CeRiSM, Sport Mountain and Health Research Centre, University of Verona, via Matteo del Ben, 5/b, 38068, Rovereto, Italy.
Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
Eur J Appl Physiol. 2018 Oct;118(10):2189-2201. doi: 10.1007/s00421-018-3945-5. Epub 2018 Jul 26.
This study investigated the effects of acute hypoxic exposure on post-exercise cardiac autonomic modulation following maximal cardiopulmonary exercise testing (CPET).
Thirteen healthy men performed CPET and recovery in normoxia (N) and normobaric hypoxia (H) (FiO = 13.4%, ≈ 3500 m). Post-exercise cardiac autonomic modulation was assessed during recovery (300 s) through the analysis of fast-phase and slow-phase heart rate recovery (HRR) and heart rate variability (HRV) indices.
Both short-term, T30 (mean difference (MD) 60.0 s, 95% CI 18.2-101.8, p = 0.009, ES 1.01), and long-term, HRRt (MD 21.7 s, 95% CI 4.1-39.3, p = 0.020, ES 0.64), time constants of HRR were higher in H. Fast-phase (30 and 60 s) and slow-phase (300 s) HRR indices were reduced in H either when expressed in bpm or in percentage of HR (p < 0.05). Chronotropic reserve recovery was lower in H than in N at 30 s (MD - 3.77%, 95% CI - 7.06 to - 0.49, p = 0.028, ES - 0.80) and at 60 s (MD - 7.23%, 95% CI - 11.45 to - 3.01, p = 0.003, ES - 0.81), but not at 300 s (p = 0.436). Concurrently, Ln-RMSSD was reduced in H at 60 and 90 s (p < 0.01) but not at other time points during recovery (p > 0.05).
Affected fast-phase, slow-phase HRR and HRV indices suggested delayed parasympathetic reactivation and sympathetic withdrawal after maximal exercise in hypoxia. However, a similar cardiac autonomic recovery was re-established within 5 min after exercise cessation. These findings have several implications in cardiac autonomic recovery interpretation and in HR assessment in response to high-intensity hypoxic exercise.
本研究旨在探讨极量心肺运动测试（CPET）后急性低氧暴露对运动后心脏自主神经调节的影响。
13 名健康男性在常氧（N）和常压低氧（H）（FiO2=13.4%，约 3500 米）下进行 CPET 和恢复。通过快速和慢速心率恢复（HRR）以及心率变异性（HRV）指数分析，在恢复期间（300 秒）评估运动后的心脏自主神经调节。
在 H 中，短期（T30，平均差异（MD）60.0 秒，95%置信区间 18.2-101.8，p=0.009，ES 1.01）和长期（HRRt，MD 21.7 秒，95%置信区间 4.1-39.3，p=0.020，ES 0.64）的 HRR 时间常数更高。在 H 中，快速（30 和 60 秒）和慢速（300 秒）HRR 指数无论是以 bpm 还是以 HR 的百分比表示，均降低（p<0.05）。在 H 中，与 N 相比，30 秒时的变时性储备恢复较低（MD-3.77%，95%置信区间-7.06 至-0.49，p=0.028，ES-0.80），在 60 秒时较低（MD-7.23%，95%置信区间-11.45 至-3.01，p=0.003，ES-0.81），但在 300 秒时没有差异（p=0.436）。同时，在 H 中，Ln-RMSSD 在 60 和 90 秒时降低（p<0.01），但在恢复期间的其他时间点没有差异（p>0.05）。
快速和慢速 HRR 以及 HRV 指数表明，在低氧环境下进行最大运动后，迷走神经再激活和交感神经撤离延迟。然而，在运动停止后 5 分钟内，心脏自主神经恢复再次建立。这些发现对心脏自主神经恢复的解释和对高强度低氧运动的 HR 评估有一定的影响。
