Table 3. Correlations between heart rate variability indices and other study variables: chronic neck pain (n=30) and chronic low back pain (n=30).
| Chronic neck pain (n=30) | Chronic low back pain (n=30) | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CPM | NPRSa | NPRSb | PCTS | TSK | PSEQ | NDI | CPM | NPRSa | NPRSb | PCTS | TSK | PSEQ | RMDQ | ||
| HRV supine (linear) | |||||||||||||||
| Mean RR (ms) | 0.184 | -0.026 | -0.226 | -0.085 | -0.112 | 0.144 | 0.069 | -0.033 | -0.024 | -0.337 | -0.397 * | -0.264 | 0.121 | -0.210 | |
| STD-RR (ms) | -0.063 | -0.248 | -0.242 | -0.140 | -0.050 | 0.571 * | -0.444 * | -0.224 | 0.038 | -0.308 | -0.414 * | -0.180 | 0.216 | -0.123 | |
| Mean HR (bpm) | -0.186 | 0.022 | 0.224 | 0.088 | 0.116 | -0.142 | -0.069 | 0.033 | 0.024 | 0.337 | 0.397 * | 0.264 | -0.121 | 0.210 | |
| rMSSD (ms) | -0.093 | -0.211 | -0.130 | -0.211 | -0.181 | 0.504 * | -0.466 * | -0.117 | -0.048 | -0.362 * | -0.516 * | -0.246 | 0.286 | -0.199 | |
| RR Tri | -0.114 | -0.361 | -0.386 * | 0.042 | -0.049 | 0.462 * | -0.376 * | -0.161 | -0.094 | -0.472 * | -0.475 * | -0.215 | 0.193 | -0.245 | |
| TINN (ms) | -0.107 | -0.239 | -0.226 | -0.162 | -0.059 | 0.548 * | -0.448 * | -0.196 | 0.040 | -0.244 | -0.422 * | -0.210 | 0.249 | -0.112 | |
| LF (nu) | 0.099 | 0.117 | 0.053 | 0.189 | 0.427 * | -0.409 * | 0.336 | -0.184 | 0.219 | 0.052 | 0.339 | 0.018 | -0.322 | 0.092 | |
| HF (nu) | -0.099 | -0.117 | -0.053 | -0.189 | -0.427 * | 0.409 * | -0.336 | 0.179 | -0.217 | -0.050 | -0.349 | -0.025 | 0.323 | -0.091 | |
| LF/HF (ratio) | 0.095 | 0.120 | 0.051 | 0.188 | 0.425 * | -0.410 * | 0.330 | -0.179 | 0.217 | 0.050 | 0.349 | 0.025 | -0.323 | 0.091 | |
| Power LF (ms2) | -0.104 | -0.165 | -0.281 | 0.139 | 0.233 | 0.125 | -0.084 | -0.305 | 0.118 | -0.244 | -0.234 | -0.145 | -0.087 | -0.071 | |
| Power HF (ms2) | -0.228 | -0.251 | -0.349 | -0.057 | -0.203 | 0.493 * | -0.442 * | -0.115 | -0.109 | -0.426 * | -0.518 * | -0.170 | 0.229 | -0.216 | |
| HRV supine (nonlinear) | |||||||||||||||
| SD1 (ms) | -0.093 | -0.211 | -0.130 | -0.211 | -0.181 | 0.504 * | -0.466 * | -0.117 | -0.048 | -0.362 * | -0.516 * | -0.246 | 0.286 | -0.199 | |
| SD2 (ms) | -0.095 | -0.251 | -0.348 | -0.102 | -0.007 | 0.531 * | -0.432 * | -0.281 | 0.052 | -0.261 | -0.354 | -0.149 | 0.107 | -0.084 | |
| SD2/SD1 (ratio) | 0.146 | -0.011 | -0.157 | 0.086 | 0.270 | -0.223 | 0.263 | -0.200 | 0.053 | 0.096 | 0.267 | 0.145 | -0.307 | 0.145 | |
| Stress Index | -0.038 | 0.291 | 0.310 | 0.091 | -0.012 | -0.549 * | 0.381 * | 0.174 | -0.059 | 0.302 | 0.443* | 0.222 | -0.224 | 0.157 | |
| HRV standing (linear) | |||||||||||||||
| Mean RR (ms) | -0.049 | 0.125 | -0.334 | 0.043 | -0.072 | 0.074 | -0.136 | -0.088 | -0.040 | -0.112 | -0.451 * | -0.389 * | -0.074 | -0.090 | |
| STD-RR (ms) | -0.448 * | -0.002 | -0.236 | -0.090 | -0.225 | 0.196 | -0.408 * | -0.397 * | -0.042 | -0.178 | -0.224 | -0.164 | -0.102 | 0.083 | |
| Mean HR (bpm) | 0.049 | -0.125 | 0.334 | -0.043 | 0.072 | -0.074 | 0.136 | 0.088 | 0.040 | 0.112 | 0.451 * | 0.389 * | 0.074 | 0.090 | |
| rMSSD (ms) | -0.432 * | 0.121 | -0266 | 0.021 | -0.211 | 0.126 | -0.215 | -0.269 | -0.104 | -0.218 | -0.453 * | -0.373 * | -0.074 | -0.012 | |
| RR Tri | -0.277 | 0.007 | -0.270 | -0.069 | -0.074 | 0.112 | -0.414 * | -0.278 | 0.028 | -0.142 | -0.270 | -0.240 | -0.142 | 0.085 | |
| TINN (ms) | -0.484 * | 0.039 | -0.169 | -0.041 | -0.179 | 0.079 | -0.309 | -0.424 * | -0.042 | -0.181 | -0.197 | -0.175 | -0.093 | 0.135 | |
| LF (nu) | 0.393 * | -0.118 | 0.074 | -0.205 | 0.128 | -0.019 | 0.041 | 0.051 | 0.099 | 0.059 | 0.336 | 0.326 | 0.016 | 0.042 | |
| HF (nu) | -0.393 * | 0.118 | -0.074 | 0.205 | -0.128 | 0.019 | -0.041 | -0.051 | -0.099 | -0.059 | -0.336 | -0.326 | -0.016 | -0.042 | |
| LF/HF (ratio) | 0.393 * | -0.118 | 0.074 | -0.205 | 0.128 | -0.019 | 0.041 | 0.051 | 0.099 | 0.059 | 0.336 | 0.326 | 0.016 | 0.042 | |
| Power LF (ms2) | -0.087 | -0.135 | -0.324 | -0.212 | -0.106 | 0.298 | -0.447 * | -0.321 | 0.032 | -0.078 | 0.074 | -0.027 | -0.170 | 0.111 | |
| Power HF (ms2) | -0.444 * | 0.093 | -0.264 | 0.037 | -0.213 | 0.232 | -0.343 | -0.268 | 0.015 | 0.013 | -0.244 | -0.416 * | -0.079 | 0.112 | |
| HRV standing (nonlinear) | |||||||||||||||
| SD1 (ms) | -0.432 * | 0.121 | -0.266 | 0.021 | -0.211 | 0.126 | -0.215 | -0.269 | -0.104 | -0.218 | -0.453 * | -0.373 * | -0.074 | -0.012 | |
| SD2 (ms) | -0.403 * | -0.038 | -0.267 | -0.055 | -0.110 | 0.175 | -0.427 * | -0.424 * | -0.020 | -0.175 | -0.158 | -0.127 | -0.132 | 0.113 | |
| SD2/SD1 (ratio) | 0.340 | -0.168 | 0.138 | -0.148 | 0.081 | 0.020 | -0.088 | -0.031 | 0.008 | 0.037 | 0.440 * | 0.350 | 0.003 | 0.001 | |
| Stress Index | 0.435 * | -0.034 | 0.262 | 0.082 | 0.289 | -0.183 | 0.368 * | 0.367 * | 0.076 | 0.229 | 0.309 | 0.214 | 0.092 | -0.078 | |
CPM: chronicity of pain in months; NPRSa: Numeric Pain Rating Scale at rest; NPRSb: Numeric Pain Rating Scale after movements; PCTS: Pain-Related Catastrophizing Thoughts Scale; TSK: Tampa Scale of kinesiophobia; PSEQ: Pain Self-Efficacy Questionnaire; NDI: Neck Disability Index; RMDQ: Rolan-Morris Disability Questionnaire; HRV: heart rate variability; Mean RR: RR intervals mean; STD-RR: standard deviation of all RR intervals between two consecutive normal heartbeats; Mean HR: heart rate mean; rMSSD: root mean square differences of successive RR intervals; RR Tri: triangular index; TINN: triangular interpolation of the interval histogram; LF: low-frequency band in arbitrary units and in absolute values; HF: high-frequency band in arbitrary units and in absolute values; SD1: standard deviation of the instantaneous beat-to-beat variability; SD2: long-term standard deviation of continuous RR intervals.
Significant correlation (Spearman’s correlation coefficient, p<0.05).