Table 2.
Mean (s.d.) HRV indices and ventilatory variables during cycling exercise (100 W) whilst breathing hypoxic gas (
) before (first exposure) and after (second exposure) the water immersions in thermoneutral (TW) or cold-water (CW)
| CW group | TW group | |||
|---|---|---|---|---|
| First exposure | Second exposure | First exposure | Second exposure | |
 (%) |
74.4 (4.3) | 72.1 (4.6) | 75.1 (3.7) | 73.9 (4.9) |
| fC (beats min−1) | 142 (13) | 134 (13)*† | 141 (12) | 144 (9) |
| R-R intervals (ms) | 426 (40) | 447 (47)*† | 428 (38) | 417 (27) |
| SDNN (ms) | 12 (11) | 9 (5) | 16 (20) | 14 (11) |
| ln total power | 4.0 (1.4) | 4.0 (1.3) | 4.1 (1.3) | 3.5 (0.8) |
| ln HF | 1.3 (1.1) | 2.4 (1.2)* | 1.5 (1.4) | 1.6 (1.3) |
| ln LF | 2.3 (1.5) | 1.5 (0.9) | 2.4 (1.4) | 2.1 (1.4) |
| ln LF:HF | 1.4 (0.6) | 0.7 (0.3)*† | 1.4 (0.7) | 1.2 (0.5) |
| VT (L) | 2.3 (0.2) | 2.6 (0.3)*† | 2.3 (0.2) | 2.4 (0.3) |
| fR (breaths min−1) | 27 (6) | 22 (5)*† | 27 (4) | 26 (4) |
 (L·min−1) |
50.9 (7.1) | 47.2 (3.9)*† | 50.1 (6.2) | 50.5 (6.2) |
 (L·min−1) |
1.8 (0.3) | 1.7 (0.2)† | 1.9 (0.4) | 2.0 (0.3) |
 (L·min−1) |
2.3 (0.2) | 1.8 (0.3)*† | 2.2 (0.3) | 2.3 (0.3) |
| RER | 1.2 (0.1) | 1.1 (0.1)*† | 1.3 (0.1) | 1.2 (0.1) |
*
Different from the first exposure P < 0.05.
†
Different from the TW group P < 0.05.