TABLE 1.
Absolute values are means ± SD.
| NN | HH3000 | HH5500 | |
| HR (bpm) | 73.4 ± 7.0 | 81.4 ± 10.2* | 93.0 ± 14.2***§§§ |
| RMSSD (ms) | 46.1 ± 15.6 | 37.5 ± 20.1* | 25.5 ± 16.1*** |
| LF (ms2) | 2381 ± 1311 | 1405 ± 1162** | 783 ± 536*** |
| HF (ms2) | 816 ± 442 | 606 ± 531 | 311 ± 314** |
| LF (n.u.) | 73.9 ± 9.4 | 72.3 ± 13.5 | 75.1 ± 14.1 |
| HF (n.u.) | 25.8 ± 9.5 | 25.5 ± 10.7 | 24.9 ± 14.0 |
| LF/HF ratio | 3.3 ± 1.2 | 3.4 ± 1.8 | 4.4 ± 2.9 |
| Total Power (LF + HF) | 3197 ± 1629 | 1703 ± 112** | 999 ± 602*** |
| SpO2 (%) | 99.5 ± 0.4 | 95.4 ± 2.7** | 81.3 ± 5.5***§§§ |
Physiological variables (n = 15): HR, Heart rate; RMSSD, root mean square of the successive differences; LF, low frequency; HF, high frequency; SpO2, pulse oxygen saturation in NN, normobaric normoxia in hypobaric hypoxia at 3000 m and 5500 m (HH3000 and HH5500). * p < 0.05, ** p < 0.01, *** p < 0.001 for difference with NN. §p < 0.05, §§§p < 0.001 for difference with HH3000.