Upright dynamic one-legged exercise significantly decreased muscle sympathetic nerve activity from 30 to 22 bursts/min (P<0.05), contrasting with known responses to arm exercise.
Does dynamic one-legged exercise affect muscle sympathetic nerve activity?
Dynamic one-legged exercise in the upright position suppresses muscle sympathetic nerve activity, likely due to increased cardiac filling pressures stimulating cardiopulmonary baroreceptors.
Absolute Event Rate: 22% vs 30%
p-value: p=<0.05
Previous studies examining muscle sympathetic nerve activity (MSNA) during dynamic exercise have focused on upper extremity exercise. The present study was undertaken to investigate 1) MSNA responses to dynamic one-legged knee extensions (DLE) and 2) the role of the cardiopulmonary baroreflexes in the modulation of MSNA responses to DLE. MSNA was measured during 4 min of DLE at 20 (n = 10) and 30 W (n = 9) and during 3 min of DLE at 40 W (n = 9). DLE was performed in the upright (sitting) position and MSNA was recorded in the contralateral leg (peroneal nerve). DLE elicited significant increases in mean arterial pressure (MAP) and heart rate (HR; P < 0.05). In contrast to previous studies using dynamic arm exercise, MSNA (bursts/min) decreased by 25% (P < 0.05) during the first minute of DLE from resting control and remained suppressed during the remaining 3 min of DLE at 20 and 30 W. During the first minute of DLE at 40 W, MSNA (bursts/min) decreased by 18% (P < 0.05), but returned to control levels during the last minute of exercise. Because dynamic leg exercise in the upright position increases venous return, we postulated that upright DLE might increase cardiac filling pressures and stimulate the cardiopulmonary baroreceptors resulting in suppression of MSNA. To investigate this possibility, we measured MSNA and central venous pressure (CVP) during 4 min of both supine and upright DLE at 30 W. MAP, HR, and CVP increased and MSNA decreased from 30 +/- 3 to 22 +/- 3 bursts/min (mean exercise value; P < 0.05) during upright DLE.(ABSTRACT TRUNCATED AT 250 WORDS)
Ray et al. (1993) studied this question. Dynamic one-legged knee extensions (DLE) vs. Resting control / supine position was evaluated on Muscle sympathetic nerve activity (MSNA) (p=<0.05). Upright dynamic one-legged exercise significantly decreased muscle sympathetic nerve activity from 30 to 22 bursts/min (P<0.05), contrasting with known responses to arm exercise.