Microneurographic studies of the mechanisms of sympathetic nerve responses to static exercise in XXXX .

@entity1 @entity63 @entity2472
The purpose of this study was to determine the contribution of muscle afferents and central command in regulating sympathetic nerve activity during static exercise in @entity1 . In 20 healthy subjects, we recorded heart rate, arterial pressure, and efferent sympathetic nerve activity in the leg during arm exercise. Microelectrodes were inserted percutaneously into a fascicle of the peroneal nerve to measure sympathetic discharge to muscle. Measurements were obtained in nine subjects during sustained handgrip (30% maximal @entity2472 ) followed by relaxation or by arrested circulation of the forearm. Heart rate and arterial pressure increased during the first and second minutes of handgrip. Muscle sympathetic nerve activity increased from 261 +/- 46 to 504 +/- 97 units (mean +/- SE; units = burst frequency X amplitude; P less than 0.05) during the second minute of handgrip. During @entity63 following handgrip, heart rate returned promptly to control, whereas arterial pressure and muscle sympathetic nerve activity (631 +/- 115 units) remained elevated. In contrast, muscle sympathetic nerve activity returned toward control during relaxation without arrested circulation. These data indicate that muscle sympathetic nerve activity is increased by stimulation of chemically sensitive muscle afferents. To determine the influence of central command on muscle sympathetic nerve activity, we compared responses during an involuntary and a @entity2472 , each at 20% maximal @entity2472 . Both maneuvers raised arterial pressure, but heart rate increased only during @entity2472 . More importantly, muscle sympathetic nerve activity rose during involuntary contraction, but fell during voluntary effort.(ABSTRACT TRUNCATED AT 250 WORDS)
