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: 2.89). 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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    • "Supposing, then, that treating postural impairments associated with LBP is of value, current motor retraining protocols appear to require improvement in order to better address the spectrum of known motor impairments associated with LBP. Clinical outcomes from patient-specific motor training might benefit from training a larger repertoire of behaviors e perhaps including postural responses to external perturbations (Jacobs et al., 2011; Tokuno et al., 2013) e in order to ensure that training comprehensively addresses the motor impairments of people with LBP. Motor retraining must also adhere to principles of motor learning in order to effectively engender new motor skills and transfer those motor skills across activities that are not specifically trained during treatment. "
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    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.
    Manual therapy 09/2015; DOI:10.1016/j.math.2015.08.006 · 1.71 Impact Factor
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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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    ABSTRACT: Anticipatory postural adjustments (APAs) stabilize potential disturbances to posture caused by movement. Impaired APAs are common with disease and injury. Brain functions associated with generating APAs remain uncertain due to a lack of paired tasks that require similar limb motion from similar postural orientations, but differ in eliciting an APA while also being compatible with brain imaging techniques (e.g., functional magnetic resonance imaging; fMRI). This study developed fMRI-compatible tasks differentiated by the presence or absence of APAs during leg movement. Eighteen healthy subjects performed two leg movement tasks, supported leg raise (SLR) and unsupported leg raise (ULR), to elicit isolated limb motion (no APA) versus multi-segmental coordination patterns (including APA), respectively. Ground reaction forces under the feet and electromyographic activation amplitudes were assessed to determine the coordination strategy elicited for each task. Results demonstrated that the ULR task elicited a multi-segmental coordination that was either minimized or absent in the SLR task, indicating that it would serve as an adequate control task for fMRI protocols. A pilot study with a single subject performing each task in an MRI scanner demonstrated minimal head movement in both tasks and brain activation patterns consistent with an isolated limb movement for the SLR task versus multi-segmental postural coordination for the ULR task.
    Physiological Measurement 09/2013; 34(10):N97-N105. DOI:10.1088/0967-3334/34/10/N97 · 1.81 Impact Factor
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    • "In other studies, patients with low back pain showed decreased gluteus medius activity, which could be associated with reduced hip stability [13]. Jacobs et al. [14] reported that subjects with chronic low back pain revealed less early-phase activity at the internal oblique muscle and the gastrocnemius muscle and less late-phase activity at the erector spinae muscle, the rectus abdominis muscle, and the tibialis anterior muscle. Pandy et al. [23] reported that one's mediolateral balance during walking was maintained by the hip abductor, the vastus muscle groups, the soleus muscle, and the gastrocnemius muscle. "
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    ABSTRACT: To evaluate the changes in static and dynamic postural control after the development of acute low back pain. Thirty healthy right-handed volunteers were divided into three groups; the right back pain group, the left back pain group, and the control group. 0.5 mL of 5% hypertonic saline was injected into L4-5 paraspinal muscle for 5 seconds to cause muscle pain. The movement of the center of gravity (COG) during their static and dynamic postural control was measured with their eyes open and with their eyes closed before and 2 minutes after the injection. The COGs for the healthy adults shifted to the right quadrant and the posterior quadrant during their static and dynamic postural control test (p<0.05). The static and dynamic instability index while they had their eyes closed was significantly increased than when they had their eyes open with and without acute back pain. After pain induction, their overall and anterior/posterior instability was increased in both the right back pain group and the left back pain group during the static postural control test (p<0.05). A right deviation and a posterior deviation of the COG still remained, and the posterior deviation was greater in the right back pain group (p<0.05). The static instability, particularly the anterior/posterior instability was increased in the presence of acute low back pain, regardless of the visual information and the location of pain.
    Annals of Rehabilitation Medicine 02/2013; 37(1):17-25. DOI:10.5535/arm.2013.37.1.17
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