Mohamad Parnianpour

• Occupational Biomechanics, NYU
• Sharif University of Technology

Objectives: The comfort questionnaire for hand tools (CQH) is a subjective measure for exploring the starting points for improving hand tool design. This study aimed to investigate the psychometric properties of the Farsi version of the CQH. Methods: In this cross-sectional study, which was conducted among 163 university students, the 17-question C...

The kinetic redundancy present in the biomechanical models of complex joints has presented an obstacle in estimating the joint reaction forces during simulation of complex physical activities. Six anatomical models used for the spinal loading studies and six cost functions suggested by various groups were considered in determining their effects on...

The normal axial shortening of the thoracolumbar spine, TLS, under the body weight during the diurnal cycle ranges from 0.5 to 2% of the total body height and is fully recuperated during the night in the absence of the vertical load [1]. Workplace automation has led to an increased number of occupations requiring to sustain prolonged seated or stan...

In neutral standing and sitting postures, the human lumbar spine is known to be subjected to both compression force and flexion/lateral moments. For the whole trunk, the centre of mass has been reported to be about 2.0 cm anterior to the L1-L2 vertebral centroid [1]. Due to the asymmetry of the upper body about the sagittal plane, lateral moments l...

A computational method is proposed for simulation of the trunk movement. The present study emphasizes the importance of including realistic constraints on the maximum performance of the neuro-muscular system. The application areas of this study are: 1) providing optimized trajectories for biofeedback to patients during the rehabilitation process; a...

The axial compressive cyclic loading was applied to a nonlinear viscoelastic finite element model of an L2-L3 motion segment to investigate its dynamic response. In this validated model, the material properties of the anulus matrix, anulus fibers and nucleus pulposus (NP) have been represented by the viscoelastic constitutive laws. The detailed str...

Background: Unloading knee orthosis is prescribed for people with unicompartmental knee osteoarthritis (OA) to unload the damaged compartment. However, despite its benefits, wearing unloading knee orthoses in the long term may decrease knee muscle activity and have a side effect on knee OA progression rate. Objectives: Therefore, this study aime...

Low-back and knee injuries are the most common musculoskeletal disorders that can be caused by lifting tasks. Several task-related parameters as well as adapting different lifting techniques (LT) may affect knee/spinal loads. Here, we aim to investigate the effects of LTs and its interaction effects with the hand-load weight (LW)/horizontal distanc...

The central nervous system (CNS) dynamically employs a sophisticated weighting strategy of sensory input, including vision, vestibular and proprioception signals, towards attaining optimal postural control during different conditions. Non-specific low back pain (NSLBP) patients frequently demonstrate postural control deficiencies which are generall...

Background Wearing unloader knee orthoses for the long term may have a side effect on knee adduction moment (KAM). Research question This study sought to determine whether equipping an unloader knee orthosis with vibrators improves its effectiveness in pain, stiffness, function, and reducing the KAM. Methods The authors performed a clinical evalu...

The use of both hands is often required for force/torque exertions, particularly when using hand tools. This study investigated the effects of handle diameter (3-5 cm), between-handle distance (0.5–1.5 shoulder span (SS), workpiece orientation (horizontal/frontal), working height (shoulder/elbow/knuckle), and exertion direction (clockwise/counter-c...

Chronic obstructive pulmonary disease (COPD) is increasingly being recognized as a systemic disease rather than a mere disorder of the lungs. Central (respiratory) and peripheral (limb) muscle weakness are among the main pronounced systemic effects of COPD. While the disease primarily affects the lower limb muscles and contributes to gait impairmen...

Background/Purpose: To prevent falling, a common incident with debilitating health consequences among stroke survivors, it is important to identify significant fall risk factors (FRFs) towards developing and implementing predictive and preventive strategies and guidelines. This review provides a systematic approach for identifying the relevant FRFs...

Purpose Although the extent of which the central nervous system uses muscle synergies as a movement control strategy remains an open area of research, it is widely agreed that synergies facilitate the robustness of the neuromuscular system, allowing for effective postural control and flexible movement. This work aimed to investigate the muscle acti...

Purpose Although the extent of which the central nervous system uses muscle synergies as a movement control strategy remains an open area of research, it is widely agreed that synergies facilitate the robustness of the neuromuscular system, allowing for effective postural control and flexible movement. This work aimed to investigate the muscle acti...

Anxiety is among the most debilitating nonmotor symptoms of Parkinson's disease (PD). This study aimed to determine how PD patients with low and high levels of anxiety (LA‐PD and HA‐PD, respectively) compare with age‐ and sex‐matched controls at the level of motor control of reach‐to‐grasp movements during single‐ and dual‐task conditions with vary...

Central nervous system (CNS) uses vision, vestibular, and somatosensory information to maintain body stability. Research has shown that there is more lumbar proprioception error among low back pain (LBP) individuals as compared to healthy people. In this study, two groups of 20 healthy people and 20 non-specific low back pain (NSLBP) participants t...

PurposeThis study aimed to investigate the biomechanical impact of laminectomy on cervical intersegmental motion and load sharing using a parametric patient-specific finite element (FE) model towards providing clinicians with a viable quantitative tool for informed decision-making and improved surgical planning.Methods Ten subject-specific nonlinea...

The varus deformity of the femur and the tibia leads to an increase in the medial condylar force, which may result in osteoarthritis in the medial condyle, if left untreated. Through Medial Open Wedge Osteotomy for these patients, it is possible to realign the load bearing surfaces of the knee joint which can lead to the tightening of some of the l...

Background: Workers usually perform lifting and reaching tasks as part of their daily job. Having proper posture plays a key role for reducing the loads implemented to spine during lifting and prevention of further injuries. We aimed to extend a previously published work on spinal load estimation that used different biomechanical tools, by using ar...

Low back pain (LBP), the leading cause of disability worldwide, remains one of the most common and challenging problems in occupational musculoskeletal disorders. The effective assessment of LBP injury risk, and the design of appropriate treatment modalities and rehabilitation protocols, require accurate estimation of the mechanical spinal loads du...

Objective This study aimed to employ nonlinear dynamic approaches to assess trunk dynamic stability with speed, symmetry, and load during repetitive flexion-extension (FE) movements for individuals with and without nonspecific low back pain (NSLBP). Background Repetitive trunk FE movement is a typical work-related LBP risk factor contingent on spe...

Central nervous system (CNS) uses vision, vestibular, and somatosensory information to maintain body stability. Research has shown that there is more lumbar proprioception error among low back pain (LBP) individuals as compared to healthy people. In this study, two groups of 20 healthy people and 20 non-specific low back pain participants (LBP) too...

Objective: The main objective of this study was to assess the accuracy of bottom-up solution for three-dimensional (3D) inverse dynamics analysis of squat lifting using a 3D full body linked segment model. Least squares solution was used in this study as reference for assessment of the accuracy of bottom-up solution. Findings of this study may clar...

Nonspecific low back pain (NSLBP) constitutes a critical health challenge that impacts millions of people worldwide with devastating health and socioeconomic consequences. In today’s clinical settings, practitioners continue to follow conventional guidelines to categorize NSLBP patients based on subjective approaches, such as the STarT Back Screeni...

The successful clinical application of patient-specific personalized medicine for the management of low back patients remains elusive. This study aimed to classify chronic nonspecific low back pain (NSLBP) patients using our previously developed and validated wearable inertial sensor (SHARIF-HMIS) for the assessment of trunk kinematic parameters. O...

Background: Controlling pelvic excursions is the focus of stabilization exercises such as legs loading tasks in rehabilitation of non-specific chronic low back pain (NSCLBP) patients. Progression of these exercises is based on the ability to perform tasks with minimal sagittal pelvic excursions. In spite of emphasis on minimizing pelvic motions, no...

It has been hypothesized that the muscular efforts exerted during standing may be altered by changes in personal factors, such as the body stature and muscular strength. The goal of this work was to assess the contribution of leg muscles using a biomechanical model in different physical conditions and various initial postures. An optimized inverse...

An open research question is how the central nervous system (CNS) to find a solution for the problem of redundancy or degree of freedom in the human shoulder motion control. We used time-varying synergy theory in which assumed that the relative activation between muscles is time-varying, to investigate the combination of activation patterns of musc...

Low back pain (LBP) remains a critical health issue impacting literally millions of people worldwide. Currently, clinical practitioners rely on subjective measures such as the STarT Back Screening Tool to categorize LBP patients, which then informs specific treatment regimens. This study sought to develop a machine learning model to classify LBP pa...

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...

According to the literature, changes in muscle activity patterns are considered as one of the causes of non-specific chronic low back pain. Recent studies have introduced muscle synergy as a valuable tool for analyzing how muscles work in body movements. In this way, a new study method is proposed for modeling upper body and extracting time-varying...

Background: Lumbosacral orthosis (LSO) is commonly used for the treatment of back pain. The clinical and mechanical effectiveness of this device has been repeatedly investigated in several studies; however, its sensorimotor effectiveness has been rarely considered. Regarding this, the aim of the current study was to investigate the effect of a non...

The characteristics of postural sway were assessed in quiet standing under three different postural task conditions in 14 patients with nonspecific chronic low back pain and 12 healthy subjects using linear and nonlinear center of pressure parameters. The linear parameters consisted of area, the mean total velocity, sway amplitude, the SD of veloci...

Objective: This study was conducted to evaluate the changes occurring in the thickness of deep trunk muscles, measured using ultrasound imaging, after 4 wks of lumbosacral orthosis use in conjunction with routine physical therapy. Design: This parallel-group, randomized, controlled trial was conducted on 44 patients with nonspecific chronic low...

Background: Spinal load and muscle activity in occupation settings is an area of increasing concern. Regarding technological advancements, in diverse occupations the spinal loads have increased through constrained seated postures. Back belts are consequently used in prophylactic and conservative management of occupational low back pain (LBP) in two...

Background: Although impaired postural control may be a risk factor for distal radius fractures (wrist fractures), which often are caused by falls, little attention has been given thus far to the various performance and neurophysiologic aspects involved. Although studies suggest that external focus and cognitive tasks can improve postural control,...

We present a novel method for deriving the governing equations of the musculoskeletal system, a new class of multibody systems in which the constituent components are connected together via anatomical joints which behave differently compared with traditional mechanical joints. In such systems, the kinematics of the joints and the corresponding cons...

Introduction: Validated Persian version of STarT divides the patients with chronic non-specific chronic low back pain into three subgroups of low, moderate, and high risk. The questionnaire covers social psychosocial aspects and has clinical application due to its easy use. Purpose of this study is to use the SHARIF-HMIS portable and repeatable new...

Introduction:

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...

Objectives: To investigate the effects of competitive and noncompetitive volleyball exercises on the functional performance and motor control of the upper limbs in chronic stroke survivors. Design: Randomized clinical trial. Setting: Outpatient rehabilitation center. Participants: Chronic stroke survivors (N=48). Interventions: Participant...

The interest in wearable systems among the biomedical engineering and clinical community continues to escalate as technical refinements enhance their potential use for both indoor and outdoor applications. For example, an important wearable technology known as a microelectromechanical system (MEMS) is demonstrating promising applications in the are...

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 c...

Understanding the effect of impact loading on the mechanical response of the intervertebral disc (IVD) is valuable for investigating injury mechanisms and devising effective therapeutic modalities. This study used 24 porcine thoracic motion segments to characterize the mechanical response of intact (N = 8), degenerated (Trypsin-denatured, N = 8), a...

This study aimed to investigate the variability in postural sway patterns during quiet standing in stroke survivors. The postural sway was measured in 19 stroke survivors, as well as 19 healthy demographically matched participants, at 3 levels of postural difficulty (rigid surface with closed and open eyes, and foam surface with closed eyes), and 3...

Study design. A test-retest design. Objectives: To study the reliability of the postural stability measures during whole body dynamic conditions in healthy and low back pain (LBP) subjects. Summary of Background Data: Postural control is an essential prerequisite for dynamic motions such as lifting, lowering, and repetitive trunk bending tasks. Tes...

This paper presents a novel approach for evaluating LBP in various settings. The proposed system uses cost-effective inertial sensors, in conjunction with pattern recognition techniques, for identifying sensitive classifiers towards discriminate identification of LB patients. 24 healthy individuals and 28 low back pain patients performed trunk moti...

Underlying mechanisms of obesity-related back pain remain unexplored. Thus, we aim to determine the effect of obesity and its shapes on the spinal loads and the associated risks of injury. Obesity shapes were initially constructed by principal component analysis based on datasets on 5852 obese individuals. Spinal loads, cycles to vertebral failure...

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 to chronicity and recurrence of symptoms. Therefore, the present study aimed at investigating t...

Human movement analysis is an important part of biomechanics and rehabilitation, for which many measurement systems are introduced. Among these, wearable devices have substantial biomedical applications, primarily since they can be implemented both in indoor and outdoor applications. In this study, a Trunk Motion System (TMS) using printed Body-Wor...

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...

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 weakn...

Degenerative disc disease, associated with discrete structural changes in the peripheral annulus and vertebral endplate, is one of the most common pathological triggers of acute and chronic low back pain, significantly depreciating an individual's quality of life and instigating huge socioeconomic costs. Novel emerging therapeutic techniques are he...

This study developed and validated a lumped parameter model for the FLEXI-BAR, a popular training instrument that provides vibration stimulation. The model which can be used in conjunction with musculoskeletal-modeling software for quantitative biomechanical analyses, consists of 3 rigid segments, 2 torsional springs, and 2 torsional dashpots. Two...

Objectives: Musculoskeletal disorders (MSDs) are prevalent among airline baggage handlers due to manual materials handling. In this study, the Nordic musculoskeletal questionnaire (NMQ), the revised NIOSH (National Institute for Occupational Safety and Health) lifting equation, and the University of Michigan 3D Static Strength Prediction Program(T...

Objectives. Musculoskeletal disorders (MSDs) are prevalent among airline baggage handlers due to manual materials handling. In this study, the Nordic musculoskeletal questionnaire (NMQ), the revised National Institute for Occupational Safety and Health (NIOSH) lifting equation, and the University of Michigan 3D Static Strength Prediction Program™ (...

Optimal trajectory and muscle forces of a human-like musculoskeletal arm are predicted for planar point-to-point movements using optimal control theory. The central nervous system (CNS) is modeled as an optimal controller that performs a reaching motion to final states via minimization of an objective function. For the CNS strategy, a cubic functio...

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...

The articular surfaces of the tibiofemoral jointcommonly appear to have gaps in between during Arthroscopy operations. However, the same joint surfaces appear to be in contact inMR images. This discrepancy may be attributed to the pressure of the saline injected into the joint duringarthroscopy operations, insertion of cannulas, or anesthesia and t...

Objectives: To evaluate the reliability of head and trunk acceleration measured by MTx sensors during walking on Level and Irregular surfaces and to compare the differences between healthy young and old adults. Methods: Participants were 20 young female university students and 20 non-faller elderly women in Iran, 2013. Two MTX sensors were used to...

A numerical study was conducted to investigate the effect of the initial hand position while holding a flexible bar on the lumbar disc and back muscle forces during a training exercise. First, the mechanical response of the FLEXI-BAR was modeled based on a lumped parameter method with an approximate error of 8%. Then, the model was imported into a...

A single-degree-of-freedom model is considered for flexible exercise bars based on the lumped-element approach. By considering the side segment of a flexible exercise bar as a cantilever beam with an equivalent mass at the free end, its free-vibration response and forced one under excitation of the grip of the flexible bar is written parametrically...

Vibration training is increasingly gaining popularity as an effective warm-up/training modality for athletes and as a therapeutic strategy in rehabilitation. Several research studies have investigated the effect of different exercises using flexible bars on the musculoskeletal system [Gonçalves et al, 2011]. Despite the abundance of studies on flex...

To translate the STarT Back Screening Tool (SBT) into Persian and to investigate the psychometric properties of the new version in a group of patients with Non-Specific Low Back Pain (NSLBP). The STarT is a validated questionnaire used for subgrouping LBP patients at three levels of low-, medium-, and high-risk, based on the risk of chronicity. It...

The risk of low back pain resulted from cyclic loadings is greater than that resulted from prolonged static postures. Disk degeneration results in degradation of disk solid structures and decrease of water contents, which is caused by activation of matrix digestive enzymes. The mechanical responses resulted from internal solid–fluid interactions of...

The investigation of dynamic response of intervertebral disc is beneficial for the development of new synthetic and engineered tissues for treating diseased or injured disc. There are limited experimental studies on comparing the effect of loading mode and rate on global response of intervertebral disc. In this study, in-vitro experiments were perf...

Background: Spinal injuries and associated litigation continue to pose significant human and economic challenges globally. Biomechanical predictive simulation models of the spine provide time and cost effective tools for forensic injury biomechanical quantitative analysis. Methods: A 3-D computational model that includes 18 muscles was developed to...

Osteoporosis is a progressive bone disease characterized by deterioration in the quantity and quality of bone, leading to inferior mechanical properties and an increased risk of fracture. Current assessment of osteoporosis is typically based on bone densitometry tools such as Quantitative Computed Tomography (QCT) and Dual Energy X-ray absorptiomet...

Study design: A cross-sectional study to quantify trunk motor control during multidirectional isometric tracking tasks. Objective: To investigate the effect of chronic low back pain (LBP) on trunk neuromuscular performance while participants performed isometric exertions of trunk muscles to track targets in different angles with various magnitud...

The goal of this study was to quantify the effect of experience and handrail presence on trunk muscle activities, rotational spinal stiffness and postural stability of construction workers. We evaluated spinal stability, and objective and subjective postural stability in 4 expert and 4 novice construction workers who were performing a manual task i...

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 du...

Despite development of accurate musculoskeletal models for human lumbar spine, the methods for prediction of muscle activity patterns in movements lack proper association with corresponding sensorimotor integrations. This paper uses the directional information of the Jacobian of the musculoskeletal system to orchestrate adaptive critic-based fuzzy...

Aims: The reaction forces of the Milwaukee Brace’s (MB’s) several areas were measured during normal daily activities (24 hr) by a new measurement device improved in order to force acquisition by groups of sensors distributed in all of the MB’s internal areas. Methodology: In the current study, a new measurement system using Force Sensitive Resistan...

Background: The ratio of total lumbar rotation over pelvic rotation (lumbopelvic rhythm) during trunk sagittal movement is essential to evaluate spinal loads and discriminate between low back pain and asymptomatic population. Methods: Angular rotations of the pelvis and lumbar spine as well as their sagittal rhythm during forward flexion and bac...

Tests on animals of different species with large differences in intervertebral disc size are commonly used to investigate the therapeutic efficacy of intravenously injected solutes in the disc. We hypothesize that disc size markedly affects outcome. Here, using a small non-metabolized molecule, glucosamine (GL) as a model solute, we calculate the i...

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). Bu...

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 structur...

There are different methods to assess forward head posture (FHP) but the accuracy and discrimination ability of these methods are not clear. Here, we want to compare three postural angles for FHP assessment and also study the discrimination accuracy of three photogrammetric methods to differentiate groups categorized based on observational method....

In this study, a nonlinear poroelastic model of intervertebral disc as an infrastructure was developed. Moreover, a new element was defined consisting a disc (Viscoelastic Euler Beam Element) and a vertebra (Rigid Link) as a unit element. Using the new element, three different viscoelastic finite element models were prepared for lumbar motion segme...