Objectively measured physical activity and 12-month trajectories of neck–shoulder pain in workers: A prospective study in DPHACTO

Aims: This study aimed to investigate the association between objectively measured physical activity at work and leisure and the intensity (mean level and time course) of neck–shoulder pain (NSP) over 12 months among male and female blue collar workers. Methods: Data were obtained from 625 blue collar workers from the Danish cohort DPHACTO. Physical activity was measured objectively at baseline using accelerometers. The percentage of time spent in physical activity (walking, climbing stairs, running and cycling) was calculated for both work and leisure time. Longitudinal data on the intensity of NSP (numerical rating scale 0–10) were collected using text messages every fourth week over 12 months. Linear mixed models were used to investigate the associations between occupational physical activity (OPA) and leisure time physical activity (LTPA) and the trajectories of the intensity of NSP, adjusted for individual, biomechanical and psychosocial factors, and baseline pain. Results: OPA was not associated with the mean intensity of NSP over 12 months. LTPA was negatively associated with the mean intensity of NSP both among men (B=−0.71, 95% CI −1.31 to −0.11) and women (B=−0.85, 95% CI −1.57 to −0.13). Sex interactions on the 12-month trajectories of NSP showed that higher physical activity was associated with a slower reduction in NSP among men for OPA only (B=0.03, 95% CI 0.01-0.05) and women for LTPA only (B=0.05, 95% CI 0.00-0.09). Conclusions: We found that more time in LTPA was associated with a lower overall intensity of NSP over 12 months among blue collar workers. However, depending on sex and domain, high physical activity had an unfavourable effect on the course of NSP over 12 months.