Muscle sympathetic nerve activity during dynamic exercise in humans: contributions to blood flow responses
This study investigated muscle sympathetic nerve activity (MSNA) and superficial femoral artery (SFA) blood flow during rhythmic handgrip (RHG), one-legged cycling, and concurrent arm and leg dynamic exercise. Thirty-five healthy young participants completed two study visits. MSNA was acquired during 3-minutes of RHG, one-legged cycling, and concurrent exercise. On the second day, SFA blood flow was assessed during identical exercise protocols. SFA blood flow and MSNA were both recorded from the inactive leg. SFA vascular conductance was unchanged during RHG but reduced similarly during concurrent and cycling exercise. RHG increased MSNA burst frequency but not burst amplitude or total MSNA. Cycling and concurrent exercise did not change MSNA burst frequency but increased burst amplitude, and total MSNA. With cycling and concurrent exercise, reductions in resting SFA vascular conductance occurred in parallel to increases in MSNA burst strength and total activity but not MSNA burst frequency.