Department of Natural Sciences in Kinanthropology, Faculty of Physical Culture, Palacky University Olomouc, 771 11 Olomouc, Czech Republic.
Int J Environ Res Public Health. 2020 Oct 19;17(20):7579. doi: 10.3390/ijerph17207579.
This study focuses on the determination of the vagal threshold (T) during exercise with increasing intensity in normoxia and normobaric hypoxia. The experimental protocol was performed by 28 healthy men aged 20 to 30 years. It included three stages of exercise on a bicycle ergometer with a fraction of inspired oxygen (FiO) 20.9% (normoxia), 17.3% (simulated altitude 1500 m), and 15.3% (2500 m) at intensity associated with 20% to 70% of the maximal heart rate reserve (MHRR) set in normoxia. T level in normoxia was determined at exercise intensity corresponding with (M ± SD) 45.0 ± 5.6% of MHRR. Power output at T (PO), representing threshold exercise intensity, decreased with increasing degree of hypoxia (normoxia: 114 ± 29 W; FiO = 17.3%: 110 ± 27 W; FiO = 15.3%: 96 ± 32 W). Significant changes in PO were observed with FiO = 15.3% compared to normoxia ( = 0.007) and FiO = 17.3% ( = 0.001). Consequentially, normoxic %MHRR adjusted for hypoxia with FiO = 15.3% was reduced to 39.9 ± 5.5%. Considering the convenient altitude for exercise in hypoxia, PO did not differ excessively between normoxic conditions and the simulated altitude of ~1500 m, while more substantial decline of PO occurred at the simulated altitude of ~2500 m compared to the other two conditions.
本研究旨在确定在常氧和常压低氧条件下，运动强度递增时的迷走神经阈值（T）。实验方案由 28 名年龄在 20 至 30 岁的健康男性完成。它包括三个阶段的自行车测力计运动，吸入氧气分数（FiO）分别为 20.9%（常氧）、17.3%（模拟海拔约 1500 米）和 15.3%（模拟海拔约 2500 米），运动强度与常氧时 20%至 70%的最大心率储备（MHRR）相关。常氧下 T 水平是在与（M ± SD）45.0 ± 5.6%的 MHRR 相对应的运动强度下确定的。代表阈下运动强度的 T 时功率输出（PO）随着低氧程度的增加而降低（常氧：114 ± 29 W；FiO = 17.3%：110 ± 27 W；FiO = 15.3%：96 ± 32 W）。与常氧相比，FiO = 15.3%时 PO 发生显著变化（= 0.007）和 FiO = 17.3%（= 0.001）。因此，用 FiO = 15.3%校正低氧的常氧 %MHRR 降低至 39.9 ± 5.5%。考虑到低氧条件下运动的方便海拔，PO 在常氧条件和模拟海拔约 1500 米之间没有太大差异，而在模拟海拔约 2500 米时，PO 的下降幅度比其他两种条件更为明显。
