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There is increasing evidence that individuals with non-specific low back pain (LBP) have altered movement coordination., hHowever, 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 maymay contribute to recurrent episodes of LBP.

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. Twofactor 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.

Background Classification schemas for low back pain (LBP), such as the Treatment Based Classification and the Movement System Impairment schemas, use common clinical features to subgroup patients with LBP and are purported to improve treatment outcomes. Purpose To assess if providing matched treatments based on patient specific clinical features led to superior treatment outcomes compared to an unmatched treatment for subjects with chronic, recurrent LBP. Study Design A randomized controlled trial. Patient Sample Subjects (n=124) with LBP (≥ 12 months) with or without recurrences underwent a standardized clinical exam to group them into one of 2 strata: (1) ineligible or (2) eligible for stabilization exercises based on the Treatment Based Classification schema. Subjects underwent additional clinical tests to assign them to one of the 5 possible Movement System Impairment categories. Outcome Measures Questionnaires were collected electronically at: Week 0, prior to treatment; Week 7 (following the 6 weekly, one hour treatment sessions); and 12 months. Using the Oswestry Disability Index (0-100) and the Numeric Pain Rating Scale (0-10), the primary analysis was performed using the intention-to-treat principle. Secondary outcomes included fear-avoidance beliefs as well as psychosocial, work related and general health status. Methods After subjects were categorized based on their particular clinical features using both the Treatment Based Classification and Movement System Impairment schemas, they were randomized into one of two treatments using a 3:1 ratio for matched or unmatched treatments. The treatments were (1) trunk stabilization exercise, or (2) Movement System Impairment-directed exercises. The study was funded by National Institutes of Health (NCMRR/R01HD040909; $1,485,000). There are no study specific conflicts of interest to report. Results Of the patients allocated to treatment for this study, 76 received a matched treatment and 25 received an unmatched treatment. Following treatment, both groups showed a statistically significant improvement in the primary outcome measures and almost all of the secondary measures; however, the matched treatment group did not demonstrate superior outcomes at Week 7 or 12 months, except on one of the secondary measures (Graded Chronic Pain Scale – Disability Scale) (P=0.01). Conclusion Providing a matched treatment based on either the Treatment Based Classification or the Movement System Impairment classification schemas did not improve treatment outcomes compared to an unmatched treatment for patients with chronic LBP, except on one secondary disability measure.