Carotid chemoreceptor modulation of muscle blood flow during leg‐extension exercise in healthy humans

Abstract

Previously, we have shown that transient carotid chemoreceptor (CC) inhibition causes vasodilation in limb muscle in exercising dogs, and a reduction in muscle sympathetic nerve activity during handgrip exercise in humans. The purpose of the present investigation was to determine if CC inhibition causes an increase in exercising muscle blood flow during leg‐extension exercise in humans. Healthy subjects (N = 5) breathed hyperoxic gas (FIO2 = 1.0) for 2 minutes at rest and during submaximal one‐legged knee‐extension exercise. Femoral arterial blood flow data was obtained from continuous Doppler recordings at rest and during exercise. Leg‐extension exercise increased heart rate (64 vs. 87 beats · min−1), mean blood pressure (84 vs. 96 mmHg), muscle blood flow (0.37 vs. 1.60 L · min−1) and muscle conductance (4.75 vs. 16.82 units). Transient hyperoxia had no effect on muscle blood flow or conductance at rest. In contrast, during exercise both muscle blood flow and muscle conductance were increased with hyperoxia. The mean peak increase in muscle blood flow and conductance was 30 +/− 6% and 30 +/− 8%, respectively, above steady state normoxic values. Blood pressure was unchanged with hyperoxia at rest or during exercise. These preliminary findings suggest that the CC plays a role in muscle blood flow control during exercise in healthy humans.