Exercise may reduce disability from chronic low back pain; however, the mechanism of this effect remains unclear. These findings were reported in a study published in Behaviour Research and Therapy.
Individuals (N=393) with chronic low back pain were recruited to participate in a study via advertisements in a community in Australia between June 2016 and September 2019. Participants were informed that this study was designed to assess activity and treatment choices by people with chronic low back pain over the course of a year. Data were collected every 3 months.
The mean age of study participants was 39.2±12.2 years, and 45% reported experiencing low back pain for a duration of 1 to 5 years.
Retention remained high throughout the study (range, 91%-96%).
In general, average Oswestry Disability Index (ODI) scores decreased from 23.6±11.2 points at baseline to 19.6±12.8 points at 12 months. Similarly, between baseline and the 12-month follow-up, visual analog scale scores for pain (mean, 4.3 vs 3.6), Fear-Avoidance Beliefs Questionnaire scores (mean, 13.3 vs 10.6), Paint Catastrophizing Scale scores (mean, 20.8 vs 15.5), Hospital Anxiety and Depression Scale (HADS) anxiety scores (mean, 7.6 vs 6.5), and HADS depression scores (mean, 7.2 vs 6.0) decreased over time. Chronic Pain Self-Efficacy Questionnaire self-efficacy scores increased from 54.2±17.6 at baseline to 58.5±15.4 at 12 months.
Throughout the study, 59% to 74% of study participants engaged in physical exercise and 51% to 59% took pain medication.
Stratified by change in ODI scores, the individuals who documented no change reported engaging in exercise at significantly fewer follow-up assessments (mean, 2.6; P <.05) compared with those who reported improvement in ODI scores (mean, 3.4) or worsening of ODI scores (mean, 3.2). The individuals who documented improvement in ODI scores reported using pain medication at fewer follow-up assessments (mean, 2.0; P <.001) compared with those who had experienced worsening of ODI scores (mean, 2.9) or no change (mean, 3.2).
In the mediation analysis, exercise performed in the first 6 months had a significant total effect on disability at 12 months (β, -2.09; 95% CI, -1.01 to -3.18). More than half of the effect (56%) of exercise on disability was explained by the mediators of pain, fear, catastrophizing, depression, anxiety, and self-efficacy. After correcting for bias, the indirect effects of pain (β, -0.46; 95% CI, -0.15 to -0.85) and catastrophizing (β, -0.27; 95% CI, -0.05 to -0.59) remained significant.
In the reverse pathway analysis, disability had a direct effect on exercise at 6 months (β, 0.012; 95% CI, -0.02 to 0.05) with a significant indirect effect of fear (β, -0.01; 95% CI, -0.0004 to -0.021).
This study was limited by the lack of evaluation of specific treatment histories.
Study authors concluded, “The key finding of this study was that the relationship between exercise and disability over both 6- and 12-month time periods was mediated by pain and catastrophizing. Exercise can reduce disability through the effect on pain and catastrophizing, but there is a need to identify the active ingredient within or in addition to an exercise program that explains how this is achieved. Indeed, people with chronic [low back pain] who reported worsening of symptoms over the year had similar reporting of exercise throughout the 12-months to people who had improvements in disability.”
Marshall PW, Morrison NMV, Gibbs M, Schabrun SM. The effect of exercise engagement on low back disability at 12-months is mediated by pain and catastrophizing in a community sample of people with chronic low back pain. Behav Res Ther. Published online October 4, 2022. doi:10.1016/j.brat.2022.104205