute hypotension was induced nonpharmacologically in six healthy subjects by releasing bilateral thigh cuffs after nine minutes of suprasystolic resting ischemia with and without muscle metaboreflex activation (via post exercise muscle ischemia after one minute static handgrip exercise at 50% MVC). We simultaneously measured beat-to-beat mean arterial blood pressure (MAP), heart rate (HR), cardiac output (CO), forearm blood flow (FBF) and middle cerebral artery mean blood velocity (MCAVM). The thigh cuff release evoked rapid reductions in MAP, FBF, forearm vascular conductance and MCAVM and rises in HR, CO, TVC and cerebrovascular conductance index to similar extent in control and during muscle metaboreflex activation.