Document Type : Full Research Paper


1 Ph.D Student, Facualty of Biomechanics, Department of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran

2 Associate Professor, Facualty of Biomechanics, Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran

3 Instructor, Faculty of Paramedical Sciences, Department of Radiological Technology, Babol University of Medical Sciences, Babol, Iran

4 Associate Professor, Facualty of Biomechanics, Department of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran


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).


Main Subjects

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