Fig. 3

A. Partial correlation (n = 20) between the HR at rest and pain duration. The correlation analysis indicated that there was a strong negative association between heart rate at rest and pain duration independent of age and sex (r = −0.743, p = < 0.001). B. Partial correlation (n = 22) between the HR under stimulation and pain duration. No significant correlation was found between the HR under stimulation and pain duration independent of age and sex (r = − 0.383, p = 0.096). The gray area is the 95% confidence interval with the regression line displayed