4650m 상당의 평압·저산소 조건에서 근지구성 운동이 심박변이도에 미치는 영향

Abstract

The purpose of this study was to investigate the effect of extreme normobaric hypoxia exposure corresponding to 4650m altitude on heart rate variability during muscular endurance exercise. In a cross-over design, 19 young (21.7±2.4years) healthy males were asked to perform the isokinetic leg endurance exercise twice in hypoxia and control(sea level) condition with a week interval. Subjects assigned to the hypoxia condition group was breathed in hypoxia air corresponding to 4,650m altitude condition for 30minutes through the hypoxic control device(Altrainer, SMTEC Sports & Medical Technologies SA, Nyon, Switzerland). Each Subject conducted iso-kinetic knee flexion and extension exercise at 180°/sec, 10bouts, and 10sets using isokinetic dynamometer(Biodex system 4, Medical System Inc, USA). The parameters of heart rate variability were obtained from both time-and frequency domain analysis of 5min EC G recording at rest, post exercise, and post 10min(3 time) after exercise. Mean RR interval and its standard deviation(SDNN), the mean square successive differences(RMSSD), the low and high frequency components were calculated as normalized units. Arterial oxygen saturation was also measured by pulse oximetry at rest, post exercise, and post 10minute. The results were as follows. First, following the hypoxia exposure a significant decrease in arterial oxygen saturation was found(p.05). Second, analysis of HRV revealed a significant increase in sympathetic activity and a significant decrease in parasympathetic activity following muscular endurance exercise both group(p0.1~0.05). Third, no significantly different in parameters of HRV was not found between the hypoxia group and the control group. These findings suggest that the dropped level of arterial oxygen saturation induced by hypoxia exposure may not affect heart rate variability at resting status, during exercise and recovery period. The results also showed that exercise itself rather than status of blood might have more powerful effect on autonomic nerve activities.