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    PRI (Palm Rotation Indicator): a metric for postural stability in dynamic nonprehensile manipulation [electronic resource]

    , Article Journal of MECHANIKA ; 2012, Vol. 18, No. 4, pp. 461-466 Beigzadeh, B. (Borhan) ; Meghdar, Ali ; Sohrabpour, Saeed ; Sharif University of Technology
    In this study, we discuss the postural stability of a nonprehensile manipulation problem, which deals with multibody objects. As a metric for postural stability, we define PRI. Then, the system is posturally stable, if PRI is inside the convex hull of the object-manipulator contact surface. We then discuss that dynamic biped locomotion is a special case of dynamic nonprehensile manipulation in all aspects; we prove that ZMP (zero-moment point) and FRI (zoot rotation indicator) are special cases of PRI (palm rotation indicator). Simulations and experiments corresponding to simple examples support the results  

    The effects of a short-term memory task on postural control of stroke patients

    , Article Topics in Stroke Rehabilitation ; Volume 22, Issue 5 , 2015 , Pages 335-341 ; 10749357 (ISSN) Mehdizadeh, H ; Taghizadeh, G ; Ghomashchi, H ; Parnianpour, M ; Khalaf, K ; Salehi, R ; Esteki, A ; Ebrahimi, I ; Sangelaji, B ; Sharif University of Technology
    Taylor and Francis Ltd  2015
    Background: Many studies have been conducted on the changes in the balance capabilities of stroke patients. However, results regarding the effects of dual-task activities on postural control in these patients have been variable. Objective: To evaluate the effects of a short-term memory task on the sway characteristics of stroke patients. Method: Center of pressure (COP) fluctuations were measured in three levels of postural difficulty (rigid surface with closed and open eyes and foamsurface with closed eyes), aswell as two levels of cognitive difficulty (easy and difficult). COP parameters included mean velocity, standard deviation of velocity in both medial-lateral (M.L) and... 

    Evaluation of spinal internal loads and lumbar curvature under holding static load at different trunk and knee positions

    , Article Pakistan Journal of Biological Sciences ; Volume 10, Issue 7 , 2007 , Pages 1036-1043 ; 10288880 (ISSN) Kahrizi, S ; Parnianpour, M ; Firoozabadi, S. M ; Kasemnejad, A ; Karimi, E ; Sharif University of Technology
    Asian Network for Scientific Information  2007
    A study was performed to investigate how different trunk and knee positions while holding static loads affect the lumbar curvature and internal loads on the lumbar spine at L4-L5. Ten healthy male subjects participated in this study. Two inclinometers were used to evaluate the curvature of lumbar spine, lordosis, while a 3D static biomechanical model was used to predict the spinal compression and shear forces at L4-L 5. Eighteen static tasks while holding three level of load (0, 10 and 20 kg), two levels of knee position (45 and 180° of flexion) and three levels of trunk position (neutral, 15 and 30 degree of flexion) were simulated for 10 healthy male subjects. The results of this study... 

    Evaluation of trunk muscle forces and internal loads using kinematics-based modeling

    , Article Proceedings of the IASTED International Conference on Biomedical Engineering, Salzburg, 25 June 2003 through 27 June 2003 ; 2003 , Pages 114-119 ; 0889863539 (ISBN) Shirazi Adl, A ; El-Rich, M ; Parnianpour, M ; Sharif University of Technology
    Trunk muscle forces and internal loads are computed under simulated standing postures while carrying a load using a nonlinear finite element model of the T1-S1 spine with realistic nonlinear load-displacement properties. A novel kinematics-based algorithm is applied that exploits a set of a priori known spinal sagittal rotations to solve the redundant active-passive system. The loads consist of upper body gravity distributed along the spine plus 200 N held in hands either in front or on sides. Predictions are in good agreement with reported measurements of posture, muscle EMG and intradiscal pressure. Minimal changes in posture (posterior pelvic tilt and lumbar flattening) substantially... 

    Muscle force evaluation and the role of posture in human lumbar spine under compression

    , Article European Spine Journal ; Volume 11, Issue 6 , 2002 , Pages 519-526 ; 09406719 (ISSN) Shirazi Adl, A ; Sadouk, S ; Parnianpour, M ; Pop, D ; El-Rich, M ; Sharif University of Technology
    Using two nonlinear finite element models of the lumbar spine, the concept of optimal posture is explored by minimizing the segmental sagittal moments required for the equilibrium of the passive lumbar spine under a total of 2800 N axial compression while varying the pelvic tilt and lumbar lordosis. The redundant active-passive system is subsequently solved for this posture using a novel kinematics-based muscle calculation algorithm along with minimization approach. Some flattening in the lumbar spine substantially reduces the required moments and internal passive shear forces under 2800 N axial compression force. Small muscle forces are calculated for this optimal posture. The role of... 

    Effect of vibration on postural control and gait of elderly subjects: a systematic review

    , Article Aging Clinical and Experimental Research ; 2017 , Pages 1-14 ; 15940667 (ISSN) Aboutorabi, A ; Arazpour, M ; Bahramizadeh, M ; Farahmand, F ; Fadayevatan, R ; Sharif University of Technology
    Background and aim: Gait and balance disorders are common in the elderly populations, and their prevalence increases with age. This systematic review was performed to summarize the current evidence for subthreshold vibration interventions on postural control and gait in elderly. Method: A review of intervention studies including the following words in the title/abstract: insole, foot and ankle appliances, vibration, noise and elderly related to balance and gait. Databases searched included PubMed, ISI Web of Knowledge, Ovid, Scopus, and Google Scholar. Fifteen articles were selected for final evaluation. The procedure was followed using the preferred reporting items for systematic reviews... 

    Comparing lumbosacral orthosis to routine physical therapy on postural stability in patients with chronic low back pain: A randomized trial

    , Article Medical Journal of the Islamic Republic of Iran ; Volume 31 , 2017 ; 10161430 (ISSN) Azadinia, F ; Ebrahimi Takamjani, I ; Kamyab, M ; Parnianpour, M ; Asgari, M ; Sharif University of Technology
    Tehran University of Medical Sciences  2017
    Background: Poor balance performance and impaired postural control have been frequently reported in patients with low back pain.However, postural control is rarely monitored during the course of treatment even though poor postural control may contribute tochronicity and recurrence of symptoms. Therefore, the present study aimed at investigating the effect of a nonextensible lumbosacralorthosis (LSO) versus routine physical therapy on postural stability of patients with nonspecific chronic low back pain.Methods: This was a randomized controlled trial conducted between November 2015 and May 2016 at the outpatient physical therapyclinic of the School of Rehabilitation Sciences. Patients with... 

    Effect of dual-tasking on postural control in subjects with nonspecific low back pain

    , Article Spine ; Volume 34, Issue 13 , 2009 , Pages 1415-1421 ; 03622436 (ISSN) Salavati, M ; Mazaheri, M ; Negahban, H ; Ebrahimi, I ; Jafari, A. H ; Kazemnejad, A ; Parnianpour, M ; Sharif University of Technology
    STUDY DESIGN. Three factors mixed-design with 1 between-subject and 2 within-subject factors. OBJECTIVE. To compare the main effects and interactions of postural and cognitive difficulty on quiet stance between subjects with and without nonspecific low back pain (LBP). SUMMARY OF BACKGROUND DATA. The interference between postural control and cognitive tasks depends on factors such as sensorimotor/cognitive integrity. Changes in peripheral sensory and muscular systems as well as cognitive processes have been observed in LBP patients. It was hypothesized that the effect of cognitive task on postural performance might be different in subjects with nonspecific LBP as compared with healthy... 

    Development of 3D Upper Body Posture Prediction Model for Static Lifting at Standing Posture

    , M.Sc. Thesis Sharif University of Technology Abrishamkar, Amin (Author) ; Arjmand, Navid (Supervisor) ; Zohoor, Hassan (Co-Advisor)
    One of the main causes of low back pain is mechanical loads acting on it. These loads can be measured by in vivo measurement using force and pressure sensors. Although this method leads to accurate results, it is invasive and costly. Currently the only noninvasive way to estimate these loads is to utilize biomechanical models. Using these models requires body posture as an input. Imaging techniques are suitable for determining the posture accurately, but these equipments are expensive and often impractical. So today posture prediction models are used as an alternative cost effective with acceptable accuracy. These mechanisms predict body posture using body mass, height, position and the... 

    Artificial neural networks to predict 3D spinal posture in reaching and lifting activities; Applications in biomechanical models

    , Article Journal of Biomechanics ; Volume 49, Issue 13 , Volume 49, Issue 13 , 2016 , Pages 2946-2952 ; 00219290 (ISSN) Gholipour, A ; Arjmand, N ; Sharif University of Technology
    Elsevier Ltd 
    Spinal posture is a crucial input in biomechanical models and an essential factor in ergonomics investigations to evaluate risk of low back injury. In vivo measurement of spinal posture through the common motion capture techniques is limited to equipped laboratories and thus impractical for workplace applications. Posture prediction models are therefore considered indispensable tools. This study aims to investigate the capability of artificial neural networks (ANNs) in predicting the three-dimensional posture of the spine (S1, T12 and T1 orientations) in various activities. Two ANNs were trained and tested using measurements from spinal postures of 40 male subjects by an inertial tracking... 

    Investigation of cervical spine curvature in females with postural neck pain

    , Article Journal of Zanjan University of Medical Sciences and Health Services ; Volume 25, Issue 110 , 2017 , Pages 110-119 ; 16069366 (ISSN) Salahzadeh, Z ; Maroufi, N ; Ahmadi, A ; Behtash, H ; Hazhir Sahneh, S ; Parnianpour, M ; Sharif University of Technology
    Zanjan University of Medical Sciences and Health Services  2017
    Background and Objective: Changes in the cervical spine curvature leads to increased shear force and compression stress on cervical spine and axial loading in different cervical segments. The objective of this study was to compare the general and segmental curvature in the upper and lower cervical spine of women with postural neck pain and Forward Head Posture (FHP), women without neck pain but with FHP and healthy women. Material and Methods: 45 women were divided into three groups: 15 women with postural neck pain and FHP, 15 women without neck pain but with FHP and 15 healthy women. Photography was used to assess neck posture while cervical spine curvature was measured using fluoroscopy... 

    Principles of Designing a Chair for Iranian Kitchen, Concerning Kansei Engineering Approach

    , M.Sc. Thesis Sharif University of Technology Khyat Ardestani, Fahimeh Sadat (Author) ; Eshraghniaye Jahromi, Abdolhamid (Supervisor) ; Sadeghi Naeini, Hassan ($item.subfieldsMap.e)
    Iranian women spend a lot of times in the kitchen area in order to have good effects on the family. Unfortunately, we see many of them are suffering from body injuries and particularly musculoskeletal disorders in their middle ages. Many factors cause such problems among which awkward postures are mentioned and with identifying these postures, corrective solutions could be proposed.In this study, firstly, relationship of body injuries with working in the kitchen area is considered, awkward postures are identified and expedient actions are suggested. The aim of this study is chosen designing a suitable task chair for kitchen among the proposed solutions. Then, chair specifications are... 

    Complexity and variability of the center of pressure time series during quiet standing in patients with knee osteoarthritis

    , Article Clinical Biomechanics ; Volume 32 , 2016 , Pages 280-285 ; 02680033 (ISSN) Negahban, H ; Sanjari, M. A ; Karimi, M ; Parnian Pour, M ; Sharif University of Technology
    Elsevier Ltd 
    Background While several studies have investigated the traditional linear measures in patients with knee osteoarthritis, no study has yet reported the non-linear structure of postural sway in these patients. Methods We used two non-linear methods, recurrence quantification analysis (percent of determinism-%DET) and central tendency measure, to respectively investigate differences in the complexity and variability of sway dynamics between two groups of knee osteoarthritis patients (n = 27) and healthy controls (n = 27) under different conditions of postural and cognitive tasks. The experimental conditions included standing on (1) rigid surface with open eyes; (2) rigid surface with closed... 

    Postural control learning dynamics in Parkinson's disease: Early improvement with plateau in stability, and continuous progression in flexibility and mobility

    , Article BioMedical Engineering Online ; Volume 19, Issue 1 , 2020 Rahmati, Z ; Behzadipour, S ; Schouten, A. C ; Taghizadeh, G ; Firoozbakhsh, K ; Sharif University of Technology
    BioMed Central Ltd  2020
    Background: Balance training improves postural control in Parkinson's disease (PD). However, a systematic approach for the development of individualized, optimal training programs is still lacking, as the learning dynamics of the postural control in PD, over a training program, are poorly understood. Objectives: We investigated the learning dynamics of the postural control in PD, during a balance-training program, in terms of the clinical, posturographic, and novel model-based measures. Methods: Twenty patients with PD participated in a balance-training program, 3 days a week, for 6 weeks. Clinical tests assessed functional balance and mobility pre-training, mid-training, and post-training.... 

    Nonlinear dynamical structure of sway path during standing in patients with multiple sclerosis and in healthy controls is affected by changes in sensory input and cognitive load

    , Article Neuroscience Letters ; Volume 553 , 2013 , Pages 126-131 ; 03043940 (ISSN) Negahban, H ; Sanjari, M. A ; Mofateh, R ; Parnianpour, M ; Sharif University of Technology
    Although several studies have applied traditional linear measures to evaluate postural control of patients with multiple sclerosis (MS), little is known about the nonlinear dynamics of this patient group. In this study, recurrence quantification analysis (RQA), a well documented nonlinear method, was used to compare the nonlinear dynamical structure of postural sway in two groups consisting of MS patients (. n=. 23) and healthy matched controls (. n=. 23). The study focuses on three levels of postural difficulty consisting of (1) standing on a rigid surface (force platform) with eyes open, (2) standing on a rigid surface with eyes closed, and (3) standing on a foam surface with eyes closed.... 

    Postural sway in low back pain: Effects of dual tasks

    , Article Gait and Posture ; Volume 31, Issue 1 , 2010 , Pages 116-121 ; 09666362 (ISSN) Mazaheri, M ; Salavati, M ; Negahban, H ; Sanjari, M. A ; Parnianpour, M ; Sharif University of Technology
    Recurrence quantification analysis (RQA), a nonlinear method of postural analysis, was used to explore the effects of dual-tasking on postural performance in people with nonspecific low back pain (LBP) compared with healthy participants. Postural performance was quantified by RQA % recurrence, % determinism, entropy and trend. People with nonspecific LBP (n = 22) and unimpaired individuals (n = 22) randomly performed quiet standing tasks with three levels of difficulty (rigid-surface eyes open, rigid-surface eyes closed and foam-surface eyes closed). These tasks were performed in isolation or concurrently with an easy or difficult cognitive task. Increasing postural difficulty was associated... 

    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... 

    Test-retest reliability of postural stability measures during quiet standing in patients with a history of nonspecific low back pain

    , Article Biomedical Engineering - Applications, Basis and Communications ; Volume 22, Issue 3 , 2010 , Pages 255-262 ; 10162372 (ISSN) Mazaheri, M ; Salavati, M ; Negahban, H ; Parnianpour, M ; Sharif University of Technology
    As balance is the foundation for all voluntary motor skills, considerable research has been conducted to evaluate postural control in patients with low back pain (LBP). Although reliability is a population-specific property, to the authors' knowledge, there has been no study to determine the test-retest reliability of the center of pressure (COP) measures in the general population of LBP patients. As many as 11 patients with a history of nonspecific LBP randomly completed postural measurements with three levels of difficulty (rigid surface-eyes open, rigid surface-eyes closed, and foam surface-eyes closed) in two sessions. The COP data were used to calculate standard deviation of amplitude,... 

    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... 

    Development of a Fall Risk Assessment Method Based on COP Data in Parkinson’s Disease

    , M.Sc. Thesis Sharif University of Technology Shokouhi, Shabnam (Author) ; Behzadipour, Saeed (Supervisor)
    In recent years, there has been an increasing interest in posturography methods as an objective quantitative tool for assessing balance and indicating patient with high risk of fall. Although many posturographic studies tried to describe balance deficiencies in PD, little success has been achieved in utilizing static posturography as a tool for discriminating faller and non-faller PD patients. Furthermore, Dynamic posturography studies have delivered valuable insight into the potentiality of these methods for assessing balance, but these devices are very high in price and cumbersome to move that can limit the feasibility of their use in the clinical settings. The aims of this study were: 1)...