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    Non-linear dynamical features of center of pressure extracted by recurrence quantification analysis in people with unilateral anterior cruciate ligament injury

    , Article Gait and Posture ; Volume 31, Issue 4 , 2010 , Pages 450-455 ; 09666362 (ISSN) Negahban, H ; Salavati, M ; Mazaheri, M ; Sanjari, M. A ; Hadian, M. R ; Parnianpour, M ; Sharif University of Technology
    Knowledge about the non-linear dynamical pattern of postural sway may provide important insights into the adaptability (flexibility) of human postural control in response to everyday stresses imposed on the body. A commonly used non-linear tool, i.e. recurrence quantification analysis, was chosen to investigate the effect of prior anterior cruciate ligament injury on the deterministic pattern of postural sway under different conditions of postural and cognitive difficulty. In double leg stance, as postural difficulty increased from open-eyes to closed-eyes and rigid-surface to foam-surface, the centre of pressure regularity (%determinism) increased as well. In comparison to healthy... 

    The effects of anxiety and external attentional focus on postural control in patients with Parkinson’s disease

    , Article PLoS ONE ; Volume 13, Issue 2 , 2018 ; 19326203 (ISSN) Jazaeri, S. Z ; Azad, A ; Mehdizadeh, H ; Habibi, S. A ; Mandehgary Najafabadi, M ; Saberi, Z. S ; Rahimzadegan, H ; Moradi, S ; Behzadipour, S ; Parnianpour, M ; Taghizadeh, G ; Khalaf, K ; Sharif University of Technology
    Public Library of Science  2018
    Background Although anxiety is a common non-motor outcome of Parkinson's disease (PD) affecting 40% of patients, little attention has been paid so far to its effects on balance impairment and postural control. Improvement of postural control through focusing on the environment (i.e. external focus) has been reported, but the role of anxiety, as a confounding variable, remains unclear. Objectives This study aimed to investigate the influence of anxiety and attentional focus instruction on the standing postural control of PD patients. Methods Thirty-four patients with PD (17 with high anxiety (HA-PD) and 17 with low anxiety (LA-PD)), as well as 17 gender- and age-matched healthy control... 

    Kinematic analysis of dynamic lumbar motion in patients with lumbar segmental instability using digital videofluoroscopy

    , Article European Spine Journal ; Volume 18, Issue 11 , 2009 , Pages 1677-1685 ; 09406719 (ISSN) Ahmadi, A ; Maroufi, N ; Behtash, H ; Zekavat, H ; Parnianpour, M ; Sharif University of Technology
    The study design is a prospective, case-control. The aim of this study was to develop a reliable measurement technique for the assessment of lumbar spine kinematics using digital video fluoroscopy in a group of patients with low back pain (LBP) and a control group. Lumbar segmental instability (LSI) is one subgroup of nonspecific LBP the diagnosis of which has not been clarified. The diagnosis of LSI has traditionally relied on the use of lateral functional (flexion-extension) radiographs but use of this method has proven unsatisfactory. Fifteen patients with chronic low back pain suspected to have LSI and 15 matched healthy subjects were recruited. Pulsed digital videofluoroscopy was used... 

    Effects of lumbosacral orthosis on dynamical structure of center of pressure fluctuations in patients with non-specific chronic low back pain: A randomized controlled trial

    , Article Journal of Bodywork and Movement Therapies ; Volume 23, Issue 4 , 2019 , Pages 930-936 ; 13608592 (ISSN) Azadinia, F ; Ebrahimi Takamjani, I ; Kamyab, M ; Asgari, M ; Parnianpour, M ; Sharif University of Technology
    Churchill Livingstone  2019
    Background: A few clinical trials have examined the effect of treatment interventions on postural control in patients with chronic low back pain, all of which have exclusively evaluated postural stability using traditional linear measures of postural sway. However, postural control improvement cannot be determined by exclusively relying on linear measurements, because these parameters provide no information on underlying motor control mechanisms. Objective: This study aimed to compare the effect of using lumbosacral orthoses (LSO) together with routine physical therapy, compared to routine physical therapy alone on postural control, using nonlinear analysis techniques. Methods: Forty-four... 

    Time-course investigation of postural sway variability: Does anxiety exacerbate the sensory reweighting impairment in chronic stroke survivors?

    , Article Neuropsychologia ; Volume 127 , 2019 , Pages 185-194 ; 00283932 (ISSN) Jamali, S ; Azad, A ; Mehdizadeh, H ; Doostdar, A ; Hoseinpour, F ; Mehdizadeh, M ; Niazi Khatoon, J ; Shokouhyan, M. R ; Parnianpour, M ; Taghizadeh, G ; Khalaf, K ; Sharif University of Technology
    Elsevier Ltd  2019
    Although anxiety is one of the most prevalent psychological disorders in stroke survivors, its effect on sensory reweighting has not yet been fully studied. The aim of this work was to investigate how anticipation of collision avoidance events affects sensory reweighting in chronic stroke survivors with low and high levels of anxiety (LA-stroke and HA-stroke, respectively), as compared with healthy controls (HC), under the condition of perturbed proprioception. Eighteen LA-stroke and 18 HA-stroke survivors, as well as 18 gender- and age-matched HC, participated in this study. Postural sway variability (i.e. Root Mean Square (RMS) of the COP velocity) was measured for a duration of 180 s... 

    Effect of changes in the lumbar posture in lifting on trunk muscle and spinal loads: A combined in vivo, musculoskeletal, and finite element model study

    , Article Journal of Biomechanics ; Volume 104 , February , 2020 Khoddam Khorasani, P ; Arjmand, N ; Shirazi Adl, A ; Sharif University of Technology
    Elsevier Ltd  2020
    Irrespective of the lifting technique (squat or stoop), the lumbar spine posture (more kyphotic versus more lordotic) adopted during lifting activities is an important parameter affecting the active-passive spinal load distribution. The advantages in either posture while lifting remains, however, a matter of debate. To comprehensively investigate the role on the trunk biomechanics of changes in the lumbar posture (lordotic, free or kyphotic) during forward trunk flexion, validated musculoskeletal and finite element models, driven by in vivo kinematics data, were used to estimate detailed internal tissue stresses-forces in and load-sharing among various joint active-passive tissues. Findings... 

    Interaction analysis of a pregnant female uterus and fetus in a vehicle passing a speed bump

    , Article Journal of Biomechanics ; Volume 118 , March , 2021 ; 00219290 (ISSN) Irannejad Parizi, M ; Ahmadian, M. T ; Mohammadi, H ; Sharif University of Technology
    Elsevier Ltd  2021
    Pregnant vehicle occupants experience relatively large acceleration when the vehicle passes a speed-bump. In this paper, the effect of such sudden acceleration on a pregnant uterus is investigated. A biomechanical model representing the fundamental dynamic behaviors of a pregnant uterus has been developed. The model relates to the 32nd week of gestation when the fetus is in head-down, occipito-anterior position. Considering the drag and squeeze effects of the amniotic fluid, we derive a comprehensive differential equation that represents the interaction of the uterus and fetus. Solving the governing equation, we obtain the system response to different speed-bump excitations. Using the fetal... 

    Subject-specific 2D/3D image registration and kinematics-driven musculoskeletal model of the spine

    , Article Journal of Biomechanics ; Volume 57 , 2017 , Pages 18-26 ; 00219290 (ISSN) Eskandari, A. H ; Arjmand, N ; Shirazi Adl, A ; Farahmand, F ; Sharif University of Technology
    An essential input to the musculoskeletal (MS) trunk models that estimate muscle and spine forces is kinematics of the thorax, pelvis, and lumbar vertebrae. While thorax and pelvis kinematics are usually measured via skin motion capture devices (with inherent errors on the proper identification of the underlying bony landmarks and the relative skin-sensor-bone movements), those of the intervening lumbar vertebrae are commonly approximated at fixed proportions based on the thorax-pelvis kinematics. This study proposes an image-based kinematics measurement approach to drive subject-specific (musculature, geometry, mass, and center of masses) MS models. Kinematics of the thorax, pelvis, and... 

    Modeling and validation of a detailed FE viscoelastic lumbar spine model for vehicle occupant dummies

    , Article Computers in Biology and Medicine ; Volume 99 , 2018 , Pages 191-200 ; 00104825 (ISSN) Amiri, S ; Naserkhaki, S ; Parnianpour, M ; Sharif University of Technology
    Elsevier Ltd  2018
    The dummies currently used for predicting vehicle occupant response during frontal crashes or whole-body vibration provide insufficient information about spinal loads. Although they aptly approximate upper-body rotations in different loading scenarios, they overlook spinal loads, which are crucial to injury assessment. This paper aims to develop a modified dummy finite element (FE) model with a detailed viscoelastic lumbar spine. This model has been developed and validated against in-vitro and in-silico data under different loading conditions, and its predicted ranges of motion (RoM) and intradiscal pressure (IDP) maintain close correspondence with the in-vitro data. The dominant frequency... 

    Subject-specific loads on the lumbar spine in detailed finite element models scaled geometrically and kinematic-driven by radiography images

    , Article International Journal for Numerical Methods in Biomedical Engineering ; Volume 35, Issue 4 , 2019 ; 20407939 (ISSN) Dehghan Hamani, I ; Arjmand, N ; Shirazi Adl, A ; Sharif University of Technology
    Wiley-Blackwell  2019
    Traditional load-control musculoskeletal and finite element (FE) models of the spine fail to accurately predict in vivo intervertebral joint loads due mainly to the simplifications and assumptions when estimating redundant trunk muscle forces. An alternative powerful protocol that bypasses the calculation of muscle forces is to drive the detailed FE models by image-based in vivo displacements. Development of subject-specific models, however, both involves the risk of extensive radiation exposures while imaging in supine and upright postures and is time consuming in terms of the reconstruction of the vertebrae, discs, ligaments, and facets geometries. This study therefore aimed to introduce a... 

    Coupled artificial neural networks to estimate 3D whole-body posture, lumbosacral moments, and spinal loads during load-handling activities

    , Article Journal of Biomechanics ; Volume 102 , 2020 Aghazadeh, F ; Arjmand, N ; Nasrabadi, A. M ; Sharif University of Technology
    Elsevier Ltd  2020
    Biomechanical modeling approaches require body posture to evaluate the risk of spine injury during manual material handling. The procedure to measure body posture via motion-analysis techniques as well as the subsequent calculations of lumbosacral moments and spine loads by, respectively, inverse-dynamic and musculoskeletal models are complex and time-consuming. We aim to develop easy-to-use yet accurate artificial neural networks (ANNs) that predict 3D whole-body posture (ANNposture), segmental orientations (ANNangle), and lumbosacral moments (ANNmoment) based on our measurements during load-handling activities. Fifteen individuals each performed 135 load-handling activities by reaching (0... 

    Marker-less versus marker-based driven musculoskeletal models of the spine during static load-handling activities

    , Article Journal of Biomechanics ; Volume 112 , 2020 Asadi, F ; Arjmand, N ; Sharif University of Technology
    Elsevier Ltd  2020
    Evaluation of workers’ body posture in workstations is a prerequisite to estimate spinal loads and assess risk of injury for the subsequent design of preventive interventions. The Microsoft Kinect™ sensor is, in this regard, advantageous over the traditional skin-marker-based optical motion capture systems for being marker-less, portable, cost-effective, and easy-to-use in real workplaces. While several studies have demonstrated the validity/reliability of the Kinect for posture measurements especially during gait trials, its capability to adequately drive a detailed spine musculoskeletal model for injury risk assessments remains to be investigated. Lumbosacral (L5-S1) load predictions of a... 

    A new postural stability-indicator to predict the level of fear of falling in Parkinson's disease patients

    , Article BioMedical Engineering Online ; Volume 19, Issue 1 , 2020 Pourghayoomi, E ; Behzadipour, S ; Ramezani, M ; Joghataei, M. T ; Shahidi, G. A ; Sharif University of Technology
    BioMed Central  2020
    Background: Fear of falling (FoF) is defined as a lasting concern about falling that causes a person to limit or even stop the daily activities that he/she is capable of. Seventy percent of Parkinson's disease (PD) patients report activity limitations due to FoF. Timely identification of FoF is critical to prevent its additional adverse effects on the quality of life. Self-report questionnaires are commonly used to evaluate the FoF, which may be prone to human error. Objectives: In this study, we attempted to identify a new postural stability-indicator to objectively predict the intensity of FoF and its related behavior(s) in PD patients. Methods: Thirty-eight PD patients participated in the... 

    A novel coupled musculoskeletal finite element model of the spine – Critical evaluation of trunk models in some tasks

    , Article Journal of Biomechanics ; Volume 119 , 2021 ; 00219290 (ISSN) Rajaee, M. A ; Arjmand, N ; Shirazi Adl, A ; Sharif University of Technology
    Elsevier Ltd  2021
    Spine musculoskeletal (MS) models make simplifying assumptions on the intervertebral joint degrees-of-freedom (rotational and/or translational), representation (spherical or beam-like joints), and properties (linear or nonlinear). They also generally neglect the realistic structure of the joints with disc nuclei/annuli, facets, and ligaments. We aim to develop a novel MS model where trunk muscles are incorporated into a detailed finite element (FE) model of the ligamentous T12-S1 spine thus constructing a gold standard coupled MS-FE model. Model predictions are compared under some tasks with those of our earlier spherical joints, beam joints, and hybrid (uncoupled) MS-FE models. The coupled... 

    The validity and inter-rater reliability of a video-based posture-matching tool to estimate cumulative loads on the lower back

    , Article Journal of Biomedical Physics and Engineering ; Volume 12, Issue 4 , 2022 , Pages 417-430 ; 22517200 (ISSN) Ghaneh Ezabadi, S ; Abdoli Eramaki, M ; Arjmand, N ; Abouhossein, A ; Zakerian, S. A ; Sharif University of Technology
    Shriaz University of Medical Sciences  2022
    Background: Low back pain (LBP) is known as one of the most common workrelated musculoskeletal disorders. Spinal cumulative loads (CLs) during manual material handling (MMH) tasks are the main risk factors for LBP. However, there is no valid and reliable quantitative lifting analysis tool available for quantifying CLs among Iranian workers performing MMH tasks. Objective: This study aimed to investigate the validity and inter-rater reliability of a posture-matching load assessment tool (PLAT) for estimating the L5-S1 static cumulative compression (CC) and shear (CS) loads based on predictive regression equations. Material and Methods: This experimental study was conducted among six... 

    Novel force–displacement control passive finite element models of the spine to simulate intact and pathological conditions; comparisons with traditional passive and detailed musculoskeletal models

    , Article Journal of Biomechanics ; Volume 141 , 2022 ; 00219290 (ISSN) Abbasi-Ghiri, A ; Ebrahimkhani, M ; Arjmand, N ; Sharif University of Technology
    Elsevier Ltd  2022
    Passive finite element (FE) models of the spine are commonly used to simulate intact and various pre- and postoperative pathological conditions. Being devoid of muscles, these traditional models are driven by simplistic loading scenarios, e.g., a constant moment and compressive follower load (FL) that do not properly mimic the complex in vivo loading condition under muscle exertions. We aim to develop novel passive FE models that are driven by more realistic yet simple loading scenarios, i.e., in vivo vertebral rotations and pathological-condition dependent FLs (estimated based on detailed musculoskeletal finite element (MS-FE) models). In these novel force–displacement control FE models,... 

    Improved artificial neural networks for 3D body posture and lumbosacral moment predictions during manual material handling activities

    , Article Journal of Biomechanics ; Volume 131 , 2022 ; 00219290 (ISSN) Mohseni, M ; Aghazadeh, F ; Arjmand, N ; Sharif University of Technology
    Elsevier Ltd  2022
    Body posture measurement approaches, required in biomechanical models to assess risk of musculoskeletal injuries, are usually costly and/or impractical for use in real workplaces. Therefore, we recently developed three artificial neural networks (ANNs), based on measured posture data on several individuals, to predict whole body 3D posture (coordinates of 15 markers located on body's main joints), segmental orientations (Euler angles of 14 body segments), and lumbosacral (L5-S1) moments during static manual material handling (MMH) activities (ANNPosture, ANNAngle, and ANNMoment, respectively). These ANNs require worker's body height, body weight (only for ANNMoment), hand-load 3D position,... 

    Revised NIOSH Lifting Equation May generate spine loads exceeding recommended limits

    , Article International Journal of Industrial Ergonomics ; Volume 47 , 2015 , Pages 1-8 ; 01698141 (ISSN) Arjmand, N ; Amini, M ; Shirazi Adl, A ; Plamondon, A ; Parnianpour, M ; Sharif University of Technology
    Elsevier  2015
    The 1991 NIOSH Lifting Equation (NLE) is widely used to assess the risk of injury to spine by providing estimates of the recommended weight limit (RWL) in hands. The present study uses the predictive equations developed based on a detailed trunk musculoskeletal biomechanical model to verify whether the RWL generates L5-S1 loads within the limits (e.g., 3400N for compression recommended by NIOSH and 1000N for shear recommended in some studies). Fifty lifting activities are simulated here to evaluate the RWL by the NLE and the L5-S1 loads by the predictive equations. In lifting activities involving moderate to large forward trunk flexion, the estimated RWL generates L5-S1 spine loads exceeding... 

    Hypersensitivity of trunk biomechanical model predictions to errors in image-based kinematics when using fully displacement-control techniques

    , Article Journal of Biomechanics ; Volume 84 , 2019 , Pages 161-171 ; 00219290 (ISSN) Eskandari, A. H ; Arjmand, N ; Shirazi Adl, A ; Farahmand, F ; Sharif University of Technology
    Elsevier Ltd  2019
    Recent advances in medical imaging techniques have allowed pure displacement-control trunk models to estimate spinal loads with no need to calculate muscle forces. Sensitivity of these models to the errors in post-imaging evaluation of displacements (reported to be ∼0.4–0.9° and 0.2–0.3 mm in vertebral displacements) has not yet been investigated. A Monte Carlo analysis was therefore used to assess the sensitivity of results in both musculoskeletal (MS) and passive finite element (FE) spine models to errors in measured displacements. Six static activities in upright standing, flexed, and extended postures were initially simulated using a force-control hybrid MS-FE model. Computed vertebral...