Study design: Cross-sectional study of lumbopelvic muscle activation during rapid limb movements ... more Study design: Cross-sectional study of lumbopelvic muscle activation during rapid limb movements in chronic low back pain (CLBP) patients and healthy controls. Introduction: Controversy exists over whether bilateral anticipatory activation of the deep abdominal muscles represents a normal motor control strategy prior to all rapid limb movements, or if this is simply a task-specific strategy appropriate for only certain movement conditions. Objective: To assess the onset timing of the transversus abdominis/internal oblique muscles (TrA/IO) during two rapid limb movement tasks with different postural demands-bilateral shoulder flexion in standing, unilateral hip extension in prone lying-as well as differences between CLBP and controls. Methods: Twelve CLBP and 13 controls performed the two tasks in response to an auditory cue. Surface EMG was acquired bilaterally from five muscles, including TrA/IO. Results: In both groups, 50% of bilateral shoulder flexion trials showed bilateral anticipatory TrA/IO activation. This was rare, however, in unilateral hip extension for which only the TrA/IO contralateral to the moving leg showed anticipatory activation. The only significant difference in lumbo-pelvic muscle onset timing between CLBP and controls was a delay in semitendinosus activation during bilateral shoulder flexion in standing. Conclusion: Our data suggest that bilateral anticipatory TrA/IO activation is a task-specific motor control strategy, appropriate for only certain rapid limb movement conditions. Furthermore, the presence of altered semitendinosus onset timing in the CLBP group during bilateral shoulder flexion may be reflective of other possible lumbo-pelvic motor control alterations among this population.
The activation of transversus abdominis muscle during rapid limb movements depends on the anticip... more The activation of transversus abdominis muscle during rapid limb movements depends on the anticipation of postural demand rather than on respiratory reflexes ☆ We thank the Editor and Mr Mal to provide us the chance to discuss further the contribution of abdominal muscles in postural and respiratory control. Mr Mal's Letter to the Editor gathered evidences of the role of the transversus abdominis (TrA) in respiration. It is suggested that the activation of TrA observed in rapid limb movement studies could be mostly explained by a respiration reflex response to the distortion of the ribcage that is secondary to the arm movement attached on the thorax. We have to rebut this hypothesis and further discuss on the role of TrA but also of diaphragm and pelvic floor muscles in the control of both posture and respiration. It is also noteworthy that surface EMG electrodes were used in our study [1] to record the activity of lower region of TrA/obliquus internus which is difficult to compare with intramuscular EMG studies using finewire electrodes. This reply will mainly focus on studies having used fine-wire recordings of trunk muscles and concerns the differences in motor control between periphery-related feedback and preprogrammed feedforward. Mr Mal's Letter to the Editor quoted a specific study on flexion/extension trunk movement produced by a dropping weight and in which TrA activation was observed within 50 ms after the perturbation [2]. This has been used as evidence to suggest that TrA activation during rapid arm movement is the result of a respiratory reflex due to the distortion of the ribcage. However, the nature of TrA activation during rapid arm movement cannot be inferred by a weight-dropping task that involves a contraction of the trunk muscles in reaction to the perturbation. Precisely, the activation of the trunk proprioceptive receptors induces a reflex contraction of the trunk muscle to counteract this force. This feedback loop is different from the feedforward response of the muscle (or anticipatory postural adjustment [APA] including TrA activation before limb movement onset). Indeed, feedforward does not depend on feedback from the periphery and is rather pre-programmed as an inherent part of the motor command, i.e. in function of the context of the task [3-5]. In line, Hodges et al. (1996) published the first study showing that TrA was part of the trunk APA following rapid unilateral arm movements [6]. TrA activation was observed 24-39 ms before the agonist of movement (deltoid muscle) and thus could not have been triggered by a reflex or a feedback loop [3-5]. Also, if the sole movement of the arm produces a respiratory reflex triggering TrA activation, then it could be expected that any arm movement could trigger activation of TrA independently of the velocity of arm movement. It was conversely reported that TrA activation actually depends on the velocity of arm movement, the faster the arm movement, the earlier the TrA activation. In shoulder flexion performed at slow, natural and fast velocities, TrA was activated 406 ± 146 ms after the deltoid activation, 32 ± 21 ms after the deltoid and 39 ± 8 before the deltoid, respectively [7]. This suggests that TrA is activated in anticipation of the expected reactive force/perturbation produced by the upcoming arm movement. Also, TrA is composed of different regions of different anatomical morphology that can be divided in upper, middle and lower parts [8]. These different regions present different fascicle orientation: upper region is more or less horizontal, middle and lower are oriented caudomedially (−13°and −20°, respectively) [8]. Interestingly, in rapid shoulder flexion movement, the middle and lower TrA regions are activated earlier than the upper region [9]. However, this upper region of TrA mostly inserts onto the ribcage, thus if TrA activation had to be explained by a respiratory reflex, then the upper part should be the first activated, not the latest. This clearly suggests that the different regions of the TrA are activated according to their fascicle orientation rather than their attachment onto the ribcage [9,10]. Nevertheless, although the abovementioned studies provided compelling evidences of the role of TrA muscle in postural control and APA (anticipation of perturbation), it remains unclear whether respiration could have modulated the trunk muscle activation and been a confounding factor in these studies. As described by Mr Mal, TrA is an expiratory muscle [11] thus its activation could depend on both the postural context and the respiratory phase in which the muscle is tested. For instance, the APA-related activation of TrA during expiration could be earlier than during inspiration because of a prior facilitation of TrA motoneuron pools coming from the ponto-medullary respiratory center. It was shown however that the phase of the respiration cycle in quiet breathing did not influence TrA onset [12]. It is only during a forceful expiration (below functional residual capacity) that TrA activation is fastened whereas it is delayed by a static expulsive maneuver (expiration against closed glottis) [12]. This emphasised the complex supraspinal control of TrA in both posture and respiration that depends on the task requirements. More precisely, a mere facilitation of TrA excitability at the motoneuronal level during different respiratory challenges did not systematically result in earlier activation of TrA. A series of studies by P Hodges and S Gandevia investigated the postural control of the diaphragm and abdominal muscles (including TrA) during single rapid arm movement and during repeated arm movements [13-16]. These articles enlightened the role of diaphragm and of TrA muscles in the control of posture, spine and respiration. Both the diaphragm and the TrA were activated in a feedforward manner, i.e. before the activation of the agonist muscle during a rapid arm movement, thus suggesting that these activations did belong to the pre-programmed motor command [13]. Interestingly, repeated arm flexion and extension produced a tonic activation of both TrA and diaphragm muscles with a phasic increase of diaphragm activation during inspiration and a phasic increase of TrA activation during expiration [14,15]. The power spectra of both muscles EMG activity were locked with the frequency of the respiration cycle and with the frequency of the arm movement [14,15]. The increase of arm movement frequency augmented the tonic activation of the diaphragm similarly to other trunk muscles involved in the control of trunk posture but not involved in the
in both tasks. People with right-sided CLBP presented with increased M1 excitability in both hemi... more in both tasks. People with right-sided CLBP presented with increased M1 excitability in both hemispheres and earlier MF APA. These results likely rely on cortical motor adaptation related to the tasks and axial muscles tested. Future studies should investigate whether CLBP side-related differences have a clinical impact, e.g. in diagnosis and intervention.
h i g h l i g h t s • Isometric vs. global exercises of multifidus muscles had different effects.... more h i g h l i g h t s • Isometric vs. global exercises of multifidus muscles had different effects. • Isometric exercise influenced brain plasticity and fastened postural adjustment. • Changes persisting after 3-week training and long-term effects are questioned.
This study defines the limits of stability in sitting, and quantitatively assesses two measures o... more This study defines the limits of stability in sitting, and quantitatively assesses two measures of postural control relative to these limits. Young, healthy subjects sat, feet unsupported, on an elevated force plate. The limits of stability were determined by a least square fit of an ellipse to the center of pressure (CoP) excursion during maximal leaning in 8 directions. These were highly symmetrical and centered within the base of support. The ellipses had a mean eccentricity of 0.66 (major axis in the sagittal plane) and covered an area approx. 1/3 of the base of support. The CoP was then monitored over 4 min of quiet sitting, during which the postural sway covered an area <0.05% of the limits of stability and was closely centered within the latter. Finally, targetdirected trunk movements were performed, in 5 directions, at 4 movement speeds and 3 target distances. Increased target distance and movement speed both decreased the margin of stability (distance between the CoP and the limits of stability), as did movement in the frontal plane, reflecting the eccentricity of the limits of stability. These combined findings support the validity of this quantitative method of defining the limits of stability in sitting, for healthy individuals.
Combining repetitive peripheral magnetic neurostimulation and motor training immediately decrease... more Combining repetitive peripheral magnetic neurostimulation and motor training immediately decreased chronic low back pain. • This intervention helped normalize the control of spine one week after study onset. • These motor and pain changes were paralleled by an increase of intracortical motor facilitation. ABSTRACT OBJECTIVE. The study tested whether combining repetitive peripheral magnetic neurostimulation (RPMS) and motor training of the superficial multifidus muscle (MF) better improved the corticomotor control of spine than training alone in chronic low back pain (CLBP). METHODS Twenty-one participants with CLBP were randomly allocated to [RPMS+training] and [Sham+training] groups for three sessions (S1-S3) over a week where MF was stimulated before training (volitional contraction). Training was also home-practiced twice a day. Changes were tested at S1 and S3 for anticipatory postural adjustments (APAs) of MF and semi-tendinosus (ST), MF EMG activation, cortical motor plasticity (transcranial magnetic stimulation) and pain/disability. 3 RESULTS The RPMS group showed immediate decrease of pain at S1, then improvement of MF activation, ST APA, M1 facilitation, and pain/disability at S3. Changes were larger when brain excitability was lower at baseline. Disability index remained improved one month later. CONCLUSIONS Combining RPMS with training of MF in CLBP impacted motor planning, MF and lumbopelvic spine motor control and pain/disability one week after the onset of protocol. Brain plasticity might have favoured motor learning and improved daily lumbopelvic spine control without pain generation. SIGNIFICANCE Clinically, RPMS impacted the function by improving the gains beyond those reached by training alone in CLBP.
plasticity of cortical maps controlling paravertebral muscles and likely including a different mo... more plasticity of cortical maps controlling paravertebral muscles and likely including a different motor strategy for the control of MF. Changes of M1 function may thus underlie impaired motor control of lumbopelvic spine and pain persistence in CLBP.
The purpose of this study was to assess whether changing the stance width has an effect on the ra... more The purpose of this study was to assess whether changing the stance width has an effect on the range of motion of hip flexion, knee flexion, and ankle dorsiflexion during an unloaded back squat, and whether these joint movements are affected by anthropometric differences. Thirty-two healthy, young adults performed unloaded back squats at three different stance widths, normalized to pelvic width. Joint angles were assessed using electromagnetic motion capture sensors on the sacrum, and thigh, shank and foot of the dominant leg. ANOVA comparison of joint angles for the three stance widths, at 10° intervals of thigh orientation during the squat, indicated that joint angles tended to be larger when stance width was narrower, with the most significant effects on ankle dorsiflexion. A greater trunk/thigh length ratio (relatively long trunk) also tended to be associated with lower ankle and knee angles, while a greater thigh/shank length ratio (relatively long thigh) tended to be associated with higher ankle and knee angles, for the two narrower stance widths. The most practical implication of our findings is that individuals with limited ankle dorsiflexion, or with particularly long legs / thighs, may benefit from a wider stance width when squatting.
Background: Motion assessment of the body's head-arms-trunk (HAT) using linked-segment models, al... more Background: Motion assessment of the body's head-arms-trunk (HAT) using linked-segment models, along with an inverse dynamics approach, can enable in vivo estimations of inter-vertebral moments. However, this mathematical approach is prone to experimental errors because of inaccuracies in (i) kinematic measurements associated with soft tissue artifacts and (ii) estimating individual-specific body segment parameters (BSPs). The inaccuracy of the BSPs is particularly challenging for the multi-segment HAT due to high inter-participant variability in the HAT's BSPs and no study currently exists that can provide a less erroneous estimation of the joint moments along the spinal column. Research question: This study characterized three-dimensional (3D) inter-segmental moments in a multi-segment HAT model during multi-directional trunk-bending, after minimizing the experimental errors. Method: Eleven healthy individuals participated in a multi-directional trunk-bending experiment in five directions with three speeds. A seven-segment HAT model was reconstructed for each participant, and its motion was recorded. After compensating for experimental errors due to soft tissue artifacts, and using optimized individualspecific BSPs, and center of pressure offsets, the inter-segmental moments were calculated via inverse dynamics. Results: Our results show a significant effect of the inter-segmental level and trunk-bending directions on the obtained moments. Compensating for soft tissue artifacts contributed significantly to reducing errors. Our results indicate complex, task-specific patterns of the 3D moments, with high inter-participant variability at different inter-segmental levels, which cannot be studied using single-segment models or without error compensation. Significance: Interpretation of inter-segmental moments after compensation of experimental errors is important for clinical evaluations and developing injury prevention and rehabilitation strategies.
Journal of biomechanical engineering, Jun 21, 2018
Kinetics assessment of the human head-arms-trunk (HAT) complex via a multisegment model is a usef... more Kinetics assessment of the human head-arms-trunk (HAT) complex via a multisegment model is a useful tool for objective clinical evaluation of several pathological conditions. Inaccuracies in body segment parameters (BSPs) are a major source of uncertainty in the estimation of the joint moments associated with the multisegment HAT. Given the large intersubject variability, there is currently no comprehensive database for the estimation of BSPs for the HAT. We propose a nonlinear, multistep, optimization-based, noninvasive method for estimating individual-specific BSPs and calculating joint moments in a multisegment HAT model. Eleven nondisabled individuals participated in a trunk-bending experiment and their body motion was recorded using cameras and a force plate. A seven-segment model of the HAT was reconstructed for each participant. An initial guess of the BSPs was obtained by individual-specific scaling of the BSPs calculated from the male visible human (MVH) images. The intersegmental moments were calculated using both bottom-up and top-down inverse dynamics approaches. Our proposed method adjusted the scaled BSPs and center of pressure (COP) offsets to estimate optimal individual-specific BSPs that minimize the difference between the moments obtained by top-down and bottom-up inverse dynamics approaches. Our results indicate that the proposed method reduced the error in the net joint moment estimation (defined as the difference between the net joint moment calculated via bottom-up and top-down approaches) by 79.3% (median among participants). Our proposed method enables an optimized estimation of individual-specific BSPs and, consequently, a less erroneous assessment of the three-dimensional (3D) kinetics of a multisegment HAT model.
Background: Lumbar belts have been shown to increase lumbar stiffness, but it is unclear if this ... more Background: Lumbar belts have been shown to increase lumbar stiffness, but it is unclear if this is associated with trunk muscle co-contraction, which would increase the compression on the spine. It has been hypothesized that lumbar belts increase lumbar stiffness by increasing intra-abdominal pressure, which would increase spinal stability without increasing the compressive load on the spine. Methods: Trunk muscle activity and lumbar stiffness and damping were measured in healthy and low-back pain subjects during three conditions: no lumbar belt; wearing an extensible lumbar belt; wearing a non-extensible lumbar belt. Muscle activity was measured while subjects performed controlled forward and backward 20°trunk sways. Lumbar stiffness and damping were measured by applying random continuous perturbation to the chest. Findings: External oblique activity was decreased when wearing either lumbar belt during all phases of movement, while rectus abdominis and iliocostalis activity were decreased during the phase of movement where the muscles were maximally active while wearing either belt. Trunk stiffness was greatly increased by wearing either belt. There were no consistent differences in either lumbar stiffness or muscle activity between the two belts. Wearing a lumbar belt had little to no effect on damping. There were no group differences in any of the measures between healthy and low-back pain populations. Interpretation: The findings are consistent with the hypothesis that lumbar belts can increase spinal stability by increasing intra-abdominal pressure, without any increase in the compressive load on the spine. The findings can also be generalized, for the first time, to subjects with low-back pain.
A major challenge in the assessment of intersegmental spinal column angles during trunk motion is... more A major challenge in the assessment of intersegmental spinal column angles during trunk motion is the inherent error in recording the movement of bony anatomical landmarks caused by soft tissue artifacts (STAs). This study aims to perform an uncertainty analysis and estimate the typical errors induced by STA into the intersegmental angles of a multisegment spinal column model during trunk bending in different directions by modeling the relative displacement between skin-mounted markers and actual bony landmarks during trunk bending. First, we modeled the maximum displacement of markers relative to the bony landmarks with a multivariate Gaussian distribution. In order to estimate the distribution parameters, we measured these relative displacements on five subjects at maximum trunk bending posture. Then, in order to model the error depending on trunk bending angle, we assumed that the error grows linearly as a function of the bending angle. Second, we applied our error model to the trunk motion measurement of 11 subjects to estimate the corrected trajectories of the bony landmarks and investigate the errors induced into the intersegmental angles of a multisegment spinal column model. For this purpose, the trunk was modeled as a seven-segment rigid-body system described using 23 reflective markers placed on various bony landmarks of the spinal column. Eleven seated subjects performed trunk bending in five directions and the three-dimensional (3D) intersegmental angles during trunk bending were calculated before and after error correction. While STA minimally affected the intersegmental angles in the sagittal plane (&lt;16%), it considerably corrupted the intersegmental angles in the coronal (error ranged from 59% to 551%) and transverse (up to 161%) planes. Therefore, we recommend using the proposed error suppression technique for STA-induced error compensation as a tool to achieve more accurate spinal column kinematics measurements. Particularly, for intersegmental rotations in the coronal and transverse planes that have small range and are highly sensitive to measurement errors, the proposed technique makes the measurement more appropriate for use in clinical decision-making processes.
Conflicts of interest statement The authors have no relevant financial activities and no conflict... more Conflicts of interest statement The authors have no relevant financial activities and no conflicts of interest to disclose in relation to this work. Highlights (3-5 bullets, maximum 85 characters with space per bullet) Pain catastrophizing is associated with altered neuromotor behavior during gait. Catastrophizers had higher EMG activation in certain trunk muscles during gait. Catastrophizers had less phasic modulation of other trunk muscles during gait. Activation of most muscles was correlated with pain catastrophizing scores.
Patients with chronic low back pain (CLBP) exhibit remodelling of the lumbar soft tissues such as... more Patients with chronic low back pain (CLBP) exhibit remodelling of the lumbar soft tissues such as muscle fatty infiltrations (MFI) and fibrosis of the lumbar multifidus (LuM) muscles, thickness changes of the thoracolumbar fascia (TLF) and perimuscular connective tissues (PMCT) surrounding the abdominal lateral wall muscles. Rehabilitative ultrasound imaging (RUSI) parameters such as thickness and echogenicity are sensitive to this remodelling. This experimental laboratory study aimed to explore whether these RUSI parameters (LuM echogenicity and fascia thicknesses), hereafter called dependent variables (DV) were linked to independent variables (IV) such as (1) other RUSI parameters (trunk muscle thickness and activation) and (2) physical and psychological measures. RUSI measures, as well as a clinical examination comprising physical tests and psychological questionnaires, were collected from 70 participants with LBP. The following RUSI dependent variables (RUSI‐DV), measures of passive tissues were performed bilaterally: (1) LuM echogenicity (MFI/fibrosis) at three vertebral levels (L3/L4, L4/L5 and L5/S1); (2) TLF posterior layer thickness, and (3) PMCT thickness of the fasciae between subcutaneous tissue thickness (STT) and external oblique (PMCTSTT/EO), between external and internal oblique (PMCTEO/IO), between IO and transversus abdominis (PMCTIO/TrA) and between TrA and intra‐abdominal content (PMCTTrA/IA). RUSI measures of trunk muscle's function (thickness and activation), also called measures of active muscle tissues, were considered as independent variables (RUSI‐IV), along with physical tests related to lumbar stability (n = 6), motor control deficits (n = 7), trunk muscle endurance (n = 4), physical performance (n = 4), lumbar posture (n = 2), and range of motion (ROM) tests (n = 6). Psychosocial measures included pain catastrophizing, fear‐avoidance beliefs, psychological distress, illness perceptions and concepts related to adherence to a home‐based exercise programme (physical activity level, self‐efficacy, social support, outcome expectations). Six multivariate regression models (forward stepwise selection) were generated, using RUSI‐DV measures as dependent variables and RUSI‐IV/physical/psychosocial measures as independent variables (predictors). The six multivariate models included three to five predictors, explaining 63% of total LuM echogenicity variance, between 41% and 46% of trunk superficial fasciae variance (TLF, PMCTSTT/EO) and between 28% and 37% of deeper abdominal wall fasciae variance (PMCTEO/IO, PMCTIO/TrA and PMCTTrA/IA). These variables were from RUSI‐IV (LuM thickness at rest, activation of IO and TrA), body composition (percent fat) and clinical physical examination (lumbar and pelvis flexion ROM, aberrant movements, passive and active straight‐leg raise, loaded‐reach test) from the biological domain, as well as from the lifestyle (physical activity level during sports), psychological (psychological distress—cognitive subscale, fear‐avoidance beliefs during physical activities, self‐efficacy to exercise) and social (family support to exercise) domains. Biological, psychological, social and lifestyle factors each accounted for substantial variance in RUSI‐passive parameters. These findings are in keeping with a conceptual link between tissue remodelling and factors such as local and systemic inflammation. Possible explanations are discussed, in keeping with the hypothesis‐generating nature of this study (exploratory). However, to impact clinical practice, further research is needed to determine if the most plausible predictors of trunk fasciae thickness and LuM fatty infiltrations have an effect on these parameters.
BACKGROUND Wearing a lumbosacral orthosis (LSO) is known to influence spine mechanics, but less i... more BACKGROUND Wearing a lumbosacral orthosis (LSO) is known to influence spine mechanics, but less is known about how LSOs affect motor control. Whether the use of a LSO can negatively affect motor control of the lumbar spine is still under debate. OBJECTIVE The current study examined the immediate effects of two flexible LSOs (extensible and non-extensible) on the anticipatory postural adjustments that prepare the spine for a predictable perturbation. DESIGN A comparative study using a repeated measures design in a laboratory setting. METHODS Healthy controls (n = 20) and participants with low back pain (n = 40) performed a rapid arm flexion/extension cycle with and without these LSOs. The latency between the activations of the shoulder and different back (iliocostalis lumborum) and abdominal (rectus abdominis, internal and external obliques) muscles, as measured with surface electromyography, was used as the outcome. RESULTS The effects, which were comparable between groups and between LSOs, were mixed, with some muscles showing significantly (p ˂ 0.05) earlier activation and others showing delayed activation with the use of a LSO, relative to the control condition. The corresponding effect sizes were low to average (Hedges's g range: 0.17-0.48). CONCLUSIONS These findings suggest a change in the motor program before task initiation, which might be generalizable to other activities of daily living or work. However, none of the effects were large, making it difficult to provide clear conclusions with regard to their clinical relevance. It remains to be tested whether these immediate adaptations in motor planning can induce long term detrimental effects to the control of lumbar stability.
BackgroundLumbar stabilization exercise programs (LSEPs) act positively on clinical outcome measu... more BackgroundLumbar stabilization exercise programs (LSEPs) act positively on clinical outcome measures in patients with low back pain (LBP), but the underlying mechanisms are not well understood. Among the various neuromuscular mechanisms, a good candidate is better activation of the abdominal wall, as measured with rehabilitative ultrasound imaging (RUSI).ObjectivesTo determine whether RUSI measures are (1) sensitive to LBP status and treatment (LSEP) and (2) correlate with clinical outcomes following the LSEP.DesignAn exploratory one‐arm clinical trial with healthy participants as a control group.SettingLSEP was delivered in a clinical setting; outcomes were measured in a laboratory setting.ParticipantsThirty‐one patients with nonacute LBP and 30 healthy controls.MethodsOutcome measures were performed before and after an 8‐week LSEP in patients with LBP, and with the same time interval for control participants to compare with patients at baseline.Main Outcome MeasurementsPain, disability, as well as static (at rest) and dynamic (percent thickness change) RUSI measures for abdominal muscles (transversus abdominis, internal oblique [IO], and external oblique [EO]).ResultsPatients did not produce systematic changes in RUSI measures relative to controls, even if patients had significant improvement in pain and disability. However, the correlational analyses between the absolute change (pre‐ to post‐LSEP) (1) of EO and IO thickness (in mm) at rest (bilaterally), and (2) in pain following the LSEP were significant and consistent (range: .36‐.45) in patients.ConclusionsAlthough positive clinical improvements were observed following LSEP, there were minimal systematic changes in RUSI measures, likely because patients were not different from controls at baseline. Correlational analyses, however, indicated that greater reductions in pain were associated with reduced thickness of the EO and IO following the LSEP, suggesting the presence of some heterogeneity (or clinical subgroups) among the patients.Level of EvidenceII
Background: Previous findings suggest that wearing a lumbar belt may benefit some patients with l... more Background: Previous findings suggest that wearing a lumbar belt may benefit some patients with low back pain; however, the mechanisms of action are not yet fully understood. Research question: The effect of wearing two flexible (extensible and non-extensible) lumbar belts on trunk postural control was investigated during an unstable sitting task. Methods: Healthy subjects and subjects with LBP sat on a wobbling chair, with and without the lumbar belts. Chair rotation was measured in the sagittal and frontal planes, and 10 linear and nonlinear measures of balance were computed to assess the quantity (3 measures) and quality (7 measures) of the movements. Results: Both lumbar belts induced similar changes in specific measures of trunk postural control, for both subject groups, generally indicative of more instability and less controllability, but with low effect sizes (0.14 and 0.40). Subjects with LBP also showed lower entropy (complexity; effect size 0.93) and higher determinism (predictability; effect size 0.56) than healthy controls, under all test conditions. These findings indicate that the subjects with LBP used a less complex, more predictable trunk postural control strategy, suggestive of impaired adaptability and responsiveness to dynamic trunk postural control demands. The findings also suggest other factors related to dynamic adaptability may be impaired by lumbar belt use. Significance: The effects of the lumbar belts on trunk postural control were small, however, their practical implications for the management of LBP remain to be determined in relation to other effects of lumbar belts (e.g. increased mechanical stiffness).
Journal of Electromyography and Kinesiology, Aug 1, 2017
Disturbances to balance arising from forces applied to the upper limb have received relatively li... more Disturbances to balance arising from forces applied to the upper limb have received relatively little attention compared to disturbances arising from support surface perturbations. In this study we applied fast ramp perturbations to the hand in anterior, posterior, medial and lateral directions. The effects of perturbation predictability and amplitude on the postural response of upper limb, trunk and lower limb muscles were investigated. Perturbations were applied either in blocks of constant amplitude and direction (predictable) or with direction and amplitude varying randomly (random) from trial to trial. The spatial-temporal patterns of anticipatory muscle activation under the predictable condition and the reactionary responses following the perturbation under both conditions were similarly organized. The size of the response increased systematically with the perturbation magnitude for both anticipatory and reactionary changes in muscle activation. However, the slope of the relation between perturbation amplitude and the magnitude of the change in muscle activation was greater when perturbations were predictable than when they were randomly selected. The timing of both the anticipatory and reactionary increases in muscle activation was invariant across perturbation amplitudes. The characteristics of the reactionary responses have a similar organization to the long latency muscle responses to support surface perturbations.
Study design: Cross-sectional study of lumbopelvic muscle activation during rapid limb movements ... more Study design: Cross-sectional study of lumbopelvic muscle activation during rapid limb movements in chronic low back pain (CLBP) patients and healthy controls. Introduction: Controversy exists over whether bilateral anticipatory activation of the deep abdominal muscles represents a normal motor control strategy prior to all rapid limb movements, or if this is simply a task-specific strategy appropriate for only certain movement conditions. Objective: To assess the onset timing of the transversus abdominis/internal oblique muscles (TrA/IO) during two rapid limb movement tasks with different postural demands-bilateral shoulder flexion in standing, unilateral hip extension in prone lying-as well as differences between CLBP and controls. Methods: Twelve CLBP and 13 controls performed the two tasks in response to an auditory cue. Surface EMG was acquired bilaterally from five muscles, including TrA/IO. Results: In both groups, 50% of bilateral shoulder flexion trials showed bilateral anticipatory TrA/IO activation. This was rare, however, in unilateral hip extension for which only the TrA/IO contralateral to the moving leg showed anticipatory activation. The only significant difference in lumbo-pelvic muscle onset timing between CLBP and controls was a delay in semitendinosus activation during bilateral shoulder flexion in standing. Conclusion: Our data suggest that bilateral anticipatory TrA/IO activation is a task-specific motor control strategy, appropriate for only certain rapid limb movement conditions. Furthermore, the presence of altered semitendinosus onset timing in the CLBP group during bilateral shoulder flexion may be reflective of other possible lumbo-pelvic motor control alterations among this population.
The activation of transversus abdominis muscle during rapid limb movements depends on the anticip... more The activation of transversus abdominis muscle during rapid limb movements depends on the anticipation of postural demand rather than on respiratory reflexes ☆ We thank the Editor and Mr Mal to provide us the chance to discuss further the contribution of abdominal muscles in postural and respiratory control. Mr Mal's Letter to the Editor gathered evidences of the role of the transversus abdominis (TrA) in respiration. It is suggested that the activation of TrA observed in rapid limb movement studies could be mostly explained by a respiration reflex response to the distortion of the ribcage that is secondary to the arm movement attached on the thorax. We have to rebut this hypothesis and further discuss on the role of TrA but also of diaphragm and pelvic floor muscles in the control of both posture and respiration. It is also noteworthy that surface EMG electrodes were used in our study [1] to record the activity of lower region of TrA/obliquus internus which is difficult to compare with intramuscular EMG studies using finewire electrodes. This reply will mainly focus on studies having used fine-wire recordings of trunk muscles and concerns the differences in motor control between periphery-related feedback and preprogrammed feedforward. Mr Mal's Letter to the Editor quoted a specific study on flexion/extension trunk movement produced by a dropping weight and in which TrA activation was observed within 50 ms after the perturbation [2]. This has been used as evidence to suggest that TrA activation during rapid arm movement is the result of a respiratory reflex due to the distortion of the ribcage. However, the nature of TrA activation during rapid arm movement cannot be inferred by a weight-dropping task that involves a contraction of the trunk muscles in reaction to the perturbation. Precisely, the activation of the trunk proprioceptive receptors induces a reflex contraction of the trunk muscle to counteract this force. This feedback loop is different from the feedforward response of the muscle (or anticipatory postural adjustment [APA] including TrA activation before limb movement onset). Indeed, feedforward does not depend on feedback from the periphery and is rather pre-programmed as an inherent part of the motor command, i.e. in function of the context of the task [3-5]. In line, Hodges et al. (1996) published the first study showing that TrA was part of the trunk APA following rapid unilateral arm movements [6]. TrA activation was observed 24-39 ms before the agonist of movement (deltoid muscle) and thus could not have been triggered by a reflex or a feedback loop [3-5]. Also, if the sole movement of the arm produces a respiratory reflex triggering TrA activation, then it could be expected that any arm movement could trigger activation of TrA independently of the velocity of arm movement. It was conversely reported that TrA activation actually depends on the velocity of arm movement, the faster the arm movement, the earlier the TrA activation. In shoulder flexion performed at slow, natural and fast velocities, TrA was activated 406 ± 146 ms after the deltoid activation, 32 ± 21 ms after the deltoid and 39 ± 8 before the deltoid, respectively [7]. This suggests that TrA is activated in anticipation of the expected reactive force/perturbation produced by the upcoming arm movement. Also, TrA is composed of different regions of different anatomical morphology that can be divided in upper, middle and lower parts [8]. These different regions present different fascicle orientation: upper region is more or less horizontal, middle and lower are oriented caudomedially (−13°and −20°, respectively) [8]. Interestingly, in rapid shoulder flexion movement, the middle and lower TrA regions are activated earlier than the upper region [9]. However, this upper region of TrA mostly inserts onto the ribcage, thus if TrA activation had to be explained by a respiratory reflex, then the upper part should be the first activated, not the latest. This clearly suggests that the different regions of the TrA are activated according to their fascicle orientation rather than their attachment onto the ribcage [9,10]. Nevertheless, although the abovementioned studies provided compelling evidences of the role of TrA muscle in postural control and APA (anticipation of perturbation), it remains unclear whether respiration could have modulated the trunk muscle activation and been a confounding factor in these studies. As described by Mr Mal, TrA is an expiratory muscle [11] thus its activation could depend on both the postural context and the respiratory phase in which the muscle is tested. For instance, the APA-related activation of TrA during expiration could be earlier than during inspiration because of a prior facilitation of TrA motoneuron pools coming from the ponto-medullary respiratory center. It was shown however that the phase of the respiration cycle in quiet breathing did not influence TrA onset [12]. It is only during a forceful expiration (below functional residual capacity) that TrA activation is fastened whereas it is delayed by a static expulsive maneuver (expiration against closed glottis) [12]. This emphasised the complex supraspinal control of TrA in both posture and respiration that depends on the task requirements. More precisely, a mere facilitation of TrA excitability at the motoneuronal level during different respiratory challenges did not systematically result in earlier activation of TrA. A series of studies by P Hodges and S Gandevia investigated the postural control of the diaphragm and abdominal muscles (including TrA) during single rapid arm movement and during repeated arm movements [13-16]. These articles enlightened the role of diaphragm and of TrA muscles in the control of posture, spine and respiration. Both the diaphragm and the TrA were activated in a feedforward manner, i.e. before the activation of the agonist muscle during a rapid arm movement, thus suggesting that these activations did belong to the pre-programmed motor command [13]. Interestingly, repeated arm flexion and extension produced a tonic activation of both TrA and diaphragm muscles with a phasic increase of diaphragm activation during inspiration and a phasic increase of TrA activation during expiration [14,15]. The power spectra of both muscles EMG activity were locked with the frequency of the respiration cycle and with the frequency of the arm movement [14,15]. The increase of arm movement frequency augmented the tonic activation of the diaphragm similarly to other trunk muscles involved in the control of trunk posture but not involved in the
in both tasks. People with right-sided CLBP presented with increased M1 excitability in both hemi... more in both tasks. People with right-sided CLBP presented with increased M1 excitability in both hemispheres and earlier MF APA. These results likely rely on cortical motor adaptation related to the tasks and axial muscles tested. Future studies should investigate whether CLBP side-related differences have a clinical impact, e.g. in diagnosis and intervention.
h i g h l i g h t s • Isometric vs. global exercises of multifidus muscles had different effects.... more h i g h l i g h t s • Isometric vs. global exercises of multifidus muscles had different effects. • Isometric exercise influenced brain plasticity and fastened postural adjustment. • Changes persisting after 3-week training and long-term effects are questioned.
This study defines the limits of stability in sitting, and quantitatively assesses two measures o... more This study defines the limits of stability in sitting, and quantitatively assesses two measures of postural control relative to these limits. Young, healthy subjects sat, feet unsupported, on an elevated force plate. The limits of stability were determined by a least square fit of an ellipse to the center of pressure (CoP) excursion during maximal leaning in 8 directions. These were highly symmetrical and centered within the base of support. The ellipses had a mean eccentricity of 0.66 (major axis in the sagittal plane) and covered an area approx. 1/3 of the base of support. The CoP was then monitored over 4 min of quiet sitting, during which the postural sway covered an area <0.05% of the limits of stability and was closely centered within the latter. Finally, targetdirected trunk movements were performed, in 5 directions, at 4 movement speeds and 3 target distances. Increased target distance and movement speed both decreased the margin of stability (distance between the CoP and the limits of stability), as did movement in the frontal plane, reflecting the eccentricity of the limits of stability. These combined findings support the validity of this quantitative method of defining the limits of stability in sitting, for healthy individuals.
Combining repetitive peripheral magnetic neurostimulation and motor training immediately decrease... more Combining repetitive peripheral magnetic neurostimulation and motor training immediately decreased chronic low back pain. • This intervention helped normalize the control of spine one week after study onset. • These motor and pain changes were paralleled by an increase of intracortical motor facilitation. ABSTRACT OBJECTIVE. The study tested whether combining repetitive peripheral magnetic neurostimulation (RPMS) and motor training of the superficial multifidus muscle (MF) better improved the corticomotor control of spine than training alone in chronic low back pain (CLBP). METHODS Twenty-one participants with CLBP were randomly allocated to [RPMS+training] and [Sham+training] groups for three sessions (S1-S3) over a week where MF was stimulated before training (volitional contraction). Training was also home-practiced twice a day. Changes were tested at S1 and S3 for anticipatory postural adjustments (APAs) of MF and semi-tendinosus (ST), MF EMG activation, cortical motor plasticity (transcranial magnetic stimulation) and pain/disability. 3 RESULTS The RPMS group showed immediate decrease of pain at S1, then improvement of MF activation, ST APA, M1 facilitation, and pain/disability at S3. Changes were larger when brain excitability was lower at baseline. Disability index remained improved one month later. CONCLUSIONS Combining RPMS with training of MF in CLBP impacted motor planning, MF and lumbopelvic spine motor control and pain/disability one week after the onset of protocol. Brain plasticity might have favoured motor learning and improved daily lumbopelvic spine control without pain generation. SIGNIFICANCE Clinically, RPMS impacted the function by improving the gains beyond those reached by training alone in CLBP.
plasticity of cortical maps controlling paravertebral muscles and likely including a different mo... more plasticity of cortical maps controlling paravertebral muscles and likely including a different motor strategy for the control of MF. Changes of M1 function may thus underlie impaired motor control of lumbopelvic spine and pain persistence in CLBP.
The purpose of this study was to assess whether changing the stance width has an effect on the ra... more The purpose of this study was to assess whether changing the stance width has an effect on the range of motion of hip flexion, knee flexion, and ankle dorsiflexion during an unloaded back squat, and whether these joint movements are affected by anthropometric differences. Thirty-two healthy, young adults performed unloaded back squats at three different stance widths, normalized to pelvic width. Joint angles were assessed using electromagnetic motion capture sensors on the sacrum, and thigh, shank and foot of the dominant leg. ANOVA comparison of joint angles for the three stance widths, at 10° intervals of thigh orientation during the squat, indicated that joint angles tended to be larger when stance width was narrower, with the most significant effects on ankle dorsiflexion. A greater trunk/thigh length ratio (relatively long trunk) also tended to be associated with lower ankle and knee angles, while a greater thigh/shank length ratio (relatively long thigh) tended to be associated with higher ankle and knee angles, for the two narrower stance widths. The most practical implication of our findings is that individuals with limited ankle dorsiflexion, or with particularly long legs / thighs, may benefit from a wider stance width when squatting.
Background: Motion assessment of the body's head-arms-trunk (HAT) using linked-segment models, al... more Background: Motion assessment of the body's head-arms-trunk (HAT) using linked-segment models, along with an inverse dynamics approach, can enable in vivo estimations of inter-vertebral moments. However, this mathematical approach is prone to experimental errors because of inaccuracies in (i) kinematic measurements associated with soft tissue artifacts and (ii) estimating individual-specific body segment parameters (BSPs). The inaccuracy of the BSPs is particularly challenging for the multi-segment HAT due to high inter-participant variability in the HAT's BSPs and no study currently exists that can provide a less erroneous estimation of the joint moments along the spinal column. Research question: This study characterized three-dimensional (3D) inter-segmental moments in a multi-segment HAT model during multi-directional trunk-bending, after minimizing the experimental errors. Method: Eleven healthy individuals participated in a multi-directional trunk-bending experiment in five directions with three speeds. A seven-segment HAT model was reconstructed for each participant, and its motion was recorded. After compensating for experimental errors due to soft tissue artifacts, and using optimized individualspecific BSPs, and center of pressure offsets, the inter-segmental moments were calculated via inverse dynamics. Results: Our results show a significant effect of the inter-segmental level and trunk-bending directions on the obtained moments. Compensating for soft tissue artifacts contributed significantly to reducing errors. Our results indicate complex, task-specific patterns of the 3D moments, with high inter-participant variability at different inter-segmental levels, which cannot be studied using single-segment models or without error compensation. Significance: Interpretation of inter-segmental moments after compensation of experimental errors is important for clinical evaluations and developing injury prevention and rehabilitation strategies.
Journal of biomechanical engineering, Jun 21, 2018
Kinetics assessment of the human head-arms-trunk (HAT) complex via a multisegment model is a usef... more Kinetics assessment of the human head-arms-trunk (HAT) complex via a multisegment model is a useful tool for objective clinical evaluation of several pathological conditions. Inaccuracies in body segment parameters (BSPs) are a major source of uncertainty in the estimation of the joint moments associated with the multisegment HAT. Given the large intersubject variability, there is currently no comprehensive database for the estimation of BSPs for the HAT. We propose a nonlinear, multistep, optimization-based, noninvasive method for estimating individual-specific BSPs and calculating joint moments in a multisegment HAT model. Eleven nondisabled individuals participated in a trunk-bending experiment and their body motion was recorded using cameras and a force plate. A seven-segment model of the HAT was reconstructed for each participant. An initial guess of the BSPs was obtained by individual-specific scaling of the BSPs calculated from the male visible human (MVH) images. The intersegmental moments were calculated using both bottom-up and top-down inverse dynamics approaches. Our proposed method adjusted the scaled BSPs and center of pressure (COP) offsets to estimate optimal individual-specific BSPs that minimize the difference between the moments obtained by top-down and bottom-up inverse dynamics approaches. Our results indicate that the proposed method reduced the error in the net joint moment estimation (defined as the difference between the net joint moment calculated via bottom-up and top-down approaches) by 79.3% (median among participants). Our proposed method enables an optimized estimation of individual-specific BSPs and, consequently, a less erroneous assessment of the three-dimensional (3D) kinetics of a multisegment HAT model.
Background: Lumbar belts have been shown to increase lumbar stiffness, but it is unclear if this ... more Background: Lumbar belts have been shown to increase lumbar stiffness, but it is unclear if this is associated with trunk muscle co-contraction, which would increase the compression on the spine. It has been hypothesized that lumbar belts increase lumbar stiffness by increasing intra-abdominal pressure, which would increase spinal stability without increasing the compressive load on the spine. Methods: Trunk muscle activity and lumbar stiffness and damping were measured in healthy and low-back pain subjects during three conditions: no lumbar belt; wearing an extensible lumbar belt; wearing a non-extensible lumbar belt. Muscle activity was measured while subjects performed controlled forward and backward 20°trunk sways. Lumbar stiffness and damping were measured by applying random continuous perturbation to the chest. Findings: External oblique activity was decreased when wearing either lumbar belt during all phases of movement, while rectus abdominis and iliocostalis activity were decreased during the phase of movement where the muscles were maximally active while wearing either belt. Trunk stiffness was greatly increased by wearing either belt. There were no consistent differences in either lumbar stiffness or muscle activity between the two belts. Wearing a lumbar belt had little to no effect on damping. There were no group differences in any of the measures between healthy and low-back pain populations. Interpretation: The findings are consistent with the hypothesis that lumbar belts can increase spinal stability by increasing intra-abdominal pressure, without any increase in the compressive load on the spine. The findings can also be generalized, for the first time, to subjects with low-back pain.
A major challenge in the assessment of intersegmental spinal column angles during trunk motion is... more A major challenge in the assessment of intersegmental spinal column angles during trunk motion is the inherent error in recording the movement of bony anatomical landmarks caused by soft tissue artifacts (STAs). This study aims to perform an uncertainty analysis and estimate the typical errors induced by STA into the intersegmental angles of a multisegment spinal column model during trunk bending in different directions by modeling the relative displacement between skin-mounted markers and actual bony landmarks during trunk bending. First, we modeled the maximum displacement of markers relative to the bony landmarks with a multivariate Gaussian distribution. In order to estimate the distribution parameters, we measured these relative displacements on five subjects at maximum trunk bending posture. Then, in order to model the error depending on trunk bending angle, we assumed that the error grows linearly as a function of the bending angle. Second, we applied our error model to the trunk motion measurement of 11 subjects to estimate the corrected trajectories of the bony landmarks and investigate the errors induced into the intersegmental angles of a multisegment spinal column model. For this purpose, the trunk was modeled as a seven-segment rigid-body system described using 23 reflective markers placed on various bony landmarks of the spinal column. Eleven seated subjects performed trunk bending in five directions and the three-dimensional (3D) intersegmental angles during trunk bending were calculated before and after error correction. While STA minimally affected the intersegmental angles in the sagittal plane (&lt;16%), it considerably corrupted the intersegmental angles in the coronal (error ranged from 59% to 551%) and transverse (up to 161%) planes. Therefore, we recommend using the proposed error suppression technique for STA-induced error compensation as a tool to achieve more accurate spinal column kinematics measurements. Particularly, for intersegmental rotations in the coronal and transverse planes that have small range and are highly sensitive to measurement errors, the proposed technique makes the measurement more appropriate for use in clinical decision-making processes.
Conflicts of interest statement The authors have no relevant financial activities and no conflict... more Conflicts of interest statement The authors have no relevant financial activities and no conflicts of interest to disclose in relation to this work. Highlights (3-5 bullets, maximum 85 characters with space per bullet) Pain catastrophizing is associated with altered neuromotor behavior during gait. Catastrophizers had higher EMG activation in certain trunk muscles during gait. Catastrophizers had less phasic modulation of other trunk muscles during gait. Activation of most muscles was correlated with pain catastrophizing scores.
Patients with chronic low back pain (CLBP) exhibit remodelling of the lumbar soft tissues such as... more Patients with chronic low back pain (CLBP) exhibit remodelling of the lumbar soft tissues such as muscle fatty infiltrations (MFI) and fibrosis of the lumbar multifidus (LuM) muscles, thickness changes of the thoracolumbar fascia (TLF) and perimuscular connective tissues (PMCT) surrounding the abdominal lateral wall muscles. Rehabilitative ultrasound imaging (RUSI) parameters such as thickness and echogenicity are sensitive to this remodelling. This experimental laboratory study aimed to explore whether these RUSI parameters (LuM echogenicity and fascia thicknesses), hereafter called dependent variables (DV) were linked to independent variables (IV) such as (1) other RUSI parameters (trunk muscle thickness and activation) and (2) physical and psychological measures. RUSI measures, as well as a clinical examination comprising physical tests and psychological questionnaires, were collected from 70 participants with LBP. The following RUSI dependent variables (RUSI‐DV), measures of passive tissues were performed bilaterally: (1) LuM echogenicity (MFI/fibrosis) at three vertebral levels (L3/L4, L4/L5 and L5/S1); (2) TLF posterior layer thickness, and (3) PMCT thickness of the fasciae between subcutaneous tissue thickness (STT) and external oblique (PMCTSTT/EO), between external and internal oblique (PMCTEO/IO), between IO and transversus abdominis (PMCTIO/TrA) and between TrA and intra‐abdominal content (PMCTTrA/IA). RUSI measures of trunk muscle's function (thickness and activation), also called measures of active muscle tissues, were considered as independent variables (RUSI‐IV), along with physical tests related to lumbar stability (n = 6), motor control deficits (n = 7), trunk muscle endurance (n = 4), physical performance (n = 4), lumbar posture (n = 2), and range of motion (ROM) tests (n = 6). Psychosocial measures included pain catastrophizing, fear‐avoidance beliefs, psychological distress, illness perceptions and concepts related to adherence to a home‐based exercise programme (physical activity level, self‐efficacy, social support, outcome expectations). Six multivariate regression models (forward stepwise selection) were generated, using RUSI‐DV measures as dependent variables and RUSI‐IV/physical/psychosocial measures as independent variables (predictors). The six multivariate models included three to five predictors, explaining 63% of total LuM echogenicity variance, between 41% and 46% of trunk superficial fasciae variance (TLF, PMCTSTT/EO) and between 28% and 37% of deeper abdominal wall fasciae variance (PMCTEO/IO, PMCTIO/TrA and PMCTTrA/IA). These variables were from RUSI‐IV (LuM thickness at rest, activation of IO and TrA), body composition (percent fat) and clinical physical examination (lumbar and pelvis flexion ROM, aberrant movements, passive and active straight‐leg raise, loaded‐reach test) from the biological domain, as well as from the lifestyle (physical activity level during sports), psychological (psychological distress—cognitive subscale, fear‐avoidance beliefs during physical activities, self‐efficacy to exercise) and social (family support to exercise) domains. Biological, psychological, social and lifestyle factors each accounted for substantial variance in RUSI‐passive parameters. These findings are in keeping with a conceptual link between tissue remodelling and factors such as local and systemic inflammation. Possible explanations are discussed, in keeping with the hypothesis‐generating nature of this study (exploratory). However, to impact clinical practice, further research is needed to determine if the most plausible predictors of trunk fasciae thickness and LuM fatty infiltrations have an effect on these parameters.
BACKGROUND Wearing a lumbosacral orthosis (LSO) is known to influence spine mechanics, but less i... more BACKGROUND Wearing a lumbosacral orthosis (LSO) is known to influence spine mechanics, but less is known about how LSOs affect motor control. Whether the use of a LSO can negatively affect motor control of the lumbar spine is still under debate. OBJECTIVE The current study examined the immediate effects of two flexible LSOs (extensible and non-extensible) on the anticipatory postural adjustments that prepare the spine for a predictable perturbation. DESIGN A comparative study using a repeated measures design in a laboratory setting. METHODS Healthy controls (n = 20) and participants with low back pain (n = 40) performed a rapid arm flexion/extension cycle with and without these LSOs. The latency between the activations of the shoulder and different back (iliocostalis lumborum) and abdominal (rectus abdominis, internal and external obliques) muscles, as measured with surface electromyography, was used as the outcome. RESULTS The effects, which were comparable between groups and between LSOs, were mixed, with some muscles showing significantly (p ˂ 0.05) earlier activation and others showing delayed activation with the use of a LSO, relative to the control condition. The corresponding effect sizes were low to average (Hedges's g range: 0.17-0.48). CONCLUSIONS These findings suggest a change in the motor program before task initiation, which might be generalizable to other activities of daily living or work. However, none of the effects were large, making it difficult to provide clear conclusions with regard to their clinical relevance. It remains to be tested whether these immediate adaptations in motor planning can induce long term detrimental effects to the control of lumbar stability.
BackgroundLumbar stabilization exercise programs (LSEPs) act positively on clinical outcome measu... more BackgroundLumbar stabilization exercise programs (LSEPs) act positively on clinical outcome measures in patients with low back pain (LBP), but the underlying mechanisms are not well understood. Among the various neuromuscular mechanisms, a good candidate is better activation of the abdominal wall, as measured with rehabilitative ultrasound imaging (RUSI).ObjectivesTo determine whether RUSI measures are (1) sensitive to LBP status and treatment (LSEP) and (2) correlate with clinical outcomes following the LSEP.DesignAn exploratory one‐arm clinical trial with healthy participants as a control group.SettingLSEP was delivered in a clinical setting; outcomes were measured in a laboratory setting.ParticipantsThirty‐one patients with nonacute LBP and 30 healthy controls.MethodsOutcome measures were performed before and after an 8‐week LSEP in patients with LBP, and with the same time interval for control participants to compare with patients at baseline.Main Outcome MeasurementsPain, disability, as well as static (at rest) and dynamic (percent thickness change) RUSI measures for abdominal muscles (transversus abdominis, internal oblique [IO], and external oblique [EO]).ResultsPatients did not produce systematic changes in RUSI measures relative to controls, even if patients had significant improvement in pain and disability. However, the correlational analyses between the absolute change (pre‐ to post‐LSEP) (1) of EO and IO thickness (in mm) at rest (bilaterally), and (2) in pain following the LSEP were significant and consistent (range: .36‐.45) in patients.ConclusionsAlthough positive clinical improvements were observed following LSEP, there were minimal systematic changes in RUSI measures, likely because patients were not different from controls at baseline. Correlational analyses, however, indicated that greater reductions in pain were associated with reduced thickness of the EO and IO following the LSEP, suggesting the presence of some heterogeneity (or clinical subgroups) among the patients.Level of EvidenceII
Background: Previous findings suggest that wearing a lumbar belt may benefit some patients with l... more Background: Previous findings suggest that wearing a lumbar belt may benefit some patients with low back pain; however, the mechanisms of action are not yet fully understood. Research question: The effect of wearing two flexible (extensible and non-extensible) lumbar belts on trunk postural control was investigated during an unstable sitting task. Methods: Healthy subjects and subjects with LBP sat on a wobbling chair, with and without the lumbar belts. Chair rotation was measured in the sagittal and frontal planes, and 10 linear and nonlinear measures of balance were computed to assess the quantity (3 measures) and quality (7 measures) of the movements. Results: Both lumbar belts induced similar changes in specific measures of trunk postural control, for both subject groups, generally indicative of more instability and less controllability, but with low effect sizes (0.14 and 0.40). Subjects with LBP also showed lower entropy (complexity; effect size 0.93) and higher determinism (predictability; effect size 0.56) than healthy controls, under all test conditions. These findings indicate that the subjects with LBP used a less complex, more predictable trunk postural control strategy, suggestive of impaired adaptability and responsiveness to dynamic trunk postural control demands. The findings also suggest other factors related to dynamic adaptability may be impaired by lumbar belt use. Significance: The effects of the lumbar belts on trunk postural control were small, however, their practical implications for the management of LBP remain to be determined in relation to other effects of lumbar belts (e.g. increased mechanical stiffness).
Journal of Electromyography and Kinesiology, Aug 1, 2017
Disturbances to balance arising from forces applied to the upper limb have received relatively li... more Disturbances to balance arising from forces applied to the upper limb have received relatively little attention compared to disturbances arising from support surface perturbations. In this study we applied fast ramp perturbations to the hand in anterior, posterior, medial and lateral directions. The effects of perturbation predictability and amplitude on the postural response of upper limb, trunk and lower limb muscles were investigated. Perturbations were applied either in blocks of constant amplitude and direction (predictable) or with direction and amplitude varying randomly (random) from trial to trial. The spatial-temporal patterns of anticipatory muscle activation under the predictable condition and the reactionary responses following the perturbation under both conditions were similarly organized. The size of the response increased systematically with the perturbation magnitude for both anticipatory and reactionary changes in muscle activation. However, the slope of the relation between perturbation amplitude and the magnitude of the change in muscle activation was greater when perturbations were predictable than when they were randomly selected. The timing of both the anticipatory and reactionary increases in muscle activation was invariant across perturbation amplitudes. The characteristics of the reactionary responses have a similar organization to the long latency muscle responses to support surface perturbations.
Uploads
Papers by Richard Preuss