The use of isometric exercise as a means of evaluating the parasympathetic contribution to the tachycardia induced by dynamic exercise in normal man.

摘要: Fourteen normal subjects were submitted to isometric exercise (IE), dynamic (DE) and a combination of the two (IE+DE). The main purpose present study was use IE as means evaluating mechanism heart rate (HR) increase induced by DE. To this end, magnitude (handgrip) standardized so cause an elevation HR almost exclusively vagal withdrawal: performed using dynamometer straingauge system with linear response at 75% maximum voluntary contraction (MVC) for 10s, repeated 1 min intervals. change in evoked under control conditions compared that during DE, corresponding recovery period. DE legs, subject seated position 4 min, workloads 55 105 watts, separated rest In combined protocol, beginning well 1, 2 3 0, 2, 5 following results obtained: (1) associated always smaller than alone, effect more marked 55W; finding suggested workload-dependent withdrawal very sustained until end effort. (2) During each similar HR, even workload W, when increased gradually itself; these suggest that, gradual tachycardia (from 1st 4th DE) not vagus dependent. (3) used here permitted functional evaluation dynamics without resorting pharmacological blockade autonomic nervous system.