Precision of trunk movement in people with chronic low back pain

Background: Motor control exercise is commonly applied in people with chronic low back pain (CLBP), but possibly not all people with CLBP have motor control impairments. We suggest movement precision as measure to identify motor control impairments. Movement precision has been operationalized as trunk movement variability (TMV) and as trunk tracking error(s) (TTE). Objectives: To compare the known-group validity and the responsiveness of TMV and TTE. Design: We used a case-control comparison (Healthy controls (n = 30) vs CLBP (n = 60)) to assess the known-group validity. A cohort study, (measurements in week 3 and week 12 of treatment), was used to assess responsiveness. Methods: TMV (temporal (CyclSD) and spatial (MeanSD)) was analyzed during standing, repetitive flexion and rotation tasks (35x). TTE was measured during movement target tracking tasks, again in flexion and rotation. Participants with CLBP followed a multidisciplinary intervention and both measures were assessed in week 3 and week 12 of treatment. 2-way MANOVA and 2-way ANOVA were used to assess the effect of Group (CLBP vs healthy controls) and direction (flexion vs rotation) on TMV and TTE. For responsiveness, 2-way MANOVA and 2-way ANOVA were used to assess the effect of treatment and direction on both measures. Findings: At baseline, TMV was not different between groups, while TTE was higher in the people with CLBP (p = 0.005, n_p² = 0.09). Treatment strongly decreased temporal TMV (p = 0.025, n_p² = 0.33) and TTE (p < 0.001, n_p² = 0.844). Conclusions: These results demonstrate that TTE is more sensitive to CLBP and more responsive to treatment than TMV.