Table 3.
Heart rate variability of the two study groups by mixed model.
| Variables | Control (n = 20) | Experimental (n = 20) | P-value |
|---|---|---|---|
| HR (bpm) | |||
| Baseline | 76.15 ± 11.71 | 75.95 ± 9.46 | .093 |
| 4th week | 75.20 ± 11.46† | 71.70 ± 10.00† | .399 |
| 8th week | 78.65 ± 12.17† | 71.30 ± 7.54† | .060 |
| 12th week | 75.75 ± 7.95† | 71.20 ± 7.14† | .331 |
| SDNN (ms) | |||
| Baseline | 27.74 ± 12.63 | 28.95 ± 11.04 | .609 |
| 4th week | 25.29 ± 12.32 | 42.51 ± 21.62† | .024* |
| 8th week | 25.40 ± 13.25 | 37.47 ± 12.90 | .029* |
| 12th week | 24.93 ± 12.75 | 37.84 ± 13.11 | .105 |
| RMSSD (ms) | |||
| Baseline | 28.44 ± 16.40 | 22.94 ± 17.02 | .079 |
| 4th week | 32.83 ± 24.97 | 19.48 ± 11.81 | .082 |
| 8th week | 27.68 ± 15.69 | 20.40 ± 16.21 | .125 |
| 12th week | 26.16 ± 11.84 | 20.61 ± 13.33 | .629 |
| Total power (ms2) | |||
| Baseline | 591.67 ± 479.69 | 830.37 ± 773.41 | .225 |
| 4th week | 589.58 ± 766.77 | 1837.12 ± 2060.79 | .049* |
| 8th week | 608.76 ± 761.64 | 1160.05 ± 866.09 | .066 |
| 12th week | 553.31 ± 610.40 | 1272.76 ± 1126.29 | .158 |
| LF (ms2) | |||
| Baseline | 177.61 ± 205.10 | 244.26 ± 270.26 | .409 |
| 4th week | 186.34 ± 434.22 | 498.67 ± 522.62 | .130 |
| 8th week | 157.74 ± 244.64 | 346.60 ± 336.71 | .114 |
| 12th week | 162.73 ± 233.30 | 433.18 ± 533.66 | .360 |
| HF (ms2) | |||
| Baseline | 161.50 ± 229.62 | 185.87 ± 265.58 | .643 |
| 4th week | 113.33 ± 159.14 | 266.32 ± 383.74 | .152 |
| 8th week | 150.99 ± 232.14 | 183.19 ± 161.47 | .420 |
| 12th week | 127.57 ± 157.84 | 161.13 ± 120.27 | .980 |
| LF nu | |||
| Baseline | 52.76 ± 25.30 | 57.22 ± 20.96 | .285 |
| 4th week | 64.04 ± 16.35 | 54.35 ± 16.58 | .441 |
| 8th week | 61.84 ± 18.12 | 55.28 ± 16.56 | .902 |
| 12th week | 61.94 ± 18.93 | 54.94 ± 16.24 | .725 |
| HF nu | |||
| Baseline | 47.24 ± 25.30 | 42.78 ± 20.96 | .285 |
| 4th week | 35.96 ± 16.35 | 45.65 ± 16.58 | .441 |
| 8th week | 38.16 ± 18.12 | 44.72 ± 19.75 | .902 |
| 12th week | 38.06 ± 19.83 | 45.06 ± 16.24 | .725 |
| LF/HF ratio | |||
| Baseline | 2.24 ± 2.36 | 2.47 ± 3.31 | .541 |
| 4th week | 1.56 ± 1.18 | 3.06 ± 3.70 | .299 |
| 8th week | 1.99 ± 2.37 | 2.62 ± 2.94 | .644 |
| 12th week | 1.50 ± 0.87 | 2.60 ± 2.37 | .345 |
HR, heart rate; SDNN, standard deviation of normal-to-normal RR intervals; RMSSD, the square root of the mean squared differences of successive NN intervals; LF, low frequency; HF, high frequency; LF nu, LF in normalized unit; HF nu, HF in normalized unit; Data were presented as mean ± SD. Work, occupation and working stress were adjusted. Bonferroni correction with adjusted α-level (α′ = 0.05/3 = 0.0167) was used for multiple comparisons between each time point and the baseline.
*Significantly different between two groups, P < .05; †Significantly different between the present time point and the baseline, P < .0167.