Table 1.
Ergospirometric and electromyographic responses during the last 30 s of the incremental exercise to exhaustion in normoxia (PIO2 ≈ 142 mmHg) and severe hypoxia (PIO2 ≈ 73 mmHg).
| Hypoxia (PIO2 = 73 mmHg) | Normoxia | P | |
|---|---|---|---|
| FIO2 (%) | 10.8 ± 0.07 | 20.8 ± 0.04 | < 0.001 |
| SpO2 (%) | 63.8 ± 5.7 | 92.8 ± 3.1 | < 0.001 |
| Wmax (W) | 170.5 ± 17.9 | 213 ± 19.7 | < 0.001 |
| VO2peak (L.min−1) | 2.28 ± 0.19 | 3.44 ± 0.43 | < 0.001 |
| VE (L.min−1) | 115.2 ± 18.6 | 124.8 ± 15.6 | < 0.001 |
| RR (breaths.min−1) | 50.6 ± 7.0 | 55.9 ± 7.1 | < 0.001 |
| HR (beats.min−1) | 179.0 ± 8.4 | 184.8 ± 5.2 | < 0.001 |
| PETO2 (mmHg) | 51.3 ± 2.3 | 108.2 ± 7.4 | < 0.001 |
| PETCO2 (mmHg) | 28.1 ± 2.5 | 30.8 ± 3.1 | < 0.001 |
| RER | 1.34 ± 0.13 | 1.05 ± 0.06 | < 0.001 |
| VCO2 (L.min−1) | 3.06 ± 0.36 | 3.55 ± 0.41 | < 0.001 |
| RPM | 71.9 ± 4.1 | 68.4 ± 4.2 | 0.08 |
| VM RMSraw (μV) | 111.2 ± 38.6 | 128.3 ± 42.4 | < 0.01 |
| VL RMSraw (μV) | 97.5 ± 30.8 | 110.4 ± 28.0 | < 0.01 |
| Average RMSraw (μV) | 104.4 ± 29.0 | 119.4 ± 28.8 | < 0.005 |
| VM RMSNz (A.U.) | 178.1 ± 35.2 | 209.2 ± 58.4 | < 0.05 |
| VL RMSNz (A.U.) | 173.3 ± 35.4 | 200.0 ± 49.1 | < 0.005 |
| Average RMSNz (A.U.) | 175.4 ± 31.2 | 204.6 ± 50.3 | < 0.01 |
| VM TAINz (A.U.) | 111.5 ± 33.5 | 138.7 ± 47.8 | < 0.005 |
| VL TAINz (A.U.) | 97.3 ± 21.0 | 117.4 ± 22.7 | < 0.001 |
| Average TAINz (A.U.) | 102.9 ± 25.5 | 126.7 ± 30.9 | < 0.001 |
| VM MPF (Hz) | 89.8 ± 16.9 | 85.2 ± 16.6 | < 0.001 |
| VL MPF (Hz) | 89.6 ± 16.5 | 85.5 ± 17.1 | < 0.001 |
| Average MPF (Hz) | 89.7 ± 16.7 | 85.4 ± 16.9 | < 0.001 |
| VM MdPF (Hz) | 71.3 ± 12.1 | 69.2 ± 11.8 | 0.06 |
| VL MdPF (Hz) | 70.6 ± 12.1 | 68.9 ± 12.2 | 0.06 |
| Average MdPF (Hz) | 70.9 ± 12.1 | 69.0 ± 12.0 | 0.06 |
| VM Burst (ms) | 305.4 ± 51.5 | 334.3 ± 34.8 | < 0.05 |
| VL Burst (ms) | 283.0 ± 34.5 | 306.2 ± 26.7 | < 0.05 |
| Average Burst (ms) | 294.2 ± 42.1 | 320.2 ± 29.6 | < 0.05 |
FIO2, inspiratory oxygen fraction; SpO2, hemoglobin saturation in capillary blood measured by pulse oximetry; Wmax, power output at exhaustion; VO2, oxygen consumption; VE, pulmonary ventilation; RR, respiratory rate; HR, heart rate; PETO2, end-tidal O2 pressure; PETCO2, end-tidal CO2 pressure; RER, respiratory exchange ratio; VCO2, CO2 production; RPM, revolutions per minute; VL, vastus lateralis; VM, vastus medialis; RMSraw, raw root mean square; RMSNz, normalized root mean square; TAINz, normalized total activation index (arbitrary units, A.U.); MPF, mean power frequency; MdPF, median power frequency; Burst, contraction burst duration. n = 10.