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Background: Individuals with chronic low back pain demonstrate impaired responses to volitional and externally-generated postural perturbations that may impact stability whilst performing activities of daily living. Understanding how balance may be impaired by strategy selection is an important consideration during rehabilitation from low back pain to prevent future injurious balance loss.Research Question: This cross-sectional study explored the influence of an active pain episode on volitional movement patterns and stability during a sit-to-stand task in individuals with chronic low back pain compared to those with no low back pain history.Methods: Thirteen participants with low back pain who were in an active flare-up and 13 without pain sat on a height-adjusted chair and performed 5 sit-to-stand movements. Sagittal plane kinematics, kinetics, and surface electromyography were used to compute neuromuscular variables across Acceleration, Transition and Deceleration phases. Stability was assessed using times to contact of body centers of mass and pressure to base of support boundaries. Independent samples t-tests were used to examine group effects, and repeated measures analyses of variance assessed within-subjects effects across movement phases.Results: Individuals with low back pain tended to restrict proximal joint motions through heightened muscle activity while increasing distal joint movement and distal muscle contributions. Individuals with low back pain used a greater driving force, indicated by a longer time to contact of the center of pressure, to achieve comparable center of mass stability. Individuals with low back pain may prioritize trunk restriction and stability through the sit-to-stand movement, possibly related to fear of pain or movement.Significance: The tendency for individuals with active low back pain to restrict trunk movements may require additional effort to maintain stability. Further research should examine whether trunk restriction is related to pain-related fear of movement and whether additional cognitive resources are required to maintain movement stability. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Interventions that target trunk muscle impairments in people with LBP have been promoted; however, the treatment effects on muscle activation impairments during postural tasks remain unclear. Thus, our objective was to evaluate the effects trunk stabilization vs. general strength and conditioning exercises on the automatic postural response in persons with chronic low back pain (LBP). Fifty-eight subjects with chronic, recurrent LBP ( n = 58) (i.e., longer than six months) were recruited and randomly assigned to one of two, 10-week physical therapy programs: stabilization ( n = 29) or strength and conditioning ( n = 29). Pain and function were measured at 11 weeks and 6 months post-treatment initiation. To quantify postural following support surface perturbations, surface electrodes recorded electromyography (EMG) of trunk and leg muscles and force plates recorded forces under the feet, to calculate the center of pressure. Both groups demonstrated significant improvements in pain and function out to 6 months. There were also changes in muscle activation patterns immediately post-treatment, but not at 6 months. However, changes in center of pressure (COP) responses were treatment specific. Following treatment, the stabilization group demonstrated later onset of COP displacement, while the onset of COP displacement in the strengthening group was significantly earlier following treatment. Despite two different treatments, clinical improvements and muscle activation patterns were similar for both groups, indicating that the stabilization treatment protocol does not preferentially improve treatment outcomes or inter-muscle postural coordination patterns for persons with LBP. Clinical Trial Registration Number NCT01611792. [ABSTRACT FROM AUTHOR]

Abstract: Background: Low back pain is associated with abnormal movement strategies due to changes in neuromuscular control. A plausible contributing factor to low back pain is poor control of trunk muscles, thus understanding motor control alterations in this population can guide rehabilitation. Quantification of postural responses following support surface translations is one way to examine motor control impairments in people with low back pain. Methods: Twenty-four healthy subjects [mean 33 (SD 11) years] who had no low back pain and 26 subjects [mean 39 (SD 13) years] with chronic, recurrent low back pain were instructed to stand with feet placed on separate force plates, which were mounted on a moveable platform. The platform was translated unexpectedly in one of 12 directions for a total of 72 trials. For both the sagittal and frontal planes, the net center of pressure displacement was derived and the total body center of mass was calculated by combining kinematic and anthropometric data. Findings: For sagittal plane responses, subjects with low back pain had reduced and delayed sagittal plane center of pressure responses (P <0.01) compared to the subjects without low back pain. In contrast, the sagittal plane center of mass responses were larger in magnitude (P =0.03) yet similarly delayed in onset (P =0.04) for the low back pain group. Frontal plane responses did not differ between groups. Interpretation: Subjects with low back pain have altered automatic postural coordination, both in terms of magnitude and timing of responses, indicating alterations in neuromuscular control. [Copyright &y& Elsevier]

Abstract: Background:: To date, no direct measurement has been done that quantitatively characterizes the foot–ground contact during Tai Chi Chuan movements. The goal of this study was to quantify the biomechanical characteristics of foot–ground contact during a Tai Chi gait (TCG), one of the basic but common Tai Chi Chuan movements. Methods:: The ground reaction force profiles, center of pressure (COP) and plantar pressure patterns under the stance foot of TCG were directly measured in a sample of 10 healthy young individuals. Results:: The medial force reached a peak value of 12 ± 2% body weight (BW) during early stance. The vertical force reached and maintained a peak value of 109 ± 2% BW during single stance, and shifted within a range of 10% and 70% BW during double stance phases. There was a uniformly small rate of loading in all three directions throughout stance. The peak plantar pressure was fairly constant throughout stance in the rear-foot region (maximum value of 0.27 ± 0.07kPa/kg), but changed from 0 to 0.16 ± 0.04kPa/kg in the fore-foot region. The peak pressure difference between the fore-foot and rear-foot regions was less than 0.06 ± 0.01kPa/kg during single stance and the second double stance. The maximum plantar contact area during TCG was 60 ± 9% of the foot area. The foot COP displaced largely during the early and late part of the stance and maintained fairly stationary during single stance. The maximum COP displacement in the medial–lateral direction was 64 ± 8% of foot width. Conclusions:: TCG had a low impact force, a fairly evenly distributed body weight between the fore-foot and rear-foot regions, and a large medial–lateral displacement of the foot COP. [Copyright &y& Elsevier]

This study sought to determine the effects of chronic low back pain (LBP) on the cortical evoked potentials, muscle activation, and kinematics of postural responses to perturbations of standing balance. Thirteen subjects with chronic, recurrent, non-specific LBP and 13 subjects without LBP participated. The subjects responded to unpredictably timed postural perturbations while standing on a platform that randomly rotated either “toes up” or “toes down”. Electroencephalography (EEG) was used to calculate the negative peak (N1) and subsequent positive peak (P2) amplitudes of the perturbation-evoked cortical potentials. Passive-marker motion capture was used to calculate joint and center-of-mass (CoM) displacements. Surface electromyography was used to record muscle onset latencies. Questionnaires assessed pain, interference with activity, fear of activity, and pain catastrophizing. Results demonstrated that subjects with LBP exhibited significantly larger P2 potentials, delayed erector spinae, rectus abdominae, and external oblique onset latencies, as well as smaller trunk extension yet larger trunk flexion, knee flexion, and ankle dorsiflexion displacements compared to subjects without LBP. For the subjects with LBP, CoM displacements significantly and positively correlated with knee displacements as well as activity interference and fear scores. The P2 potentials significantly and negatively correlated with CoM displacements as well as activity interference, catastrophizing, and fear scores. These results demonstrate that people with LBP exhibit altered late-phase cortical processing of postural perturbations concomitant with altered kinematic and muscle responses, and these cortical and postural response characteristics correlate with each other as well as with clinical reports of pain-related fears and activity interference. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

This study was to quantitatively characterize the spatial, temporal, and neuromuscular activation patterns of Tai Chi gait (TCG). Ten healthy young subjects were tested. The kinematics of TCG and normal gait (NG) were measured using a marker-based motion analysis system and two biomechanical force plates. Surface electromyography (EMG) was recorded from six left-side muscles: tibialis anterior, soleus, peronaeus longus, rectus femoris, semitendinosus, and tensor fasciae latae. The results showed that TCG had (1) a longer cycle duration (11.9±2.4 vs. 1.3±0.2 s) and a longer duration of single-leg stance time (1.8±0.6 vs. 0.4±0.05 s); (2) a larger joint motion in ankle dorsi/plantar flexion (40±9° vs. 20±8°), knee flexion (82±8° vs. 53±10°), hip flexion (81±7° vs. 24±4°), and hip abduction (20±8° vs. 0±3°); (3) a larger lateral body shift (>25% vs. 5% body height); and (4) significant involvement of ankle dorsiflexors, knee extensors/hip flexors and hip abductors, as indicated by significantly higher peak (88±14%, 80±18% and 83±17% vs. 35±10%, 14±8% and 28±19% peak amplitude, respectively) and root-mean-square values of their EMG (37±6%, 32±7% and 33±7% vs. 23±7%, 11±8% and 22±11% peak amplitude, respectively), longer proportions of action (76±19%, 68±8% and 65±19% vs. 59±23%, 16±23% and 40±32% gait cycle duration, respectively), longer proportions of isometric and eccentric actions, and longer proportions of co-activations. These results demonstrate that the biomechanical characteristics of TCG can be quantified. The quantification of TCC movements is important for understanding its effect on balance, flexibility, strength, and health. [Copyright &y& Elsevier]

Background context Classification schemas for low back pain (LBP), such as the Treatment-Based Classification and the Movement System Impairment, 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 with an unmatched treatment for subjects with chronic recurrent LBP. Study design This study is a randomized controlled trial. Patient sample Subjects (n=124) with LBP (≥12 months) with or without recurrences underwent a standardized clinical examination to group them into one of two strata: ineligible or eligible for stabilization exercises based on the Treatment-Based Classification schema. Subjects underwent additional clinical tests to assign them to one of the five possible Movement System Impairment categories. Outcome measures Questionnaires were collected electronically at Week 0 (before treatment), Week 7 (after the 6-week 1-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 and 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 trunk stabilization exercise or Movement System Impairment–directed exercises. Results Of the patients allocated to treatment for this study, 76 received a matched treatment and 25 received an unmatched treatment. After treatment, both groups showed a statistically significant improvement in the primary outcome measures and almost all 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=.01). Conclusions Providing a matched treatment based on either the Treatment-Based Classification or the Movement System Impairment classification schema did not improve treatment outcomes compared with an unmatched treatment for patients with chronic LBP, except on one secondary disability measure. [ABSTRACT FROM AUTHOR]

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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]