Could sensorimotor factors in acute low back pain explain long-term pain and disability? A secondary analysis of longitudinal data from a randomised controlled trial

Treatments for chronic low back pain (LBP) provide only small improvements in pain and disability compared with placebo. Targeting mechanisms involved in the persistence of pain and disability following an episode of acute LBP (ALBP) may enhance treatment effectiveness. Sensorimotor alterations have been observed in individuals with chronic LBP (CLBP), but their role in the development of CLBP remains unclear. In this secondary analysis of longitudinal data from 99 participants with ALBP, the causal associations between pain sensitivity and erector spinae muscle activation measured in the acute phase of LBP and pain and disability at 6- and 12-month follow-ups were explored. Negative binomial regressions revealed that greater lumbar muscle activation at baseline was associated with lower disability at 6 months (incidence rate ratio [IRR] 0.33 [95% CI 0.13 to 0.85], p=0.02). Higher lumbar pressure pain threshold was also associated with lower disability at 6 months (IRR 0.87 [95% CI 0.79 to 0.97], p=0.009). At 12 months, greater lumbar and thoracic muscle activation were associated with lower disability (IRR 0.11 [95% CI 0.03 to 0.35], p<0.001 and IRR 0.09 [95% CI 0.02 to 0.33], p<0.001, respectively). The findings suggest that increased thoracolumbar muscle activation during the acute phase may act as a protective mechanism and support recovery. However, the association with pain sensitivity should be interpreted with caution, as only one of 16 models reached statistical significance. Longitudinal studies assessing the evolution of these sensorimotor factors could improve the understanding of their contribution in the development of CLBP. Perspective: This article presents exploratory analyses of causal associations between sensorimotor outcomes in acute low back pain and levels of pain and disability in the long-term. Increased muscle activation explained better long-term outcomes, whereas increased pain sensitivity explained poorer long-term outcomes.