Sharif Digital Repository

Selection of muscle activation pattern to reach a specific goal by considering the complexities of neuromuscular system and the way it overcomes these complications, are of researchers’ space interest in motor control. One proposed solution for resolving these complexities is the concept of simple module (synergies) that suggests the combination of them leads to more complex activities. In the present work, the existence and arrangement of synergies in the lumbar spine have been studied. For this purpose, a model with 18- muscles at level of L4-L5 under utilized in the static condition. In order to obtain the muscular and stability synergies, a biomechanical model predicting muscle... 

According to the statistical studies, knee pain is the most common and costliest disorder after low back pain. One of its types is the patello-femoral disorder and instability. Patellar instability can be affected by different factors, such as: low depth of the trochlear groove, low height of the lateral femoral condyle, high length of the patellar tendon, abnormal lateral rotation of the tibia, unusual tibial attachment of the patellar tendon, small patellar size, general loosening of ligaments, etc. So, the mechanical properties of knee joint including patello-femoral joint, surrounding soft tissues, and incoming forces must be examined carefully, in order to find out suitable and... 

Spine is one of the most important musculoskeletal systems of the human body. Any problem which is related to this part of human body causes pain and disability. Spinal compression forces are one of the main reasons of this disability and pain. It is assumed that intra-abdominal pressure causes spinal unloading in lifting. Studies usually don’t consider the role of intra-abdominal pressure and introduce it as an effective parameter which can increases spinal stability and influences spinal mechanics.Generation mechanism of intra-abdominal pressure remain enigmatic, studies that advocate the unloading effect of IAP usually consider a raise in IAP to be primarily due to the activity of... 

No considerable investigation of inlet aerodynamics has been done in our country up to now. Some numerical study in this field has been accomplished without any experimental test. To solve the inner and outer flow field of the inlet in this investigation, the numerical methods has been used and also experimental tests for code validation has been done. The inlet is an axisymmetric external compression one. In the numerical simulation the Navier-Stokes equations with explicit finite volume method have been used to model the axisymmetric, steady and turbulent flow field of the inlet in a structured grid. Viscous fluxes with a finite volume method, molecular viscosity coefficient with the... 

Human body movements are achieved by activating a number of muscles. It has been shown that the central nervous system (CNS) plays the main role in controlling rhythmic activities (including walking, chewing, etc.). However, the way the central nervous system works in controlling different parts of the body has always been discussed due to the excess degrees of freedom to perform certain tasks. Controlling a group of muscles (under the name of muscle synergy analysis) instead of each one of them has been one of the most attractive and efficient recent ideas to better understand the CNS function. Also, a similar concept can be expressed for kinematic synergies (by the degrees of freedom of... 

Laparoscopy is a minimally invasive surgical (MIS) procedure specific to the surgical sites within the abdomen. For this surgical method a laparoscope, a camera (endoscope), and a grasping instrument is needed. They all inserted in to the abdomen through openings (5 - 10 mm diameter side port). Currently used grasper heads are small and often with steel material. With respect to these two properties applying large forces that cause damage in the organs is inevitable. The aim of this project is to design a new large laparoscopic grasper head that applies pressure along the length of the lever arms and can take up tissues of large sizes. Based on surveys and estimations SMA, artificial muscles... 

The Quadriceps Muscle as one of the major muscles of the human body plays a key role in knee function. Strengthening of this muscle is recommanded to prevent knee pain and even cure some diseases. Many believe that by strengthening the medial part with respect to the lateral part of the quadriceps muscles, patellofemoral pain syndrome can be prevented or treated. In this regard, a muscle strengthening system, based on magneticorheological brake is designed which provides isometric, isotonic and isokinetic exercise of knee joint and also enables the selective muscle strengthening. Beforehand a musculoskeletal model of lower extremity is developed in OpenSim software, capable to estimate force... 

Torsional misalignment of lower extremities is a bone deformity of femur, tibia, knee twist or a complex of all these factors. These deformities affect the patient's gait kinematics. These patients are usually treated with osteotomy surgery with the aim of correction of anatomy. But it doesn't necessarily lead to the modification of gait. Therefor development and application of subject-specific musculoskeletal models to analyze patient's specific condition and predict corrective surgery results are considered. Accordingly, the aim of this project is to create a subject-specific musculoskeletal model for a patient with femoral anteversion in order to predict result of anatomical correction... 

The effects of combined task demands on the way muscles are recruited to balance external loads during posture and movement is of great importance in quantitative analysis of upper arm function. Pain and disability of shoulder joint is becoming more important as population spends more often interacting with computers in seated position and carrying repetitive tasks using upper extremities. Shoulder joint that is more dependent on the muscles for its normal function than other joints such as hip due to its small articular surface and large range motion has been used here to study its coordination during isometric exertions. Since, the numbers of tasks that could be performed are enormous. In... 

Spasticity is a common phenomenon following stroke, which causes increase in muscle resistance to imposed movements. Most of the clinical measurements used by physiotherapists to evaluate spasticity are qualitative. Consequently, the reported results are subjective. The objective of this study was to develop a musculoskeletal model of the upper limb to simulate spasticity of muscles activating in wrist flexion-extension. Subjects in two groups of normal and stroke survivors participated in this study. Six normal subjects and three hemiplegia patients were exercised by the robotic instrument. Simultaneously, the resistive moment, the wrist joint position and the EMG of muscles were recorded.... 

Nowadays, the developments in control and robotics provide rehabilitation and power augmentation applications for the exoskeleton robots. In the rehabilitation applications, the goal is to help elderly and persons with paraplegia to do their daily activities and movements. One of this applications is to help these individuals for postural stability and recovering balance after receiving perturbations. In this research, we propose a control strategy for a lower limb exoskeleton to help the wearer to recover balance after a perturbation without using crutches. Here, we concentrate on the stance phase when a push is exerted to the robot and try to make the system quite upright. Therefore, a... 

The purpose of this project is to design and build a motorized walker with sit to stand ability, by means of which the user can get up from a chair or the edge of the bed and stand with complete independence; Relying on it, the patient could walk easily and finally sit down on the chair, the edge of the bed, or the toilet seat. For this purpose, the conducted researches and previously built devices were studied and the strengths and weaknesses of each were examined. The stages of conceptual design including the design of the sit to stand mechanism, the design of the structure and finally the control algorithm were completed, then the detailed design of the mentioned topics was carried out.... 

The main scope of this research is to develop an anthropometric lower extremity exoskeleal system in a virtual environment for augmentation purposes. The main challenge in the process of doing this research is to employ the biomechanical analysis of the human locomotion to provide the necessary background information for the design of devices that closely mimic the dynamics of the operator's motion. In this case, the appropriate degrees-of-freedom and associated range of motions for each joint should be determined. In addition, the kind of necessary actuators and measurement systems should be selected based on the muscle torque consumption analysis provided by a musculoskeletal model,... 

Cerebral palsy (CP) is one of the most common motor disability among children that caused by damage to brain or defective development of brain before, during or just after birth. Due to this damage, children with CP have cognitive and motor problems. As an important activity of daily living, walking enhances independence, social activities and quality of life. Much of therapy for children is aimed to improve their gait. A usual technique to evaluate how a person walk and detect abnormal features in walking pattern is gait analysis. Lots of studies have been done on gait kinematics of CPs and classified them based on their kinematis. The purpose of this thesis is studying muscles activity of... 

Endothelial derived nitric oxide (NO) and its role in regulating the physiological conditions of blood vessels is one of the favorite topics among researchers. The majority of previous studies have focused on nitric oxide transport in blood vessels, less attention has been paid to its vasodilative effects in blood vessels. The main aim of this study is to propose an integrated model to study the effects of endothelial-derived nitric oxide on hemodynamic conditions of blood vessels. Nitric oxide is produced by endothelial cells upon exposure to mechanical forces such as hemodynamic shear stress. The synthesized nitric oxide then diffuses into the neighboring vascular smooth cells, where it... 

Human walking as a rhythmic movement, despite of being simple in implementation, is so complex in biomechanical modeling and has attracted the attention of most of the researchers. Numerous theories and assumptions have been proposed for modeling this motor pattern. Central pattern generators are neural circuits in the spinal cord responsible for generating rhythmic motor patterns in rhythmic activities such as walking. On the other hand, muscle synergy has been introduced as a solution for alleviating the redundancy of the muscular system. In this hypothesis, the central nervous system activates muscle groups that are called muscle modules. Using this hypothesis facilitates the... 

Spine biomechanical models suffers from either simplification in passive disc components modeling (modeling via torsional spring or beam elements) in musculoskeletal (MS) models or shortcomings in detailed muscles modeling (via a simple force and torque vector) in detailed finite element (FE) models. Considering these, that is aimed in this study to develop a hybrid MS-FE model which the calculated muscle forces by a MS model (developed based on geometrical and mechanical properties of FE model) for a desired static posture, being applied to a detailed FE model. Considering the change of discs stiffness in FE model under the applied muscles and gravity forces, the equivalent stiffness in MS... 

Low back pain (LBP), the leading cause of disability worldwide, remains one of the most common and challenging 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 during different activities. This study aimed to: 1) develop a novel 2D beam-column finite element control-based model of the lumbar spine and compare its predictions for muscle forces and spinal loads to those resulting from a geometrically-matched equilibrium-based model; 2) test, using the foregoing control-based finite element model, the validity of the... 

Low back pains (LBP) are prevalent and costly. One of the important factors causing LBP is excessive axial compression and shear forces that are applied on the intervertebral discs during different activities. Due to lack of direct in vivo measurement methods for estimating these loads, musculoskeletal biomechanical models have been emerged as indispensable tools under various activities. Different biomechanical models have been suggested to estimate muscle forces and spinal loads base on optimization, EMG and hybrid (EMG assisted optimization, EMGAO) methods. Although there have been a number of studies on the differences between various optimization and EMG-based methods, there has been no... 

Cerebral palsy (CP) is one the most prevalent neuromusculoskeletal disease amongst children. Damage in the central nervous system (CNS) causes defective growth of the musculoskeletal system during infancy to maturity, then leading to impairment of selective motor control (SMC), spasticity and sometimes contracture of musculotendinous junction. Treatment of Cerebral Palsy is limited to reduce complications. Medical procedures such as neurosurgery and orthopaedic surgeries or rehabilitation used as a common operation. Recently studies in the field of synergy directed a new path to understanding of human motor control complexity besides identification of functionality of musculoskeletal...