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Changes in Morphometry of Trunk Muscles, Pain, and Disability Associated With Motor Control Training in People With Chronic Low Back Pain: a Systematic Review and Meta-analysis


 Background: This study aimed to review studies investigating the effects of motor control training (MCT) on the morphometry of trunk muscles (measured by ultrasound imaging; USI) and pain/or disability in individuals with chronic low back pain (CLBP).Method: PubMed, Web of Science, Scopus, and Cochrane Library databases were searched from inception until January 2020. Randomized control trials (RCTs) which included measurements of both muscle morphometry using USI and assessments of pain or disability in individuals with CLBP were included. Study selection, data extraction and quality assessment were done by two reviewers independently. Modified Downs and Black tool and grading of recommendations assessment, development, and evaluation tool were used to assess risk of bias and quality of evidence, respectively. A meta-analysis was performed using a random-effects model with mean difference (MD) or standardized mean difference (SMD). Results: Fifteen RCTs were included. The results revealed that there were no differences in the size (thickness) of the transversus abdominis (TrA), internal and external oblique, and lumbar multifidus muscles in studies which did and did not include MCT interventions. However, the contraction ratio for the TrA muscle was greater in response to MCT, with a high effect size (SMD= 0.93 CI: - 0.0 to 1.85). Pain (visual analogue scale, MD=1.00, 95%CI -1.77 to -0.24) and disability (SMD=-0.55, 95% CI: -0.94 to -0.16) scores were lower in the groups who underwent MCT compared with other interventions, with moderate and low effect sizes.Conclusions: MCT interventions were superior to other interventions for measures of TrA muscle function. Despite changes in pain and disability following MCT interventions, corresponding changes in trunk muscle morphometry (evaluated using thickness measures) were not evident. This could be due to the effect of other factors such as psychosocial factors that impact the clinical outcomes for those with CLBP.Systematic review registration: PROSPERO: CRD42019144768