A history of low back pain associates with altered electromyographic activation patterns in response to perturbations of standing balance

Department of Rehabilitation and Movement Science, University of Vermont, Burlington, Vermont 05405, USA.
Journal of Neurophysiology (Impact Factor: 3.04). 07/2011; 106(5):2506-14. DOI: 10.1152/jn.00296.2011
Source: PubMed

ABSTRACT People with a history of low back pain (LBP) exhibit altered responses to postural perturbations, and the central neural control underlying these changes in postural responses remains unclear. To characterize more thoroughly the change in muscle activation patterns of people with LBP in response to a perturbation of standing balance, and to gain insight into the influence of early- vs. late-phase postural responses (differentiated by estimates of voluntary reaction times), this study evaluated the intermuscular patterns of electromyographic (EMG) activations from 24 people with and 21 people without a history of chronic, recurrent LBP in response to 12 directions of support surface translations. Two-factor general linear models examined differences between the 2 subject groups and 12 recorded muscles of the trunk and lower leg in the percentage of trials with bursts of EMG activation as well as the amplitudes of integrated EMG activation for each perturbation direction. The subjects with LBP exhibited 1) higher baseline EMG amplitudes of the erector spinae muscles before perturbation onset, 2) fewer early-phase activations at the internal oblique and gastrocnemius muscles, 3) fewer late-phase activations at the erector spinae, internal and external oblique, rectus abdominae, and tibialis anterior muscles, and 4) higher EMG amplitudes of the gastrocnemius muscle following the perturbation. The results indicate that a history of LBP associates with higher baseline muscle activation and that EMG responses are modulated from this activated state, rather than exhibiting acute burst activity from a quiescent state, perhaps to circumvent trunk displacements.

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Available from: Jesse V Jacobs, Jan 15, 2014
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    • "abdominis (RA), rectus femoris (RF), long head of biceps femoris (BF) and the ipsilateral tibialis anterior (TIB) muscles. Trunk-muscle electrode placement was standardized based on anatomical landmarks (Jacobs et al 2011), and electrodes were placed over the BF and RF muscles according to recommendations by Hermens et al (2006). Signals were sampled at 1000 Hz, pre-amplified by 1000 at the skin's surface and then amplified further for a total amplification of 2000–10000. "
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