Article

Individuals with non-specific low back pain use a trunk stiffening strategy to maintain upright posture

Department of Rehabilitation and Movement Science, University of Vermont, Burlington, VT, USA.
Journal of electromyography and kinesiology: official journal of the International Society of Electrophysiological Kinesiology (Impact Factor: 1.65). 11/2011; 22(1):13-20. DOI: 10.1016/j.jelekin.2011.10.006
Source: PubMed

ABSTRACT

There is increasing evidence that individuals with non-specific low back pain (LBP) have altered movement coordination. However, the relationship of this neuromotor impairment to recurrent pain episodes is unknown. To assess coordination while minimizing the confounding influences of pain we characterized automatic postural responses to multi-directional support surface translations in individuals with a history of LBP who were not in an active episode of their pain. Twenty subjects with and 21 subjects without non-specific LBP stood on a platform that was translated unexpectedly in 12 directions. Net joint torques of the ankles, knees, hips, and trunk in the frontal and sagittal planes as well as surface electromyographs of 12 lower leg and trunk muscles were compared across perturbation directions to determine if individuals with LBP responded using a trunk stiffening strategy. Individuals with LBP demonstrated reduced peak trunk torques, and enhanced activation of the trunk and ankle muscle responses following perturbations. These results suggest that individuals with LBP use a strategy of trunk stiffening achieved through co-activation of trunk musculature, aided by enhanced distal responses, to respond to unexpected support surface perturbations. Notably, these neuromotor alterations persisted between active pain periods and could represent either movement patterns that have developed in response to pain or could reflect underlying impairments that may contribute to recurrent episodes of LBP.

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Available from: Sharon Henry, Oct 28, 2015
    • "Integrated EMG amplitudes of each epoch were analyzed separately due to their unique functional implications. Responses to lateral (combined left and right), forward, and backward perturbations were also analyzed separately because LBP, and treatment for LBP, may differentially affect responses across these conditions based on different mechanical constraints (Jacobs et al., 2011; Jones et al., 2012a,b). Neural mechanisms controlling individual abdominal and oblique muscles are also task-specific to different directions of surface translations (Carpenter et al., 2008). "
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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.
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    • "Jones et al.[24]suggested that individuals with low back pain in situations of postural imbalance increased trunk coactivation regardless of disturbance direction to compensate for a lack of accurate proprioceptive information , aiming to restrict movement to avoid pain. As a result, trunk coactivation leads to a lower capacity to produce torque in these individuals[24]. "
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    ABSTRACT: Background: Investigation and discrimination of neuromuscular variables related to the complex aetiology of low back pain could contribute to clarifying the factors associated with symptoms. Objective: Analysing the discriminative power of neuromuscular variables in low back pain. Methods: This study compared muscle endurance, proprioception and isometric trunk assessments between women with low back pain (LBP, n=14) and a control group (CG, n=14). Multivariate analysis of variance and discriminant analysis of the data were performed. Results: The muscle endurance time (s) was shorter in the LBP group than in the CG (p=0.004) with values of 85.81 (37.79) and 134.25 (43.88), respectively. The peak torque (Nm/kg) for trunk extension was 2.48 (0.69) in the LBP group and 3.56 (0.88) in the GG (p=0.001); for trunk flexion, the mean torque was 1.49 (0.40) in the LBP group and 1.85 (0.39) in the CG (p=0.023). The repositioning error (degrees) before the endurance test was 2.66 (1.36) in the LBP group and 2.41 (1.46) in the CG (p=0.664), and after the endurance test, it was 2.95 (1.94) in the LBP group and 2.00 (1.16) in the CG (p=0.06). Furthermore, the variables showed discrimination between the groups (p=0.007), with 78.6% of the individuals with low back pain correctly classified in the LBP group. In turn, variables related to muscle activation showed no difference in discrimination between the groups (p=0.369). Conclusion: Based on these findings, the clinical management of low back pain should consist of both resistance and strength training, particularly in the extensor muscles.
    Full-text · Article · Aug 2014 · Journal of Back and Musculoskeletal Rehabilitation
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    • "Their overactivity involves both timing (too early) and degree of activity (too much) e further interfering with the mechanisms of deep system control. This augmented muscle activity is being increasingly reported (Hodges et al., 2009; Van der Hulst et al., 2010; Jones et al., 2012). This creates greater trunk stiffness e and so, and contrary to popular belief CLBP subjects actually move their spines less (Mok et al., 2007) and move with excess muscle tension and effort e and breath holding. "
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