Sensory and psychological factors predict exercise-induced shoulder injury responses in a high-risk phenotype cohort.
Our prior studies identified a high-risk phenotype (i.e. high pain sensitivity variant of the catechol-O-methyltransferase (COMT) gene (SNP rs6269) and pain catastrophizing scores) for shoulder pain. The current study identified sensory and psychological predictors of heightened pain responses following exercise-induced shoulder injury. Healthy participants (N=131) with the SNP rs6269 COMT gene and Pain Catastrophizing Scale scores ≥5 underwent baseline sensory and psychological testing followed by an established shoulder fatigue protocol, to induce muscle injury. Movement-evoked pain, pain intensity, disability, and strength were assessed 24 hours post-injury. Demographic, sensory, and psychological variables were included as predictors in full and parsimonious models for each outcome. The highest variance explained was for the shoulder disability outcome (full model R2=0.20, parsimonious R2=0.13). In parsimonious models, the individual predictors identified were: a) 1st pulse heat pain sensitivity for isometric shoulder movement-evoked pain and pain intensity; b) pressure pain threshold for shoulder disability; c) fear of pain for active shoulder movement-evoked pain and shoulder disability; and d) depressive symptoms for shoulder strength. Findings indicate specific pain sensitivity and psychological measures may have additional prognostic value for self-reported disability within a high-risk phenotype. These findings should be tested in a clinical cohort for validation. PERSPECTIVE: The current study extends previous work by providing insight regarding how poor shoulder outcomes may develop within a high-risk phenotype. Specifically, 1st pulse heat pain sensitivity and pressure pain threshold were sensory measures, and fear of pain and depressive symptoms were psychological measures, that improved prediction of different shoulder outcomes.