Key result
Cardiopulmonary baroreflex responses to lower body negative pressure and albumin infusion did not differ significantly between rest and exercise, indicating the reflex resets during exercise.
Why the study?
Does dynamic exercise reset the cardiopulmonary baroreflex compared to rest in healthy men?
Does dynamic exercise reset the cardiopulmonary baroreflex compared to rest in healthy men?
The cardiopulmonary baroreflex resets to a higher operating point during dynamic exercise to accommodate increased cardiac filling volumes.
Small physiological study in healthy men does not inform practice; leaves open baroreflex resetting mechanisms in exercise.
The purpose of this study was to examine the hypothesis that the operating point of the cardiopulmonary baroreflex resets to the higher cardiac filling pressure of exercise associated with the increased cardiac filling volumes. Eight men (age 26 +/- 1 yr; height 180 +/- 3 cm; weight 86 +/- 6 kg; means +/- SE) participated in the present study. Lower body negative pressure (LBNP) was applied at 8 and 16 Torr to decrease central venous pressure (CVP) at rest and during steady-state leg cycling at 50% peak oxygen uptake (104 +/- 20 W). Subsequently, two discrete infusions of 25% human serum albumin solution were administered until CVP was increased by 1.8 +/- 0.6 and 2.4 +/- 0.4 mmHg at rest and 2.9 +/- 0.9 and 4.6 +/- 0.9 mmHg during exercise. During all protocols, heart rate, arterial blood pressure, and CVP were recorded continuously. At each stage of LBNP or albumin infusion, forearm blood flow and cardiac output were measured. During exercise, forearm vascular conductance increased from 7.5 +/- 0.5 to 8.7 +/- 0.6 U (P = 0.024) and total systemic vascular conductance from 7.2 +/- 0.2 to 13.5 +/- 0.9 l.min(-1).mmHg(-1) (P < 0.001). However, there was no significant difference in the responses of both forearm vascular conductance and total systemic vascular conductance to LBNP and the infusion of albumin between rest and exercise. These data indicate that the cardiopulmonary baroreflex had been reset during exercise to the new operating point associated with the exercise-induced change in cardiac filling volume.
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Ogoh et al. (2005) studied this question. Lower body negative pressure and albumin infusion vs. Rest was evaluated on Responses of forearm and total systemic vascular conductance to LBNP and albumin infusion. Cardiopulmonary baroreflex responses to lower body negative pressure and albumin infusion did not differ significantly between rest and exercise, indicating the reflex resets during exercise.
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