Role of central command on the visceral flow regulation during exercise

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Central command is well known to control cardiac and skin sympathetic nervous activities but still equivocal for visceral circulatory adjustments during voluntary exercise. The present study focused on whether central command is essential for the blood flow regulation in renal and gastrointestinal arteries during voluntary exercise. We firstly tested active (voluntary) and passive (non-voluntary and motor-driven) elbow-flexion exercises with various amplitudes and velocities of movements. This experiment provided that the elbow-flexion moving from 40 to 90 degree with a speed of 90 degree/sec was the most relevant to manifest a clear difference between passive and active exercises in the cardiovascular variables. In the second experiments, we investigated the blood flow responses in renal artery (RA) during static handgrip exercise with a load of 30 % of maximum voluntary contraction (MVC) by using ultrasound method. This experiment showed that the renal arterial blood flow began to de … More crease significantly immediately after the onset of exercise (within 10 sec), suggesting that central command and/or muscle mechanoreflex were probably responsible for the rapid adjustment to exercise. In the third experiments, the blood flow responses in the superior mesenteric artery (SMA) were similarly studied at the onset of dynamic elbow flexion with a load of 30 % MVC. In contrast to the RA responses, the blood flow in SMA did not change at the onset of exercise suggesting no contribution of central command and/or mechanoreflex to the flow responses in SMA. In fourth experiments, we compared the flow responses between passive and active exercises in RA and SMA to determine which is more important between central command or mechanoreflex for the rapid adjustment to exercise. There was no difference in flow responses between passive and active exercises in both RA and SMA. From these results, we concluded that central command does not play an important role in regulating flow responses in visceral regions during voluntary exercise. Less