Occupational Health and Safety Research Institute Robert Sauve

Montréal, Canada

Occupational Health and Safety Research Institute Robert Sauve

Montréal, Canada
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LariviEre C.,Occupational Health and Safety Research Institute Robert Sauve | LariviEre C.,The Interdisciplinary Center | Da Silva R.A.,The Interdisciplinary Center | Da Silva R.A.,University of Northern Paraná | And 6 more authors.
Medicine and Science in Sports and Exercise | Year: 2010

Purpose: To determine whether dynamic back muscle endurance exercises in a semisitting position induce more fatigue in back muscles than that in hip extensors in healthy controls as well as in patients with nonspecific chronic low back pain. Methods: Sixteen healthy volunteers and 18 volunteers with nonspecific chronic low back pain performed trunk flexion-extension cycles until exhaustion at 60% of their strength in a machine designed for back exercise in a semisitting position with knees' angle at 135°. The number of cycles and perceived muscle fatigue (Borg CR-10 scale) at five areas (upper and lower back, gluteus, hamstrings, and quadriceps) were used as fatigue criteria. EMG signals were recorded bilaterally on four back muscles, two hip extensors (gluteus maximus and biceps femoris), and the vastus medialis. The slope values of the instantaneous median frequency values computed over time were retained as EMG indices of fatigue. Results: The number of cycles was equivalent in healthy controls (n = 23 ± 13) and patients with back pain (n = 27 ± 16). EMG indices of fatigue disclosed evidence of muscle fatigue in all the back muscles and the vastus medialis, contrary to hip extensors. EMG revealed significantly more muscle fatigue of lower back muscles, which was further corroborated by the Borg scale assessment. No between-group difference was obtained in any EMG comparison. Conclusion: These results showed that this type of exercise machine can specifically train the back muscles, and this as much in subjects with nonspecific chronic low back pain as in healthy controls. This has implications for the training of back muscle endurance, especially in patients with back pain for whom poor back muscle endurance is sometimes of concern. Copyright © 2010 by the American College of Sports Medicine.


Ludvig D.,University of Montréal | Ludvig D.,The Interdisciplinary Center | Lariviere C.,Occupational Health and Safety Research Institute Robert Sauve | Lariviere C.,The Interdisciplinary Center
Journal of Electromyography and Kinesiology | Year: 2016

Low-back pain (LBP) has been recognized as the leading cause of disability worldwide. Lumbar instability has been considered as an important mechanism of LBP and one potential contributor to lumbar stability is trunk muscle reflex activity. However, due to the differences in experimental paradigms used to quantify trunk mechanics and trunk reflexes it remains unclear as to what extent the reflex pathway contributes to overall lumbar stability. The goal of this work was to determine to what extent reflexes of various trunk muscles were elicited by the small continuous perturbations normally used to quantify trunk mechanics. Electromyographic (EMG) activity was measured bilaterally from 3 trunk extensor muscles and 3 trunk flexor muscles at four epochs: 25–50 ms, 50–75 ms, 75–100 ms and 100–125 ms following each perturbation. Reflex activity was seen in all muscles as 34 of the 48 muscle-epoch combinations showed a significant reflex response to either perturbations in the forward or backward direction. However, the reflex EMG activity did not correlate with mechanical estimates of the reflex response. Thus, even though reflexes are indeed elicited by the small perturbations used to quantify trunk mechanics, their exact contribution to overall lumbar stability remains unknown. © 2016 Elsevier Ltd


Butler H.L.,McGill University | Lariviere C.,Occupational Health and Safety Research Institute Robert Sauve | Hubley-Kozey C.L.,Dalhousie University | Sullivan M.J.L.,McGill University
European Spine Journal | Year: 2010

In chronic low back pain patients (CLBP), neuromuscular and pain intensity have been identified as contributing factors in the disability of the individual. However, it is unclear whether pain intensity influences neuromuscular activation and if directed attention mediates this relationship. Thus, the purpose of this study was to determine the effect of directed attention in individuals with different pain intensities on back extensor activation profiles. Fifty-four CLBP patients were separated into either high- or low-pain groups. Surface electromyograms were recorded from back muscles while the subjects performed a trunk flexion motion for four different attention conditions. Pattern recognition and repeated measures ANOVAs were used to examine the effect of sex, attention and pain intensity on temporal muscle activation patterns. The results showed that there was a significant sex × attention × pain interaction. The largest changes in muscle timing were observed in the low-pain group when their attention was focused on their pain, but the pattern of muscle activation differed between sexes. For males, a rapid decline in activation at mid-extension occurred, whereas females showed delayed activation at the beginning of extension. Overall, this study demonstrated that directed attention on pain had an effect on trunk muscle temporal recruitment, and that this relationship differed between sexes and pain groups. This suggests that sex-specific mechanisms may alter the neuromuscular control of the spine in CLBP patients for different pain levels. © 2010 Springer-Verlag.


Lariviere C.,Occupational Health and Safety Research Institute Robert Sauve | Lariviere C.,The Interdisciplinary Center | Gagnon D.,Université de Sherbrooke | Genest K.,Université de Sherbrooke
Journal of Electromyography and Kinesiology | Year: 2014

To assess the electromyographic (EMG) activation of trunk muscle during exertions performed in one primary plane (sagittal, frontal, transverse), we previously proposed a protocol allowing minimizing out-of-plane efforts (coupled moments - CMs) with the use of a static dynamometer combined with a visual feedback system. The aims of this study were to go further by testing motor learning and reliability issues related to such a protocol. Three identical sessions were conducted, where maximal voluntary contractions and submaximal ramp contractions were performed in six different directions while standing in the dynamometer. Two feedback conditions were tested, the simple 1D-feedback in the primary plane and the full 3D-feedback in all planes simultaneously. Surface EMG signals were collected from back and abdominal muscles and EMG amplitude and CMs were computed during the ramp contractions. Providing a 3D feedback to minimize CMs did not improve EMG reliability or in other words, did not reduce the within-subject variability. Providing three assessment days had practically no effect (no learning) on CMs and EMG variables. Overall, the reliability of EMG was at best moderate. However, although this limits its use on an individual basis, it still allows within- and between-group comparisons for research applications. © 2014 Elsevier Ltd.


Shahvarpour A.,Ecole Polytechnique de Montréal | Shirazi-Adl A.,Ecole Polytechnique de Montréal | Lariviere C.,Occupational Health and Safety Research Institute Robert Sauve | Bazrgari B.,University of Kentucky
Journal of Biomechanics | Year: 2015

Understanding the central nervous system (CNS) response strategy to trunk perturbations could help in prevention of back injuries and development of rehabilitation and treatment programs. This study aimed to investigate biomechanical response of the trunk musculoskeletal system under sudden forward loads, accounting for pre-perturbation conditions (preloading, initial posture and abdominal antagonistic coactivation) and perturbation magnitudes. Using a trunk kinematics-driven iterative finite element (FE) model, temporal profiles of measured kinematics and external load along with subjects' weights were prescribed to predict thoracolumbar muscle forces/latencies and spinal loads for twelve healthy subjects when tested in six conditions during pre- and post-perturbation periods. Results demonstrated that preloading the trunk significantly (i.e., p<0.05) increased pre-perturbation back muscle forces but significantly decreased post-perturbation peak muscle active forces and muscle latencies. Initial trunk flexion significantly increased muscle active and passive forces before the perturbation and their peak values after the perturbation, which in turn caused much larger spinal loads. Abdominal muscles antagonistic pre-activation did not alter the internal variables investigated in this study. Increase in sudden applied load increased muscle reflex activities and spinal forces; a 50. N increase in sudden load (i.e., when comparing 50. N to 100. N) increased the L5-S1 compression force by 1327. N under 5. N preload and by 1374. N under 50. N preload. Overall, forces on the spine and hence risk of failure substantially increased in sudden forward loading when the magnitude of sudden load increased and when the trunk was initially in a flexed posture. In contrast, a higher initial preload diminished reflex latencies and compression forces. © 2014 Elsevier Ltd.


Lariviere C.,Occupational Health and Safety Research Institute Robert Sauve | Lariviere C.,The Interdisciplinary Center | Da Silva R.A.,The Interdisciplinary Center | Da Silva R.A.,University of Northern Paraná | And 6 more authors.
Medicine and Science in Sports and Exercise | Year: 2011

Purpose: Roman chair exercises are popular for improving back muscle endurance but do not specifically target back muscles. This study aimed to determine whether an adaptation of the Roman chair exercise would induce more fatigue in back muscles than in hip extensors. Methods: For this study, 16 healthy subjects and 18 patients with nonspecific chronic low back pain performed trunk flexion-extension cycles until exhaustion in a Roman chair with hips flexed at 40°. Surface EMG signals were recorded bilaterally on four back muscles and two hip extensors (gluteus maximus and biceps femoris). Motion analysis of the trunk segments (pelvis, lumbar, and thoracic spines) was also carried out. Results: In both groups, EMG revealed clear evidence of muscle fatigue for the gluteus maximus, less clear evidence of fatigue for the lower back muscles, and motor unit recruitment (without fatigue) for the upper back muscles and biceps femoris. A change of muscle activation pattern was emphasized throughout the exercise bout, with some lower back muscles showing an increase followed by a decrease or leveling off of activation and with upper back muscles showing an increased activation at the end. Kinematic analyses revealed a progressive decrease (11°) in the lumbar range of motion (ROM) and a progressive increase in hip (2°) and thoracic (7°) ROM during the exercise bout. Conclusions: Roman chairs allow more freedom to change the kinematics of the spine during the exercise (less lumbar and more thoracic motion) to delay lower back muscle fatigue by sharing the load between the lower and upper back muscles. Even with adaptations to reduce hip extensors fatigue, this may make this exercise not as specific as wanted for fatiguing lower back muscles. © 2010 by the American College of Sports Medicine.


Shahvarpour A.,Ecole Polytechnique de Montréal | Shirazi-Adl A.,Ecole Polytechnique de Montréal | Lariviere C.,Occupational Health and Safety Research Institute Robert Sauve | Bazrgari B.,University of Kentucky
Journal of Biomechanics | Year: 2015

Spine stability demand influences active-passive coordination of the trunk response, especially during sudden perturbations. The objective of this study was to look at the role of passive, stationary active and reflexive subsystems on spinal stability. Spine stability was evaluated here during pre- and post-perturbation phases by computing the minimum (i.e., critical) muscle stiffness coefficient required to maintain stability. The effects of pre-perturbation conditions (preloading, initial posture and abdominal antagonistic coactivation) as well as perturbation magnitude were studied. Results revealed that higher preload, initially flexed trunk posture and abdominal pre-activation enhanced pre-perturbation stiffness and stability. In contrast to the preload, however, larger sudden load, initial flexion and abdominal preactivation significantly increased post-perturbation stability margin. As a result, much lower critical muscle stiffness coefficient was required post-perturbation. Compared to the pre-perturbation phase, the trunk stiffness and stability substantially increased post-perturbation demanding thus a much lower critical muscle stiffness coefficient. Overall, these findings highlight the crucial role of the ligamentous spine and muscles (in both passive and active states) in augmenting the trunk stiffness and hence stability during pre- and post-perturbation phases; a role much evident in the presence of initial trunk flexion. © 2015 Elsevier Ltd.


Lariviere C.,Occupational Health and Safety Research Institute Robert Sauve | Lariviere C.,The Interdisciplinary Center | Butler H.,Dalhousie University | Sullivan M.J.L.,The Interdisciplinary Center | And 3 more authors.
Clinical Journal of Pain | Year: 2013

OBJECTIVES: This study examined the effect of pain interference and attentional interference on the anticipatory postural adjustments of trunk muscles in patients with nonspecific chronic low back pain. METHODS: Fifty-nine patients performed rapid flexion movements of the right arm under 6 conditions, namely a control condition and conditions with different attention demands. The latency between the activations of the shoulder and different trunk muscles, as measured with surface electromyography, was used as the outcome. Using repeated measures analysis of variance, attention conditions and group comparisons were tested between those who scored high and low on pain intensity, fear of movement, or pain catastrophizing. RESULTS: There were significant (although minimal) interactive effects but significant and potentially clinically relevant group and attention main effects. The group with the lowest scores showed delayed activity (14 to 29 ms) relative to those with higher scores. One attention-demanding condition delayed (20 to 35 ms) the latencies of some trunk muscles relative to the control condition, namely the one that was the most attention-demanding according to the reaction time results. DISCUSSION: These findings suggest that patients with chronic low back pain, who are characterized by higher scores on some pain-related variables (visual analog scale, Tampa Scale of Kinesiophobia, Pain Catastrophizing Scale), react favorably to protect the spine from further pain and injuries but would be at greater risk of injury when performing a complex physical task requiring more attention demand. Copyright © 2012 by Lippincott Williams &Wilkins.


Lariviere C.,Occupational Health and Safety Research Institute Robert Sauve | Lariviere C.,The Interdisciplinary Center | Mecheri H.,Occupational Health and Safety Research Institute Robert Sauve | Mecheri H.,The Interdisciplinary Center | And 3 more authors.
Journal of Electromyography and Kinesiology | Year: 2013

Introduction: Adequate neuromuscular control of the lumbar spine is required to prevent lumbar injuries. A trunk postural stability test has been proposed earlier, using a chair wobbling on a central pivot and four springs with adjustable positions to modulate task difficulty. An inertial sensor is fixed on the chair to measure postural sway. The aim of this study is to assess the criterion validity and between-day reliability of the calibration and testing components. Methods: Thirty six subjects (with and without low back pain) followed a calibration procedure, four practice trials and three 60-s trials on 2. days. The criterion validity of the inertial sensor was tested against an optoelectronic system and a force platform. The reliability of 38 body sway measures obtained from the inertial sensor angular measures was estimated. Results: The inertial sensor led to valid estimates of postural sway. The reliability of the calibration procedure was moderate. Practically no learning effect was detected except for a few body sway measures in patients with CLBP. Three 60-s trials provided acceptable reliability for approximately half of the body sway measures, although this is more difficult to achieve in patients with CLBP. Discussion: The use of an easy to use inertial sensor led to valid measures of postural sway. A number of body sway measures were identified as reliable tools for individual follow-ups but inter-subject comparisons were anticipated as more difficult when patients with CLBP are involved. © 2013 Elsevier Ltd.


Shahvarpour A.,Ecole Polytechnique de Montréal | Shirazi-Adl A.,Ecole Polytechnique de Montréal | Mecheri H.,Occupational Health and Safety Research Institute Robert Sauve | Lariviere C.,Occupational Health and Safety Research Institute Robert Sauve
Journal of Electromyography and Kinesiology | Year: 2014

Unexpected loading of the spine is a risk factor for low back pain. The trunk neuromuscular and kinematics responses are likely influenced by the perturbation itself as well as initial trunk conditions. The effect of four parameters (preload, sudden load, initial trunk flexed posture, initial abdominal antagonistic activity) on trunk kinematics and back muscles reflex response were evaluated. Twelve asymptomatic subjects participated in sudden forward perturbation tests under six distinct conditions. Preload did not change the reflexive response of back muscles and the trunk displacement; while peak trunk velocity and acceleration as well as the relative load peak decreased. Sudden load increased reflex response of muscles, trunk kinematics and loading variables. When the trunk was initially flexed, back muscles latency was delayed, trunk velocity and acceleration increased; however, reflex amplitude and relative trunk displacement remained unchanged. Abdominal antagonistic preactivation increased reflexive response of muscles but kinematics variables were not affected. Preload, initial flexed posture and abdominal muscles preactivation increased back muscles preactivity. Both velocity and acceleration peaks of the trunk movement decreased with preload despite greater total load. In contrast, they increased in the initial flexed posture and to some extent when abdominal muscles were preactivated demonstrating the distinct effects of pre-perturbation variables on trunk kinematics and risk of injury. © 2014 Elsevier Ltd.

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