Vigorous regular leisure-time physical activity is associated with a clinically important improvement in back pain – a secondary analysis of randomized controlled trials

BACKGROUND: Neck and back pain are musculoskeletal conditions with serious individual and societal consequences. Current evidence about the prognostic value for neck and back pain is limited and conflicting. This prospective cohort study aimed to assess the association between leisure-time physical activity (LPA) and improvement of neck and/or back pain in a working population receiving manual therapy or general care in one of two randomized controlled trials (RCTs). METHODS: Analyses of data from two RCTs evaluating the effect of manual therapies for neck and/or back pain was conducted. Participants (n = 1 464) answered questionnaires about frequency and effort level of LPA at baseline. LPA on moderate or vigorous levels was compared to no or low/irregular moderate and vigorous levels. Pain intensity was assessed with numerical scales at baseline and 3-, 6-, and 12-month follow-up. The outcome was minimal clinically important improvement in pain intensity, defined as ≥2 points improvement in mean pain intensity at follow-up. Crude- and adjusted risk ratios (RR) with 95% confidence intervals (CI) were calculated with Poisson regression analysis and stratified by pain location. RESULTS: Participants with neck and/or back pain performing vigorous LPA showed a minimal clinically important improvement after 12 months compared to the control group; RR 1.35 (95% CI; 1.06-1.73). No effect was observed at 3 or 6 months. Moderate LPA did not improve pain intensity in any follow-up. Stratified analyses revealed that the effect of vigorous LPA at 12 months in back pain was RR 1.83 (95% CI; 1.26-2.66) and neck pain RR 1.06 (95% CI; 0.75-1.49). CONCLUSIONS: Persons with neck and/or back pain receiving manual therapy or general evidence-based care have greater chance of improvement after 12 months if they prior to treatment frequently practice vigorous LPA. When analyzed separately, the effect was only present for back pain. TRIAL REGISTRATION: Registration in Current Controlled Trials (ISRCTN), Stockholm Manual Intervention Trial (MINT), ISRCTN92249294 BJORN-trial, ISRCTN56954776