Search for: abdominal-wall-musculature
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    Relative efficiency of abdominal muscles in spine stability

    , Article Computer Methods in Biomechanics and Biomedical Engineering ; Volume 11, Issue 3 , 2008 , Pages 291-299 ; 10255842 (ISSN) Arjmand, N ; Shirazi Adl, A ; Parnianpour, M ; Sharif University of Technology
    Using an iterative kinematics-driven nonlinear finite element model, relative efficiency of individual abdominal muscles in spinal stability in upright standing posture was investigated. Effect of load height on stability and muscle activities was also computed under different coactivity levels in abdominal muscles. The internal oblique was the most efficient muscle (compared with the external oblique and rectus abdominus) in providing stability while generating smaller spinal loads with lower fatigue rate of muscles. As the weight was held higher, stability deteriorated requiring additional flexor-extensor activities. The stabilising efficacy of abdominal muscles diminished at higher... 

    Normal postural responses preceding shoulder flexion: Co-activation or asymmetric activation of transverse abdominis?

    , Article Journal of Back and Musculoskeletal Rehabilitation ; Vol. 27, issue. 4 , 2014 , p. 545-551 Davarian, S ; Maroufi, N ; Ebrahimi, E ; Parnianpour, M ; Farahmand, F ; Sharif University of Technology
    BACKGROUND AND OBJECTIVES: It is suggested that activation of the transverse abdominis muscle has a stabilizing effect on the lumbar spine by raising intra-abdominal pressure without added disc compression. However, its feedforward activity has remained a controversial issue. In addition, research regarding bilateral activation of trunk muscles during a unilateral arm movement is limited. The aim of this study was to evaluate bilateral anticipatory activity of trunk muscles during unilateral arm flexion.MATERIALS AND METHODS: Eighteen healthy subjects (aged 25 ± 3.96 years) participated in this study and performed 10 trials of rapid arm flexion in response to a visual stimulus. The... 

    A novel stability and kinematics-driven trunk biomechanical model to estimate muscle and spinal forces

    , Article Medical Engineering and Physics ; Vol. 36, issue. 10 , 2014 , p. 1296-1304 Hajihosseinali, M ; Arjmand, N ; Shirazi-Adl, A ; Farahmand, F ; Ghiasi, M. S ; Sharif University of Technology
    An anatomically detailed eighteen-rotational-degrees-of-freedom model of the human spine using optimization constrained to equilibrium and stability requirements is developed and used to simulate several symmetric tasks in upright and flexed standing postures. Predictions of this stability and kinematics-driven (S. +. KD) model for trunk muscle forces and spine compressive/shear loads are compared to those of our existing kinematics-driven (KD) model where both translational and rotational degrees-of-freedom are included but redundancy is resolved using equilibrium conditions alone. Unlike the KD model, the S. +. KD model predicted abdominal co-contractions that, in agreement with... 

    Comparison of spinal stability following motor control and general exercises in nonspecific chronic low back pain patients

    , Article Clinical Biomechanics ; Volume 48 , 2017 , Pages 42-48 ; 02680033 (ISSN) Shamsi, M ; Sarrafzadeh, J ; Jamshidi, A ; Arjmand, N ; Ghezelbash, F ; Sharif University of Technology
    Background Motor control exercise was claimed to improve spinal stability in patients with chronic non-specific back pain, but to investigate the effectiveness of this exercise, other outcome measures have been used rather than spinal stability itself. The aim of our study is to assess motor control exercise effects on spinal stability using a biomechanical model. Methods Fifty-one patients were assigned to either motor control or general exercises. Before and after trainings, participants were tested for spinal stability at seven isometric tasks. Electromyography signals were recorded from ten superficial muscles, and a hybrid EMG-driven musculoskeletal model estimated spinal stability... 

    Can lumbosacral orthoses cause trunk muscle weakness? A systematic review of literature

    , Article Spine Journal ; Volume 17, Issue 4 , 2017 , Pages 589-602 ; 15299430 (ISSN) Azadinia, F ; Ebrahimi Takamjani, E ; Kamyab, M ; Parnianpour, M ; Cholewicki, J ; Maroufi, N ; Sharif University of Technology
    Elsevier Inc  2017
    Background Wearing lumbosacral orthosis (LSO) is one of the most common treatments prescribed for conservative management of low back pain. Although the results of randomized controlled trials suggest effectiveness of LSO in reducing pain and disability in these patients, there is a concern that prolonged use of LSO may lead to trunk muscle weakness and atrophy. Purpose The present review aimed to evaluate available evidence in literature to determine whether LSO results in trunk muscle weakness or atrophy. Study Design This is a systematic review. Methods A systematic search of electronic databases including PubMed, Scopus, ScienceDirect, and Medline (via Ovid) followed by hand search of... 

    Spinal muscle forces, internal loads and stability in standing under various postures and loads - Application of kinematics-based algorithm

    , Article European Spine Journal ; Volume 14, Issue 4 , 2005 , Pages 381-392 ; 09406719 (ISSN) Shirazi Adl, A ; El-Rich, M ; Pop, D. G ; Parnianpour, M ; Sharif University of Technology
    This work aimed to evaluate trunk muscle forces, internal loads and stability margin under some simulated standing postures, with and without external loads, using a nonlinear finite element model of the T1-S1 spine with realistic nonlinear load-displacement properties. A novel kinematics-based algorithm was applied that exploited a set of spinal sagittal rotations, initially calculated to minimize balancing moments, to solve the redundant active-passive system. The loads consisted of upper body gravity distributed along the spine with or without 200 N held in the hands, either in the front of the body or on the sides. Nonlinear and linear stability/perturbation analyses at deformed,... 

    Is there a reliable and invariant set of muscle synergy during isometric biaxial trunk exertion in the sagittal and transverse planes by healthy subjects?

    , Article Journal of Biomechanics ; Volume 48, Issue 12 , Sep , 2015 , Pages 3234-3241 ; 00219290 (ISSN) Sedaghat Nejad, E ; Mousavi, S. J ; Hadizadeh, M ; Narimani, R ; Khalaf, K ; Campbell Kyureghyan, N ; Parnianpour, M ; Sharif University of Technology
    Elsevier Ltd  2015
    It has been suggested that the central nervous system simplifies muscle control through basic units, called synergies. In this study, we have developed a novel target-matching protocol and used non-negative matrix factorization (NMF) technique to extract trunk muscle synergies and corresponding torque synergies. Isometric torque data at the L5/S1 level and electromyographic patterns of twelve abdominal and back muscles from twelve healthy participants (five females) were simultaneously recorded. Each participant performed a total number of 24 isometric target-matching tasks using 12 different angular directions and 2 levels of uniaxial and biaxial exertions. Within- and between-subject... 

    Investigation of trunk muscle activities during lifting using a multi-objective optimization-based model and intelligent optimization algorithms

    , Article Medical and Biological Engineering and Computing ; Volume 54, Issue 2-3 , 2016 , Pages 431-440 ; 01400118 (ISSN) Ghiasi, M. S ; Arjmand, N ; Boroushaki, M ; Farahmand, F ; Sharif University of Technology
    Springer Verlag  2016
    A six-degree-of-freedom musculoskeletal model of the lumbar spine was developed to predict the activity of trunk muscles during light, moderate and heavy lifting tasks in standing posture. The model was formulated into a multi-objective optimization problem, minimizing the sum of the cubed muscle stresses and maximizing the spinal stability index. Two intelligent optimization algorithms, i.e., the vector evaluated particle swarm optimization (VEPSO) and nondominated sorting genetic algorithm (NSGA), were employed to solve the optimization problem. The optimal solution for each task was then found in the way that the corresponding in vivo intradiscal pressure could be reproduced. Results... 

    Trunk biomechanics during maximum isometric axial torque exertions in upright standing

    , Article Clinical Biomechanics ; Volume 23, Issue 8 , 2008 , Pages 969-978 ; 02680033 (ISSN) Arjmand, N ; Shirazi Adl, A ; Parnianpour, M ; Sharif University of Technology
    Background: Activities involving axial trunk rotations/moments are common and are considered as risk factors for low back disorders. Previous biomechanical models have failed to accurately estimate the trunk maximal axial torque exertion. Moreover, the trunk stability under maximal torque exertions has not been investigated. Methods: A nonlinear thoracolumbar finite element model along with the Kinematics-driven approach is used to study biomechanics of maximal axial torque generation during upright standing posture. Detailed anatomy of trunk muscles with six distinct fascicles for each abdominal oblique muscle on each side is considered. While simulating an in vivo study of maximal axial...