title: The carotid baroreflex is reset following prolonged exercise in humans.
abstract: OBJECTIVE
  Alterations in the carotid baroreflex (CBR) control of arterial pressure may explain the reduction in arterial pressure and left ventricular (LV) function 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.
  
  
  METHODS
  Seven males (age, mean ± SEM; 29 ± 4 years) completed 4 h of ergometer rowing at a workload of 10-15% below the lactate threshold. The CBR control of HR and MAP was assessed via the rapid neck-suction/pressure protocol. LV systolic function was measured by echocardiography, where ejection fraction (EF), the ratio of systolic blood pressure to end systolic volume (SBP/ESV) and stroke volume (SV) were estimated.
  
  
  RESULTS
  Following exercise MAP was reduced (12 ± 3%) and HR was elevated (35 ± 5%; P < 0.05). Furthermore, CBR control of MAP was relocated to the left on the stimulus-response curve (P < 0.05) demonstrating that the CBR operated around a lower arterial pressure. Concomitantly, LV systolic function was reduced, indicated by a decrease in EF (22 ± 2%), SBP/ESV (32 ± 14%) and SV (25 ± 5%, P < 0.05). The reduced EF and SBP/ESV were associated with the decreased MAP operating point (r² = 0.71 and r² = 0.47, respectively, P < 0.05).
  
  
  CONCLUSIONS
  The CBR is reset after prolonged exercise to a lower prevailing arterial pressure. This resetting of the CBR may contribute to the reduction arterial pressure and LV function after exercise.
authors.affiliation: Centre for Sports Medicine and Human Performance, Brunel University, London, UK. hart.emma@mayo.edu
authors.forename: E C
authors.initials: EC
authors.lastname: Hart
authors.forename: P
authors.initials: P
authors.lastname: Rasmussen
authors.forename: N H
authors.initials: NH
authors.lastname: Secher
authors.forename: K P
authors.initials: KP
authors.lastname: George
authors.forename: N T
authors.initials: NT
authors.lastname: Cable
authors.forename: S
authors.initials: S
authors.lastname: Volianitis
authors.forename: R
authors.initials: R
authors.lastname: Shave
mesh_terms: D000328:Adult; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D002339:Carotid Arteries / Q000502:physiology*; D004452:Echocardiography; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics; D006801:Humans; D008297:Male; D013318:Stroke Volume / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology