Diminished forearm vasomotor response to central hypervolemic loading in aerobically fit individuals

Area of Science:

• Cardiovascular Physiology
• Exercise Physiology
• Baroreflex Regulation

Background:

• Cardiopulmonary baroreflexes are crucial for maintaining blood pressure homeostasis.
• Exercise training is known to induce significant cardiovascular adaptations.
• The impact of exercise training on baroreflex sensitivity during fluid shifts requires further investigation.

Purpose of the Study:

• To test the hypothesis that cardiopulmonary baroreflex control of forearm vascular resistance (FVR) is less sensitive in highly fit (HF) individuals compared to average fit (AF) individuals.
• To investigate the influence of exercise training on autonomic cardiovascular regulation.

Main Methods:

• Comparison of forearm vascular resistance (FVR) and central venous pressure (CVP) responses to fluid loading and unloading.
• Utilized lower body negative pressure (LBNP) for hypovolemia and passive leg elevation with lower body positive pressure (LE+LBPP) for hypervolemia.
• Measured hemodynamic parameters including mean arterial pressure (MAP), forearm blood flow (FBF), and CVP.

Main Results:

• Maximal aerobic power, plasma volume, and blood volume were significantly higher in HF individuals.
• Despite similar baseline hemodynamic parameters, the FVR response to changes in CVP was significantly diminished in HF individuals compared to AF individuals.
• The sensitivity of the FVR/CVP relationship was significantly lower in the exercise-trained HF group.

Conclusions:

• Cardiopulmonary baroreceptor-mediated FVR reflex response is significantly less sensitive to changes in CVP in individuals who engage in regular exercise training.
• Exercise training may alter autonomic cardiovascular control mechanisms.
• These findings highlight potential adaptations in cardiovascular regulation contributing to enhanced physical performance.