CARDIOVASCULAR AND HUMORAL RESPONSES TO SUSTAINED MUSCLE METABOREFLEXACTIVATION IN HUMANS

The cardiovascular and humoral responses to sustained muscle metaboref lex activation were examined in eight male volunteers while they perfo rmed two 24-min exercise protocols. Each of these consisted of six 1-m in bouts of isometric handgrip exercise (the left and right hands bein g used alternately) at 50% of maximal voluntary contraction; after eac h bout, there was either 3-min postexercise occlusion (occlusion proto col) or S-min rest (control protocol). In the occlusion protocol, mean arterial blood pressure was similar to 25 mmHg higher than during the control protocol, indicating that the muscle metaboreflex was activat ed during occlusion. During the control protocol, plasma renin activit y, plasma vasopressin, and adrenocorticotropic hormone values were not significantly different from the values at rest. During the occlusion protocol, however, plasma renin activity, plasma vasopressin, and adr enocorticotropic hormone were all significantly increased at 25 min. T hese data demonstrate that, in humans, the sustained activation of the muscle metaboreflex causes the secretion of several hormones originat ing from different regions.