Juvena R. Hitt

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

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.

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

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.

Responses to multi-directional surface translations involve redistribution of proximal versus distal strategies to maintain upright posture

Evaluation of postural control in multiple planes is necessary to determine the movement strategies used to respond to unexpected perturbations. The present study quantified net joint torques of the lower limbs and trunk in the sagittal and frontal planes following multi-directional surface translations. Twenty-one healthy subjects stood with feet on separate force plates mounted on a moveable platform, translated unexpectedly in one of 12 directions. Peak net torque magnitudes and latencies following perturbation onset were determined as were the relative contributions of each joint to total torque production. Magnitude of net torque generated by each leg varied by perturbation direction, with the largest individual joint magnitude elicited in directions of limb loading. Relative contributions of individual joint torques to the total response were dependent upon perturbation direction. Results suggest that a redistribution of the relative contributions of hip/trunk versus ankle strategies occurs dependent on perturbation direction, with a significant contribution by the knee joint in response to forward perturbations. Direction-specific redistribution of proximal versus distal strategies appears to depend upon the biomechanical constraints imposed by a given perturbation direction. Thus, it appears that sagittal and frontal plane posture-righting responses may not be uniquely controlled, and may instead be governed similarly, with modulation of relative torque contributions among joints when necessary, given direction-specific anatomical constraints.

Individuals with Non-Specific Low Back Pain in an Active Episode Demonstrate Temporally Altered Torque Responses and Direction-Specific Enhanced Muscle Activity Following Unexpected Balance Perturbations

Individuals with a history of non-specific low back pain (LBP) while in a quiescent pain period demonstrate altered automatic postural responses (APRs) characterized by reduced trunk torque contributions and increased co-activation of trunk musculature. However, it is unknown whether these changes preceded or resulted from pain. To further delineate the relationship between cyclic pain recurrence and APRs, we quantified postural responses following multi-directional support surface translations, in individuals with non-specific LBP, following an active pain episode. Sixteen subjects with and 16 without LBP stood on two force plates that were translated unexpectedly in 12 directions. Net joint torques of the ankles, knees (sagittal only), hips, and trunk, in the frontal and sagittal planes, were quantified and the activation of 12 muscles of the lower limb unilaterally and the dorsal and ventral trunk, bilaterally, were recorded using surface electromyography (EMG). Peaks and latencies to peak joint torques, rates of torque development (slopes), and integrated EMGs characterizing baseline and active muscle contributions were analyzed for group by perturbation direction (torques) and group by perturbation by epoch interaction (EMG) effects. In general, the LBP cohort demonstrated APRs that were of similar torque magnitude and rate but peaked earlier compared to individuals without LBP. Individuals with LBP also demonstrated increased muscle activity following perturbation directions in which the muscle was acting as a prime mover and reduced muscle activity in opposing directions, proximally and distally, with some proximal asymmetries. These altered postural responses may reflect increased muscle spindle sensitivity. Given that these motor alterations are demonstrated proximally and distally, they likely reflect the influence of central nervous system processing in this cohort.

Effects of low back pain stabilization or movement system impairment treatments on voluntary postural adjustments: a randomized controlled trial

BACKGROUND People with low back pain (LBP) exhibit impaired anticipatory postural adjustments (APAs). OBJECTIVE To evaluate whether current motor retraining treatments address LBP-associated changes in movement coordination during tasks that do and do not require APAs. DESIGN Prospectively registered randomized controlled trial with a blinded assessor. SETTING Outcome evaluations occurred in a university laboratory; treatments were carried out in outpatient physical therapy clinics. PATIENTS Fifteen subjects without LBP and 33 subjects with chronic, recurrent, and nonspecific LBP. INTERVENTION Twelve subjects with LBP received stabilization treatment, 21 received movement system impairment-based treatment, for more than 6 weekly 1-hour sessions plus home exercises. MEASUREMENTS Pre- and post-treatment, surface electromyography (EMG) was recorded bilaterally from trunk and leg muscles during unsupported and supported leg-lifting tasks, which did and did not require an APA, respectively. Vertical reaction forces under the contralateral leg were recorded to characterize the APA. Oswestry disability scores and numeric pain ratings were also recorded. RESULTS Persons with LBP demonstrated an impaired APA compared with persons without LBP, characterized by increased premovement contralateral force application and increased postmovement trunk EMG amplitude, regardless of the task. After treatments, both groups similarly improved in disability and function; however, APA characteristics did not change (ie, force application or EMG amplitude) in either task. LIMITATIONS Treating clinicians were not blinded to treatment allocation, only short-term outcomes were assessed, and main effects of treatment do not rule out nonspecific effects of time or repeated exposure. CONCLUSIONS Movement impairments in persons with LBP are not limited to tasks requiring an APA. Stabilization and movement system impairment-based treatments for LBP do not ameliorate and may exacerbate APA impairments (ie, excessive force application and increased post-movement trunk muscle activation).

A neural network approach to motor-sensory relations during postural disturbance

This study explored whether artificial neural networks (ANN) can be used to quantify the motor-sensory relationship during postural disturbance. An ANN model was constructed with seven mechanical stimuli to the visual, vestibular and somatosensory systems (i.e., head angular and linear accelerations, eye-target distance, ankle joint rotation and velocity, as well as normal and shear ground contact forces under the feet) as inputs, and electromyographic activities of tibialis anterior and gastrocnemius muscles as outputs. These inputs and outputs were directly measured during a sudden toes-up-down rotation of the supporting base in two groups of elderly subjects: people with peripheral neuropathy (NP) who have severe loss of mechanoreception in the sole of their feet and people without NP. The products of ANN weights were used in a summary statistic called the Q-value to estimate the contribution of each mechanical stimulus to sensory systems in determining each leg muscle activity. It was found that: (1) the stimuli to the vestibular system and/or ankle proprioceptors have greater contributions to leg muscle activities, especially the TA muscle, in people with NP than people without NP; (2) the stimuli to somatosensory receptors have the greatest contribution, and the stimuli to the vestibular system have the least contribution to both muscle activities in both groups. These findings are supported by previous studies and have demonstrated the potential of the Q-value concept in the ANN model in studying the motor-sensory relationship in human postural control.

Protocol to assess the neurophysiology associated with multi-segmental postural coordination.

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.

Development and validation of a measure of primary care behavioral health integration.

INTRODUCTION We developed the Practice Integration Profile (PIP) to measure the degree of behavioral health integration in clinical practices with a focus on primary care (PC). Its 30 items, completed by providers, managers, and staff, provide an overall score and 6 domain scores derived from the Lexicon of Collaborative Care. We describe its history and psychometric properties. METHOD The PIP was tested in a convenience sample of practices. Linear regression compared scores across integration exemplars, PC with behavioral services, PC without behavioral services, and community mental health centers without PC. An additional sample rated 4 scenarios describing practices with varying degrees of integration. RESULTS One hundred sixty-nine surveys were returned. Mean domain scores ran from 49 to 65. The mean total score was 55 (median 58; range 0-100) with high internal consistency (Cronbachs alpha = .95). The lowest total scores were for PC without behavioral health (27), followed by community mental health centers (44), PC with behavioral health (60), and the exemplars (86; p < .001). Eleven respondents rerated their practices 37 to 194 days later. The mean change was + 1.5 (standard deviation = 11.1). Scenario scores were highly correlated with the degree of integration each scenario was designed to represent (Spearmans ρ = -0.71; P = 0.0005). DISCUSSION These data suggest that the PIP is useful, has face, content, and internal validity, and distinguishes among types of practices with known variations in integration. We discuss how the PIP may support practices and policymakers in their integration efforts and researchers assessing the degree to which integration affects patient health outcomes. (PsycINFO Database Record

The Practice Integration Profile: Rationale, development, method, and research.

Insufficient knowledge exists regarding how to measure the presence and degree of integrated care. Prior estimates of integration levels are neither grounded in theory nor psychometrically validated. They provide scant guidance to inform improvement activities, compare integration efforts, discriminate among practices by degree of integration, measure the effect of integration on quadruple aim outcomes, or address the needs of clinicians, regulators, and policymakers seeking new models of health care delivery and funding. We describe the development of the Practice Integration Profile (PIP), a novel instrument designed to measure levels of integrated behavioral health care within a primary care clinic. The PIP draws upon the Agency for Health care Research & Qualitys (AHRQ) Lexicon of Collaborative Care which provides theoretic justification for a paradigm case of collaborative care. We used the key clauses of the Lexicon to derive domains of integration and generate measures corresponding to those key clauses. After reviewing currently used methods for identifying collaborative care, or integration, and identifying the need to improve on them, we describe a national collaboration to describe and evaluate the PIP. We also describe its potential use in practice improvement, research, responsiveness to multiple stakeholder needs, and other future directions. (PsycINFO Database Record

Task-related and person-related variables influence the effect of low back pain on anticipatory postural adjustments

BACKGROUND People with low back pain exhibit altered postural coordination that has been suggested as a target for treatment, but heterogeneous presentation has rendered it difficult to identify appropriate candidates and protocols for such treatments. This study evaluated the associations of task-related and person-related factors with the effect of low back pain on anticipatory postural adjustments. METHODS Thirteen subjects with and 13 without low back pain performed seated, rapid arm flexion in self-initiated and cued conditions. Mixed-model ANOVA were used to evaluate group and condition effects on APA onset latencies of trunk muscles, arm-raise velocity, and pre-movement cortical potentials. These measures were evaluated for correlation with pain ratings, Fear Avoidance Beliefs Questionnaire scores, and Modified Oswestry Questionnaire scores. FINDINGS Delayed postural adjustments of subjects with low back pain were greater in the cued condition than in the self-initiated condition. The group with low back pain exhibited larger-amplitude cortical potentials than the group without pain, but also significantly slower arm-raise velocities. With arm-raise velocity as a covariate, the effect of low back pain remained significant for the latencies of postural adjustments but not for cortical potentials. Latencies of the postural adjustments significantly correlated with Oswestry and Fear Avoidance Beliefs scores. INTERPRETATION Delayed postural adjustments with low back pain appear to be influenced by cueing of movement, pain-related disability and fear of activity. These results highlight the importance of subject characteristics, task condition, and task performance when comparing across studies or when developing treatment of people with low back pain.