Motor Control Changes in Low Back Pain: Divergence in Presentations and Mechanisms

Impairment of Proprioception in Young Adult Nonradicular Patients with Lumbar Derangement Syndrome

Maintaining body balance is a complex function based on the information deriving from the vestibular, visual, and proprioceptive systems. The aim of the study was to evaluate quiet single stance stability in young adults with lumbar derangement syndrome (LDS) and in the control group of the healthy subjects. The second aim of this study was to determine whether pain intensity, degree of disability, and the level of physical activity can influence postural control in patients with LDS. It is important to underline that selecting a homogeneous group of LBP patients using, for example, mechanical diagnosis and therapy method and Quebec Task Force Classification, can result in an increased sensitivity of the study. The study included 126 subjects: 70 patients with LDS (37 women, 33 men) and the control group 56 healthy volunteers (36 women, 20 men). In case of multiple group comparisons for variables with normal distribution, ANOVA post hoc test was used or, as the nonparametric equivalent, Kruskal-Wallis test. In all these calculations, the statistical significance level was set to p < 0.05. The stability index eyes open for the study group was 88.34 and for the control group 89.86. There was no significant difference in the level of postural control between the study and control groups (p > 0.05). The level of stability index eyes closed (SI EC) for the study group was 71.44 and for the control group 77.1. SI EC results showed significant differences in proprioceptive control during single leg stance between the study and control groups (p < 0.05). The level of pain intensity, the degree of disability, and physical activity level did not influence postural control in the study group with LDS. In summary, patients with LDS showed significantly worse proprioceptive control.

Neuromuscular adaptations to experimentally induced pain in the lumbar region: protocol for a systematic review and meta-analysis

BACKGROUND

Numerous studies report changes in neuromuscular control in people with low back pain (LBP). However, the relationship between pain and altered neuromuscular control is challenging to unravel given the heterogeneity that exists in clinical populations. One approach commonly adopted to overcome this issue is the use of experimental pain models, but it is currently unclear if the effects of experimental pain are consistent between studies. Therefore, this planned study will systematically evaluate and summarise the effect of experimentally induced pain in the lumbar region on neuromuscular control at sites both locally and remote to the low back.

METHODS

This protocol has been developed following the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P). MEDLINE, EMBASE, CINAHL, ZETOC, Web of Science, and grey literature will be searched up to August 31, 2021. Screening processes (title/abstract and full-text), data extraction, and risk of bias assessment will be conducted by two independent reviewers. Studies investigating the effects of exogenous pain models delivered to the low back region on neuromuscular control in healthy individuals will be included. Muscle activity and body kinematics will be the outcomes of interest. The comparisons of interest will be between baseline or control conditions and the experimental pain condition, as well as between the experimental pain and post-pain conditions. Randomised crossover and non-randomised studies of interventions will be included and their risk of bias will be evaluated with the Cochrane Risk-of-Bias tool or with the Risk Of Bias In Non-randomised Studies of Interventions tool, respectively. A random-effect meta-analysis will be conducted for quantitative synthesis when clinical and methodological consistency is ensured. Quality of evidence will be evaluated using the Grading of Recommendations, Assessment, Development and Evaluation guidelines.

DISCUSSION

The current review will provide new insights to understand if and what neuromuscular adaptations are caused by pain experimentally induced in the lumbar region. Our findings will reveal which experimental pain model is able to better reproduce adaptations similar to those identified in people with low back pain, possibly contributing to improving our understanding of motor adaptation to low back pain in the long term.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020220130.

Machine learning approaches applied in spinal pain research

The purpose of this narrative review is to provide a critical reflection of how analytical machine learning approaches could provide the platform to harness variability of patient presentation to enhance clinical prediction. The review includes a summary of current knowledge on the physiological adaptations present in people with spinal pain. We discuss how contemporary evidence highlights the importance of not relying on single features when characterizing patients given the variability of physiological adaptations present in people with spinal pain. The advantages and disadvantages of current analytical strategies in contemporary basic science and epidemiological research are reviewed and we consider how analytical machine learning approaches could provide the platform to harness the variability of patient presentations to enhance clinical prediction of pain persistence or recurrence. We propose that machine learning techniques can be leveraged to translate a potentially heterogeneous set of variables into clinically useful information with the potential to enhance patient management.

Lumbar movement control in non-specific chronic low back pain: Evaluation of a direction-specific battery of tests using item response theory

QUESTION

What tests are most useful to identify poor lumbar movement control (LMC) and what are the dimensional and psychometric properties of these tests?

DESIGN

Multicenter, cross-sectional cohort study.

PARTICIPANTS

Adults with non-specific chronic low back pain (NSCLBP).

METHODS

A literature review was conducted to identify LMC tests with good reliability (κ≥ 0.61) and their dimensionality was examined. Based on item response theory, psychometric properties of individual items and the entire battery of LMC tests were determined.

RESULTS

277 participants with NSCLBP were included and tested by 21 physiotherapists in 19 clinics in Germany and Austria. 15 tests for LMC were assessed. The battery of LMC tests showed a direction-specific structure representing extension, flexion and rotation/lateral flexion control, for which unidimensionality and local independence were confirmed (eigenvalue >1; factor loading >0.4, Yen's Q3 <0.2). 4 items for flexion control, 4 items for extension control and 5 items for rotation/lateral flexion control were extracted. The flexion control items were the easiest items (item difficulty: 1.98 to -1.31). The rotation/lateral flexion control items were the most difficult (-1.3 to -0.08). More than 80% of all participants showed at least one incorrect direction of LMC.

CONCLUSIONS

A battery of LMC tests is proposed as the most appropriate to examine individuals with precise to poor LMC. Each direction of LMC should be examined separately. Tests can be sorted according to test difficulty, so that only three tests are initially required to screen for poor LMC.

The effect of motor control training according to the Kinetic Control concept on the back pain of female football players

BACKGROUND

Due to a significant burden associated with training sessions and matches, female football players often suffer from lumbar pain. Physical exercise is considered an effective form of therapy for this condition. The exercises in the Kinetic Control concept are one of the forms of motor control training.

OBJECTIVE

The aim of the study was to evaluate the effectiveness of motor control training according to the Kinetic Control concept on the level of lumbar spine pain, degree of disability, functional level and load distribution of lower limbs in football players.

METHODS

The study included 18 football players, randomly divided into two study groups: A - female players implementing their training plan with additional Kinetic Control training (n= 9) and B (control) - female players implementing their training plan only (n= 9). Pain intensity was measured using Visual Analogue Scale (VAS) and Laitinen's questionnaire. Functional disability was assessed using Oswestry Disability Index (ODI) and Back Pain Functional Scale (BPFS). The asymmetry index was assessed in a balance test with open and closed eyes and a countermovement jump (CMJ).

RESULTS

There was a significant statistical difference between the groups (p< 0.05) in measurements using VAS, ODI and BPFS, in favor of group A. Asymmetry index values in tests on the dynamometer platform did not differ significantly between the groups (p> 0.05). A statistically significant correlation was found between the asymmetry index score in the closed-eye balance test (r= 0.567, p= 0.049) and the CMJ landing phase (r= 0.641, p= 0.033), and the level of pain measured using VAS.

CONCLUSIONS

Motor control training in the Kinetic Control concept reduced the pain symptoms of the lumbar spine and the degree of disability and increased the functional level in football female players.

WHOLE BODY PHYSICAL TRAINING IN THE TREATMENT OF CHRONIC LOW BACK PAIN

ABSTRACT Introduction Chronic low back pain (CNLBP) manifests as chronic lumbosacral and hip pain, affecting athletes’ daily training and competition. Whole-body sports training can significantly improve the strength of the core muscles of the lumbosacral region and has certain advantages in the treatment of chronic low back pain. Object We study the therapeutic effect of whole-body physical training on athletes’ chronic low back pain (CNLBP). Method We selected 60 athletes with chronic low back pain patients. At the same time, we divide it into a control group and an observation group. The control group received conventional treatment, and the observation group received full-body physical training on this basis. After two months, the relevant physiological indicators of the patients were compared. Result After treatment, all physiological indexes of the two groups have great differences. Conclusion Whole-body physical training can significantly reduce athletes’ back pain symptoms and help restore professional athletes to regular training. Level of evidence II; Therapeutic studies - investigation of treatment results.

Exergaming Using Postural Feedback From Wearable Sensors and Exercise Therapy to Improve Postural Balance in People With Nonspecific Low Back Pain: Protocol for a Factorial Pilot Randomized Controlled Trial

Background

Physical exercise is a common treatment for people with low back pain (LBP). Wearable sensors that provide feedback on body movements and posture during exercise may enhance postural balance and motor control in people with LBP.

Objective

This study aims to investigate whether physical exercising with postural feedback (EPF) improves postural balance, motor control, and patient-reported outcomes in people with LBP.

Methods

The study was an assessor-blinded 2×2 factorial trial. We planned to recruit 80 participants with nonspecific LBP who did not receive treatment for LBP. In addition, we aimed to recruit 40 patients with chronic, nonspecific LBP who were receiving exercise therapy (ET) at the University Hospital Zurich. Both ET patients and participants without treatment were randomized to receive either an additional EPF intervention or no additional intervention. This resulted in four different combinations of interventions: ET+EPF, ET, EPF, and no intervention. The participants underwent outcome assessments at inclusion (T1); 3 weeks later, at randomization (T2); after an intervention period of 3 weeks with a predefined exercise schedule for participants receiving EPF (T3); and after an additional 6 weeks, during which participants assigned to the EPF groups could exercise as much as they wished (T4). Patients receiving ET completed their regularly prescribed therapies during the study period. Balance was assessed during quiet standing on a force platform, and motor control was assessed during a lifting task and a waiter’s bow task. Physical activity was recorded using an activity tracker and the participants’ mobile phones during the study. The predefined EPF schedule consisted of nine sessions of 20 minutes of exercise with a tablet and inertial measurement unit sensors at home. Participants performed a series of trunk and hip movements and received feedback on their movements in a gamified environment displayed on the tablet.

Results

The first participant was recruited in May 2019. Data collection was completed in October 2020, with 3 patients and 32 eligible people without therapy who passed the eligibility check.

Conclusions

Although it will not be possible to investigate differences in patients and people without other therapies, we expect this pilot study to provide insights into the potential of EPF to improve balance in people with LBP and adherence to such interventions.

International Registered Report Identifier (IRRID)

DERR1-10.2196/26982

Pain and Disability in Low Back Pain Can be Reduced Despite No Significant Improvements in Mechanistic Pain Biomarkers

OBJECTIVE

Altered balance in nociception in response to noxious stimuli is commonly reported in chronic low back pain (LBP). However, it is unclear whether an improvement in the clinical presentation is contingent on a reduction in pain sensitivity. This study investigated whether the quantitative sensory testing (QST) profile changes in people undergoing rehabilitation for LBP.

DESIGN

A prospective, observational case-control study.

METHODS

Forty males and females, 18 to 40 years' old (20 with LBP) participated in 2 sessions. QST was performed at baseline and after discharge from rehabilitation (LBP) or after 3 to 8 weeks (controls). The QST battery consisted of determining pressure-pain thresholds at the low back and shoulder, temporal summation of pain, and conditioned pain modulation. Questionnaire data was used to determine pain (Numeric Rating Scale [NRS]), disability (Roland-Morris Questionnaire [RMQ]), Fear Avoidance Beliefs (FABQ), and The Örebro Musculoskeletal Pain Screening Questionnaire (ÖMPSQ) at baseline and discharge. The treatment effect was determined by calculating the Cohen d.

RESULTS

No significant group×time interactions or main factor effect was found for any of the QST measures. The LBP group reported a significant reduction in NRS (P<0.0002, d=1.23), RMQ (P<0.0001, d=1.58), FABQ (P<0.001, d=0.87), and in the ÖMPSQ (P<0.00001, d=1.44).

CONCLUSIONS

The results indicate that an improvement of clinical LBP is not contingent upon changes in the pain sensory profile. The value of screening pain sensitivity in LBP patients in primary care, needs to be investigated further, due to the patient population heterogeneity and the sensitivity of assessment methods.

Durability of the Therapeutic Effect of Restorative Neurostimulation for Refractory Chronic Low Back Pain

Objectives

The purpose of the ongoing follow‐up of ReActiv8‐A clinical trial is to document the longitudinal benefits of episodic stimulation of the dorsal ramus medial branch and consequent contraction of the lumbar multifidus in patients with refractory mechanical chronic low back pain (CLBP). We report the four‐year outcomes of this trial.

Materials and Methods

ReActiv8‐A is a prospective, single‐arm trial performed at nine sites in the United Kingdom, Belgium, and Australia. Eligible patients had disabling CLBP (low back pain Numeric Rating Scale [NRS] ≥6; Oswestry Disability Index [ODI] ≥25), no indications for spine surgery or spinal cord stimulation, and failed conventional management including at least physical therapy and medications for low back pain. Fourteen days postimplantation, stimulation parameters were programmed to elicit strong, smooth contractions of the multifidus, and participants were given instructions to activate the device for 30‐min stimulation‐sessions twice daily. Annual follow‐up through four years included collection of NRS, ODI, and European Quality of Life Score on Five Dimensions (EQ‐5D). Background on mechanisms, trial design, and one‐year outcomes were previously described.

Results

At baseline (N = 53) (mean ± SD) age was 44 ± 10 years; duration of back pain was 14 ± 11 years, NRS was 6.8 ± 0.8, ODI 44.9 ± 10.1, and EQ‐5D 0.434 ± 0.185. Mean improvements from baseline were statistically significant (p < 0.001) and clinically meaningful for all follow‐ups. Patients completing year 4 follow‐up, reported mean (±standard error of the mean) NRS: 3.2 ± 0.4, ODI: 23.0 ± 3.2, and EQ‐5D: 0.721 ± 0.035. Moreover, 73% of participants had a clinically meaningful improvement of ≥2 points on NRS, 76% of ≥10 points on ODI, and 62.5% had a clinically meaningful improvement in both NRS and ODI and 97% were (very) satisfied with treatment.

Conclusions

In participants with disabling intractable CLBP who receive long‐term restorative neurostimulation, treatment satisfaction remains high and improvements in pain, disability, and quality‐of‐life are clinically meaningful and durable through four years.

Individuals with recurrent low back pain exhibit further altered frontal plane trunk control in remission than when in pain

BACKGROUND

Movement alterations due to low back pain (LBP) could lead to long-term adverse consequences if they do not resolve after symptoms subside. This study aims to determine if altered trunk control associated with recurrent low back pain persists beyond symptom duration.

METHODS

Twenty young adults with recurrent LBP were tested once during an LBP episode and once in symptom remission, and twenty matched back-healthy participants served as controls. Participants walked on a treadmill with five prescribed step widths (0.33, 0.67, 1, 1.33, 1.67 × preferred step width). Motion capture and surface electromyography were used to record trunk kinematics and muscle activation. Thorax-pelvis coordination was calculated using vector coding, and longissimus activation and co-activation were analyzed.

FINDINGS

Young adults with recurrent LBP exhibited a "looser" trunk control strategy in the frontal plane during gait that was persistent regardless of pain status across multiple step widths compared to controls. The looser trunk control was demonstrated by a greater pelvis-only, less thorax-only coordination pattern, and decreased bilateral longissimus co-activation in individuals with recurrent LBP compared to controls. The looser trunk control strategy was further amplified when individuals were in symptom remission and exhibited greater trunk excursion and reduced in-phase coordination in the frontal plane.

INTERPRETATION

The amplification of aberrant movement during symptom remission may suggest that movement patterns or anatomical factors existing prior to the tested painful episode underlie altered trunk control in individuals with recurrent LBP. The symptom remission period of recurrent LBP may be a critical window into clinical evaluation and treatment.

Changes in Trunk Variability and Stability of Gait in Patients with Chronic Low Back Pain: Impact of Laboratory versus Daily-Living Environments

BACKGROUND

Individuals with chronic low back pain (CLBP) experience changes in gait control due to pain and/or fear. Although CLBP patients' gait has been performed in laboratory environments, changes in gait control as an adaptation to unstructured daily living environments may be more pronounced than the corresponding changes in laboratory environments. We investigated the impacts of the environment and pathology on the trunk variability and stability of gait in CLBP patients.

METHODS

CLBP patients (n=20) and healthy controls with no low-back pain history (n=20) were tasked with walking in a laboratory or daily-living environment while wearing an accelerometer on the low back. We calculated the stride-to-stride standard deviation and multiscale sample entropy as indices of "gait variability" and the maximum Lyapunov exponent as an index of "gait stability" in both the anterior-posterior and medial-lateral directions. The participants were assessed on the numerical rating scale for pain intensity, the Tampa Scale for Kinesiophobia, and the Roland-Morris Disability Questionnaire for quality of life (QOL).

RESULTS

In a repeated-measures ANOVA, the standard deviation was affected by environment in the anterior-posterior direction and by group and environment in the medial-lateral direction. Multiscale sample entropy showed no effect in the anterior-posterior direction and showed both effects in the medial-lateral direction. Maximum Lyapunov exponents showed both effects in the anterior-posterior direction, but none in the medial-lateral direction. These changes of trunk motor control by CLBP patients were found to be related to pain intensity, fear of movement, and/or QOL in the daily-living environment but not in the laboratory environment.

CONCLUSION

These results revealed that CLBP patients exhibit changes in trunk variability and stability of gait depending on the environment, and they demonstrated that these changes are related to pain, fear, and QOL. We propose useful accelerometer-based assessments of qualitative gait in CLBP patients' daily lives, as it would provide information not available in a general practice setting.

Fear-avoidance beliefs are associated with reduced lumbar spine flexion during object lifting in pain-free adults

ABSTRACT

There is a long-held belief that physical activities such as lifting with a flexed spine is generally harmful for the back and can cause low back pain (LBP), potentially reinforcing fear-avoidance beliefs underlying pain-related fear. In patients with chronic LBP, pain-related fear has been shown to be associated with reduced lumbar range of motion during lifting, suggesting a protective response to pain. However, despite short-term beneficial effects for tissue health, recent evidence suggests that maintaining a protective trunk movement strategy may also pose a risk for (persistent) LBP due to possible pronociceptive consequences of altered spinal motion, potentially leading to increased loading on lumbar tissues. Yet, it is unknown if similar protective movement strategies already exist in pain-free individuals, which would yield potential insights into the role of fear-avoidance beliefs in motor behavior in the absence of pain. Therefore, the aim of this study is to test whether fear-avoidance beliefs influence spinal motion during lifting in a healthy cohort of pain-free adults without a history of chronic pain. The study subjects (N = 57) filled out several pain-related fear questionnaires and were asked to perform a lifting task (5kg-box). High-resolution spinal kinematics were assessed using an optical motion capturing system. Time-sensitive analyses were performed based on statistical parametric mapping. The results demonstrated time-specific and negative relationships between self-report measures of pain-related fear and lumbar spine flexion angles during lifting, indicating potential unfavorable interactions between psychological factors and spinal motion during lifting in pain-free subjects.

Spinal movement variability associated with low back pain: A scoping review

Objective

To identify suggestions for future research on spinal movement variability (SMV) in individuals with low back pain (LBP) by investigating (1) the methodologies and statistical tools used to assess SMV; (2) characteristics that influence the direction of change in SMV; (3) the methodological quality and potential biases in the published studies; and (4) strategies for optimizing SMV in LBP patients.

Methods

We searched literature databases (CENTRAL, Medline, PubMed, Embase, and CINAHL) and comprehensively reviewed the relevant papers up to 5 May 2020. Eligibility criteria included studies investigating SMV in LBP subjects by measuring trunk angle using motion capture devices during voluntary repeated trunk movements in any plane. The Newcastle-Ottawa risk of bias tool was used for data quality assessment. Results were reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews.

Results

Eighteen studies were included: 14 cross-sectional and 4 prospective studies. Seven linear and non-linear statistical tools were used. Common movement tasks included trunk forward bending and backward return, and object lifting. Study results on SMV changes associated with LBP were inconsistent. Two of the three interventional studies reported changes in SMV, one of which was a randomized controlled trial (RCT) involving neuromuscular exercise interventions. Many studies did not account for the potential risk of selection bias in the LBP population.

Conclusion

Designers of future studies should recognize that each of the two types of statistical tools assesses functionally different aspects of SMV. Future studies should also consider dividing participants into subgroups according to LBP characteristics, as three potential subgroups with different SMV characteristics were proposed in our study. Different task demands also produced different effects. We found preliminary evidence in a RCT that neuromuscular exercises could modify SMV, suggesting a rationale for well-designed RCTs involving neuromuscular exercise interventions in future studies.

Understanding regional activation of thoraco-lumbar muscles in chronic low back pain and its relationship to clinically relevant domains

BACKGROUND

Altered regional activation of the lumbar extensors has been previously observed in individuals with low back pain (LBP) performing high-effort and fatiguing tasks. It is currently unknown whether similar alterations can be observed during low-effort functional tasks. Similarly, previous studies did not investigate whether side differences in regional activation are present in individuals with LBP. Finally, there is limited evidence of whether the extent of the alteration of regional activation is associated with clinical factors. Therefore, the aim of this study was to investigate whether individuals with LBP exhibit asymmetric regional activation of the thoraco-lumbar extensor muscles during functional tasks, and if the extent of neuromuscular control alteration is associated with clinical and psychosocial outcome domains.

METHODS

21 participants with and 21 without LBP performed five functional tasks (gait, sit-to-stand, forward trunk flexion, shoulder flexion and anterior pelvic tilt). The spatial distribution of activation of the thoraco-lumbar extensor muscles was assessed bilaterally using high-density electromyography. For each side, the distribution of electromyographic (EMG) amplitude was characterized in terms of intensity, location and size. Indices of asymmetry were calculated from these features and comparisons between groups and tasks were performed using ANOVA. The features that significantly differed between groups were correlated with self-reported measures of pain intensity and other outcome domains.

RESULTS

Indices of asymmetry did not differ between participants with and without LBP (p > 0.11). The cranio-caudal location of the activation differed between tasks (p < 0.05), but not between groups (p = 0.64). Participants with LBP showed reduced EMG amplitude during anterior pelvic tilt and loading response phase during gait (both p < 0.05). Pearson correlation revealed that greater pain intensity was associated with lower EMG amplitude for both tasks (R<-0.5, p < 0.05).

CONCLUSIONS

Despite clear differences between tasks, individuals with and without LBP exhibited similar distributions of EMG amplitude during low-effort functional activities, both within and between sides. However, individuals with LBP demonstrated lower activation of the thoraco-lumbar muscles during gait and anterior pelvic tilt, especially those reporting higher pain intensity. These results have implications in the development or refinement of assessment and intervention strategies focusing on motor control in patients with chronic LBP.

Effectiveness of motor control exercise on non-specific chronic low back pain, disability and core muscle morphological characteristics: A meta-analysis of randomized controlled trials

INTRODUCTION

Chronic low back pain (CLBP) has been recognized as the leading cause of disability. Up to 90% of patients with CLBP are classified as having non-specific CLBP (NSCLBP). Motor control exercise (MCE) is one of the most popular and widespread treatment options, and has many advantages in alleviating pain and disability. This meta-analysis is aimed to investigate the effectiveness of MCE on NSCLBP, disability, and core muscles reported in randomized controlled trials (RCTs).

METHODS

PubMed, Web of Science, and EMBASE were searched from inception to August 2020. Articles were eligible if they were RCTs that evaluated MCE against sham or other treatments in isolation and measured outcomes including pain intensity and disability or core muscles morphologic characteristics.

RESULTS

Two authors independently extracted the data. Eighteen studies of 897 studies with a total of 1333 individuals with NSCLBP were retained for the meta-analysis. Compared with other conservative treatments, MCE was better in reducing pain and disability posttreatment and was better in reducing pain at the 6-month follow-up period. However, it had comparable effects on pain reduction at 12-month and 24-month follow-up period, and on disability at the 6-month, 12-month and 24-month follow-up period. MCE resulted in comparable effects to other treatments in improving the core muscle thickness posttreatment. However, other important outcomes, such as the function, strength and endurance of core muscles, which could hamper a comprehensive understanding of the effects of MCE on NSCLBP.

LIMITATIONS

Publication bias was not assessed in several comparisons due to the scarcity of data in published literature. This might downgrade the strength of the evidence. The protocol of this meta-analysis was reviewed by an expert committee, but was not registered in a public trial registry.

CONCLUSIONS

Low to very low quality of evidence supported that MCE resulted in a greater reduction of pain and disability posttreatment, and a greater reduction of pain at the 6-month follow-up than other treatments for NSCBLP. The findings in this review further support that MCE may be more effective than other treatments at short-term followups, and at least has equivalent long-term effects to other forms of treatments in NSCLBP.

In vivo measurements of spinal stiffness according to a stepwise increase of axial load

Background

The spine has a complex motor control. Its different stabilization mechanisms through passive, active, and neurological subsystems may result in spinal stiffness. To better understand lumbar spinal motor control, this study aimed to measure the effects of increasing the axial load on spinal stiffness.

Methods

A total of 19 healthy young participants (mean age, 24 ± 2.1 years; 8 males and 11 females) were assessed in an upright standing position. Under different axial loads, the posterior-to-anterior spinal stiffness of the thoracic and lumbar spine was measured. Loads were 0%, 10%, 45%, and 80% of the participant’s body weight.

Results

Data were normally distributed and showed excellent reliability. A repeated-measures analysis of variance with a Greenhouse–Geisser correction showed an effect of the loading condition on the mean spinal stiffness [F (2.6, 744) = 3.456, p < 0.001]. Vertebrae and loading had no interaction [F (2.6, 741) = 0.656, p = 0.559]. Post hoc tests using Bonferroni correction revealed no changes with 10% loading (p = 1.000), and with every additional step of loading, spinal stiffness decreased: 0% or 10–45% loading (p < 0.001), 0% or 10–80% loading (p < 0.001), and 45–80% (p < 0.001).

Conclusion

We conclude that a load of ≥ 45% of the participant’s body weight can lead to changes in the spinal motor control. An axial load of 10% showed no significant changes. Rehabilitation should include high-axial-load exercise if needed in everyday living.

Abdominal Expansion versus Abdominal Drawing-In Strategy on Thickness and Electromyography of Lumbar Stabilizers in People with Nonspecific Low Back Pain: A Cross-Sectional Study

The abdominal expansion (AE) strategy, involving eccentric contraction of the abdominal muscles, has been increasingly used in clinical practices; however, its effects have not been rigorously investigated. This study aimed to investigate the immediate effects of the AE versus abdominal drawing-in (AD) strategy on lumbar stabilization muscles in people with nonspecific low back pain (LBP). Thirty adults with nonspecific LBP performed the AE, AD, and natural breathing (NB) strategies in three different body positions. Ultrasonography and surface electromyography (EMG) were, respectively, used to measure the thickness and activity of the lumbar multifidus and lateral abdominal wall muscles. The AE and AD strategies showed similar effects, producing higher EMG activity in the lumbar multifidus and lateral abdominal wall muscles when compared with the NB strategy. All muscles showed higher EMG activity in the quiet and single leg standing positions than in the lying position. Although the AE and AD strategies had similar effects on the thickness change of the lumbar multifidus muscle, the results of thickness changes of the lateral abdominal muscles were relatively inconsistent. The AE strategy may be used as an alternative method to facilitate co-contraction of lumbar stabilization muscles and improve spinal stability in people with nonspecific LBP.

Young adults with recurrent low back pain demonstrate altered trunk coordination during gait independent of pain status and attentional demands

Pain influences both attention and motor behavior. We used a dual-task interference paradigm to investigate (1) alterations in attentional performance, (2) the ability to switch task prioritization, and (3) the effect of attentional demand on trunk coordination during narrow-based walking in and out of a painful episode in individuals with recurrent low back pain (LBP). We tested twenty young adults with LBP both in and out of a painful episode and compared them to twenty matched back-healthy individuals. Participants simultaneously performed a narrow step width matching task and an arithmetic task, with and without instructions to prioritize either task. A motion capture system was used to record kinematic data, and frontal plane trunk coordination was analyzed using vector coding on the thorax and pelvis angles. Single-task performance, dual-task effect, dual-task performance variability, task prioritization switch, and trunk coordination were analyzed using paired t tests or repeated measures two-way ANOVAs. Results indicated that active pain has a detrimental effect on attentional processes, indicated by poorer single-task performance and increased dual-task performance variability for individuals with recurrent LBP. Individuals with LBP, regardless of pain status, were able to switch task prioritization to a similar degree as their back-healthy counterparts. Compared to the control group, individuals with recurrent LBP exhibited a less in-phase, more pelvis-dominated trunk coordination during narrow-based walking, independent of pain status and regardless of attentional manipulations. Thus, altered trunk coordination in persons with LBP appears to be habitual, automatic, and persists beyond symptom duration.

Slacklining as therapy to address non-specific low back pain in the presence of multifidus arthrogenic muscle inhibition

Low back pain (LBP) represents the most prevalent, problematic and painful of musculoskeletal conditions that affects both the individual and society with health and economic concerns. LBP is a heterogeneous condition with multiple diagnoses and causes. In the absence of consensus definitions, partly because of terminology inconsistency, it is further referred to as non-specific LBP (NSLBP). In NSLBP patients, the lumbar multifidus (MF), a key stabilizing muscle, has a depleted role due to recognized myocellular lipid infiltration and wasting, with the potential primary cause hypothesized as arthrogenic muscle inhibition (AMI). This link between AMI and NSLBP continues to gain increasing recognition. To date there is no 'gold standard' or consensus treatment to alleviate symptoms and disability due to NSLBP, though the advocated interventions are numerous, with marked variations in costs and levels of supportive evidence. However, there is consensus that NSLBP management be cost-effective, self-administered, educational, exercise-based, and use multi-modal and multi-disciplinary approaches. An adjuvant therapy fulfilling these consensus criteria is 'slacklining', within an overall rehabilitation program. Slacklining, the neuromechanical action of balance retention on a tightened band, induces strategic indirect-involuntary therapeutic muscle activation exercise incorporating spinal motor control. Though several models have been proposed, understanding slacklining's neuro-motor mechanism of action remains incomplete. Slacklining has demonstrated clinical effects to overcome AMI in peripheral joints, particularly the knee, and is reported in clinical case-studies as showing promising results in reducing NSLBP related to MF deficiency induced through AMI (MF-AMI). Therefore, this paper aims to: rationalize why and how adjuvant, slacklining therapeutic exercise may positively affect patients with NSLBP, due to MF-AMI induced depletion of spinal stabilization; considers current understandings and interventions for NSLBP, including the contributing role of MF-AMI; and details the reasons why slacklining could be considered as a potential adjuvant intervention for NSLBP through its indirect-involuntary action. This action is hypothesized to occur through an over-ride or inhibition of central down-regulatory induced muscle insufficiency, present due to AMI. This subsequently allows neuroplasticity, normal neuro-motor sequencing and muscle re-activation, which facilitates innate advantageous spinal stabilization. This in-turn addresses and reduces NSLBP, its concurrent symptoms and functional disability. This process is hypothesized to occur through four neuro-physiological processing pathways: finite neural delay; movement-control phenotypes; inhibition of action and the innate primordial imperative; and accentuated corticospinal drive. Further research is recommended to investigate these hypotheses and the effect of slacklining as an adjuvant therapy in cohort and control studies of NSLBP populations.

Reliability of measures to characterize lumbar movement patterns, in repeated seated reaching, in a mixed group of participants with and without low-back pain: A test-retest, within- and between session

Literature highlights the need for research on changes in lumbar movement patterns, as potential mechanisms underlying the persistence of low-back pain. Variability and local dynamic stability are frequently used to characterize movement patterns. In view of a lack of information on reliability of these measures, we determined their within- and between-session reliability in repeated seated reaching. Thirty-six participants (21 healthy, 15 LBP) executed three trials of repeated seated reaching on two days. An optical motion capture system recorded positions of cluster markers, located on the spinous processes of S1 and T8. Movement patterns were characterized by the spatial variability (meanSD) of the lumbar Euler angles: flexion-extension, lateral bending, axial rotation, temporal variability (CyclSD) and local dynamic stability (LDE). Reliability was evaluated using intraclass correlation coefficients (ICC), coefficients of variation (CV) and Bland-Altman plots. Sufficient reliability was defined as an ICC ≥ 0.5 and a CV < 20%. To determine the effect of number of repetitions on reliability, analyses were performed for the first 10, 20, 30, and 40 repetitions of each time series. MeanSD, CyclSD, and the LDE had moderate within-session reliability; meanSD: ICC = 0.60-0.73 (CV = 14-17%); CyclSD: ICC = 0.68 (CV = 17%); LDE: ICC = 0.62 (CV = 5%). Between-session reliability was somewhat lower; meanSD: ICC = 0.44-0.73 (CV = 17-19%); CyclSD: ICC = 0.45-0.56 (CV = 19-22%); LDE: ICC = 0.25-0.54 (CV = 5-6%). MeanSD, CyclSD and the LDE are sufficiently reliable to assess lumbar movement patterns in single-session experiments, and at best sufficiently reliable in multi-session experiments. Within-session, a plateau in reliability appears to be reached at 40 repetitions for meanSD (flexion-extension), meanSD (axial-rotation) and CyclSD.

Coordination of hip and spine to maintain equilibrium in unstable sitting revealed by spectral analysis

Unstable sitting paradigms have been used to assess the trunk's contribution to postural control. The coordination of spine or hip with an unstable seat that underpin postural control during this task remain unclear. This study aimed to address this issue using analysis in the frequency domain. Seventy-two healthy pain-free participants maintained balance while sitting on a seat fixed to a hemisphere. Angular motion of seat, spinal regions (lower lumber, lumbar, upper lumbar, and thoracic), and hip was recorded with a three-dimensional (3-D) motion capture system. Coordination between spinal regions and hip with the seat was quantified using cross-spectral analyses. In the sagittal plane, amplitude spectrum of hip and lumbar segments were higher than other segments, coherence between these segments and the seat was high, and their motion was generally opposite in direction to the seat. In the frontal plane, amplitude spectrum of lower lumbar and lumbar segments, but not the hip, were higher than other segments, and coherently moved in the opposite direction to the seat. Segments closest to the seat made a direction-specific and greater contribution to maintenance of equilibrium than upper body segments, which were more limited during unstable sitting. Although eye closure and higher body mass index involved larger amplitude of center of pressure movement, rather than inferring poor control, this was associated with enhanced coordination between segments and seat. Understanding how hip/spine segments are coordinated with the seat is important to interpret postural strategies used to maintain equilibrium and to interpret observations for other populations (e.g., back pain).NEW & NOTEWORTHY This is the first multidirectional spectral analysis of how the hip and spine coordinate during unstable sitting and how different factors impact this coordination. Seat movement was coherently counteracted (out-of-phase) by angular motion of the hip and lower lumbar spine in the sagittal plane and by the lumbar spine in the frontal plane. Although higher BMI and balancing with eyes closed increased movement amplitude, this did not compromise coordination between segments to control balance, instead, coherence increased.

Are neuromuscular adaptations present in people with recurrent spinal pain during a period of remission? a systematic review

A plethora of evidence supports the existence of neuromuscular changes in people with chronic spinal pain (neck and low back pain), yet it is unclear whether neuromuscular adaptations persist for people with recurrent spinal pain when in a period of remission. This systematic review aimed to synthesise the evidence on neuromuscular adaptations in people with recurrent spinal pain during a period of remission. Electronic databases, grey literature, and key journals were searched from inception up to the 4^th of September 2020. Eligibility criteria included observational studies investigating muscle activity, spine kinematics, muscle properties, sensorimotor control, and neuromuscular performance in adults (≥ 18 years) with recurrent spinal pain during a period of remission. Screening, data extraction, and quality assessment (Newcastle-Ottawa Scale) were conducted independently by two reviewers. Data synthesis was conducted per outcome domain. A meta-analysis with a random-effects model was performed where possible. The overall strength of evidence was rated using the Grading of Recommendations, Assessment, Development and Evaluation guidelines (GRADE). From 8292 records, 27 and five studies were included in a qualitative and quantitative synthesis, respectively. Very low level of evidence supports muscle activity changes in people with recurrent low back pain, especially greater co-contraction, redistribution of muscle activity, and delayed postural control of deeper trunk muscles. Reduced range of motion of the lumbar spine was also found. Meaningful conclusions regarding other outcome domains or people with recurrent neck pain could not be drawn. In conclusion, people with recurrent low back pain during a period of remission show muscle activity and spine kinematics adaptations. Future research should investigate the long-term impact of these changes, as well as adaptations in people with recurrent neck pain.

Effects of electromyographic biofeedback interventions for shoulder pain and function: Systematic review and meta-analysis

OBJECTIVE

To systematically review the effectiveness of electromyographic biofeedback interventions to improve pain and function of patients with shoulder pain.

DESIGN

Systematic review of controlled clinical trials.

LITERATURE SEARCH

Databases (Medline, EMBASE, CINAHL, PEDro, CENTRAL, Web of Science, and SCOPUS) were searched in December 2020.

STUDY SELECTION CRITERIA

Randomized clinical trials that investigated the effects of electromyographic biofeedback for individuals with shoulder pain. Patient-reported pain and functional outcomes were collected and synthesized.

DATA SYNTHESIS

The level of evidence was synthesized using GRADE and Standardized Mean Differences and 95% confidence interval were calculated using a random-effects inverse variance model for meta-analysis.

RESULTS

Five studies were included with a total sample of 272 individuals with shoulder pain. Very-low quality of evidence indicated that electromyographic biofeedback was not superior to control for reducing shoulder pain (standardized mean differences = -0.21, 95% confidence interval: -0.67 to 0.24, P = 0.36). Very-low quality of evidence indicated that electromyographic biofeedback interventions were not superior to control for improving shoulder function (standardized mean differences = -0.11, 95% confidence interval: -0.41 to 0.19, P = 0.48).

CONCLUSION

Electromyographic biofeedback may be not effective for improving shoulder pain and function. However, the limited number of included studies and very low quality of evidence does not support a definitive recommendation about the effectiveness of electromyographic biofeedback to treat individuals with shoulder pain.

Coordination of Axial Trunk Rotations During Gait in Low Back Pain. A Narrative Review

Chronic low back pain patients have been observed to show a reduced shift of thorax-pelvis relative phase towards out-of-phase movement with increasing speed compared to healthy controls. Here, we review the literature on this phase shift in patients with low back pain and we analyze the results presented in literature in view of the theoretical motivations to assess this phenomenon. Initially, based on the dynamical systems approach to movement coordination, the shift in thorax-pelvis relative phase with speed was studied as a self-organizing transition. However, the phase shift is gradual, which does not match a self-organizing transition. Subsequent emphasis in the literature therefore shifted to a motivation based on biomechanics. The change in relative phase with low back pain was specifically linked to expected changes in trunk stiffness due to 'guarded behavior'. We found that thorax-pelvis relative phase is affected by several interacting factors, including active drive of thorax rotation through trunk muscle activity, stride frequency and the magnitude of pelvis rotations. Large pelvis rotations and high stride frequency observed in low back pain patients may contribute to the difference between patients and controls. This makes thorax-pelvis relative phase a poor proxy of trunk stiffness. In conclusion, thorax-pelvis relative phase cannot be considered as a collective variable reflecting the orderly behaviour of a complex underlying system, nor is it a marker of specific changes in trunk biomechanics. The fact that it is affected by multiple factors may explain the considerable between-subject variance of this measure in low back pain patients and healthy controls alike.

Spatial distribution of lumbar erector spinae muscle activity in individuals with and without chronic low back pain during a dynamic isokinetic fatiguing task

BACKGROUND

Individuals with chronic low back pain (CLBP) commonly present with increased trunk muscle fatigability; typically assessed as reduced time to task failure during non-functional isometric contractions. Less is known about the specific neuromuscular responses of individuals with CLBP during dynamic fatiguing tasks. We investigate the regional alteration in muscle activation and peak torque exertion during a dynamic isokinetic fatiguing task in individuals with and without CLBP.

METHODS

Electromyography (EMG) was acquired from the lumbar erector spinae unilaterally of 11 asymptomatic controls and 12 individuals with CLBP, using high-density EMG (13 × 5 grid of electrodes). Seated in an isokinetic dynamometer, participants performed continuous cyclic trunk flexion-extension at 60^o/s until volitional exhaustion.

FINDINGS

Similar levels of muscle activation and number of repetitions were observed for both groups (p > 0.05). However, the CLBP group exerted lower levels of peak torque for both flexion and extension moments (p < 0.05). The centre of lumbar erector spinae activity was shifted cranially in the CLBP group throughout the task (p < 0.05), while the control participants showed a more homogenous distribution of muscle activity.

INTERPRETATION

People with CLBP displayed altered and potentially less efficient activation of their lumbar erector spinae during a dynamic fatiguing task. Future studies should consider using high-density EMG biofeedback to optimise the spatial activation of the paraspinal musculature in people with low back pain (LBP).

Combined abnormal muscle activity and pain-related factors affect disability in patients with chronic low back pain: An association rule analysis

Objectives

In patients with chronic low back pain (CLBP), reduced lumbar flexion-relaxation and reduced variability of muscle activity distribution are reported as abnormal muscle activity. It is not known how abnormal muscle activity and pain-related factors are related to CLBP-based disability. Here, we performed an association rule analysis to investigated how CLBP disability, muscle activity, and pain-related factors in CLBP patients are related.

Methods

Surface electromyographic signals were recorded from over the bilateral lumbar erector spinae muscle with four-channel electrodes from 24 CLBP patients while they performed a trunk flexion re-extension task. We calculated the average value of muscle activities of all channels and then calculated the flexion relaxation ratio (FRR) and the spatial variability of muscle activities. We also assessed the pain-related factors and CLBP disability by a questionnaire method. A clustering association rules analysis was performed to determine the relationships among pain-related factors, the FRR, and the variability of muscle activity distribution.

Results

The association rules of severe CLBP disability were divisible into five classes, including ‘low FRR-related rules.’ The rules of the mild CLBP disability were divisible into four classes, including ‘high FRR-related rules’ and ‘high muscle variability-related rules.’ When we combined pain-related factors with the FRR and muscle variability, the relationship between abnormal FRR/muscle variability and CLBP disability became stronger.

Discussion

Our findings thus highlight the importance of focusing on not only the patients’ pain-related factors but also the abnormal motor control associated with CLBP, which causes CLBP disability.

Using neuromuscular electrical stimulation in conjunction with ultrasound imaging technique to investigate lumbar multifidus muscle activation deficit

Lumbar multifidus muscle (LM) activation deficit has been proposed as a potential underlying mechanism responsible for recurrence episode of low back pain (LBP). The quantification of voluntary LM activation can provide a better understanding of the role of muscle activation deficit in LBP. The objective of this technical report is to propose a new approach using neuromuscular electrical stimulation (NMES) in combination with the ultrasound imaging technique (USI) to investigate the ability of individual to voluntarily activate the LM. We recruited ten participants with a recurrent LBP (rLBP) and twelve participants with no history of LBP (NoLBP). Theoretically, the superimposition of NMES on the LM during maximum voluntary isometric contraction (MVIC) should activate all motor units available in the LM. The percentage of LM activation (%LM) can be calculated by the changes of LM thickness during MVIC, divided by the changes of LM thickness during the combination of MVIC and NMES. This %LM was used to compare between groups. The individuals with rLBP had significantly lower %LM (p < 0.05) compared with the NoLBP counterpart (%LM = 72.4 and 92.9, respectively). Results demonstrate that this new approach can potentially differentiate %LM among individuals with rLBP and NoLBP. This new approach can be potentially used to 1) determine the extent of LM activation deficit, 2) identify the existence of muscle activation deficit in the LM, and 3) objectively measure the effect of the intervention designed to address the LM activation deficit.

Pain Catastrophizing Is Related to Static Postural Control Impairment in Patients with Nonspecific Chronic Low Back Pain: A Cross-Sectional Study

Purpose

Pain catastrophizing may contribute to the altered trunk muscle activity in patients with nonspecific chronic low back pain (NSCLBP). It is unclear if pain catastrophizing influences static postural control in patients with NSCLBP. This study aimed to investigate the relationship between pain catastrophizing and static postural control in NSCLBP patients.

Methods

Sixty-eight participants with NSCLBP and 40 healthy participants were recruited. Postural control was assessed by the sway area and the sway length of the center of pressure (COP) during balance tests. Pain catastrophizing in participants with NSCLBP was assessed by the Pain Catastrophizing Scale (PCS). Bilateral transversus abdominis (TrA) activation was evaluated by ultrasound imaging-measured percent change in muscle thickness. Associations between COP parameter and PCS/subscales of PCS were examined by multiple linear regression (MLR).

Results

Our results observed a larger COP sway area in NSCLBP group under eyes-closed condition (p < 0.001) and a lower level of voluntary activation of the bilateral TrA (p < 0.001), compared with the healthy control group. The MLR analyses revealed that the COP area sway under eyes-closed condition was significantly associated with the PCS score/helplessness score of PCS, voluntary activation of the left TrA, and age in participants with NSCLBP (β = 0.222/0.236, 0.341/0.344, and 0.328/0.325; p=0.045/0.033, 0.002, and 0.004, resp.).

Conclusions

Static postural control was associated with pain catastrophizing, voluntary activation of TrA, and age in participants with NSCLBP. This indicated that pain catastrophizing may affect postural control and should be considered when interpreting balance test results and managing NSCLBP.

Contribution of the sensory innervation of the spine in low back pain: review and clinical commentary

Few validated tests allow a precise aetiological diagnosis of Low Back Pain (LBP), and the difficulty of clinical evaluations could be one of the reasons to explain the lack of effectiveness in the therapeutic management of chronic LBP. However, an implication of a sensory impairment in the control of sensorimotor circuits could be suggested. Interactive and specific responses between nociceptive nerve fibres and the paraspinal musculature motor control could have clinical implications, in particular through kinematic evaluation. Following an introduction to the link between the sensory innervation of the spine and pain, we then summarise the maladaptive movement in LBP at the kinematic and neuropathological level. A clinical objectification of these kinematic adaptations at the lumbar spine level, would clarify the aetiological diagnosis causes of chronic LBP, and so help optimising therapeutic strategies by proposing a relevant and precise clinical model of this painful condition.

Assessing sensorimotor control of the lumbopelvic-hip region using task-based functional MRI

Recent brain imaging studies have suggested that cortical remodeling within sensorimotor regions are associated with persistent low back pain and may be a driving mechanism for the impaired neuromuscular control associated with this condition. This paper outlines a new approach for investigating cortical sensorimotor integration during the performance of small-amplitude lumbopelvic movements with functional MRI. Fourteen healthy right-handed participants were instructed in the lumbopelvic movement tasks performed during fMRI acquisition. Surface electromyography (EMG) collected on 8 lumbopelvic and thigh muscles captured organized patterns of muscle activation during the movement tasks. fMRI data were collected on 10 of 14 participants. Sensorimotor cortical activation across the tasks was identified using a whole brain analysis and further explored with regional analyses of key components of the cortical sensorimotor network. Head motion had low correlation to the tasks (r = -0.101 to 0.004) and head translation averaged 0.98 (0.59 mm) before motion correction. Patterns of activation of the key lumbopelvic and thigh musculature (average amplitude normalized 2-17%) were significantly different across tasks (P > 0.001). Neuroimaging demonstrated activation in key sensorimotor cortical regions that were consistent with motor planning and sensory feedback needed for performing the different tasks. This approach captures the specificity of lumbopelvic sensorimotor control using goal-based tasks (e.g., "lift your hip" vs. "contract your lumbar multifidus to 20% of maximum") performed within the confines of the scanner. Specific patterns of sensorimotor cortex activation appear to capture differences between bilateral and unilateral tasks during voluntary control of multisegmental movement in the lumbopelvic region.NEW & NOTEWORTHY We demonstrated the feasibility of using task-based functional magnetic resonance imaging (fMRI) protocols for acquiring the blood oxygen level-dependent (BOLD) response of key sensorimotor cortex regions during voluntary lumbopelvic movements. Our approach activated lumbopelvic muscles during small-amplitude movements while participants were lying supine in the scanner. Our data supports these tasks can be done with limited head motion and low correlation of head motion to the task. The approach provides opportunities for assessing the role of brain changes in persistent low back pain.

Balance Control in Patients with Subacute Non-Specific Low Back Pain, with and without Lumbar Instability: A Cross-Sectional Study

Background

Patients with low back pain (LBP) have poorly coordinated neuromuscular control, which may alter the normal postural stability of the spine. Altered movement control may occur at any stage of LBP.

Purpose

(1) To identify differences in balance control and proprioceptive sense between subacute non-specific LBP (NSLBP) patients with and without lumbar instability (LI) and healthy subjects and (2) to investigate the correlation between factors of motor control deficits and balance.

Patients and Methods

Thirty-six participants matched by gender, age, and body mass index (BMI) were allocated into three groups of 12: subacute NSLBP patients with LI, subacute NSLBP patients without LI, and healthy subjects. Balance, proprioceptive sense, pain, functional disability, and fear of movement were evaluated.

Results

Subacute NSLBP patients with LI exhibited greater impairments in balance control, proprioceptive sense, and functional ability than patients without LI (p<0.05). Subacute NSLBP patients showed more impairments in balance control, proprioceptive sense, and fear of movement than healthy subjects (p<0.001), with the following effect sizes (partial η²) for static balance on stable and unstable surface: 0.597 and 0.560, anticipatory balance: 0.417, and dynamic balance: 0.536; proprioceptive sense: 0.676; and fear of movement: 0.379. Significant fair correlations were found between (1) static balance and proprioceptive sense, functional disability, and fear of movement; (2) functional reach test (FRT) and pain; and (3) the five times sit to stand test (FTSTS) and functional disability.

Conclusion

Subacute NSLBP patients with LI showed greater impairment in balance control than patients without LI. Reduced proprioceptive sense, increased pain, functional disability, and fear of movement were fairly related to impaired balance.

Identification of intrinsic and reflexive contributions to trunk stabilization in patients with low back pain: a case-control study

PURPOSE

The goal of this study was to assess differences in low back stabilization and underlying mechanisms between patients with low back pain (LBP) and healthy controls. It has been hypothesized that inadequate trunk stabilization could contribute to LBP through high tissue strains and/or impingement. Evidence to support this is inconsistent, and not all methods that have been used to study trunk stabilization are equally suitable. We have recently developed a method to assess intrinsic and reflexive contributions to trunk stabilization, which aims to circumvent the limitations of previous studies.

METHODS

Forty-nine participants suffering from chronic LBP and a control group of fifty healthy subjects participated in this study. Trunk stabilization was measured using force-controlled perturbations directly applied to the trunk. The actuator displacement and contact force between the actuator and subject were measured as well as electromyography (EMG) of the M. Longissimus. Underlying mechanisms were characterized using system identification.

RESULTS

LBP patients showed lower admittance, i.e., less displacement per unit of force applied, mainly due to higher position, velocity and acceleration feedback gains. Among patients, lower trunk admittance and higher reflex gains were associated with more negative pain-related cognitions.

CONCLUSION

Trunk stabilization differs between LBP patients and controls, with the same perturbations causing less trunk movement in patients, due to stronger reflexes. We interpret these changes as reflecting protective behavior. These slides can be retrieved under Electronic Supplementary Material.

Persons in remission from recurrent low back pain alter trunk coupling under dual-task interference during a dynamic balance task

This study investigated effects of cognitive dual-task interference and task prioritization instructions on task performance and trunk control during a dynamic balance task in persons with and without recurrent low back pain (rLBP). First, we tested the hypothesis that those with rLBP rely more on cognitive resources than back-healthy controls, and therefore trunk kinematics would be altered under dual-task interference conditions. Then, we tested participants' ability to modulate task performance in accord with prioritization instructions. Persons with and without rLBP (n = 19/group) performed the Balance-Dexterity Task, which involved single-limb balance while compressing an unstable spring with the other limb, with and without a cognitive task engaging verbal working memory. Trunk coupling was quantified with the coefficient of determination (R²) of an angle-angle plot of thorax-pelvis frontal plane motion. Task performance was quantified using variability of spring compression force and of cognitive task errors. Trunk coupling in the rLBP group was lower than that of the back-healthy control group in the single-task condition (p = 0.024) and increased in the dual-task condition (p = 0.006), abolishing the difference between groups. Significant main effects of task prioritization instruction on performance were observed with no differences between groups, indicating similar performance modulation. Cognitive task error variability decreased with a switch from a single- to dual-task condition, exposing an unexpected facilitation effect. We interpret these findings in the context of movement-specific reinvestment and action-specific perception theories as they pertain to cognitive contributions to posture and how the dual-task interference paradigm may influence those contributions.

Assessment instruments of movement quality in patients with non-specific low back pain: A systematic review and selection of instruments

BACKGROUND

Observing and analyzing movement quality (MQ) in patients with non-specific low back pain (NS-LBP) is important in the clinical reasoning of primary care physiotherapists and exercise therapists. However, there is no standardized form of assessment.

RESEARCH QUESTION

which MQ domains are measured with which instruments, and which activities are relevant, appropriate and methodologically sound for assessing MQ in patients with NS-LBP?

METHODS

The study had three phases. In phase 1 we conducted a systematic review in PubMed, CINAHL and SPORTDiscus of literature published until October 2018. The selected studies measured MQ domains with instruments that enabled us to 1) compare MQ in self-paced dynamic activities of patients with NS-LBP and healthy controls, and/or 2) determine change over time of MQ in patients with NS-LBP. In phase 2 we established relevant dynamic activities to assess in patients with NS-LBP. In phase 3 we determined appropriateness and methodological qualities of the selected instruments.

RESULTS

Thirty cross-sectional and three pre-post-test studies were eligible. The instruments consisted of complex (n = 19) and simple (n = 7) instrumented motion analysis systems and standardized observational tests (n = 7). We identified three domains representative for MQ: range of motion (ROM), inter-segmental coordination, and whole-body movements. In these domains, patients with NS-LBP significantly differed from healthy controls, respectively 7/12, 12/13 and 13/20 studies. Moreover, ROM and whole-body movements significantly improved over time in patients with NS-LBP (3/3 studies). Based on phase 3, we concluded that none of the instruments are appropriate to assess MQ in patients with NS-LBP in primary care.

SIGNIFICANCE

Forward bending, lifting, and walking seem the most relevant activities to evaluate in patients with NS-LBP. However, we found no suitable instruments to measure ROM, inter-segmental coordination, or whole-body movements as determinants of MQ in these activities in daily practice. We therefore recommend such an instrument be developed.

Does manual therapy affect functional and biomechanical outcomes of a sit-to-stand task in a population with low back pain? A preliminary analysis

Introduction

Manual therapy (MT) hypothetically affects discrepant neuromuscular control and movement observed in populations with low back pain (LBP). Previous studies have demonstrated the limited influence of MT on movement, predominately during range of motion (ROM) testing. It remains unclear if MT affects neuromuscular control in mobility-based activities of daily living (ADLs). The sit-to-stand (STS) task represents a commonly-performed ADL that is used in a variety of clinical settings to assess functional and biomechanical performance.

Objective

To determine whether MT affects functional performance and biomechanical performance during a STS task in a population with LBP.

Methods

Kinematic data were recorded from the pelvis and thorax of participants with LBP, using an optoelectronic motion capture system as they performed a STS task before and after MT from November 2011 to August 2014. MT for each participant consisted of two high-velocity low-amplitude spinal manipulations, as well as two grade IV mobilizations of the lumbar spine and pelvis targeted toward the third lumbar vertebra and sacroiliac joint in a side-lying position; the order of these treatments was randomized. Pelvis and thorax kinematic data were used to derive the time-varying lumbar angle in the sagittal plane for each STS trial. The difference between the maximum and minimum lumbar angles during the STS trial determined the sagittal ROM that was used as the biomechanical outcome. Time to complete each STS trial was used as a functional measure of performance. Pre-MT and post-MT values for the lumbar sagittal ROM and time to completion were statistically analysed using paired samples t-tests.

Results

Data were obtained from 40 participants with 35 useful datasets (NRS = 3.3 ± 1.2; 32.4 ± 9.8 years; 16 females, 19 males). After MT, lumbar sagittal ROM increased by 2.7 ± 5.5 degrees (p = 0.007). Time to complete the STS test decreased by 0.4 ± 0.4 s (p < 0.001).

Discussion

These findings provide preliminary evidence that MT might influence the biomechanical and functional performance of an STS task in populations with LBP. The MT intervention in this study involved a combination of spinal manipulations and mobilizations. Future work will expand upon these data as a basis for targeted investigations on the effects of either spinal manipulation and mobilization on neuromuscular control and movement in populations with LBP.

Are neuromuscular adaptations present in people with recurrent spinal pain during a period of remission? A protocol for a systematic review

INTRODUCTION

The course of spinal pain (neck or low back pain) is often described as episodic and intermittent, with more than one-third of people continuing to experience episodic symptoms 1 year after first onset. Although ongoing neuromuscular adaptations could contribute to recurrent episodes of pain, no systematic review has synthesised evidence of ongoing neuromuscular changes in people with recurrent spinal pain during a period of symptom remission.

METHODS AND ANALYSIS

This protocol is developed and reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses-P, the Update of the Cochrane Back and Neck Group guidelines and the Methodological Expectations of Cochrane Intervention Reviews. PubMed, Web of Science, MEDLINE, EMBASE, CINAHL, ZETOC, Google Scholar, grey literature sources and key journals will be searched up to September 2019. Observational studies investigating neuromuscular changes in people with recurrent spinal pain during a period of remission will be included. Neuromuscular function will be considered under five outcome domains of muscle activity, spine kinematics, muscle properties, sensorimotor control and neuromuscular performance. Two independent reviewers will search, screen studies, extract data and assess risk of bias (Newcastle-Ottawa Scale). Data will be synthesised per outcome domain. Where clinical and methodological homogeneity across studies exists, a random-effects meta-analysis will be conducted. Otherwise, results will be synthesised narratively. The overall quality of evidence will be assessed using the Grading of Recommendations, Assessment, Development and Evaluation guidelines.

ETHICS AND DISSEMINATION

Findings of this review may aid the identification of factors that could contribute to spinal pain recurrence and aid the development of interventions for secondary prevention aimed at the restoration of optimal neuromuscular function. The results will be submitted for publication in a peer-reviewed journal and presented at conferences. No ethical approval was required.

PROSPERO REGISTRATION NUMBER

CRD42019141527.

Reduced Trunk Coupling in Persons With Recurrent Low Back Pain Is Associated With Greater Deep-to-Superficial Trunk Muscle Activation Ratios During the Balance-Dexterity Task

BACKGROUND

Motor control dysfunction persisting during symptom remission in persons with recurrent low back pain (LBP) may contribute to the recurrence of pain.

OBJECTIVES

To investigate trunk control in persons in remission from recurrent LBP and in back-healthy controls using a dynamic, internally driven balance task. No differences in task performance were expected between groups, but it was hypothesized that persons with recurrent LBP would exhibit greater trunk coupling, consistent with a trunk-stiffening strategy.

METHODS

In this cross-sectional controlled laboratory study, persons with and without recurrent LBP (n = 19 per group) completed the balance-dexterity task, which involved balancing on one limb in standing while compressing an unstable spring with the other. Task performance measures included center-of-pressure velocity under the stance limb and vertical force variability under the spring. Trunk coupling was quantified with the coefficient of determination (R²) of an angle-angle plot of thorax-pelvis frontal plane motion. Fine-wire and surface electromyography captured activations of paraspinals and abdominals.

RESULTS

There were no differences between groups for any task performance measure. The group in remission from recurrent LBP exhibited reduced trunk coupling, or more dissociated thorax and pelvis motion, compared to the healthy control group (P = .024). Trunk coupling in this group was associated moderately with the lumbar multifidus-to-erector spinae activation ratio (r = 0.618, P = .006) and weakly with the internal oblique-to-external oblique ratio (r = 0.476, P = .046).

CONCLUSION

The balance-dexterity task is a submaximal, internally driven unstable balance task during which more dissociated trunk motion was observed in persons in remission from recurrent LBP. Findings underscore the task-dependent nature of trunk control research and assessment in persons with recurrent LBP. J Orthop Sports Phys Ther 2019;49(12):887-898. Epub 15 May 2019. doi:10.2519/jospt.2019.8756.

Age- and sex-specific effects in paravertebral surface electromyographic back extensor muscle fatigue in chronic low back pain

The impact of aging on the back muscles is not well understood, yet may hold clues to both normal aging and chronic low back pain (cLBP). This study sought to investigate whether the median frequency (MF) surface electromyographic (SEMG) back muscle fatigue method—a proxy for glycolytic muscle metabolism—would be able to detect age- and sex-specific differences in neuromuscular and muscle metabolic functions in individuals with cLBP in a reliable way, and whether it would be as sensitive as when used on healthy individuals. With participants seated on a dynamometer (20° trunk anteflexion), paraspinal SEMG activity was recorded bilaterally from the multifidus (L5), longissimus (L2), and iliolumbalis (L1) muscles during isometric, sustained back extensions loaded at 80% of maximum from 117 younger (58 females) and 112 older (56 female) cLBP individuals. Tests were repeated after 1–2 days and 6 weeks. Median frequency, the SEMG variable indicating neuromuscular fatigue, was analyzed. Maximum back extensor strength was comparable between younger and older participants. Significantly less MF-SEMG back muscle fatigue was observed in older as compared to younger, and in older female as compared to older male cLBP individuals. Relative reliability was excellent, but absolute reliability appeared large for this SEMG-fatigue measure. Findings suggest that cLBP likely does not mask the age-specific diagnostic potential of the MF-SEMG back extensor fatigue method. Thus, this method possesses a great potential to be further developed into a valuable biomarker capable of detecting back muscle function at risk of sarcopenia at very early stages.

Avoidance Behavioral Difference in Acquisition and Extinction of Pain-Related Fear

Fear of movement-related pain leads to two types of avoidance behavior: excessive avoidance and pain-inhibited movement. Excessive avoidance is an absence of movement by fear, and pain-inhibited movements involve a change in motor behavior for the purpose of protecting the painful part. Here, we sought to clarify the acquisition process and adaptation of fear for each avoidance behavior. Thirty-one female and 13 male (age 20.9 ± 2.1 years) subjects could decide persistent behaviors: approach with an intense pain stimulus, pain-inhibited movement with weak pain stimulus, or excessive avoidance with no pain in acquisition and test phases. In the subsequent extinction phase, the pain stimulus was omitted. Subjects were divided into an approach group (n = 24), a pain-inhibited movement group (n = 10), and an excessive avoidance group (n = 10) by cluster analysis. The response latencies in approach and pain-inhibited movement groups were not affected by conditioned pain. The subjects in the excessive avoidance group exhibited delayed response latencies, and their high-fear responses remained in the acquisition, test, and extinction phases. In addition, the excessive avoidance group showed high harm avoidance and high trait anxiety. This study demonstrated that differences in pain-related avoidance behaviors are affected by psychological traits. Pain-related excessive avoidance behavior indicated a maladaptive fear, but pain-inhibited movement did not.

Concurrent validity of a wearable IMU for objective assessments of functional movement quality and control of the lumbar spine

Inertial measurement units (IMUs) are being recognized in clinical and rehabilitation settings for their ability to assess movement-related disorders of the spine for better guidance of treatment-planning and tracking of recovery. This study evaluated the Mbientlab MetaMotionR IMUs, relative to Vicon motion capture equipment in measuring local dynamic stability of the spine (quantified using maximum finite-time Lyapunov exponent; λ_max), lumbopelvic coordination (quantified using mean absolute relative phase; MARP), and intersegmental motor variability (quantified using deviation phase; DP) of lumbopelvic segments in 10 participants during 35 cycles of repetitive spine flexion-extension (FE). Intraclass correlations were strong between systems when using both the FE angle time-series and the sum of squares (SS) time-series to measure local dynamic stability (0.807 ≤ICC_2,1^λmax,FE ≤ 0.919; 0.738 ≤ ICC_2,1^λmax,SS ≤ 0.868), sagittal-plane lumbopelvic coordination (0.961 ≤ICC_2,1^MARP ≤ 0.963), and sagittal-plane lumbopelvic variability (0.961 ≤ICC_2,1^DP ≤ 0.963). It was concluded that the MetaMotionR IMUs can be reliably used for measuring features associated with spine movement quality and motor control during a repetitive FE task. Future work will assess the reliability of sensor placement, performance during multi-directional movements, and ability to discern clinical and healthy populations based on assessment of movement quality and control.

The Evolving Case Supporting Individualised Physiotherapy for Low Back Pain

Low-back pain (LBP) is one of the most burdensome health problems in the world. Guidelines recommend simple treatments such as advice that may result in suboptimal outcomes, particularly when applied to people with complex biopsychosocial barriers to recovery. Individualised physiotherapy has the potential of being more effective for people with LBP; however, there is limited evidence supporting this approach. A series of studies supporting the mechanisms underpinning and effectiveness of the Specific Treatment of Problems of the Spine (STOPS) approach to individualised physiotherapy have been published. The clinical and research implications of these findings are presented and discussed. Treatment based on the STOPS approach should also be considered as an approach to individualised physiotherapy in people with LBP.

Time to Reflect on the Role of Motor Control in Low Back Pain

The articles in this special issue on low back pain are the outcome of work undertaken by a series of working parties established during the meeting, "State-of-the-Art in Motor Control and Low Back Pain: International Clinical and Research Expert Forum," held in Chicago in October 2015. This multidisciplinary meeting provided an opportunity for discussion of key issues that interconnect motor control, pain, and the spine. What started as a relatively straightforward objective to summarize the field subsequently developed into an extensive process of literature review and discussion that culminated in the commentaries and articles presented in this special issue. We hope that the up-to-date information and in-depth insights into pain, motor control, and rehabilitation provide novel insights and a clear trajectory for future work and form the foundation for ongoing lively discussion. J Orthop Sports Phys Ther 2019;49(6):367-369. doi:10.2519/jospt.2019.0104.

Analysis of Motor Control in Patients With Low Back Pain: A Key to Personalized Care?

Motor control exercise has been shown to be effective in the management of low back pain (LBP). However, the effect sizes for motor control exercise are modest, possibly because studies have used a one-size-fits-all approach, while the literature suggests that patients may differ in presence or type of motor control issues. In this commentary, we address the question of whether consideration of such variation in motor control issues might contribute to more personalized motor control exercise for patients with LBP. Such an approach is plausible, because motor control changes may play a role in persistence of pain through effects on tissue loading that may cause nociceptive afference, particularly in the case of peripheral sensitization. Subgrouping systems used in clinical practice, which comprise motor control aspects, allow reliable classification that is, in part, aligned with findings in studies on motor control in patients with LBP. Motor control issues may have heuristic value for treatment allocation, as the different presentations observed suggest different targets for motor control exercise, but this remains to be proven. Finally, clinical assessment of patients with LBP should take into account more aspects than motor control alone, including pain mechanisms, musculoskeletal health, and psychosocial factors, and may need to be embedded in a stratification approach based on prognosis to avoid undue diagnostic procedures. J Orthop Sports Phys Ther 2019;49(6):380-388. Epub 12 Jun 2018. doi:10.2519/jospt.2019.7916.

Differences in brain processing of proprioception related to postural control in patients with recurrent non-specific low back pain and healthy controls

Patients with non-specific low back pain (NSLBP) show an impaired postural control during standing and a slower performance of sit-to-stand-to-sit (STSTS) movements. Research suggests that these impairments could be due to an altered use of ankle compared to back proprioception. However, the neural correlates of these postural control impairments in NSLBP remain unclear. Therefore, we investigated brain activity during ankle and back proprioceptive processing by applying local muscle vibration during functional magnetic resonance imaging in 20 patients with NSLBP and 20 controls. Correlations between brain activity during proprioceptive processing and (Airaksinen et al., 2006) proprioceptive use during postural control, evaluated by using muscle vibration tasks during standing, and (Altmann et al., 2007) STSTS performance were examined across and between groups. Moreover, fear of movement was assessed. Results revealed that the NSLBP group performed worse on the STSTS task, and reported more fear compared to healthy controls. Unexpectedly, no group differences in proprioceptive use during postural control were found. However, the relationship between brain activity during proprioceptive processing and behavioral indices of proprioceptive use differed significantly between NSLBP and healthy control groups. Activity in the right amygdala during ankle proprioceptive processing correlated with an impaired proprioceptive use in the patients with NSLBP, but not in healthy controls. Moreover, while activity in the left superior parietal lobule, a sensory processing region, during back proprioceptive processing correlated with a better use of proprioception in the NSLBP group, it was associated with a less optimal use of proprioception in the control group. These findings suggest that functional brain changes during proprioceptive processing in patients with NSLBP may contribute to their postural control impairments.

Abnormal performance of cervical stabilizer muscles in individuals with low back pain

Objectives: To compare the performance of cervical stabilizer muscles using the craniocervical flexion test (CCFT) among individuals with subacute, chronic, and asymptomatic low back pain (LBP) conditions. Methods: Individuals with subacute (N = 23) and chronic LBP (N = 23) with their age- and gender-matched controls (N = 30) participated in this study. All recruited participants were required to perform the CCFT. The activation score (AS) and the performance index (PI) were recorded by an assessor who was blinded to the group of participants. Results: Approximately, 74% of subacute LBP participants and 60-65% of chronic LBP participants obtained abnormal AS and PI. AS was significantly lower in participants with subacute (P = 0.0002) and chronic LBP (P = 0.0009) than the control group. Likewise, the PI was significantly lower in participants with subacute (P = 0.0002) and chronic LBP (P = 0.0036) than the control group. Participants in the subacute LBP group showed significantly greater percentages of abnormal responses on the AS (P < 0.0001) and the PI (P = 0.0001) than the control. Discussion: Abnormal performance of cervical stabilizer muscles using the CCFT was demonstrated in a high proportion of participants with LBP. The findings highlight the plausible association in muscle control between cervical and lumbar stabilizers. Level of Evidence: 2b.