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Total 220 records

    Muscle-driven forward dynamics simulation for the study of differences in muscle function during stair ascent and descent

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; October 1, 2009 Vol.223: 863-874 Selk Ghafari, A. (Ali) ; Meghdari, A ; Vossoughi, G. R ; Sharif University of Technology
    Abstract
    The main scope of this study is to analyse muscle-driven forward dynamics simulation of stair locomotion to understand the functional differences of individual muscles during the movement. A static optimization was employed to minimize a performance criterion based on the muscle energy consumption to resolve muscle redundancy during forward dynamics simulation. The proposed method was employed to simulate a musculoskeletal system with ten degrees of freedom in the sagittal plane and containing 18 Hill-type musculotendon actuators per leg. Simulation results illustrated that simulated joint kinematics closely tracked experimental quantities with root-mean-squared errors less than 1 degree. In... 

    Reliability of electromyographic and torque measures during isometric axial rotation exertions of the trunk

    , Article Clinical Neurophysiology ; Volume 114, Issue 12 , 2003 , Pages 2355-2361 ; 13882457 (ISSN) Ng, J. K.-F ; Parnianpour, M ; Kippers, V ; Richardson, C. A ; Sharif University of Technology
    Elsevier Ireland Ltd  2003
    Abstract
    Objective: The aim of the present study was to investigate the between-days reliability of electromyographic (EMG) measurement of 6 bilateral trunk muscles and also the torque output in 3 planes during isometric right and left axial rotation at different exertion levels. Methods: Ten healthy subjects performed isometric right and left axial rotation at 100, 70, 50 and 30% maximum voluntary contractions in two testing sessions at least 7 days apart. EMG amplitude and frequency analyses of the recorded surface EMG signals were performed for rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum and multifidus bilaterally. The primary torque in the... 

    Investigation on a developed wearable assistive device (WAD) in reduction lumbar muscles activity

    , Article Biomedical Engineering - Applications, Basis and Communications ; Volume 25, Issue 3 , 2013 ; 10162372 (ISSN) Heydari, H ; Hoviattalab, M ; Azghani, M. R ; Ramezanzadehkoldeh, M ; Parnianpour, M ; Sharif University of Technology
    2013
    Abstract
    A new wearable assistive device (WAD) was developed to decrease required force on the lumbar spine in static holding tasks. In order to obtain moments on lumbar spine in two conditions, with and without WAD, a biomechanical static model was used for estimation of external moments on lumbar spine. The results of biomechanical models indicated that there was a reduction in the lumbar moment ranging from 20% to 43% using WAD depending on the load and flexion angle. A total of 15 male healthy subjects were tested to experimentally verify the predicted reduction of external moments on the spine by wearing WAD. Normalized electromyography (EMG) of the right and left lumbar and thoracic erector... 

    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
    Abstract
    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... 

    Coordinated activities of trunk and upper extremity muscles during walker-assisted paraplegic gait: A synergy study

    , Article Human Movement Science ; Volume 62 , 2018 , Pages 184-193 ; 01679457 (ISSN) Baniasad, M ; Farahmand, F ; Arazpour, M ; Zohoor, H ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    Individuals with spinal cord injury (SCI) at lower thoracic levels might walk independently with the aid of mechanical orthoses and walker by using their unimpaired trunk and upper extremity muscles (TUEM). The required motor skills and the associated subtasks of the paraplegic locomotion, however, have not been well understood yet. The purpose of this study was to investigate the coordination of the TUEM activities throughout the paraplegic gait cycle using synergy analysis. For eight paraplegic individuals (30.6 ± 11.6 years; SCI level: T12), the kinematics data and the surface electromyography (EMG) signals of TUEM were recorded during 15 gait cycles. Non-negative matrix factorization... 

    The influence of temperature alterations on eccentric contraction-induced isometric force and desmin loss in ratmedial gastrocnemius muscle

    , Article Journal of Medical Sciences ; Volume 8, Issue 2 , 2008 , Pages 162-169 ; 16824474 (ISSN) Vasaghi Gharamaleki, B ; Keshavarz, M ; Gharibzadeh, S ; Sotodeh, M ; Marvi, H ; Mosayebnejad, J ; Ebrahimi Takamjani, I ; Sharif University of Technology
    2008
    Abstract
    In this study isolated perfused rat muscle was used to examine the direct effect of temperature changes on the eccentric contraction-induced force and desmin loss. The left medial gastrocnemius muscle was separated and the entire lower limb was transferred into a prewarmed (35°C) organ bath. Temperature was adjusted to 31 or 39°C before and during eccentric contractions. Maximal isometric force and desmin loss were measured after 15 isometric or eccentric contractions. According to our data, organ bath temperature changes before or during eccentric contractions had no significant effect on force loss. However, a strong correlation between desmin loss and temperature changes before (r = 0.93,... 

    Generating the Activation Patterns of the Leg Muscles during Human Locomotion Using the Central Pattern Generators as a Control Structure

    , Article Iranian Journal of Science and Technology - Transactions of Mechanical Engineering ; Volume 40, Issue 2 , 2016 , Pages 87-94 ; 22286187 (ISSN) Haghpanah, S. A ; Farahmand, F ; Zohoor, H ; Razeghi, M ; Sharif University of Technology
    Shiraz University 
    Abstract
    The central pattern generators have been considered as a method to simplify the control of the complex rhythmic motions, e.g., walking, by the central nervous system. In this study, a control structure was designed to control the soleus and tibialis anterior muscles in a complete gait cycle. The activation patterns of the muscles were measured experimentally and used as the reference signals of a tracking problem. The hip angle and ground reaction force were also used as a feedforward. The feedback from the Golgi tendon acted as a regulator of muscle activity. The controller was applied to two gait trials. The results indicated that the designed controller was capable of tracking the... 

    The effect of temperature on eccentric contraction-induced isometric force loss in isolated perfused rat medial gastrocnemius muscle

    , Article Tehran University Medical Journal ; Volume 66, Issue 6 , 2008 , Pages 388-395 ; 16831764 (ISSN) Vasaghi Gharamaleki, B ; Keshavarz, M ; Gharibzadeh, S ; Marvi, H ; Mosayebnejad, J ; Ebrahimi Takamjani, E ; Sharif University of Technology
    Tehran University of Medical Sciences  2008
    Abstract
    Background: The typical features of eccentric exercise-induced muscle damage are delayed-onset muscle soreness (DOMS) and prolonged loss of muscle strength. It has been shown that passive warmth is effective in reducing muscle injury. Due to the interaction of different systems in vivo, we used isolated perfused medial gastrocnemius skeletal muscle to study the direct effect of temperature on the eccentric contraction-induced force loss. Methods: After femoral artery cannulation of a rat, the left medial gastrocnemius muscle was separated and then the entire lower limb was transferred into a prewarmed (35oC) chamber. With the chamber temperature at 31, 35 and 39oC before and during eccentric... 

    Dynamic iso-resistive trunk extension simulation: Contributions of the intrinsic and reflexive mechanisms to spinal stability

    , Article Technology and Health Care ; Volume 15, Issue 6 , 2007 , Pages 415-431 ; 09287329 (ISSN) Davarani, S. Z ; Shirazi Adl, A ; Hemami, H ; Mousavi, S. J ; Parnianpour, M ; Sharif University of Technology
    IOS Press  2007
    Abstract
    The effects of external resistance on the recruitment of trunk muscles and the role of intrinsic and reflexive mechanisms to ensure the spinal stability are significant issues in spinal biomechanics. A computational model of spine under the control of 48 anatomically oriented muscle actions was used to simulate iso-resistive trunk movements. Neural excitation of muscles was attained based on inverse dynamics approach along with the stability-based optimization. The effect of muscle spindle reflex response on the trunk movement stability was evaluated upon the application of a perturbation moment. In this study, the trunk extension movement at various resistance levels while extending from... 

    The effect of local muscle vibration on clinical and biomechanical parameters in people with knee osteoarthritis: A systematic review

    , Article Medical Journal of the Islamic Republic of Iran ; Volume 35, Issue 1 , 2021 , Pages 1-9 ; 10161430 (ISSN) Barati, K ; Esfandiari, E ; Kamyab, M ; Ebrahimi Takamjani, I ; Atlasi, R ; Parnianpour, M ; Yazdi, H ; ShahaIi, S ; Bidari, S ; Sharif University of Technology
    Iran University of Medical Sciences  2021
    Abstract
    Background: To identify and synthesize available published studies on the effect of local muscle vibration (LMV) on pain, stiffness, and function in individuals with knee OA.Methods: Five databases were searched to find relevant papers on April 29, 2020, including, PubMed, Scopus, EMBASE (Ovid), Science Citation Index, and COCHRANE Central Register for Controlled Trials (CENTRAL). Randomized controlled trials (RCTs) and nonrandomized-controlled-trials (non-RCTs), such as interrupted time series and prospective cohort studies were included. Two independent reviewers screened articles and assessed inclusion through predefined criteria. Participants' characteristics, study design, intervention... 

    Lumbopelvic muscle activation patterns in three stances under graded loading conditions: Proposing a tensegrity model for load transfer through the sacroiliac joints

    , Article Journal of Bodywork and Movement Therapies ; Vol. 18, Issue. 4 , October , 2014 , pp. 633-642 ; ISSN: 13608592 Pardehshenas, H ; Maroufi, N ; Sanjari, M. A ; Parnianpour, M ; Levin, S. M ; Sharif University of Technology
    Abstract
    Purpose: According to the conventional arch model of the pelvis, stability of the sacroiliac joints may require a predominance of form and force closure mechanisms: the greater the vertical shear force at the sacroiliac joints, the greater the reliance on self-bracing by horizontally or obliquely oriented muscles (such as the internal oblique). But what happens to the arch model when a person stands on one leg? In such cases, the pelvis no longer has imposts, leaving both the arch, and the arch model theory, without support. Do lumbopelvic muscle activation patterns in one-legged stances under load suggest compatibility with a different model? This study compares lumbopelvic muscle... 

    EMG activity normalization for trunk muscles in subjects with and without back pain

    , Article Medicine and Science in Sports and Exercise ; Volume 34, Issue 7 , 2002 , Pages 1082-1086 ; 01959131 (ISSN) Ng, J.K.-F ; Kippers, V ; Parnianpour, M ; Richardson, C. A ; Sharif University of Technology
    American College of Sports Medicine  2002
    Abstract
    Purpose: The aims of the present study were to examine electromyographic (EMG) activity of six bilateral trunk muscles during maximal contraction in three cardinal planes and to determine the direction of contraction that gives maximal activation for each muscle, both for healthy subjects and back-pain patients. Methods: Twenty-eight healthy subjects and 15 back-pain patients performed maximum voluntary contractions in three cardinal planes. Surface EMG signals were recorded from rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum, and multifidus bilaterally. Root mean square values of the EMG data were calculated to quantify the amplitude of EMG... 

    Dynamic stability of spine using stability-based optimization and muscle spindle reflex

    , Article IEEE Transactions on Neural Systems and Rehabilitation Engineering ; Volume 16, Issue 1 , 2008 , Pages 106-118 ; 15344320 (ISSN) Zeinali Davarani, S ; Hemami, H ; Barin, K ; Shirazi Adl, A ; Parnianpour, M ; Sharif University of Technology
    2008
    Abstract
    A computational method for simulation of 3-D movement of the trunk under the control of 48 anatomically oriented muscle actions was developed. Neural excitation of muscles was set based on inverse dynamics approach along with the stability-based optimization. The effect of muscle spindle reflex response on the trunk movement stability was evaluated upon the application of a perturbation moment. The method was used to simulate the trunk movement from the upright standing to 60° of flexion. Incorporation of the stability condition as an additional constraint in the optimization resulted in an increase in antagonistic activities demonstrating that the antagonistic co-activation acts to increase... 

    Role and significance of trunk and upper extremity muscles in walker-assisted paraplegic gait: a case study

    , Article Topics in Spinal Cord Injury Rehabilitation ; Volume 24, Issue 1 , 2018 , Pages 18-27 ; 10820744 (ISSN) Baniasad, M ; Farahmand, F ; Arazpour, M ; Zohoor, H ; Sharif University of Technology
    Thomas Land Publishers Inc  2018
    Abstract
    Background and Purpose: Understanding the role and significance of trunk and upper extremity muscles in paraplegic gait can help in designing more effective assistive devices for these patients and also provides valuable information for improving muscle strengthening programs. Methods: In a patient with a spinal cord injury (SCI) who could walk independently (rating scale of ambulatory capacity, 9) with the aid of bilateral ankle-foot orthosis and a walker, the kinematics, kinetics and electromyographic (EMG) activities of 16 muscles from the trunk and upper and lower extremities were recorded during gait. The onset, cessation, and duration of the EMG signal were associated with the 4 phases... 

    Trunk musculoskeletal response in maximum voluntary exertions: a combined measurement-modeling investigation

    , Article Journal of Biomechanics ; Volume 70 , March , 2018 , Pages 124-133 ; 00219290 (ISSN) Ghezelbash, F ; El Ouaaid, Z ; Shirazi Adl, A ; Plamondon, A ; Arjmand, N ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    Maximum voluntary exertion (MVE) tasks quantify trunk strength and maximal muscle electromyography (EMG) activities with both clinical and biomechanical implications. The aims here are to evaluate the performance of an existing trunk musculoskeletal model, estimate maximum muscle stresses and spinal forces, and explore likely differences between males and females in maximum voluntary exertions. We, therefore, measured trunk strength and EMG activities of 19 healthy right-handed subjects (9 females and 10 males) in flexion, extension, lateral and axial directions. MVEs for all subjects were then simulated in a subject-specific trunk musculoskeletal model, and estimated muscle activities were... 

    Simulation of mechanical force in skeletal muscle according to the intracellular Ca2+ concentration level

    , Article 2017 24th Iranian Conference on Biomedical Engineering and 2017 2nd International Iranian Conference on Biomedical Engineering, ICBME 2017, 30 November 2017 through 1 December 2017 ; 2018 ; 9781538636091 (ISBN) Karami, M ; Grasa, J ; Calvo, B ; Zohoor, H ; Firoozbakhsh, K ; Sharif University of Technology
    Abstract
    Active behavior in skeletal muscle soft tissue is affected by electrical, chemical and mechanical parameters. More realistic model of skeletal muscle demands detailed formulation which is able to involve other parameters in addition to mechanical ones. In this paper a new formulation for considering Ca2+ level (as the most important chemical factor) along with mechanical parameters in force producing process of skeletal muscle is introduced and validated comparing simulated results with some experimental data. Prepared skeletal muscle behavior is able to predict the maximum generated force in muscle according to the concentration of intracellular Ca2+ level and muscle contraction velocity... 

    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
    2008
    Abstract
    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... 

    Effect of considering stability requirements on antagonistic muscle activities using a musculoskeletal model of the human lumbar spine

    , Article 2013 20th Iranian Conference on Biomedical Engineering, ICBME 2013 ; 2013 , Pages 260-264 Hajihoseinali, M ; Nickpour, H ; Arjmand, N ; Farahmand, F ; Sharif University of Technology
    2013
    Abstract
    The recruitment pattern of trunk muscles is determined using a three-dimensional model of the spine with two joints and six symmetric pairs of muscles in which both equilibrium and stability requirements are satisfied. Model predictions are verified using Anybody Modeling System (AMS) and Abaqus. The model is used to test the hypothesis that antagonistic muscle activities are necessary for the spinal stability. The model with stability constraints predicts muscle activities greater than those predicted without stability consideration. In agreement with experimental data, the stability-based model predicts antagonistic muscle activities. It is shown that spinal stability increases with trunk... 

    Efficient design of a torque actuator for lower extremity exoskeleton based on muscle function analysis

    , Article 2011 International Conference on Mechatronics and Materials Processing, ICMMP 2011, Guangzhou, 18 November 2011 through 20 November 2011 ; Volume 328-330 , 2011 , Pages 1041-1044 ; 10226680 (ISSN) ; 9783037852385 (ISBN) Safavi, S ; Selk Ghafari, A ; Meghdari, A ; Guangzhou University ; Sharif University of Technology
    2011
    Abstract
    Several lower extremity exoskeletal systems have been developed for augmentation purpose. Common actuators, have important drawbacks such as complexity, and poor torque capacities. The main scope of this research is to propose a series elastic actuator for lower extremity exoskeletal system which was designed based on muscle functional analysis. For this purpose, a biomechanical framework consisting of a musculoskeletal model with ten degrees-of-freedom actuated by eighteen Hill-type musculotendon actuators per leg is utilized to perform the muscle functional analysis for common daily human activities. The simulation study illustrated functional differences between flexor and extensor... 

    Variations in trunk muscle activities and spinal loads following posterior lumbar surgery: A combined in vivo and modeling investigation

    , Article Clinical Biomechanics ; Volume 30, Issue 10 , 2015 , Pages 1036-1042 ; 02680033 (ISSN) Jamshidnejad, S ; Arjmand, N ; Sharif University of Technology
    Abstract
    Background Iatrogenic injuries to paraspinal muscles during posterior lumbar surgery cause a reduction in their contractile cross-sectional area and thus presumably their postoperative activation. This study investigates the effect of such intraoperative injuries on postoperative patterns of muscle activations and spinal loads during various activities using a combined modeling and in vivo MR imaging approach. Methods A three-dimensional, multi-joint, musculoskeletal model was used to estimate pre- and postoperative muscle forces and spinal loads under various activities in upright and flexed postures. According to our in vivo pre- and postoperative (∼ 6 months) measurements in six patients...