Effects of low back pain and of stabilization or movement-system-impairment treatments on induced postural responses: A planned secondary analysis of a randomised controlled trial

Abstract

Background: Motor retraining for non-specific chronic low back pain (LBP) often focuses on voluntary postural tasks. This training, however, may not transfer to other known postural impairments, such as automatic postural responses to external perturbations.

Objectives: To evaluate the extent current treatments of motor retraining ameliorate impaired postural coordination when responding to a perturbation of standing balance.

Design: Planned secondary analysis of a prospectively registered (NCT01362049), randomized controlled trial with a blinded assessor.

Method: Sixty-eight subjects with chronic, recurrent, non-specific LBP were allocated to perform a postural response task as a secondary assessment one week before and one week after receiving either stabilization or Movement System Impairment (MSI)-directed treatment over 6 weekly 1-h sessions plus home exercises. For assessment, subjects completed the Oswestry disability and numeric pain rating questionnaires and then performed a postural response task of maintaining standing balance in response to 3 trials in each of 4 randomly presented directions of linear surface translations of the platform under the subjects' feet. Integrated amplitudes of surface electromyography (EMG) were recorded bilaterally from the rectus abdominis (RA), internal oblique (IO), and external oblique (EO) muscles during the postural response task.

Results: No significant effects of treatment on EMG responses were evident. Oswestry and numeric pain ratings decreased similarly following both treatments.

Conclusions: Stabilization and MSI-directed treatments do not affect trunk EMG responses to perturbations of standing balance in people with LBP, suggesting current methods of motor retraining do not sufficiently transfer to tasks of reactive postural control.

Keywords: Balance; Low back pain; Movement system impairment; Posture; Stabilization; Treatment.

Copyright © 2015 Elsevier Ltd. All rights reserved.

Figures

Fig. 1

Illustrations of (a) treatment protocols during intervention, and (b) EMG measures taken during assessment of postural responses. In (b), exemplar EMG traces from a subject with (red traces) and without (black traces) LBP illustrate the early (box with solid line; 80–120 ms) and late (box with dashed outline; 120–220 ms) EMG epochs from which integrated EMG amplitudes were calculated. These illustrated traces were derived from responses to rightward translations of muscles from the right side of the body. For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.

Fig. 2

Flow diagram of participants in the clinical trial.

Fig. 3

Integrated EMG amplitudes between groups with and without LBP. Polar plot triplets are grouped by muscle across the baseline (−75 to 0 ms), early-phase (80–120 ms), and late-phase (120–220 ms) recording epochs. Polar plot directions indicate directions of surface translation, which induce body sway in the opposite direction. Red lines indicate mean (95% confidence interval) values for the group with LBP; black lines, the group without LBP. Asterisks (*) denote significant (P

Fig. 4

Changes in integrated EMG amplitudes after treatment with either the stabilization or MSI-directed exercise protocol. Green lines indicate mean (95% confidence interval) values of change (post- minus pre-treatment) for the group receiving stabilization exercises; blue lines, the group receiving MSI-directed treatment. Gray square boxes indicate zero change with treatment. No significant main effects of session or group-by-session interactions were evident. For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.