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

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.