Efficacy of a Psychologically-Informed Physiotherapy Intervention in Patients with Chronic Low Back Pain at High Risk of Poor Prognosis: A Pilot and Feasibility Randomized Controlled Trial.

Purpose: To determine the feasibility of a randomized controlled trial (RCT) testing the efficacy of psychologically-informed physiotherapy (PIPT), which includes usual physiotherapy (UP) interventions, compared with UP, and to explore the preliminary effectiveness of the interventions. Method: People with chronic low back pain at high risk of poor prognosis (using the STarT Back screening tool) were recruited and allocated to PIPT or UP. Effectiveness of recruitment strategies, adherence to intervention, risk of contamination, and specific challenges were assessed. Functional capacity, pain, quality of life, kinesiophobia, catastrophization, central sensitization, and self-efficacy were measured at baseline, 6-, 12- and 24-week follow-ups. Results: Forty participants were recruited mainly by diffusing through Laval University's email list, and 10 physiotherapists treated the participants recruited. The retention rate of participants at 24 weeks was 72.5%. Adherence to treatment by participants and physiotherapists was very good. The risk of contamination was low, and the specific challenges identified were modifiable. Significant improvement over time in all clinical variables of interest, except self-efficacy, was observed with no difference between groups. Conclusions: As most success criteria were met, conducting an RCT evaluating PIPT and PU is feasible with modifications. PIPT and UP appear to be similarly effective.

Objectif: déterminer la faisabilité d'une étude randomisée et contrôlée (ÉRC) évaluant l'efficacité de la physiothérapie fondée sur la psychologie (PTFP), qui inclut les interventions de physiothérapie conventionelle (PC), par rapport à la PC, et explorer l'efficacité préliminaire des interventions. Méthodologie: les chercheurs ont recruté des personnes qui souffrent de douleurs lombaires chroniques, ayant une probabilité élevée de mauvais pronostic (au moyen de l'outil de dépistage STarT Back) et les ont réparties entre la PTFP et la PC. Ils ont évalué l'efficacité des stratégies de recrutement, l'adhésion à l'intervention, le risque de contamination et les difficultés particulières. Ils ont également mesuré la capacité fonctionnelle, la douleur, la qualité de vie, la kinésiophobie, la catastrophisation, la sensibilisation centrale et l'autoefficacité en début d'étude ainsi que lors des suivis à six, 12 et 24 semaines. Résultats: les chercheurs ont recruté 40 participants, principalement en diffusant le projet par courriel à la communauté de l'Université Laval, et dix physiothérapeutes les ont traités. Le taux de rétention des participants était de 72,5 % à 24 semaines. Les participants et les physiothérapeutes ont démontré une très bonne adhésion au traitement. Le risque de contamination était faible, et les difficultés particulières constatées pouvaient être modifiées. Les chercheurs ont observé une amélioration considérable au fil du temps pour toutes les variables cliniques d'intérêt, sauf l'autoefficacité, sans différence entre les groupes. Conclusions: puisque la plupart des critères de succès étaient respectés, il est faisable de réaliser une ÉRC pour évaluer la PTFP et la PU, sous réserve de modifications. La PTFP et la PC semblent avoir une efficacité similaire.

Corticomotor Control of Lumbar Erector Spinae in Postural and Voluntary Tasks: The Influence of Transcranial Magnetic Stimulation Current Direction.

Lumbar erector spinae (LES) contribute to spine postural and voluntary control. Transcranial magnetic stimulation (TMS) preferentially depolarizes different neural circuits depending on the direction of electrical currents evoked in the brain. Posteroanterior current (PA-TMS) and anteroposterior (AP-TMS) current would, respectively, depolarize neurons in the primary motor cortex (M1) and the premotor cortex. These regions may contribute differently to LES control. This study examined whether responses evoked by PA- and AP-TMS are different during the preparation and execution of LES voluntary and postural tasks. Participants performed a reaction time task. A Warning signal indicated to prepare to flex shoulders (postural; n = 15) or to tilt the pelvis (voluntary; n = 13) at the Go signal. Single- and paired-pulse TMS (short-interval intracortical inhibition-SICI) were applied using PA- and AP-TMS before the Warning signal (baseline), between the Warning and Go signals (preparation), or 30 ms before the LES onset (execution). Changes from baseline during preparation and execution were calculated in AP/PA-TMS. In the postural task, MEP amplitude was higher during the execution than that during preparation independently of the current direction (p = 0.0002). In the voluntary task, AP-MEP amplitude was higher during execution than that during preparation (p = 0.016). More PA inhibition (SICI) was observed in execution than that in preparation (p = 0.028). Different neural circuits are preferentially involved in the two motor tasks assessed, as suggested by different patterns of change in execution of the voluntary task (AP-TMS, increase; PA-TMS, no change). Considering that PA-TMS preferentially depolarize neurons in M1, it questions their importance in LES voluntary control.

Towards data-driven biopsychosocial classification of non-specific chronic low back pain: a pilot study.

The classification of non-specific chronic low back pain (CLBP) according to multidimensional data could guide clinical management; yet recent systematic reviews show this has not been attempted. This was a prospective cross-sectional study of participants with CLBP (n = 21) and age-, sex- and height-matched pain-free controls (n = 21). Nervous system, lumbar spinal tissue and psychosocial factors were collected. Dimensionality reduction was followed by fuzzy c-means clustering to determine sub-groups. Machine learning models (Support Vector Machine, k-Nearest Neighbour, Naïve Bayes and Random Forest) were used to determine the accuracy of classification to sub-groups. The primary analysis showed that four factors (cognitive function, depressive symptoms, general self-efficacy and anxiety symptoms) and two clusters (normal versus impaired psychosocial profiles) optimally classified participants. The error rates in classification models ranged from 4.2 to 14.2% when only CLBP patients were considered and increased to 24.2 to 37.5% when pain-free controls were added. This data-driven pilot study classified participants with CLBP into sub-groups, primarily based on psychosocial factors. This contributes to the literature as it was the first study to evaluate data-driven machine learning CLBP classification based on nervous system, lumbar spinal tissue and psychosocial factors. Future studies with larger sample sizes should validate these findings.

The effect of skilled motor training on corticomotor control of back muscles in different presentations of low back pain.

Transcranial magnetic stimulation (TMS) has revealed differences in the motor cortex (M1) between people with and without low back pain (LBP). There is potential to reverse these changes using motor skill training, but it remains unclear whether changes can be induced in people with LBP or whether this differs between LBP presentations. This study (1) compared TMS measures of M1 (single and paired-pulse) and performance of a motor task (lumbopelvic tilting) between individuals with LBP of predominant nociceptive (n = 9) or nociplastic presentation (n = 9) and pain-free individuals (n = 16); (2) compared these measures pre- and post-training; and (3) explored correlations between TMS measures, motor performance, and clinical features. TMS measures did not differ between groups at baseline. The nociplastic group undershot the target in the motor task. Despite improved motor performance for all groups, only MEP amplitudes increased across the recruitment curve and only for the pain-free and nociplastic groups. TMS measures did not correlate with motor performance or clinical features. Some elements of motor task performance and changes in corticomotor excitability differed between LBP groups. Absence of changes in intra-cortical TMS measures suggests regions other than M1 are likely to be involved in skill learning of back muscles.

Nociceptive withdrawal reflexes of the trunk muscles in chronic low back pain.

Individuals with chronic low back pain (CLBP) move their spine differently. Changes in brain motor areas have been observed and suggested as a mechanism underlying spine movement alteration. Nociceptive withdrawal reflex (NWR) might be used to test spinal networks involved in trunk protection and to highlight reorganization. This study aimed to determine whether the organization and excitability of the trunk NWR are modified in CLBP. We hypothesized that individuals with CLBP would have modified NWR patterns and lower NWR thresholds. Noxious electrical stimuli were delivered over S1, L3 and T12, and the 8th Rib to elicit NWR in 12 individuals with and 13 individuals without CLBP. EMG amplitude and occurrence of lumbar multifidus (LM), thoracic erector spinae, rectus abdominus, obliquus internus and obliquus externus motor responses were recorded using surface electrodes. Two different patterns of responses to noxious stimuli were identified in CLBP compared to controls: (i) abdominal muscle NWR responses were generally more frequent following 8th rib stimulation and (ii) occurrence of erector spinae NWR was less frequent. In addition, we observed a subgroup of participants with very high NWR threshold in conjunction with the larger abdominal muscle responses. These results suggest sensitization of NWR is not present in all individuals with CLBP, and a modified organization in the spinal networks controlling the trunk muscles that might explain some changes in spine motor control observed in CLBP.

Contribution of neural circuits tested by transcranial magnetic stimulation in corticomotor control of low back muscle: a systematic review.

Introduction: Transcranial magnetic stimulation (TMS) is widely used to investigate central nervous system mechanisms underlying motor control. Despite thousands of TMS studies on neurophysiological underpinnings of corticomotor control, a large majority of studies have focused on distal muscles, and little is known about axial muscles (e.g., low back muscles). Yet, differences between corticomotor control of low back and distal muscles (e.g., gross vs. fine motor control) suggest differences in the neural circuits involved. This systematic review of the literature aims at detailing the organisation and neural circuitry underlying corticomotor control of low back muscles tested with TMS in healthy humans. Methods: The literature search was performed in four databases (CINAHL, Embase, Medline (Ovid) and Web of science) up to May 2022. Included studies had to use TMS in combination with EMG recording of paraspinal muscles (between T12 and L5) in healthy participants. Weighted average was used to synthesise quantitative study results. Results: Forty-four articles met the selection criteria. TMS studies of low back muscles provided consistent evidence of contralateral and ipsilateral motor evoked potentials (with longer ipsilateral latencies) as well as of short intracortical inhibition/facilitation. However, few or no studies using other paired pulse protocols were found (e.g., long intracortical inhibition, interhemispheric inhibition). In addition, no study explored the interaction between different cortical areas using dual TMS coil protocol (e.g., between primary motor cortex and supplementary motor area). Discussion: Corticomotor control of low back muscles are distinct from hand muscles. Our main findings suggest: (i) bilateral projections from each single primary motor cortex, for which contralateral and ipsilateral tracts are probably of different nature (contra: monosynaptic; ipsi: oligo/polysynaptic) and (ii) the presence of intracortical inhibitory and excitatory circuits in M1 influencing the excitability of the contralateral corticospinal cells projecting to low back muscles. Understanding of these mechanisms are important for improving the understanding of neuromuscular function of low back muscles and to improve the management of clinical populations (e.g., low back pain, stroke).

Within-Session Test-Retest Reliability of Pressure Pain Threshold and Mechanical Temporal Summation in Chronic Low Back Pain.

OBJECTIVES: To determine the absolute and relative within-session test-retest reliability of pressure pain threshold (PPT) and temporal summation of pain (TSP) at the low back and the forearm in individuals with chronic low back pain (CLBP) and to test the impact of different sequences of measurements on reliability metrics. MATERIALS AND METHODS: Twenty-eight adults with CLBP were recruited. Relative (intraclass correlation coefficient [ICC] and coefficient of variation) and absolute reliability (standard error of measurement and minimal detectable changes) were quantified at 4 sites (back: sacrum and lumbar erector spinae; wrist: hand dorsum and wrist flexors) for PPT and 2 sites (hand and low back) for TSP, for various sequences of measurements. RESULTS: Systematic differences were found between within test and retest for most PPT sequences at the lumbar erector spinae site and 1 TSP sequence (1-2-3) at back and hand sites, precluding reliability analyses for these data. Within-session PPT relative reliability was excellent at low back (ICC = 0.83 to 0.94) and wrist (ICC = 0.88 to 0.97) sites, whereas TSP showed good to excellent reliability at hand (ICC = 0.80 to 0.90) and low back (ICC = 0.73 to 0.89). In general, 2 and 3 measurements optimized absolute and relative reliability for TSP and PPT, respectively. DISCUSSION: Within-session reliability was generally excellent for PPT and TSP at the low back and hand sites among individuals with CLBP. We recommend using 3 measurements for PPT and 2 for TSP to optimize reliability. Caution is recommended when testing PPT of the painful lower back area since a systematic difference was present between the test and retest.

The Tampa Scale of Kinesiophobia: A Systematic Review of Its Psychometric Properties in People With Musculoskeletal Pain.

OBJECTIVE: The aims of this systematic review were to identify the different versions of the Tampa Scale of kinesiophobia (TSK) and to report on the psychometric evidence relating to these different versions for people experiencing musculoskeletal pain. METHODS: Medline [Ovid] CINAHL and Embase databases were searched for publications reporting on the psychometric properties of the TSK in populations with musculoskeletal pain. Risks of bias were evaluated using the COSMIN risk of the bias assessment tool. RESULTS: Forty-one studies were included, mainly with a low risk of bias. Five versions of the TSK were identified: TSK-17, TSK-13, TSK-11, TSK-4, and TSK-TMD (for temporomandibular disorders). Most TSK versions showed good to excellent test-retest reliability (intraclass coefficient correlation 0.77 to 0.99) and good internal consistency (ɑ=0.68 to 0.91), except for the TSK-4 as its reliability has yet to be defined. The minimal detectable change was lower for the TSK-17 (11% to 13% of total score) and the TSK-13 (8% of total score) compared with the TSK-11 (16% of total score). Most TSK versions showed good construct validity, although TSK-11 validity was inconsistent between studies. Finally, the TSK-17, -13, and -11 were highly responsive to change, while responsiveness has yet to be defined for the TSK-4 and TSK-TMD. DISCUSSION: Clinical guidelines now recommend that clinicians identify the presence of kinesiophobia among patients as it may contribute to persistent pain and disability. The TSK is a self-report questionnaire widely used, but 5 different versions exist. Based on these results, the use of TSK-13 and TSK-17 is encouraged as they are valid, reliable, and responsive.

Distinctive phases and variability of vibration-induced postural reactions highlighted by center of pressure analysis.

BACKGROUND: The vibration-induced postural reaction paradigm (VIB-PR) offers a unique way for investigating sensorimotor control mechanisms. Measures of VIB-PR are usually calculated from the whole VIB period, yet recent evidence proposed that distinctive mechanisms are likely at play between the early vs. later phases of the postural reaction. OBJECTIVES: The present work verified if spatiotemporal analyses of center of pressure (COP) displacements can detect differences between these early/later phases of VIB-PR. Also, we further characterized the intra/inter-individual variability of COP measurements, since the underlying variability of VIB-PR remains largely unexplored. METHODS: Twenty young volunteers realized two experimental conditions of bipodal stance with eyes closed: (i) bilateral VIB of tibialis anterior (TIB) and (ii) Achilles' (ACH) tendons. Each condition consisted of five trials and lasted 30 s as follows: 10 s baseline, 10 s VIB and 10 s post-VIB. Linear COP variables (antero-posterior (AP) amplitude & velocity) were computed for both VIB and post-VIB periods using the following time-windows: early 2 s, the later 8 s and the whole 10 s duration. Intra- and inter-individual variability were respectively estimated using the standard error of the measurement and the coefficient of variation. Both variability metrics were obtained using five vs. the first three trials. RESULTS: Significant contrasts were found between time-windows for both VIB and post-VIB periods. COP variables were generally higher during the early 2 s phase compared to the later 8 s phase for both TIB [mean difference between 8 s- 2 s phases: Amplitude AP = -1.11 ± 1.14 cm during VIB and -2.99 ± 1.31 during post-VIB; Velocity AP = -1.17 ± 0.86 cm/s during VIB and -3.13 ± 1.31 cm/s during post-VIB] and ACH tendons [Amplitude AP = -0.37 ± 0.98 cm during VIB and -3.41 ± 1.20 during post-VIB; Velocity AP = -0.31 ± 0.59 cm/s during VIB and -3.89 ± 1.52 cm/s during post-VIB]. Most within- and between-subject variability scores were below 30% and using three instead of five trials had no impact on variability. VIB-PR patterns were quite similar within a same person, but variable behaviors were observed between individuals during the later phase. CONCLUSION: Our study highlights the relevance of identifying and separately analyzing distinct phases within VIB-PR patterns, as well as characterizing how these patterns vary at the individual level.

The Canadian version of the National Institutes of Health minimum dataset for chronic low back pain research: reference values from the Quebec Low Back Pain Study.

ABSTRACT: The National Institutes of Health (NIH) minimum dataset for chronic low back pain (CLBP) was developed in response to the challenge of standardizing measurements across studies. Although reference values are critical in research on CLBP to identify individuals and communities at risk of poor outcomes such as disability, no reference values have been published for the Quebec (Canada) context. This study was aimed to (1) provide reference values for the Canadian version of the NIH minimum dataset among individuals with CLBP in Quebec, both overall and stratified by gender, age, and pain impact stratification (PIS) subgroups, and (2) assess the internal consistency of the minimum data set domains (pain interference, physical function, emotional distress or depression, sleep disturbance, and PIS score). We included 2847 individuals living with CLBP who completed the baseline web survey of the Quebec Low Back Pain Study (age: 44.0 ± 11.2 years, 48.1% women) and were recruited through social media and healthcare settings. The mean score was 6.1 ± 1.8 for pain intensity. Pain interference, physical function, emotional distress or depression, sleep disturbance, and PIS scores were 12.9 ± 4.1, 14.4 ± 3.9, 9.8 ± 4.4, 13.0 ± 3.6, and 26.4 ± 6.6, respectively. Emotional distress or depression showed floor effects. Good-to-excellent internal consistency was found overall and by language, gender, and age subgroups for all domains (alpha: 0.81-0.93) and poor-to-excellent internal consistency for PIS subgroups (alpha: 0.59-0.91). This study presents reference values and recommendations for using the Canadian version of the NIH minimum dataset for CLBP that can be useful for researchers and clinicians.

Assessment of exercise-induced hypoalgesia in chronic low back pain and potential associations with psychological factors and central sensitization symptoms: A case-control study.

INTRODUCTION: Exercise is the most recommended treatment for chronic low back pain (CLBP) and is effective in reducing pain, but the mechanisms underlying its effects remain poorly understood. Exercise-induced hypoalgesia (EIH) may play a role and is thought to be driven by central pain modulation mechanisms. However, EIH appears to be disrupted in many chronic pain conditions and its presence in people with CLBP remains unclear. As people suffering from chronic pain often exhibit psychological factors and central sensitization symptoms influencing pain perception, EIH might be associated with these factors. OBJECTIVE: The aim of this study is to compare the level of EIH between participants with and without CLBP following back and wrist exercises and to assess the associations between EIH, psychological factors, and symptoms of central sensitization (using the central sensitization inventory - CSI) in CLBP. METHOD: Twenty-eight participants with CLBP and 23 without pain were recruited. Pressure pain thresholds (PPT) were measured at 4 sites (2 bony sites = capitate, S1|2 muscle sites = wrist flexors, lumbar erector spinae) before and after each of two exercises (wrist flexion and lumbar extension). Exercise-induced hypoalgesia was defined as percent change in PPT from pre- to post-exercise. Participants with CLBP also completed questionnaires to measure psychological factors (e.g., kinesiophobia, catastrophizing, anxiety, and self-efficacy) and symptoms of central sensitization (CSI), and correlations with EIH were calculated. RESULTS: After wrist exercise, EIH measured at the muscle sites was lower in the CLBP group compared with the pain-free group (p = 0.047) but no differences were found at bony sites (p = 0.49). No significant differences for EIH were observed following back exercise at muscle sites (p = 0.14) or at bony sites (p = 0.65). Exercise-induced hypoalgesia was not correlated with any psychological factors or with the CSI score. CONCLUSION: The lower EIH following wrist exercises may represent an alteration in pain modulation control in CLBP. However, psychological factors and central sensitization symptoms may not explain the differences observed.

UTAUT2-based questionnaire: cross-cultural adaptation to Canadian French.

PURPOSE: The extended version of the Unified Theory of Acceptance and Use of Technology (UTAUT2) aims to better understand acceptance of technology. The objective of this study was to translate the English UTAUT2-based questionnaire to Canadian French. METHODS: The translation included five steps: (1) Forward translation, (2) Synthesis of the translated versions, (3) Backward translation, (4) Synthesis by a multidisciplinary committee and proposal of the Pre-final Canadian French version, and (5) Cognitive debriefing. Cognitive debriefing included the assessment of the questionnaire items' clarity by (1) a sample of workers, and (2) rehabilitation professionals. Any item not reaching an 80% inter-rater agreement for clarity or relevance was re-evaluated. RESULTS: The multidisciplinary committee included six researchers and clinicians from four different backgrounds. Twelve workers and 12 experts participated in the cognitive debriefing. Each item (n = 40) was judged as "clear" by at least 92% of the worker sample. Six and four items were reviewed following clarity and relevance assessments. The final version was approved unanimously. CONCLUSION: A Canadian French version of the UTAUT2-based questionnaire has been developed. Studies are necessary to examine cultural and semantic equivalence of the original and translated versions, and the cultural appropriateness of the questionnaire.IMPLICATIONS FOR REHABILITATIONThere is an exponential growth in technology, including in the rehabilitation field.Implementing rehabilitation technology into clinical practice remains a challenge.The UTAUT model, and its extension, help to better understand the acceptance of technology before its implementation.The UTAUT2-based questionnaire evaluates the acceptability of rehabilitation technology prior to implementation.

Motor control of the spine in pregnancy-related lumbopelvic pain: A systematic review.

BACKGROUND: Some studies observed differences in motor control of the spine between women with pregnancy-related lumbopelvic pain and matched controls. Understanding alterations in spine motor control may help optimizing treatment in this population. The objective is to determine if there are differences in motor control of the spine in pregnant and post-partum women with and without pregnancy-related lumbopelvic pain. METHODS: Five databases were searched: MEDLINE, Embase, CINAHL, Web of Science and Evidence-Based Medicine Reviews (last search: February 4th 2021). Observational studies that compared motor control of the lumbopelvic spine (in terms of muscle activation [e.g. using EMG or ultrasound imaging] or kinematics) between women with pregnancy-related lumbopelvic pain and matched controls were included. Risk of bias was assessed with a modified version of STROBE statement for cross-sectional studies. No meta-analysis was performed. FINDING: Fifteen studies were included. Compared to matched controls, pregnant women with pregnancy-related lumbopelvic pain showed differences in lumbar spine kinematic during walking and lifting, although not consistent between studies. The only consistent results were higher transversus abdominis muscle activation during leg movements in post-partum pregnancy-related lumbopelvic pain. Differences in pelvic floor muscle function was inconsistent. INTERPRETATION: This systematic review identified multiple differences in motor control in pregnancy-related lumbopelvic pain population, predominantly in dynamic tasks. However, consistent differences in lumbopelvic spine motor control were rare. More studies are necessary to determine if motor control is different in pregnancy-related lumbopelvic pain to better understand alteration in motor control and to optimize the efficacy of rehabilitation treatments.

Changes in static balance during pregnancy and postpartum: A systematic review.

BACKGROUND: Because pregnant women show a high risk of falling, some researchers examined their balance during static standing. This systematic review summarized the findings from all studies evaluating static balance in women during pregnancy and postpartum. RESEARCH QUESTION: Do pregnant and postpartum women show differences in static balance compared to non-pregnant women, and does static balance change during pregnancy and postpartum? METHODS: Pubmed, Embase, CINAHL, and Web of Science databases were searched systematically from inception until Feb 23, 2022. Studies were eligible for inclusion if they measured COP sway with a force plate during bipedal static standing, and compared COP outcomes between healthy pregnant or postpartum women and non-pregnant women, and/or during different stages of pregnancy and the postpartum period. Methodological quality was assessed overall with a modified version of the Downs and Black checklist, and specifically related to COP measurement by using recommendations of Ruhe et al. (2010). The protocol was registered in PROSPERO (CRD42020166302). RESULTS: Thirteen studies were included. Because methodological approaches varied greatly between studies, results were summarized descriptively. Studies reported either greater overall and anteroposterior COP sway magnitude, velocity and variability in women from the second half of pregnancy until six months postpartum compared to non-pregnant controls, or no differences in static balance. Changes in static balance throughout pregnancy were generally not found. Finally, there was no clear consensus on the influence of pregnancy on the reliance on visual inputs for balance control, and on whether differences in balance in pregnant and postpartum women reflect poorer balance or positive adaptations to the physical changes experienced during pregnancy. SIGNIFICANCE: Methodological heterogeneity between studies prevented us from drawing strong conclusions regarding the effect of pregnancy on static balance. Assessing the methodological quality of the studies revealed weaknesses that should be taken into account in future studies.

The influence of experimental low back pain on neural networks involved in the control of lumbar erector spinae muscles.

Low back pain (LBP) often modifies spine motor control, but the neural origin of these motor control changes remains largely unexplored. This study aimed to determine the impact of experimental low back pain on the excitability of cortical, subcortical, and spinal networks involved in the control of back muscles. Thirty healthy subjects were recruited and allocated to pain (capsaicin and heat) or control (heat) groups. Corticospinal excitability (motor-evoked potential; MEP) and intracortical networks were assessed by single- and paired-pulse transcranial magnetic stimulation, respectively. Electrical vestibular stimulation was applied to assess vestibulospinal excitability (vestibular MEP; VMEP) and the stretch reflex for excitability of the spinal or supraspinal loop (R1 and R2, respectively). Evoked back motor responses were measured before, during, and after pain induction. Nonparametric rank-based ANOVA determined if pain modulated motor neural networks. A decrease of R1 amplitude was present after the pain disappearance (P = 0.01) whereas an increase was observed in the control group (P = 0.03) compared with the R1 amplitude measured at prepain and preheat period, respectively (group × time interaction, P < 0.001). No difference in MEP and VMEP amplitude was present during and after pain (P > 0.05). During experimental LBP, no change in cortical, subcortical, or spinal networks was observed. After pain disappearance, the reduction of the R1 amplitude without modification of MEP and VMEP amplitude suggests a reduction in spinal excitability potentially combined with an increase in descending drives. The absence of effect during pain needs to be further explored.NEW & NOTEWORTHY In the presence of experimental low back pain, spinal, subcortical, and cortical motor networks involved in the control of back muscles were not modified. However, once the pain disappeared, a reduction in motoneuronal excitability was observed without change in corticospinal and vestibulospinal excitability, suggesting a reduction in descending drive. Experimental low back pain may elicit long-term plasticity even after pain extinction.

Can training of a skilled pelvic movement change corticomotor control of back muscles? Comparison of single and paired-pulse transcranial magnetic stimulation.

Evidence suggests excitability of the motor cortex (M1) changes in response to motor skill learning of the upper limb. Few studies have examined immediate changes in corticospinal excitability and intra-cortical mechanisms following motor learning in the lower back. Further, it is unknown which transcranial magnetic stimulation (TMS) paradigms are likely to reveal changes in cortical function in this region. This study aimed to (1) compare corticospinal excitability and intra-cortical mechanisms in the lower back region of M1 before and after a single session of lumbopelvic tilt motor learning task in healthy people and (2) compare these measures between two TMS coils and two methods of recruitment curve (RC) acquisition. Twenty-eight young participants (23.6 ± 4.6 years) completed a lumbopelvic tilting task involving three 5-min blocks. Single-pulse (RC from 70% to 150% of active motor threshold) and paired-pulse TMS measures (ICF, SICF and SICI) were undertaken before (using 2 coils: figure-of-8 and double cone) and after (using double cone coil only) training. RCs were also acquired using a traditional and rapid method. A significant increase in corticospinal excitability was found after training as measured by RC intensities, but this was not related to the RC slope. No significant differences were found for paired-pulse measures after training. Finally, there was good agreement between RC parameters when measured with the two different TMS coils or different acquisition methods (traditional vs. rapid). Changes in corticospinal excitability after a single session of lumbopelvic motor learning task are seen, but these changes are not explained by changes in intra-cortical mechanisms.

Effects of different modalities of afferent stimuli of the lumbo-sacral area on control of lumbar paravertebral muscles.

Somatosensory feedback to the central nervous system is essential to plan, perform and refine spine motor control. However, the influence of somatosensory afferent input from the trunk on the motor output to trunk muscles has received little attention. The objective was to compare the effects of distinct modalities of afferent stimulation on the net motoneuron and corticomotor excitability of paravertebral muscles. Fourteen individuals were recruited. Modulation of corticospinal excitability (motor-evoked potential [MEP]) of paravertebral muscles was measured when afferent stimuli (cutaneous noxious and non-noxious, muscle contraction) were delivered to the trunk at 10 intervals prior to transcranial magnetic stimulation. Each peripheral stimulation was applied alone, and subsequent electromyography (EMG) modulation was measured to control for net motoneuron excitability. MEP modulation and MEP/EMG ratio were used as measures of corticospinal excitability with and without control of net motoneuron excitability, respectively. MEP and EMG modulation were smaller after evoked muscle contraction than after cutaneous noxious and non-noxious stimuli. MEP/EMG ratio was not different between stimulation types. Both MEP and EMG amplitudes were reduced after evoked muscle contraction, but not when expressed as MEP/EMG ratio. Noxious and non-noxious stimulation had limited impact on all variables. Distinct modalities of peripheral afferent stimulation of the lumbo-sacral area differently modulated responses of paravertebral muscles, but without an influence on corticospinal excitability with control of net motoneuron excitability. Muscle stimulation reduced paravertebral activity and was best explained by spinal mechanisms. The impact of afferent stimulation on back muscles differs from the effects reported for limb muscles.

Low back pain definitions: effect on patient inclusion and clinical profiles.

Introduction: Numerous definitions of acute low back pain (aLBP) exist. The use of different definitions results in variability in reported prevalence or incidence, conflicting data regarding factors associated with the transition to chronic LBP (cLBP), and hampers comparability among studies. Objective: Here, we compare the impact of 3 aLBP definitions on the number of aLBP cases and participants' characteristics and explore the distribution of participants across definitions. Methods: A sample of 1264 participants from the Quebec Low Back Pain Study was included. Three definitions of aLBP were used: (1) not meeting the National Institutes of Health (NIH) cLBP definition ("nonchronic"), (2) pain beginning <3 months ago ("acute"), and (3) pain beginning <3 months with a preceding LBP-free period ("new episode"). Results: There were 847, 842, and 489 aLBP cases meeting the criteria for the 3 definitions, respectively. Participants included in the "nonchronic" had lower pain interference, greater physical function scores, and fewer participants reporting >5 years of pain than in the other definitions. Half the participants meeting the "acute" definition and one-third of participants meeting the "new episode" definition were also classified as cLBP based on the NIH definition. Conclusions: Our results highlight the importance of the definition used for aLBP. Different definitions influence the sample size and clinical profiles (group's characteristics). We recommended that cohort studies examining the transition from aLBP to cLBP ensure that the definitions selected are mutually exclusive (ie, participants included [aLBP] differ from the expected outcome [cLBP]).

Influence of different transcranial magnetic stimulation current directions on the corticomotor control of lumbar erector spinae muscles during a static task.

Different directions of transcranial magnetic stimulation (TMS) can activate different neuronal circuits. Whereas posteroanterior current (PA-TMS) depolarizes mainly interneurons in primary motor cortex (M1), an anteroposterior current (AP-TMS) has been suggested to activate different M1 circuits and perhaps axons from the premotor regions. Although M1 is also involved in the control of axial muscles, no study has explored whether different current directions activate different M1 circuits that may have distinct functional roles. The aim of the study was to compare the effect of different current directions (PA- and AP-TMS) on the corticomotor control and spatial cortical organization of the lumbar erector spinae muscle (LES). Thirty-four healthy participants were recruited for two independent experiments, and LES motor-evoked potentials (MEPs) were recorded. In experiment 1 (n = 17), active motor threshold (AMT), MEP latencies, recruitment curve (90% to 160% AMT), and excitatory and inhibitory intracortical mechanisms by paired-pulse TMS (80% followed by 120% AMT stimuli at 2-, 3-, 10-, and 15-ms interstimulus intervals) were tested with a double-cone (n = 12) and a figure-of-eight (n = 5) coil. In experiment 2 (n = 17), LES cortical representations were tested with PA- and AP-TMS. AMT was higher for AP- compared with PA-TMS (P = 0.002). Longer latencies with AP-TMS were present compared with PA-TMS (P = 0.017). AP-TMS produced more inhibition compared with PA-TMS at 2 ms and 3 ms (P = 0.010), but no difference was observed for longer intervals. No difference was found for recruitment curve and mapping. These findings suggest that PA- and AP-TMS may activate different cortical circuits controlling low back muscles, as proposed for hand muscles.NEW & NOTEWORTHY For the first time, anteroposterior and posteroanterior induced electric currents in the brain were compared when targeting back muscle representation with transcranial magnetic stimulation. The use of the anteroposterior current resulted in later response latency, larger inhibition probed by paired-pulse stimulation, and higher motor threshold. These important differences between current directions suggest that each of the current directions may recruit specific cortical circuits involved in the control of back muscles, similar to that for hand muscles.