Heart rate variability and pain sensitivity in people with chronic shoulder pain during passive viewing of shoulder movement pictures

Background Chronic shoulder pain involves interactions between emotional and autonomic processes that shape pain perception. Movement-related pictures may contribute to autonomic modulation imbalance in musculoskeletal pain. We compared the effects of viewing shoulder movement pictures on autonomic modulation and pressure pain threshold in chronic shoulder pain with pain-free controls. Methods This was a cross-sectional study involving 56 chronic shoulder pain and 52 pain-free controls. Participants viewed a sequence of previously validated shoulder movement pictures. Heart rate variability, blood pressure variability, baroreflex sensitivity, pressure pain threshold, and self-reported pain intensity at rest and during the movement (using a numerical pain rating scale) were assessed before, during, and after shoulder movement pictures. Results The chronic shoulder pain group showed a reduction in parasympathetic modulation compared to the pain-free control during (high frequency-HF: p = 0.04; variance: p = 0.00) and after shoulder movement pictures (HF: p = 0.03; variance: p = 0.01). The time x group interaction was not significant in low frequency (LF) or in the LF/HF ratio and blood pressure variability. The time x group interaction was significant in the baroreflex effectiveness index ( p < 0.05). The pressure pain threshold was higher in the chronic shoulder pain group after the shoulder movement pictures, with a difference between groups ( p < 0.001). Numerical pain rating scale did not change in chronic shoulder pain before and after shoulder movement pictures. Conclusion Exposure to shoulder movement pictures resulted in reduced parasympathetic modulation and lower pressure pain threshold in chronic shoulder pain.