Stability and fluctuations in musculoskeletal disorder symptoms: the roles of chronic and acute job demands and resources

• MSDs are often treated as stable conditions, despite symptom variability. • We examined MSD stability and variability over three months. • Two-thirds of MSD variance explained by stable components, with within-person changes. • Chronic workload predicts MSDs more than short-term fluctuations. • MSD interventions should target both chronic and situational risks. Despite symptom fluctuations being a key aspect of living with a musculoskeletal condition, previous research has largely treated MSDs as stable over time, implicitly assuming a static course of symptom development. Guided by the Dynamic Equilibrium Model and the Job Demands-Resources model, this study aims to fill this gap by examining the stability and variability of MSD symptoms over a short-to-medium time frame (i.e., three months). We also investigate whether, and to what extent, temporary job demands and resources influence MSD symptoms beyond the effects of chronic work conditions. A shortitudinal design with three measurement points was conducted with 795 Italian employees (60.5 % females; mean age = 39.8), using Doubly Latent Multilevel Structural Equation Modelling. Results indicate that MSD symptoms are relatively stable, with approximately two-thirds of the reliable variance attributable to trait-like factors. Nevertheless, meaningful within-person fluctuations were also observed, partly driven by variations in work characteristics. Notably, while chronic stressful conditions (e.g., consistently high workload) had the strongest impact on MSDs, higher-than-usual workload had notable, situation-dependent effects on MSDs (both directly and indirectly via reduced psychological health). In contrast, control and support from colleagues functioned as protective factors only when consistently available. Overall, the present study highlights the need for comprehensive occupational health interventions addressing both situational and chronic work factors to reduce the risk of MSDs.