Table 3. Frequency-domain HRV parameters in the cool condition (TN-2), at thermoneutrality (TN) and in the warm condition (TN+2) during active sleep (AS) and quiet sleep (QS).
| TN-2°C | TN | TN+2°C | Thermal condition effect | Sleep Stage effect | ||||
| AS | QS | AS | QS | AS | QS | |||
| VLF (ms2) | 359.1±396.6 | 248.7±364.3 | 240.3±231.9 | 136.2±179.0 | 171.8±193.7 | 161.9±228.2 | P = 0.0112 | NS |
| LF (ms2) | 270.7±268.7 | 161.3±174.3 | 179.2±122.1 | 114.1±174.6 | 156.8±139.4 | 134.8±204.1 | NS | P = 0.0205 |
| HF (ms2) | 46.1±37.5 | 55.3±45.2 | 37.9±32.7 | 33.4±39.2 | 27.5±30.1 | 23.1±26.3 | P = 0.0102 | NS |
| VLF (%) | 45.3±17.5 | 43.6±19.3 | 46.5±18.6 | 42.2±17.6 | 44.2±15.7 | 45.3±17.4 | NS | NS |
| LF (%) | 43.2±15.0 | 35.5±14.0 | 43.5±16.3 | 39.5±16.9 | 46.5±14.4 | 44.2±17.1 | NS | P = 0.012 |
| HF (%) | 11.5±10.1 | 21.0±22.8 | 10.0±7.8 | 18.3±18.6 | 9.3±11.6 | 10.6±11.4 | NS | P = 0.0015 |
| LF/HF | 8.4±7.6 | 5.1±5.2 | 8.7±7.2 | 5.2±5.4 | 10.7±8.2 | 7.6±5.9 | NS | P = 0.0099 |
Values are quoted as the mean ± standard deviation. NS: non-significant in an analysis of variance with repeated measures.