The carotid baroreflex is reset following prolonged exercise in humans

Abstract

Alterations in the carotid baroreflex (CBR) control of arterial pressure may explain the reduction in arterial pressure and left ventricular (LV) function observed after prolonged exercise. We examined the CBR control of heart rate (HR) and mean arterial pressure (MAP), in addition to changes in LV function, pre‐ to post exercise. Seven males (age, 29 ± 7 yrs) completed 4 h of ergometer rowing at a workload 10–15% below lactate threshold. CBR control of HR and MAP was assessed before and after exercise via the rapid neck suction/pressure method. LV systolic function was assessed by echocardiography, where ejection fraction (EF), systolic pressure/volume ratio (SBP/ESV) and stroke volume (SV) were estimated. After exercise MAP was reduced (12 ± 3%) and HR was elevated (35 ± 5%; P<0.05), indicating a relocation of the CBR operating point. Furthermore, the CBR operating pressure was relocated to the left on the HR and MAP stimulus‐response curve (P<0.05) demonstrating that the CBR operated at a lower arterial pressure. Concomitantly, EF (22 ± 2%), SBP/ESV (32 ± 14%) and SV (25 ± 5%, P<0.05) were reduced after exercise. The reduced EF and SBP/ESV were associated with the decreased MAP operating point (r2=0.71 and r2=0.47, P<0.05). In conclusion, the CBR is reset to a lower prevailing arterial pressure after prolonged exercise, which may contribute to the reduction arterial pressure and LV function observed.