Peripheral and central vascular conductance influence on post-exercise hypotension

Area of Science:

• Exercise Physiology
• Cardiovascular Regulation
• Hemodynamics

Background:

• Post-exercise hypotension (PEH) is a phenomenon following prolonged dynamic exercise.
• It is characterized by a reduction in mean arterial pressure (MAP).
• Increased total vascular conductance (TVC) via skeletal muscle vasodilation is the primary mechanism, but arterial vasodilation alone doesn't fully explain the TVC increase.

Purpose of the Study:

• To investigate the contribution of vascular conductance (VC) in different body regions to TVC during PEH.
• Specifically examining the roles of the legs, arms, kidneys, and viscera.

Main Methods:

• Eight healthy subjects underwent 60 minutes of cycling at 60% heart rate reserve.
• Blood flow in femoral, brachial, renal, and mesenteric arteries was measured using Doppler ultrasonography.
• Mean arterial pressure (MAP) and heart rate (HR) were monitored continuously before, during, and after exercise.

Main Results:

• MAP significantly decreased post-exercise compared to baseline.
• TVC increased by approximately 23% post-exercise (P < 0.05).
• This increase in TVC was attributed to enhanced vascular conductance in the legs (approx. 33%) and arms (approx. 20%), but not the abdomen.

Conclusions:

• Post-exercise hypotension is caused by increased TVC, not decreased cardiac output.
• Two-thirds of the rise in TVC during PEH can be attributed to increased vascular conductance in both active and inactive limbs.