Study design: Prospective, longitudinal case-crossover study.
Objective: The aim of this study was to determine whether physical activities trigger flare-ups of pain during the course of acute low back pain (LBP).
Summary of background data: .: There exist no evidence-based estimates for the transient risk of pain flare-ups associated with specific physical activities, during acute LBP.
Methods: Participants with LBP of duration <3 months completed frequent, Internet-based serial assessments at both 3- and 7-day intervals for 6 weeks. At each assessment, participants reported whether they had engaged in specific physical activity exposures, or experienced stress or depression, during the past 24 hours. Participants also reported whether they were currently experiencing a LBP flare-up, defined as "a period of increased pain lasting at least 2 hours, when your pain intensity is distinctly worse than it has been recently." Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for associations between potential triggers during the past 24 hours, and the risk of LBP flare-ups, using conditional logistic regression.
Results: Of 48 participants followed longitudinally, 30 participants had both case ("flare") and control periods and contributed data to the case-crossover analysis. There were 81 flare periods and 247 control periods, an average of 11 periods per participant. Prolonged sitting (>6 hours) was the only activity that was significantly associated with flare-ups(OR 4.4, 95% CI 2.0-9.7; P < 0.001). Having either stress or depression was also significantly associated with greater risk of flare-ups (OR 2.5, 95% CI 1.0-6.0; P = 0.04). In multivariable analyses, prolonged sitting (OR 4.2, 95% CI 1.9-9.1; P < 0.001), physical therapy (PT) (OR 0.4, 95% CI 0.1-1.0; P = 0.05), and stress/depression (OR 2.8, 95% CI 1.2-6.7; P = 0.02) were independently and significantly associated with LBP flare-up risk.
Conclusion: Among participants with acute LBP, prolonged sitting (>6 hours) and stress or depression triggered LBP flare-ups. PT was a deterrent of flare-ups.
Level of evidence: 2.