Table 3.
Cardiorespiratory responses during the last 10 s of an incremental exercise to exhaustion in different levels of hypoxia (PIO2 = 73, 82, 92, and 99 mmHg) and during the first 10 s of oxygenation to normoxia (PIO2 = 142 mmHg).
| Exhaustion PIO2 = 99 mmHg | Start of Normoxia | Exhaustion PIO2 = 92 mmHg | Start of Normoxia | Exhaustion PIO2 = 82 mmHg | Start of Normoxia | Exhaustion PIO2 = 73 mmHg | Start of Normoxia | |
|---|---|---|---|---|---|---|---|---|
| FIO2 (%) | 14.42 ± 0.12 | 20.26 ± 0.46c | 13.41 ± 0.39 | 19.99 ± 0.53c | 11.98 ± 0.21 | 19.90 ± 0.62c | 10.91 ± 0.44 | 20.02 ± 0.74c¶§‡ |
| SpO2 (%) | 78.2 ± 4.1 | 80.2 ± 5.3a | 70.4 ± 6.7 | 73.4 ± 6.8c | 67.6 ± 4.5 | 68.2 ± 4.2b | 64.7 ± 4.8 | 66.3 ± 6.20a¶§‡ |
| Wmax (W) | 180.0 ± 21.1 | 180.0 ± 21.1 | 172.0 ± 19.3 | 172.0 ± 19.3 | 170.0 ± 17.0 | 170.0 ± 17.0 | 172.0 ± 21.5 | 172.0 ± 21.5 |
| VO2peak (L.min−1) | 2.93 ± 0.25 | 3.89 ± 0.68b | 2.87 ± 0.28 | 4.15 ± 0.45c | 2.48 ± 0.32 | 3.99 ± 0.52c | 2.37 ± 0.30 | 4.05 ± 0.59c¶§‡ |
| VE (L.min−1) | 119.9 ± 18.1 | 116.1 ± 25.6 | 118.6 ± 19.0 | 117.3 ± 16.7 | 110.8 ± 24.5 | 109.5 ± 17.8 | 117.6 ± 17.5 | 113.6 ± 21.2 |
| RR (breaths.min−1) | 53.5 ± 7.1 | 51.2 ± 5.7 | 53.2 ± 7.0 | 52.6 ± 6.0 | 49.6 ± 8.6 | 49.5 ± 5.6 | 52.7 ± 7.2 | 52.2 ± 7.7 |
| HR (beats.min−1) | 182.2 ± 7.9 | 182.1 ± 8.7 | 182.7 ± 6.2 | 182.9 ± 6.2 | 178.6 ± 7.0 | 178.5 ± 6.5 | 180.9 ± 7.9 | 180.5 ± 7.9 |
| PETO2 (mmHg) | 71.3 ± 2.6 | 96.4 ± 9.9c | 64.4 ± 3.1 | 90.6 ± 13.4c | 56.7 ± 3.4 | 91.4 ± 12.2c | 51.8 ± 2.1 | 92.3 ± 11.5c¶§‡ |
| PETCO2 (mmHg) | 29.0 ± 2.9 | 30.5 ± 3.0a | 29.0 ± 2.9 | 30.1 ± 2.5a | 28.7 ± 3.6 | 29.5 ± 3.5a | 28.3 ± 2.4 | 30.2 ± 2.7a |
| RER | 1.13 ± 0.08 | 0.92 ± 0.10c | 1.12 ± 0.08 | 0.87 ± 0.12c | 1.21 ± 0.11 | 0.84 ± 0.10c | 1.35 ± 0.14 | 0.90 ± 0.15c¶§‡ |
| VCO2 (L.min−1) | 3.28 ± 0.28 | 3.29 ± 0.51 | 3.21 ± 0.34 | 3.25 ± 0.29 | 3.00 ± 0.47 | 3.02 ± 0.37 | 3.13 ± 0.40 | 3.16 ± 0.41§ |
| RPM | 61.7 ± 9.0 | 67.0 ± 12.5 | 63.8 ± 11.4 | 69.5 ± 10.2b | 61.9 ± 11.3 | 68.1 ± 9.4T | 58.3 ± 12.6 | 65.6 ± 13.9T¶ |
| VM RMSraw (μV) | 116.9 ± 45.3 | 122.7 ± 46.6 | 120.2 ± 42.5 | 119.8 ± 39.2 | 120.1 ± 49.4 | 125.3 ± 47.6 | 102.6 ± 47.0 | 108.4 ± 44.3 |
| VL RMSraw (μV) | 116.5 ± 38.1 | 123.6 ± 43.3 | 107.3 ± 52.5 | 110.8 ± 52.6 | 118.4 ± 50.2 | 122.7 ± 52.9 | 87.2 ± 36.1 | 94.5 ± 37.0b¶ |
| Average RMSraw (μV) | 116.7 ± 32.5 | 123.2 ± 35.9 | 113.8 ± 42.6 | 115.3 ± 40.3 | 119.3 ± 41.6 | 124.0 ± 43.1 | 94.9 ± 37.5 | 101.5 ± 36.3a¶ |
| VM RMSNz (A.U.) | 182.1 ± 53.9 | 191.7 ± 57.8 | 204.3 ± 70.8 | 205.8 ± 68.7 | 189.5 ± 57.3 | 197.9 ± 51.7 | 172.9 ± 70.7 | 184.7 ± 77.1¶ |
| VL RMSNz (A.U.) | 195.4 ± 52.6 | 206.8 ± 66.6 | 177.8 ± 41.3 | 183.4 ± 43.3 | 194.5 ± 70.0 | 199.4 ± 57.5 | 155.9 ± 55.7 | 167.3 ± 53.4a¶ |
| Average RMSNz (A.U.) | 188.7 ± 43.9 | 199.2 ± 52.7 | 191.1 ± 53.8 | 194.6 ± 50.8 | 192.0 ± 61.4 | 198.6 ± 51.6 | 164.4 ± 62.0 | 176.0 ± 63.9¶ |
| VM TAINz (A.U.) | 39.9 ± 15.7 | 43.6 ± 16.2T | 42.8 ± 19.2 | 40.6 ± 11.2 | 42.1 ± 17.0 | 42.6 ± 14.5 | 36.1 ± 14.4 | 38.0 ± 16.4¶ |
| VL TAINz (A.U.) | 43.2 ± 19.3 | 42.4 ± 14.4 | 34.1 ± 9.0 | 35.3 ± 7.2 | 40.5 ± 15.2 | 40.9 ± 12.8 | 32.5 ± 13.8 | 34.1 ± 15.6 |
| Average TAINz (A.U.) | 41.5 ± 17.1 | 43.0 ± 15.1 | 38.4 ± 13.4 | 37.9 ± 8.4 | 41.3 ± 15.9 | 41.7 ± 13.5 | 34.3 ± 13.5 | 36.0 ± 15.5¶ |
| VM MPF (Hz) | 87.4 ± 20.1 | 84.9 ± 20.6 | 84.7 ± 20.2 | 86.0 ± 21.0 | 88.5 ± 14.6 | 87.0 ± 16.6 | 81.8 ± 15.2 | 81.7 ± 16.4 |
| VL MPF (Hz) | 71.4 ± 15.8 | 85.3 ± 21.9c | 85.7 ± 19.4 | 85.6 ± 21.8 | 88.1 ± 15.0 | 86.3 ± 16.9 | 81.9 ± 15.5 | 82.1 ± 16.1¶‡ |
| Average MPF (Hz) | 79.4 ± 17.8 | 85.1 ± 21.2b | 85.2 ± 19.8 | 85.8 ± 21.4 | 88.3 ± 14.8 | 86.6 ± 16.7 | 81.8 ± 15.3 | 81.9 ± 16.2‡ |
| VM MdPF (Hz) | 70.9 ± 16.2 | 69.9 ± 16.2 | 67.5 ± 13.6 | 68.7 ± 15.2 | 72.1 ± 11.8 | 70.3 ± 12.2 | 65.0 ± 10.6 | 66.1 ± 13.2 |
| VL MdPF (Hz) | 71.4 ± 15.8 | 68.8 ± 16.6a | 67.9 ± 13.6 | 68.1 ± 16.2 | 71.4 ± 12.1 | 69.2 ± 12.7 | 65.5 ± 11.0 | 65.9 ± 12.5 |
| Average MdPF (Hz) | 71.1 ± 16.0 | 69.3 ± 16.4 | 67.7 ± 13.6 | 68.4 ± 15.6 | 71.8 ± 11.8 | 69.8 ± 12.3 | 65.3 ± 10.8 | 66.0 ± 12.8 |
| VM Burst (ms) | 375.6 ± 127.2 | 363.0 ± 130.0 | 377.9 ± 196.2 | 317.6 ± 83.8 | 372.8 ± 102.7 | 322.0 ± 73.8a | 367.5 ± 85.1 | 319.2 ± 72.1a¶ |
| VL Burst (ms) | 381.7 ± 120.6 | 321.3 ± 83.7a | 343.6 ± 109.4 | 309.1 ± 73.1T | 366.7 ± 107.3 | 315.0 ± 72.4T | 371.4 ± 97.1 | 309.3 ± 60.0a¶ |
| Average Burst (ms) | 378.6 ± 113.0 | 342.2 ± 92.2T | 360.8 ± 150.4 | 313.3 ± 77.6 | 369.8 ± 104.6 | 318.5 ± 58.9a | 369.5 ± 88.6 | 314.2 ± 63.9a¶ |
| VM Timing (%) | 49.1 ± 3.4 | 46.3 ± 7.7 | 48.2 ± 3.5 | 48.1 ± 4.4 | 48.6 ± 3.0 | 47.8 ± 3.6 | 49.4 ± 3.4 | 47.4 ± 4.3a¶ |
| VL Timing (%) | 49.5 ± 3.6 | 50.2 ± 2.2 | 49.4 ± 2.5 | 49.7 ± 2.1 | 50.4 ± 1.6 | 49.4 ± 2.4 | 50.5 ± 2.3 | 49.4 ± 2.8 |
| Average Timing (%) | 49.3 ± 3.0 | 48.3 ± 4.2 | 48.8 ± 2.7 | 48.9 ± 3.0 | 49.5 ± 2.1 | 48.6 ± 2.8T | 50.0 ± 2.8 | 48.4 ± 3.4a¶ |
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; Timing, start of activation expressed as percentage of total revolution duration.
P < 0.05;
P < 0.01;
P < 0.001; and
P < 0.1 (FIO2 = 73 mmHg vs. new gas mixture).
P < 0.05 ANOVA breathing gas switch main effect;
P < 0.05 ANOVA oxygenation level main effect;
P < 0.05 ANOVA breathing gas switch x oxygenation level interaction: n = 10.