Zhang L F, Zheng J, Wang S Y, Zhang Z Y, Liu C
Department of Aerospace Physiology, The Fourth Military Medical University, Xi'an, P.R. China.
Aviat Space Environ Med. 1999 Oct;70(10):975-82.
This study was performed to investigate the effects of aerobic training on orthostatic tolerance and to quantify the post-training changes in cardiovascular response and heart rate variability (HRV).
Tolerance and circulatory responses to two types of lower body negative pressure (LBNP) were examined and compared in a group of healthy male students before and after 6 mo of aerobic training, and the results were further compared with a group of athletes (runners). Changes in HRV associated with training were analyzed by conventional and time-varying autoregressive spectral analysis, as well as by approximate entropy measurement (ApEn)--a statistic quantifying heart rate "complexity" derived from non-linear dynamics.
After aerobic training, there was an initial transient hypotension during the supine -50 mmHg LBNP testing and a significant decrease in tolerance to upright graded LBNP in most of the student-subjects. Moreover, after training, there was a significant decrease in ApEn value of the HRV time series during both supine control and LBNP testing, and the rate of cardiac vagal withdrawal and sympathetic activation during the onset of LBNP was faster than that before training.
The present study has provided further evidence that certain types of aerobic training may affect orthostatic tolerance and may be associated with a loss of complexity of HRV during supine resting and orthostatic stress.
本研究旨在探讨有氧运动训练对直立耐力的影响，并量化训练后心血管反应和心率变异性（HRV）的变化。
在一组健康男学生进行6个月有氧运动训练前后，对两种类型的下肢负压（LBNP）的耐受性和循环反应进行检查和比较，并将结果与一组运动员（跑步者）进一步比较。通过传统的和时变自回归谱分析以及近似熵测量（ApEn）——一种从非线性动力学推导出来的量化心率“复杂性”的统计量，分析与训练相关的HRV变化。
有氧运动训练后，在仰卧位-50 mmHg LBNP测试期间出现初始短暂性低血压，并且大多数学生受试者对直立分级LBNP的耐受性显著降低。此外，训练后，仰卧位对照和LBNP测试期间HRV时间序列的ApEn值显著降低，并且LBNP开始时心脏迷走神经撤离和交感神经激活的速率比训练前更快。
本研究提供了进一步的证据，表明某些类型的有氧运动训练可能会影响直立耐力，并且可能与仰卧位休息和直立应激期间HRV复杂性的丧失有关。
