Table 3.
Significant Correlations between HRV parameters and STAI-SF total score.
| HRV Parameter | HRV Domain | Correlation Coefficient | p-value |
|---|---|---|---|
| RMSSD (ms) | Time-Domain | −0.489 | 0.005 |
| SD1 in Poincaré plot (ms) | Non-linear | −0.488 | 0.005 |
| HF absolute power – FFT (ms2) | Frequency-Domain | −0.485 | 0.006 |
| LF peak frequency – FFT (Hz) | Frequency-Domain | −0.469 | 0.008 |
| HF absolute power – FFT (log) | Frequency-Domain | −0.465 | 0.008 |
| PNS index | Kubios Metric [16] | −0.461 | 0.009 |
| RPA Lmax – maximum line length (beats) | Non-linear | 0.459 | 0.009 |
| VLF absolute power – FFT (ms2) | Frequency-Domain | −0.459 | 0.009 |
| pNN50 (%) | Time-Domain | −0.454 | 0.010 |
| TINN (ms) | Time-Domain | −0.453 | 0.011 |
| SD2/SD1 ratio | Non-linear | 0.436 | 0.014 |
| SDNN (ms) | Time-Domain | −0.436 | 0.014 |
| Total power – FFT (ms2) | Frequency-Domain | −0.434 | 0.015 |
| NN50 (beats) | Time-Domain | −0.431 | 0.015 |
| DFA alpha1 – short-term fluctuation slope | Non-linear | 0.425 | 0.017 |
| HF relative power – FFT (%) | Frequency-Domain | −0.421 | 0.018 |
| HF absolute power – FFT (n.u.) | Frequency-Domain | −0.418 | 0.019 |
| LF absolute power – FFT (n.u.) | Frequency-Domain | 0.418 | 0.019 |
| Stress index | Kubios Metric [16] | 0.409 | 0.022 |
| LF relative power – FFT (ms2) | Frequency-Domain | −0.407 | 0.023 |
| RPA Shannon Entropy | Non-linear | 0.401 | 0.026 |
| D2 – correlation dimension | Non-linear | −0.393 | 0.029 |
| LF/HF ratio – FFT | Frequency-Domain | 0.391 | 0.030 |
| RPA Determinism (%) | Non-linear | 0.379 | 0.036 |
| RPA Recurrence Rate (%) | Non-linear | 0.377 | 0.037 |
| HRV Triangular Index | Time-Domain | −0.369 | 0.041 |
| VLF absolute power – FFT (log) | Frequency-Domain | −0.369 | 0.041 |
| ApEn – Approximate Entropy | Non-linear | −0.358 | 0.048 |
| SampEn – Sample Entropy | Non-linear | −0.355 | 0.050 |
RMSSD: root mean square of the successive differences between RR intervals; SD1: standard deviation perpendicular to the line-of-identity; SD2: standard deviation along the line-of-identity; HF: high-frequency band; LF: low-frequency band; VLF: very-low-frequency band; PNS: parasympathetic nervous system activity; RPA: recurrent plot analysis; NN50:Number of successive RR interval pairs that differ more than 50 ms; pNN50:NNxx divided by the total number of RR intervals; DFA: detrended fluctuation analysis; FFT: Fast Fourier Transformation; TINN: Baseline width of the RR interval histogram; SDNN: Standard deviation of RR intervals; Stress index: Square root of Baevsky’s [21] stress index.