Dose-Response Relationship Between Moderate to Vigorous Physical Activity and Risk of Back Disorders: A Large-Scale Accelerometry Study

Objectives: To investigate the associations between different moderate to vigorous physical activity (MVPA) levels and the risk of low back disorders (LBDs), dorsal disorders (DDs), and cervical disorders (CDs). Design: Prospective cohort study. Setting and participants: Overall, 74,191 participants [mean (standard deviation [SD]) age, 55.2 (7.8) years; 57% women] from the UK Biobank with valid accelerometry data were followed up for 7.9 years (interquartile range 7.3–8.4). Methods: Associations between MVPA and LBD, DD, and CD were investigated through restricted cubic splines and Cox regression. Results: There were 3297 (4.3%) cases with incident LBDs, 1224 (1.6%) with DDs, and 792 (1.0%) with CDs. The optimal dose (nadir of the curve) of MVPA for reducing the risk of LBD was 400 weekly minutes [hazard ratio (HR), 0.68; 95% confidence interval (CI), 0.59–0.78]. The optimal dose of MVPA for reducing the risk of DD was 670 minutes per week (HR, 0.53; 95% CI, 0.42–0.67). A significant inverse close-to-inverse linear association between MVPA and CD was observed within the range of 355 (HR, 0.75; 95% CI, 0.56–0.99) and 1265 (HR, 0.53; 95% CI, 0.28–0.99) weekly minutes of MVPA, with the latter also matching the optimal dose for reducing the risk of CD. Conclusions and Implications: Although approximately 1 hour of MVPA per day may be optimal for preventing back disorders in general, higher levels may confer benefits for CD and harm for LBD. Monitoring MVPA levels to achieve optimal doses may be useful for preventing back disorders and future interventions to confirm this issue may be warranted.