Exercise- and Stress-Induced Hypoalgesia in Musicians with and without Shoulder Pain: A Randomized Controlled Crossover Study

Abstract

Professional and pre-professional musicians are characterized by physical and psychological demands inherent to their musical activity, and therefore at risk for developing performance related musculoskeletal pain. Physical and psychological demands are known to influence human pain modulation. In this study we compared the influence of a physically and emotionally stressful task on pain thresholds in musicians with and without shoulder pain. A single-blinded randomized and controlled crossover study design was used to compare the effects of a physical versus emotional testing procedure on pressure pain thresholds (PPTs) in musicians with and without shoulder pain. All data were obtained in the field (e.g., at the physiotherapy accommodation in the Royal Conservatory). During the physical testing procedure, the subjects performed an isometric exercise of the glenohumeral external rotators. The emotional task comprised watching "unpleasant" images selected from the International Affective Picture System. The outcome was the assessment of change in PPTs before and after the physical and emotional task. Our results indicate similar effects of both protocols in either group, i.e., musicians with and without shoulder pain (P > 0.05). All musicians showed elevated PPTs at local and remote areas after isometric exercise (P < 0.05). The emotional stress task increased PPTs at remote areas only (P < 0.05). Despite the small sample size of musicians without shoulder pain, a power of 78.5% was achieved to detect the necessary effect size of Cohen's d = 1. Furthermore, comparing these results with those of non-musicians (both healthy subjects and patients with shoulder pain) might reveal information regarding the specific adaptations. Finally a high variability was observed in shoulder disability (i.e., SDQ-scores) as typically seen in a population with shoulder pain. In musicians with and without regional shoulder pain, no significant differences were found with respect to pain modulation during a physically and an emotionally stressful task. Both interventions adequately activated central and widespread pain inhibitory mechanisms in both groups.