ناصر فتورائی

Geometries of leaflets play an important role in designing prosthetic valves (PVs). A valve must have a high geometric orifice area (GOA) and low regurgitation to function properly. In this paper, some polymeric tri-leaflet valves were designed based on radial and free edge curves of previous designs and together with them a new radial curve, which consists of two lines and an arc between them was proposed. Mechanical properties of polystyrene polymer are assigned to leaflets using the Mooney-Rivlin hyperelastic model. The finite element method (FEM) has been utilized to evaluate GOA, regurgitation, von Mises stress, and leaflets' coaptation in a fully closed and opened state. Results were compared, and the valve with the proposed leaflet geometry exhibited better performance among all valves. 69.1% GOA, 2.6 mm coaptation width, 0.921 MPa von Mises stress for closed-form, and 0.731 MPa von Mises stress for opened form were recorded. The significance of the radial curve in designing the geometry of leaflets has been revealed especially on the case of leaflets' coaptation. The more this curve tends to a straight line the higher the geometric orifice area and the weaker the coaptation. The proposed curve establishes an equilibrium between these two parameters.

Transcatheter aortic valves have become the standard procedure for high-risk patients with severe aortic valve stenosis. This minimally invasive procedure can expand to a wider range of patients with a lower risk of surgery. The complications after the implantation and the structural malfunction of these prostheses are the obstacles of this transition. Design optimization of the stents of these prostheses can improve their performance and reduce the post-operative complications associated with them. Since all prostheses are crimped before implantation, the designs should guarantee an acceptable structural performance after expansion, especially self-expandable stents for which the fatigue behavior strongly depends on the strain. This study applies a simple, cost-effective optimization framework to optimize the geometric parameters of these stents regarding the maximum strain during the crimping process. The design parameters include diameter profile, cell size, number of repeating components, and strut cross-section. The simplified models are evaluated and verified by the 3D simulations. The results show that the middle cells' height, number of cells, and strut width have the most prominent effect on the maximum crimping strain of the stent. This framework can be applied to a wide range of stent designs and tremendously reduce the cost of stent design and optimization.

Low-density lipoprotein (LDL), which is recognized as bad cholesterol, typically has been regarded as a main cause of atherosclerosis. An abnormal accumulation of LDL in the artery wall and, as a result, in the formation of LDL oxide, can lead to atherogenesis. Therefore in present study, the concentration boundary layer of LDL in a straight artery is investigated numerically. The governing equations consist of continuity, momentum conservation and the LDL transport in the blood based on appropriate boundary conditions have been solved using one of the most powerful computational fluid dynamics techniques known as Projection method. Results are obtained and presented as profiles and contours of concentration, blood velocity and wall shear stress, which are in good agreement with numerical and analytical results of previous studies. Effects of factors such as: filtration velocity and wall shear stress on the LDL surface concentration and concentration boundary layer thickness are investigated. The results show that increasing the wall suction (high blood pressure) and reducing the Wall Shear Stress (WSS) results in an increase in the surface concentration of LDL. Increasing the Reynolds number and the Schmidt number decreases the concentration boundary layer thickness, and LDL surface concentration increase about 7% higher than that of the bulk flow.

Aortic stenosis is caused by narrowing of the orifice of the aortic valve. Stenosis is described by calcium deposition on the leaflets. With the growth of stenosis, hemodynamics, mechanical performances and blood flow through the valve are changed. This study proposes the comparison of two new fluid-structure interaction of healthy and stenotic aortic valve finite element code ADINA during a complete cardiac cycle. Due to the hardening of calcified aortic valve, the orifice area decreased from 2.4 cm2 for the healthy AV to 1.4 cm2 for the stenosis case. The axial velocity and mean pressure gradient increased in mid systole. In addition, strain concentration and higher stress values were observed on the leaflets in stenotic valve than healthy case. Pressure distribution and velocity results were in good agreement with echocardiography data in published literatures. Although improvements are still needed, our computed data were well simulated closing and opening of the healthy and the calcified aortic valves.

Coronary arteries play a vital role in heart nutrition, and if they get stenosis, they will be at risk of developing a heart attack. Coronary artery disease is a progressive disease that is caused by the accumulation of fat particles on the wall of the arteries, leading to thickening of the wall and the formation of layers of plaque on the wall of the arteries and ultimately causing stenosis. In the present study, in order to obtain the effect of percentage and position of stenosis on the pattern of flow and WALL SHEAR STRESS distribution, followed by the progression of atherosclerotic plaques, left coronary artery and its main branches, the anterior and anterior artery, in different conditions according to Medina classification, 50 and 75%, and three different positions of lesion locations based on their distance from carina relative to the center of the branching were modeled. According to the results, WALL SHEAR STRESS and flow ratio and the percentage of inflow into the lateral branch decreased with increasing percentage of stenosis. For example, in Medina type (1.1.1), in 50% diameter stenosis, the flow ratio was 41% of the main branch and it was 37% in 75% diameter stenosis. WALL SHEAR STRESS values are less than 1, even 0.5 Pascal and in critical range in 75% diameter stenosis. Increasing the spacing of the plaque from the center of the branch, the WALL SHEAR STRESS and lateral branch flow ratio increase, and the likelihood of the expansion of the plaque decreases. Based on the development of stenosis severity, modal type (1.0.1) has the highest probability of developing atherosclerotic plaques and total vein occlusion compared to other types of medina.

The aim of this study is to evaluate the changes of effective stress distribution in plaque by progressing to the stenosis throat and to assess the pulsatile pulse pressure effect on effective stress of a viscoelastic finite-element model of carotid arteries having less and more than 50% stenosis. In-vivo geometries of the arteries were reconstructed using consecutive transverse ultrasound images. Pulse pressure waveform exerted on the artery walls and Kelvin viscoelastic model parameters were extracted from consecutive longitudinal ultrasound image processing. According to the results of this study, the effective stress applied to the mild stenotic plaque decreases with progression to the throat and there after increases again. However, in more than 50% stenosis, thickness of the layer between the plaque component and artery lumen determines the trend of effective stress exerted on different sites of the plaque. Moreover, results showed that regardless of extremum effective stress locations in different cross-sections, maximum differences between the extremum effective stresses of different cross-sections accure in systole whilst in the beginning and end parts of the cardiac cycle differences are not considerable. It seems that this viscoelastic model can be used for accurate evaluation of stress distribution during the atherosclerotic stenosis progress.

The growth of low back pain and disoreders are increasing in different societies. Furthermore,the direct in vivo measurement of spinal and muscle forces is so difficult. Hence, the use of musculoskeletal biomechanical models has been emerged applicably as a tool for calculating and estimating spinal forces under various activities. Thus, the purpose of this study is to estimate the mentioned forces with different methods especially in lifting tasks. To this end, a six-joint model with eighteen degrees of freedom and 76 trunk muscle fascicles has been developed. Due to more number of unknowns (muscle forces) than equilibrium equations, the system is redundant and the problem is indeterminate to be solved. So the electromyography assisted optimization (EMGAO) approach is used for estimating muscle forces. Since foregoing EMG muscle forces do not satisfy equilibrium equations, correction coefficients have been used for satisfying equilibrium at all lumbar joint levels. According to results in an identical task, all of the approaches indicated substantial differences in correction coefficients for each muscle. Although the stability and muscle forces are different in various EMGAO methods, spinal compression and shear forces are closer to each other in these methods. For validation of results, the intradiscal pressure (IDP) at L4-L5 in various methods are in agreement with in vivo IDP value of an experimental test measurement so that both of them reported this quantity in the range of 0.3-1.8 (MPa).

In terms of mechanical behavior, human’s speaking and generating voice is a sophisticated process which is resulted in interaction between flowing air through the larynx and oscillating functionality of vocal folds. The sulcus vocalis is one of the individual cases of scarring in which the superficial lamina propria is absent over the length of the vocal fold and can procreate several disorders in voice generation. In this study, for the first time, the effects of sulcus vocalis on vibrating functionality of vocal folds have been assessed by employing finite element numerical modeling. Two-dimensional models of either healthy or sulcus vocal folds were implemented which each one is coupled and solved via LS-dyne software. Also, the three e-layer linear elastic model was utilized for the structure phase and the arbitrary Lagrangian-Eulerian (ALE), incompressible continuity, and Navier- Stokes relations were used for the fluid domain. Type II patients’ self-excited oscillations have been exhibited and compared with the healthy model. The results of the healthy model were assessed and compared with numerical and experimental results of previous studies. Moreover, the influences of the sulcus not only on the flow components but also on the oscillating functionality of the vocal folds have been evaluated. The results indicated that the frequency of vocal folds’ vibrations and the value of volume flux tends to be remarkably declined and boosted up respectively.

In the present study, a finite element model has been presented using both the in-vivo geometry of a healthy man carotid artery, which was extracted from consecutive transverse ultrasound images and the pulse pressure waveform and Kelvin viscoelastic model parameters that were obtained from processing the consecutive longitudinal ultrasound images. Extracting the internal diameter waveform from longitudinal ultrasonic image processing and calibrating it via an exponential equation, blood pressure waveform of the carotid artery was extracted. A Gaussian function was fitted to the blood pressure waveform. Differentiating the fitted Gaussian equation resulted in the pressure differentiation of the carotid artery over the cardiac cycle. Kelvin viscoelastic parameters were estimated using an optimization method. Finite element model of the carotid artery was reconstructed in ADINA software and implemented by loading over three cardiac cycles. To validate the model, radial displacement waveform resulted from finite element model and that resulted from image processing were compares in nearly the same spatial position. Percentage of the mean proportional differences between the radial displacement resulted from finite element model and that from consecutive ultrasound images was 9.3. Since the appropriate mechanical models can calculate true stress/strain distribution of the carotid artry wall and plaque and distinguish the location of the plaque areas prone to vulnireability; and because of the capability of the ultrasonic model proposed in this study for describing the pulsatile behavior of artery wall accurately, it is expected that the introduced dynamic model to be applied for accurate evaluation of the arterial disease.

Adipose tissue is a loose connective tissue distributed in two main anatomic depots including subcutaneous and visceral. Since in many pathological condition and diseases associated with adipose tissue alteration, the micro-components of adipose tissue undergoes considerable changes from mechanical characteristics point of view, it is quite vital to present an accurate structural technique for modelling tissue microstructure. Accordingly, this paper presents a structural model based on adipose tissue main components and interaction between them. Adipocytes was considered as a fluidic spheres and extracellular matrix modeled as solid media. The interaction between these two different phases simulated by solving well-known fluid-structure interaction (FSI) problem. In order to obtain the constitutive parameters for ECM, finite element simulation results fitted to experimental uniaxial compression test data. To make a comparison between the performances of different constitutive models, three conventional hyperelastic models were used for describing the mechanical behavior of ECM. The agreement between experimental data and simulation results confirm that the presented technique has a high potential for modeling adipose tissue microstructure both in normal and pathological condition. Considering the accuracy and mathematical complexity, results show that Yeoh hyperelastic model has a better performance than two others. In all three model, results reveals that the stiffness of adipose tissue ECM is ~ (2-3) times higher than that of the adipose tissue.

Brain hypothermia by reducing the temperature of the cerebrospinal fluid is done by a cooling pad in the thoracic region and protect brain from the ischemic injuries. Along with the spinal cord, the brain is an essential partner in the central nervous system, and similarly, it is surrounded and protected from the bony skull and from shock by cerebrospinal fluid. The brain analyzes information that is both internal and external to the body, transforms the information into sensations, and stores them as memories. So in this study we investigated the brain hypothermia by finite element modeling.
To investigate this phenomenon, in this study a numerical model of the head with respect to the structure of brain tissue and its contribution to heat transfer is presented in the fluid lab of the Amirkabir University of Tehran in January of 2016. In this model, Pennes's bioheat equation and finite element analysis has been used to predict temperature distribution in the brain tissue. The model geometry is designed in two state without considering the ventricles of the brain that are involved in the production of cerebrospinal fluid and with considering cerebrospinal fluid. So, in the second case, the cerebrospinal flow is considered as a heat transfer factor.
We concluded that with cooling about 5 °C, in the first model without considering the ventricles, the gray matter temperature is reduced by about 4 °C and there is no change in white matter temperature. In the second model temperature distribution became more asymmetric. The temperature reduced about 3 °C in the corners. However, the temperature reduction at the edge of brain tissue and near cerebrospinal fluid were about 0.5 °C.
It was observed that in the case of ischemia, the temperature drop was higher than normal. So, during brain injuries to prevent serious damage, the brain metabolism can be reduced by cooling the spinal fluid.

There is no consistent data on the mechanical properties of sheep intestine.
We performed a series of biaxial strain measurement experiments and extracted the constitutive model to describe the mechanical characteristics of the sheep intestinal tissue.
Eleven specimens were obtained freshly from sacrificed sheep and the planar biaxial tests were performed on the tissue specimens by applying simultaneous loads along the circumfer-ential and longitudinal directions. Then the measured data were fitted into the anisotropic four-parameter Fung-type model and also to the modified Mooney-Rivlin model.
The specimens showed some degree of anisotropy; the stiffer direction is not gener-ally predictable. Some of the specimens were stiffer in the circumferential direction, and the others in the longitudinal direction. However, the average results state the circumferential di-rection as the stiffer orientation.
It can be concluded that sheep intestine be-haves normally as a nonlinear anisotropic tissue which is well-characterized by the modified Mooney-Rivlin model.

Syrinx growth in Syringomyelia desease causes progressive neurological disorders. Thus, the examination of effective factors in syrinx development is so important for controlling this desease. One of clinical assumptions related to the reason of syrinx development, considers the propagation of pressure wave shock in subarachnoid-space fluid as the main reason for fluid motion in syrinx and syrinx development and increasing damage to spinal cord. Modeling and analysis have been performed to test the theory in this research using finite element method. So a 3d model was created including syrinx, spinal cord, cerebrospinal-fluid in subarachnoid-space, dura mater and stenosis. Pressure puls stimulation was applied to the superior surface of the subarachnoid-space fluid model simulating arterial puls of skull. Cerebrospinal-fluid has been assumed as a Newtonian fluid with laminar flow. The solid phase has been considered to be linear elastic. The fluid-solid interface was analized using ADINA software and fluid flow characteristics were extracted including velocity and pressure field as well as tissue stresses. Results show that pressure wave propagation in subarachnoid-space fluid causes the induction of motion in syrinx fluid, and stress concentration is created in spinal tissue due to the fluid cessation in syrinx and increasing local pressure, however these stress values are lower than spinal tissue strength and pressure wave propagation in this situation cannot be the main reason of syrinx development.

In this study, numerical simulation of the effect of hyperthermia using FePt magnetic nanoparticles with alternating magnetic field for skin cancer treatment is carried out. The numerical solution is presented to analyze bioheat transfer and magnetic induction equations, in cylindrical skin tumor situated in healthy tissue with considering evaporation and convection heat transfer. In order to show the validity of the study, the obtained results are compared with those of the studies already exist in the literature. Bioheat equation is used to predict the temperature rise in terms of characteristics of the magnetic nanoparticles, applied magnetic field and the tissue. The results reveal that nanoparticles diameter has a major effect on the temperature rise. The results also show that the temperature field in axial direction (from surface to depth) of tissue and the effects of hyperthermia decreases by increasing the convection heat transfer coefficient. In other words hyperthermia is more effective in the presence of the environmental natural convection. Moreover, the position of maximum temperature inside the tumor, varies by changing the heat transfer coefficient. Also, the amount of evaporation has a negligible effect on hyperthermia treatment.

The variation of wall shear stress (WSS) in the microvessels may damage the endothelial layers. It also changes the mass diffusion and sediment and may be considered as an important factor in the formation of the fatty plaques and causing heart disease. According to the importance of the issue, the aim of this paper is to study the effective parameters on the wall shear stress in microvessels. In this paper, the hybrid method, combined lattice Boltzmann and immersed boundary methods is used to simulate the red blood cell (RBC) motion in the plasma flow. It should be mentioned that red blood cell has significant effect on WSS, in this regard; the present results show that the blood rheological behavior has the important effect on WSS. The results also demonstrate the effect of stenosis severity and RBC location in different regions on wall shear stress and consequently causing heart, coronary disease. It should be noted that the presented results have been evaluated by previous numerical results for microvessels and the results show the ability of lattice Boltzmann method to simulate complex problems especially for modeling the deformable solid objects suspended in the fluid.

In this paper motion of some blood clots with different mechanical properties in the cerebrovascular arteries is investigated. Blood clots mostly are originated from heart or other cardiovascular arteries and by entering the cerebrovascular arteries trigger occlusion and deprive the brain’s tissue from proper perfusion. To study this phenomenon, we used a patient-specific geometry of cerebrovascular arteries and due to obtain the motion of clot and blood’s flow in cerebral arteries, algorithm of fluid-structure interactions was used. Although previous researches have not considered the effect of mechanical properties on the motion of clot, our results demonstrate the variation of the dynamic parameters of the clot’s motion by changing the mechanical properties. We show that by increasing the rigidity of the clot, their tendency for entering to the larger arteries is raised. Also other dynamic parameters like clot’s average velocity altered when the mechanical property of the clots changes. Mechanical parameters have the main role in the motion of clots and by investigating them, our sight to the mechanism of pathologies would expand, moreover, strategies of the cerebrovascular treatments would be fascinated in the future.

Every organ has its own metabolic and functional requirements and needs a variable amount of blood; hence, autoregulation is an important phenomenon. Shear stress induced autoregulation is defined as the innate ability of an organ to keep its hemodynamic conditions stable against changes in heart rate and perfusion pressure. For example, when heart rate changes arterial vessels undergo vasodilation or vasoconstriction in order to stabilize the hemodynamic forces and stresses with respect to the flow needed. The current study examines the local mechanisms employed in automatic control. Local regulatory mechanisms function independently of external control mechanisms, such as sympathetic nerves and endocrine hormones. Therefore, they can be considered isolated mechanisms.The application of boundary conditions in numerical modeling is of utmost importance, hence, using arterial tree modeling to achieve appropriate boundary conditions seems necessary. Thus, we have presented a zero-dimensional (lumped parameter) extensive model first. Then, we used this model to achieve boundary conditions for the common carotid artery. As one of the most important hemodynamic parameters, shear stress regulation will then be modeled in an axisymmetric model of this artery.

The mechanical properties of the ureter altered by different diseases. So having the properties of the healthy ureter to detect tissue abnormalities is necessary.Wall tension alterations of the ureter can occur, leading to some abnormalities such as reflex mechanisms. Numerical analysis of urine flow in the ureter can help advance our understanding of the reflux phenomenon. To that end, a constitutive model that can predict the mechanical response of ureteral tissue under complex mechanical loading is required.Therefore, in this study the twenty-six human ureter samples were taken and uniaxial and biaxial tension tests were performed by loading in longitudinal and circumferential directions. Then the stress-strain curves achieved from the uniaxial tests were modeled with a mathematical function and the Young modulus was obtained. The biaxial stress-stretch curve was plotted and fitted to a hyperelastic four-parameter Choi-Vito type model. The specimens showed some degree of anisotropy. The specimens were stiffer in the longitudinal than in the circumferential direction.

Spinal deformities are generally associated with lumbar and cervical chronic pain and additionally they disturb the health. In these deformities, lumbar spinal curvature undergone changes in three dimensional space and in most cases, they cause reduction of lung capacities, breathing problems and negative effects on cardiovascular system. In critical deformity cases, in order to correct the deformity and prevent its progression, surgeons determine to perform posterior spinal fusion. As a result, they need to extract some important clinical parameters of spine such as Cobb angle, sagittal and coronal balance, spinal curvature, vertebraes angles and their rotations. In this study, edited tomographic images in MIMICS, were used to prepare a three dimensional model of the spine. Then by using curve fitting techniques and different clustering methods such as self-organization nueral network, k-means and hierarchical method, vertebras were separated and important geometrical data such as curvature of the spine and vertebras angle were obtained. In addition, through implementation of certain algorithms, other clinical features of each vertebra, including minimum and maximum height, length and width of the vertebral body and the relative displacement of vertebras were calculated automatically. In order to validate the proposed methods, measures and angles; derived values obtained automatically at each stage, were again calculated manually in MIMICS. Automatic values were verified by being compared with these manual results. In conclusion the reliability, accuracy and performance of the proposed automatic algorithms were demonstrated.

Neurological diseases such as cancer damage blood brain barrier and consequently cause more permeability in tissues. Generally, if there is damage to the brain tissues the contrast agent used in MRI diffuses outside the capillaries and the MRI picture brightness changes. The purpose of this paper is to show the effects of different parameters on the contrast agent diffusion in the brain capillary. In this study, the lattice Boltzmann method with multi-relaxation time (MRT) is used to simulate the flow in the capillary and porous media around it. The results show that the porosity in extravascular tissues (it shows the tissue damage), the kind of contrast agent and capillaries curvature have an impact on the contrast agent diffusion in the tissues. The presented results show the effects of curvature on shear stress and thus on mass transfer in the capillary. It should be noted that the presented results have been evaluated by previous statistical and analytical results for flow in the damaged brain capillary with different permeability. It has been shown that the lattice Boltzmann method is able to simulate the complex problems, especially in porous media.

Constitutive model of passive myocardium of lamb: Experimental tests and equations on the continuum mechanics are used in order to obtaining the constitutive models of soft tissue using in predictive heart simulation. Considering the myocardium as one of the important tissues, in this paper first the morphology and structure of myocardium has been reviewed and the mechanical response of passive form of this tissue has been investigated. The myocardium of left ventricle was considered as non linear elastic, in-compressible and non homogeneous material and using of bi-axial test in 3 lambs myocardium on fiber direction; a constitutive model of this tissue has been proposed. The model so constructed is then evaluated against the biaxial data, and values of the material constants have been obtained by curve fitting so the final model states the strain-energy function as cauchy's invariants which can be helpful in heart simulation. Key words: ventricular wall, continuum mechanics, strain energy tensor, local kinematics, bi-axial test.

Coronary Artery Diseases are one of the main reasonsof mortality. When these arteries occlude, usually a CoronaryArtery Bypass Graft (CABG) surgery is performed. Sine humanSaphenous Veins (SV) are used for CABG, they are of interest forresearchers. In this study human SV samples undergo inflationtest, using an inflation test device. Displacements of the samplesfor different pressures are analyzed, and average values are usedas input of a computational method. In the numerical simulationthe tissue is assumed as an elastic, isotropic, and homogenoussolid material, and its output is Young’s Modulus (E) ofthetissue. Results show that E of the SV increases linearly with thedistension pressure. Although simplifications were applied in thisstudy, it can be helpful for giving a basic insight aboutmechanical properties of human Saphenous Vein, which can befollowed by more realistic studies in the future.

Occlusion of cerebrospinal fluid path increases the pressure exerted by the liquid on the walls of the ventricles and ultimately leads to hydrocephalus. This research investigated a numerical index to diagnosis the non-communicating hydrocephalus disease. At first, the diagram of velocity in Sylvius aqueduct of a healthy subject, which was obtained through a 3D FSI analysis, was compared to the similar velocity diagram extracted from CINE-PC-MRI of the same subject. Then after ensuring that the two diagrams coincide with each other, was to make sure that the problem assumptions and solution are correct. The Reynolds number in Sylvius aqueduct of a healthy subject was less than 275.7 and the maximum pressure of CSF was 616.3 Pa. Further, the conditions of ventricular system in a patient suffering from non-communicating hydrocephalus were modeled. The maximum pressure has increased to 2958.5 Pa. Regarding the cause of hydrocephalus, the maximum pressure of CSF on the brain tissue in Sylvius aqueduct was introduced as an index to assess non-communicating hydrocephalus. Finally calculated CSF pressure data of this study were compared to the data obtained through the lumber puncture (LP) test and it was found that these values are proportional to each other. Based on this finding, the CSF pressure obtained by LP test was introduced as a practical numerical index for diagnosis of non-communicating hydrocephalus.

Cardiovascular diseases are a major cause of death in the world and are closely related to the dynamics of the blood and arterial wall mechanics. Not only in the cardiovascular system, but also in the whole body system, the heart is the most important organ that if the blood vessels of it blockage, heart function will impaired. Effective solutions to resolve blockage of coronary is the bypass surgery in which a replacement vessel for the blood supplying to the heart is using. So study the behavior of the vessels that use for the bypass is important. The goal of this study is the investigation of the mechanical behavior of saphenous vein by using the tensile biaxial tests. So eight human saphenous samples obtained and the planar biaxial tests were performed on the tissue specimens by applying simultaneous loads along the circumferential and longitudinal directions. Then the measured data were fitted into the four-parameter Fung-type model and also to the five-parameter Mooney–Rivlin model this could be used in finite element packages for numerical analysis. The specimens were stiffer in the longitudinal than in the circumferential direction. The specimens showed some degree of anisotropy.

Nowadays personal lifting assistive devices، in order to reduce the load applied from the lifted weight to muscles - in particular lower back muscles، become more widely used. The objective of our study is to analyze an empirical model of a Weight Lifting Aid Vest (WLAV) during anterior flexion (anteflexion) and studying its effects on reduction of loads on the muscles in particular back muscles. To analyze this، the intensity of signals captured from involved muscles، during the lifting in two case of with and without WLAV، was studied by the use of electromyography amplifier. In this process، 20 subjects who lifted 10-kilogram loads in semi-squatting position were participated. With the use of a tensile-compressive spring، embedded at the back of WLAV، the amount of body stretch and deflection of their hip and knees were measured. The influence of the WLAV on satisfaction during the lifting was studied. Data were collected from electromyography findings from eight involved muscles in back، stomach and feet. The results depicted that there are a overall reduction of 25. 12-percent in activation of all the muscles and particularly a reduction of 57%، 28% and 26. 5% in activation of external oblique، lateral hamstring، and erector spine، respectively. In contrast، there is 11% increase in activation of Gluteus Maximus in the case of usage of WLAV. WLAV can significantly mitigate the activation of back muscles and rate of load insertion on muscles) P<0. 005). It also clarified the tendency of the subjects towards users WLAV) P<0. 005).