Vestibular control of deep and superficial lumbar muscles.

The active control of the lumbar musculature provides a stable platform critical for postures and goal-directed movements. Voluntary and perturbation-evoked motor commands can recruit individual lumbar muscles in a task-specific manner according to their presumed biomechanics. Here, we investigated the vestibular control of the deep and superficial lumbar musculature. Ten healthy participants were exposed to noisy electrical vestibular stimulation while balancing upright with their head facing forward, left, or right to characterize the differential modulation in the vestibular-evoked lumbar extensor responses in generating multidirectional whole body motion. We quantified the activation of the lumbar muscles on the right side using indwelling [deep multifidus, superficial multifidus, caudal longissimus (L4), and cranial longissimus (L1)] and high-density surface recordings. We characterized the vestibular-evoked responses using coherence and peak-to-peak cross-covariance amplitude between the vestibular and electromyographic signals. Participants exhibited responses in all lumbar muscles. The vestibular control of the lumbar musculature exhibited muscle-specific modulations: responses were larger in the longissimus (combined cranio-caudal) compared with the multifidus (combined deep-superficial) when participants faced forward (P < 0.001) and right (P = 0.011) but not when they faced left. The high-density surface recordings partly supported this observation: the location of the responses was more lateral when facing right compared with left (P < 0.001). The vestibular control of muscle subregions within the longissimus or the multifidus was similar. Our results demonstrate muscle-specific vestibular control of the lumbar muscles in response to perturbations of vestibular origin. The lack of differential activation of lumbar muscle subregions suggests the vestibular control of these subregions is co-regulated for standing balance.NEW & NOTEWORTHY We investigated the vestibular control of the deep and superficial lumbar extensor muscles using electrical vestibular stimuli. Vestibular stimuli elicited preferential activation of the longissimus muscle over the multifidus muscle. We did not observe clear regional activation of lumbar muscle subregions in response to the vestibular stimuli. Our findings show that the central nervous system can finely tune the vestibular control of individual lumbar muscles and suggest minimal regional variations in the activation of lumbar muscle subregions.

Effect of movement-evoked and tonic experimental pain on muscle force production.

INTRODUCTION: When performing an exercise or a functional test, pain that is evoked by movement or muscle contraction could be a stronger stimulus for changing how individuals move compared to tonic pain. We investigated whether the decrease in muscle force production is larger when experimentally-induced knee pain is directly associated to the torque produced (movement-evoked) compared to a constant painful stimulation (tonic). METHODS: Twenty-one participants performed three isometric knee extension maximal voluntary contractions without pain (baseline), during pain, and after pain. Knee pain was induced using sinusoidal electrical stimuli at 10 Hz over the infrapatellar fat pad, applied continuously or modulated proportionally to the knee extension torque. Peak torque and contraction duration were averaged across repetitions and normalized to baseline. RESULTS: During tonic pain, participants reported lower pain intensity during the contraction than at rest (p < 0.001), whereas pain intensity increased with contraction during movement-evoked pain (p < 0.001). Knee extension torque decreased during both pain conditions (p < 0.001), but a larger reduction was observed during movement-evoked compared to tonic pain (p < 0.001). Participants produced torque for longer during tonic compared to movement-evoked pain (p = 0.005). CONCLUSION: Our results indicate that movement-evoked pain was a more potent stimulus to reduce knee extension torque than tonic pain. The longer contraction time observed during tonic pain may be a result of a lower perceived pain intensity during muscle contraction. Overall, our results suggest different motor adaptation to tonic and movement-evoked pain and support the notion that motor adaptation to pain is a purposeful strategy to limit pain. This mechanistic evidence suggests that individuals experiencing prevalently tonic or movement-evoked pain may exhibit different motor adaptations, which may be important for exercise prescription.

Remote assessment of pelvic kinematics during single leg squat using smartphone sensors: Between-day reliability and identification of acute changes in motor performance.

The biomechanical assessment of pelvic kinematics during a single leg squat (SLS) commonly relies on expensive equipment, which precludes its wider implementation in ecological settings. Smartphone sensors could represent an effective solution to objectively quantify pelvic kinematics remotely, but their measure properties need to be evaluated before advocating their use in practice. This study aimed to assess whether measures of pelvic kinematics collected remotely using smartphones during SLS are repeatable between days, and if changes in pelvic kinematics can be identified during an endurance task. Thirty-three healthy young adults were tested remotely on two different days using their own smartphones placed on the lumbosacral region. Pelvic orientation and acceleration were collected during three sets of seven SLS and an endurance task of twenty consecutive SLS. The intersession reliability was assessed using Intraclass Correlation Coefficient (ICC2,k), Standard Error of Measurement, and Minimal Detectable Change. T-tests were used to identify pelvic kinematics changes during the endurance task and to assess between-day bias. Measures of pelvic orientation and frequency features of the acceleration signals showed good to excellent reliability (multiple ICC2,k ≥ 0.79), and a shift of the power spectrum to lower frequencies on the second day (multiple p<0.05). The endurance task resulted in larger contralateral pelvic drop and rotation (multiple p<0.05) and increased spectral entropy (multiple p<0.05). Our findings demonstrate that reliable measures of pelvic kinematics can be obtained remotely using participants' smartphones during SLS. Smartphone sensors can also identify changes in motor control, such as contralateral pelvic drop during an endurance task.

Cervical musculoskeletal impairments and pressure pain sensitivity in office workers with headache.

BACKGROUND: Office workers are specifically vulnerable to headache conditions. Neck pain is reported by almost 80% of patients with headaches. Associations between currently recommended tests to examine cervical musculoskeletal impairments, pressure pain sensitivity and self-reported variables in headache, are unknown. The aim of this study is to evaluate whether cervical musculoskeletal impairments and pressure pain sensitivity are associated with self-reported headache variables in office workers. METHODS: This study reports a cross-sectional analysis using baseline data of a randomized controlled trial. Office workers with headache were included in this analysis. Multivariate associations, controlled for age, sex and neck pain, between cervical musculoskeletal variables (strength, endurance, range of motion, movement control) and pressure pain threshold (PPT) over the neck and self-reported headache variables, such as frequency, intensity, and the Headache-Impact-Test-6, were examined. RESULTS: Eighty-eight office workers with a 4-week headache frequency of 4.8 (±5.1) days, a moderate average headache intensity (4.5 ± 2.1 on the NRS), and "some impact" (mean score: 53.7 ± 7.9) on the headache-impact-test-6, were included. Range of motion and PPT tested over the upper cervical spine were found to be most consistently associated with any headache variable. An adjusted R2 of 0.26 was found to explain headache intensity and the score on the Headache-Impact-Test-6 by several cervical musculoskeletal and PPT variables. DISCUSSION: Cervical musculoskeletal impairments can explain, irrespective of coexisting neck pain, only little variability of the presence of headache in office workers. Neck pain is likely a symptom of the headache condition, and not a separate entity.

Lumbar muscle adaptations to external perturbations are modulated by trunk posture.

PURPOSE: To investigate if the recruitment of different regions within the lumbar extensor muscles in response to unexpected perturbations depends on trunk posture. METHODS: In a semi-seated posture, healthy adult participants experienced unexpected posterior-anterior trunk perturbations in three different postures: neutral, trunk flexion and left trunk rotation. High-density surface electromyography was used to identify the regional distribution of activation within the lumbar erector spinae muscles. The effect of posture and side (left vs right) on muscle activity and centroid coordinates was investigated at baseline and in response to perturbations. RESULTS: Higher muscle activity was observed in trunk flexion compared to neutral and rotation postures at baseline (multiple p < 0.001) and in response to the perturbation (multiple p < 0.01). At baseline, the centroid of the electromyographic amplitude distribution was localized more medially in trunk flexion compared to trunk neutral posture (p = 0.003), while activation was localized more laterally in response to the perturbation (multiple p < 0.05). When the trunk was rotated, the electromyographic amplitude distribution was localized more cranially on the left than the right side, both at baseline (p = 0.001) and in response to the perturbation (p = 0.001). Finally, a more lateral location of the centroid on the left side in rotation compared to neutral posture was observed in response to the perturbation (multiple p < 0.001). CONCLUSIONS: Regional differences in the distribution of electromyographic amplitude indicate that different muscle regions were recruited in different trunk postures and in response to perturbations, possibly based on regional mechanical advantage of the erector spinae muscle fibers.

Comparison between two patient-reported outcome measures for patients with cervical radiculopathy: A think-aloud study.

BACKGROUND: The Cervical Radiculopathy Impact Scale (CRIS) and Patient Specific Functional Scale 2.0 (PSFS 2.0) are patient-reported outcome measures (PROMs) used to assess activity limitations in patients with cervical radiculopathy (CR). This study a) compared the CRIS subscale 3 and the PSFS 2.0 in patients with CR with respect to completeness and patient preference, b) established the correlation between both PROMs in assessing the individual patient's level of functional limitations and c) assessed the frequency of reported functional limitations. METHODS: Participants with CR participated in semi-structured, individual, face-to-face interviews as part of a "think-aloud" process; verbalising their thoughts while completing both PROMs. Sessions were digitally recorded and transcribed verbatim for analysis. RESULTS: Twenty-two patients were recruited. The most frequently reported functional limitation on the CRIS was: 'working at a computer' (n = 17) and overhead activities' (n = 10) for the PSFS 2.0. There was significant moderate positive correlation between the scores on the PSFS 2.0 and the CRIS (Spearman's r = 0.55, n = 22 p = .008). Most patients (n = 18; 82%) preferred the ability to present their own individual functional limitations of the PSFS 2.0. Eleven participants (50%) preferred the 11-point scale of the PSFS 2.0 over the 5-point Likert scale scoring option of the CRIS. CONCLUSION: Both easy to complete PROMs capture functional limitations in patients with CR. Most patients prefer the PSFS 2.0 over the CRIS. The wording and layout of both PROMs need refinement to enhance user-friendliness and avoid misinterpretation.

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

ABSTRACT: Experimental pain models are frequently used to understand the influence of pain on the control of human movement. In this systematic review, we assessed the effects of experimentally induced pain in the lumbar region of healthy individuals on trunk muscle activity and spine kinematics. Databases were searched from inception up to January 31, 2022. In total, 26 studies using either hypertonic saline injection (n = 19), heat thermal stimulation (n = 3), nociceptive electrical stimulation (n = 3), or capsaicin (n = 1) were included. The identified adaptations were task dependent, and their heterogeneity was partially explained by the experimental pain model adopted. Meta-analyses revealed an increase of erector spinae activity (standardized mean difference = 0.71, 95% confidence interval [CI] = 0.22-1.19) during full trunk flexion and delayed onset of transversus abdominis to postural perturbation tasks (mean difference = 25.2 ms, 95% CI = 4.09-46.30) in the presence of pain. Low quality of evidence supported an increase in the activity of the superficial lumbar muscles during locomotion and during voluntary trunk movements during painful conditions. By contrast, activity of erector spinae, deep multifidus, and transversus abdominis was reduced during postural perturbation tasks. Reduced range of motion of the lumbar spine in the presence of pain was supported by low quality of evidence. Given the agreement between our findings and the adaptations observed in clinical populations, the use of experimental pain models may help to better understand the mechanisms underlying motor adaptations to low back pain.

Between-day reliability of trunk orientation measured with smartphone sensors during sit-to-stand in asymptomatic individuals.

BACKGROUND: Trunk kinematics during sit-to-stand is often impaired in individuals with musculoskeletal disorders. Trunk kinematics is commonly assessed in laboratories using motion capture; however, this equipment is often not available outside research centers. Smartphones are widely available and may be a suitable alternative to assess trunk orientation during sit-to-stand remotely. OBJECTIVES: We investigated whether trunk orientation in the sagittal plane during sit-to-stand can be measured reliably between days when collected remotely using smartphones. DESIGN: Cross-sectional study. METHOD: Forty-three asymptomatic participants performed 15 sit-to-stand movements in two separate sessions remotely over videoconferencing. Trunk orientation was measured using each participant's smartphone. Absolute peak trunk orientation in the sagittal plane was extracted during standing, sitting, stand up and sit down. Relative trunk orientation was calculated as the difference between sitting and stand up, or sitting and sit down. Reliability was assessed using Intraclass Correlation Coefficient (ICC2,k), Standard Error of Measurement (SEM) and Minimal Detectable change (MDC). Between day bias and between-gender differences were assessed using T tests. RESULTS: All measures showed good reliability (ICC2,k > 0.80; SEM < 5.6°; MDC < 13.6°) and no between-day bias (p > 0.31). Relative measures were more consistent (ICC2,k > 0.88; SEM < 3.6°; MDC < 9.9°). No between-gender differences were observed for relative orientation (p > 0.75). CONCLUSIONS: Sagittal trunk orientation during sitting, standing, and sit-to-stand can be measured reliably when asymptomatic individuals use their own smartphones supervised over videoconferencing. These findings support the use of smartphone sensors for assessing how trunk orientation changes over time, which may assist physiotherapists assess movement patterns of individuals with musculoskeletal disorders remotely.

Conservative management for lumbar radiculopathy based on the stage of the disorder: a Delphi study.

PURPOSE: Conservative management of lumbar radiculopathy (LR) is the first treatment option. To date, systematic reviews and clinical practice guidelines have not considered the most appropriate timing of management. This study aimed to establish consensus on effective conservative treatment modalities across different stages (i.e., acute, sub-acute, or chronic) of LR. MATERIALS AND METHODS: Through an iterative multistage Delphi process, experts rated agreement with proposed treatment modalities across stages of LR and could suggest additional treatment modalities. The agreement was measured using a 5-point Likert scale. Descriptive statistics were used to measure agreement (median, interquartile ranges, and percentage of agreement). Consensus criteria were defined a priori for each round. RESULTS: Fourteen panelists produced a consensus list of effective treatment modalities across stages of LR. Acute stage management should focus on providing patients with information about the condition including pain education, individualized physical activity, and directional preference exercises, supported with NSAIDs. In the sub-acute stage, strength training and neurodynamic mobilization could be added and transforaminal/epidural injections considered. In the chronic stage, spinal manipulative therapy, specific exercise, and function-specific physical training should be combined with individualized vocational, ergonomic and postural advice. CONCLUSIONS: Experts agree effectiveness of interventions differs through the evolution of LR.IMPLICATIONS FOR REHABILITATIONTo date clinical guideline for conservative management of lumbar radiculopathy do not consider the evolution of the condition.Acute stage management of lumbar radiculopathy should focus on providing information about the condition and support individualized physical activity with pain medication.Sub-acute management should add neurodynamic mobilization to strength training, while transforaminal and/or epidural injections could be considered.Chronic stage management should consider spinal manipulative therapy and focus on restoring personalized functional capacity.

Inter-rater reliability, discriminatory and predictive validity of neck movement control tests in office workers with headache and/or neck pain.

BACKGROUND: Movement control tests (MCTs) are clinical tests to evaluate impairment of movement and associated neuromuscular control and are commonly used to evaluate people with neck pain or headache conditions. The aim of this study was to establish inter-rater reliability as well as discriminatory and predictive validity for seven MCTs of the upper (UCS) and lower cervical spine (LCS) in office workers with headache or neck pain. METHODS: Seven MCTs of the UCS (3) and LCS (4) were performed at baseline on 140 office workers which were included in a cluster randomized controlled trial. The occurrences of headache and neck pain were established at baseline (discriminatory validity) and at a 15-month follow-up (predictive validity). Inter-rater-reliability was established in a separate cross-sectional study. RESULTS: MCTs showed slight to almost perfect inter-rater reliability but limited discriminatory (baseline) and limited to small predictive validity (15-month follow up) for different subgroups of office workers with headache and/or neck pain. MCTs of the UCS showed limited discriminatory validity, especially for rotation in participants with headache and neck pain compared to those with headache only (Negative Likelihood-ratio: 0.82, 95% CI: 0.69-0.98). Participants with neck pain only and ≥1/4 positive MCTs for the sagittal plane had an increased risk for future neck pain (Relative risk: 3.33, 95% CI: 1.05-10.56). DISCUSSION: MCTs of the UCS and LCS are reliable but have only limited to small validity to predict future headache events in office workers. Insufficient sagittal plane movement control may predict neck pain relapses in the future.

Perceived pain and disability but not fear of movement are associated with altered cervical kinematics in people with acute neck pain following a whiplash injury.

OBJECTIVES: To determine if measures of cervical kinematics are altered in people with acute whiplash associated disorders (WAD) and secondarily, to examine whether kinematic variables are associated with self-reported outcomes. METHODS: We recruited people with acute WAD within 15 days after a motor vehicle collision and asymptomatic control participants. All participants performed active neck movements at a self-determined velocity. Maximal range of motion (ROM), peak and mean velocity of movement, smoothness of movement, and cervical joint position error were assessed. Moreover, self-reported measures of perceived pain and disability, pain catastrophising, and fear of movement were obtained. RESULTS: Sixty people participated: 18 with acute WAD (mean age [SD] 38.7 [12.0]) and 42 as asymptomatic controls (mean age [SD] 38.4 [10.2]). Participants with acute WAD showed significantly decreased ROM in all movement directions (p < 0.0001). All participants with acute WAD showed a reduction in the mean and peak velocity of movement in all directions (p < 0.0001) and the number of velocity peaks was significantly higher (i.e., reduced smoothness of movement) in those with acute WAD in all directions (p < 0.0001). Repositioning acuity following cervical rotation was not significantly different between groups. Neck pain-related disability showed the largest number of significant associations with kinematic features, while fear of movement was not associated with measures of cervical kinematics. CONCLUSIONS: Participants with acute WAD presented with altered cervical kinematics compared to asymptomatic participants. Several measures of cervical kinematics were associated with the level of pain and disability in people with acute WAD but not their fear of movement.

Assessment of Neuromuscular and Psychological Function in People with Recurrent Neck Pain during a Period of Remission: Cross-Sectional and Longitudinal Analyses.

The aim of this study was to examine for the presence of differences in neuromuscular and psychological function in individuals with recurrent neck pain (RNP) or chronic neck pain (CNP) following a whiplash trauma compared to healthy controls. A secondary aim was to examine whether neuromuscular characteristics together with psychological features in people with RNP were predictive of future painful episodes. Multiple features were assessed including neck disability, kinesiophobia, quality of life, cervical kinematics, proprioception, activity of superficial neck flexor muscles, maximum neck flexion and extension strength, and perceived exertion during submaximal contractions. Overall, those with RNP (n = 22) and CNP (n = 8) presented with higher neck disability, greater kinesiophobia, lower quality of life, slower and irregular neck movements, and less neck strength compared to controls (n = 15). Prediction analysis in the RNP group revealed that a higher number of previous pain episodes within the last 12 months along with lower neck flexion strength were predictors of higher neck disability at a 6-month follow-up. This preliminary study shows that participants with RNP presented with some degree of altered neuromuscular features and poorer psychological function with respect to healthy controls and these features were similar to those with CNP. Neck flexor weakness was predictive of future neck disability.

Consensus for experimental design in electromyography (CEDE) project: High-density surface electromyography matrix.

High-density surface electromyography (HDsEMG) can be used to measure the spatial distribution of electrical muscle activity over the skin. As this distribution is associated with the generation and propagation of muscle fiber action potentials, HDsEMG is processed to extract information on regional muscle activation, muscle fiber characteristics and behaviour of individual motor units. This matrix, developed by the Consensus for Experimental Design in Electromyography (CEDE) project, summarizes recommendations on the use of HDsEMG in experimental studies. For each application, recommendations are included regarding electrode montage, electrode type and configuration, electrode location and orientation, data analysis, and interpretation. Cautions and reporting standards are also included. The steps of the Delphi process to reach consensus are contained in an appendix. This matrix is intended to help researchers when collecting, reporting, and interpreting HDsEMG data. It is hoped that this document will be used to generate new empirical evidence to improve how HDsEMG is used in research and in clinical applications.

Timing of Evidence-Based Nonsurgical Interventions as Part of Multimodal Treatment Guidelines for the Management of Cervical Radiculopathy: A Delphi Study.

OBJECTIVE: Conservative management of cervical radiculopathy (CR) is a first treatment option because the risk-benefit ratio for surgery is less favorable. Systematic reviews and clinical practice guidelines reporting on the effectiveness of nonsurgical management have not considered the timing of management. The aim of this study was to establish consensus on effective nonsurgical treatment modalities at different stages (ie, acute, subacute, or chronic) of CR using the Delphi method approach. METHODS: Through an iterative multistage process, experts within the field rated their agreement with a list of proposed treatment modalities according to the stage of CR and could suggest missing treatment modalities. Agreement was measured using a 5-point Likert scale. Descriptive statistics were used to measure agreement (median, interquartile ranges, and percentage of agreement). Consensus criteria were defined a priori for each round. Consensus for Round 3 was based on ≥2 of the following: a median Likert scale value of ≥4, interquartile range value of ≤1, and/or a percentage of agreement ≥70%. RESULTS: Data analysis produced a consensus list of effective treatment modalities in different stages of recovery. CONCLUSION: According to experts, the focus of multimodal management in the acute stage should consist of patient education and spinal manipulative therapy, specific (foraminal opening) exercises, and sustained pain-relieving positions. In the subacute stage, increasing individualized physical activity including supervised motor control, specific exercises, and/or neurodynamic mobilization could be added. In the chronic stage, focus should shift to include general aerobic exercise as well as focused strength training. Postural education and vocational ergonomic assessment should also be considered. IMPACT: Multimodal conservative management of individuals with CR should take the stage of the condition into consideration. The focus of therapeutic interventions should shift from passive pain-relieving intervention in the acute stage to increasingly more individualized physical activity and self-management in the chronic stage.

Are Measures of Physical Function of the Neck Region Associated With Poor Prognosis Following a Whiplash Trauma?: A Systematic Review.

OBJECTIVE: The objective of this study was to synthesize the current evidence regarding the predictive ability of measures of physical function (PF) of the neck region and perceived PF on prognosis following a whiplash injury. MATERIALS AND METHODS: Electronic databases were searched by 2 independent reviewers up to July 2020, including MEDLINE, EMBASE, CINAHL, PsycINFO, Scopus, and Web of Science as well as gray literature. Eligible studies were selected by 2 reviewers who then extracted and assessed the quality of evidence. Observational cohort studies were included if they involved participants with acute whiplash-associated disorders (WAD), followed for at least 3 months postinjury, and included objective measures of neck PF or self-reported measures of PF as prognostic factors. Data could not be pooled and therefore were synthesized qualitatively. RESULTS: Fourteen studies (13 cohorts) were included in this review. Low to very low quality of evidence indicated that initial higher pain-related disability and higher WAD grade were associated with poor outcome, while there was inconclusive evidence that neck range of motion, joint position error, activity of the superficial neck muscles, muscle strength/endurance, and perceived functional capacity are not predictive of outcome. The predictive ability of more contemporary measures of neck PF such as the smoothness of neck movement, variability of neck motion, and coactivation of neck muscles have not been assessed. DISCUSSION: Although initial higher pain-related disability and higher WAD grade are associated with poor outcome, there is little evidence available investigating the role of neck PF on prognosis following a whiplash injury.

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.

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.

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 4th 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.

Novel Insights Into Biarticular Muscle Actions Gained From High-Density Electromyogram.

Biarticular muscles have traditionally been considered to exhibit homogeneous neuromuscular activation. The regional activation of biarticular muscles, as revealed from high-density surface electromyograms, seems however to discredit this notion. We thus hypothesize the regional activation of biarticular muscles may contribute to different actions about the joints they span. We then discuss the mechanistic basis and methodological implications underpinning our hypothesis.

Timing of evidence-based non-surgical interventions as part of multimodal treatment guidelines for the management of cervical radiculopathy: a Delphi study protocol.

INTRODUCTION: Cervical radiculopathy (CR) is a clinical condition whereby motor, reflex and/or sensory changes such as radicular pain, paraesthaesia or numbness can exist. Conservative management is a preferred first treatment option as the risk-benefit ratio for surgery is less favourable. Systematic reviews and treatment guidelines gather evidence on the effectiveness of non-surgical management of patients with CR from randomised controlled trials, which do not consider the natural course of recovery to modify the management strategy accordingly. The aim of this study is to establish consensus on effective non-surgical treatment modalities for patients in different stages (acute, subacute and chronic) of CR, using the Delphi method approach. METHODS AND ANALYSIS: Through an iterative multistage process, experts within the field will rate their agreement with a list of proposed treatment modalities and suggest any missing treatment modalities during each round. Agreement will be measured using a five-point Likert scale. Descriptive statistics will be used to measure agreement (median, IQR and percentage of agreement). Consensus criteria will be defined a priori for each round. Data analysis at the end of round three will produce a consensus list of effective treatment modalities for the management of patients with CR in different stages of recovery. ETHICS AND DISSEMINATION: Ethical approval has been granted from the University of Birmingham ethics committee under ERN_20-1121. The study findings will be submitted to a peer-reviewed journal and to relevant conferences for dissemination of the study results.