A finite element model for the investigation of surface EMG signals during dynamic contraction

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dc.contributor.advisor Hanekom, Tania en
dc.contributor.advisor Farina, D. en
dc.contributor.postgraduate Joubert, Michelle en
dc.date.accessioned 2013-09-07T12:10:10Z
dc.date.available 2008-09-09 en
dc.date.available 2013-09-07T12:10:10Z
dc.date.created 2008-04-09 en
dc.date.issued 2008-09-09 en
dc.date.submitted 2008-09-04 en
dc.description Dissertation (MEng)--University of Pretoria, 2008. en
dc.description.abstract A finite element (FE) model for the generation of single fiber action potentials (SFAPs) in a muscle undergoing various degrees of fiber shortening has been developed. The muscle is assumed to be fusiform with muscle fibers following a curvilinear path described by a Gaussian function. Different degrees of fiber shortening are simulated by changing the parameters of the fiber path and maintaining the volume of the muscle constant. The conductivity tensor is adapted to the muscle fiber orientation. At each point of the volume conductor, the conductivity of the muscle tissue in the direction of the fiber is larger than that in the transversal direction. Thus, the conductivity tensor changes point-by-point with fiber shortening, adapting to the fiber paths. An analytical derivation of the conductivity tensor is provided. The volume conductor is then studied with an FE approach using the analytically derived conductivity tensor (Mesin, Joubert, Hanekom, Merletti&Farina 2006). Representative simulations of SFAPs with the muscle at different degrees of shortening are presented. It is shown that the geometrical changes in the muscle, which imply changes in the conductivity tensor, determine important variations in action potential shape, thus affecting its amplitude and frequency content. The model is expanded to include the simulation of motor unit action potentials (MUAPs). Expanding the model was done by assigning each single fiber (SF) in the motor unit (MU) a random starting position chosen from a normal distribution. For the model 300 SFs are included in an MU, with an innervation zone spread of 12 mm. Only spatial distribution was implemented. Conduction velocity (CV) was the same for all fibers of the MU. Representative simulations for the MUAPs with the muscle at different degrees of shortening are presented. The influence of interelectrode distance and angular displacement are also investigated as well as the influence of the inclusion of the conductivity tensor. It has been found that the interpretation of surface electromyography during movement or joint angle change is complicated owing to geometrical artefacts i.e. the shift of the electrodes relative to the muscle fibers and also because of the changes in the conductive properties of the tissue separating the electrode from the muscle fibers. Detection systems and electrode placement should be chosen with care. The model provides a new tool for interpreting surface electromyography (sEMG) signal features with changes in muscle geometry, as happens during dynamic contractions. en
dc.description.availability unrestricted en
dc.description.department Electrical, Electronic and Computer Engineering en
dc.identifier.citation a 2007 en
dc.identifier.other E1083/gm en
dc.identifier.upetdurl http://upetd.up.ac.za/thesis/available/etd-09042008-105943/ en
dc.identifier.uri http://hdl.handle.net/2263/27722
dc.language.iso en
dc.publisher University of Pretoria en_ZA
dc.rights © University of Pretoria 2007 E1083/ en
dc.subject Modelling en
dc.subject Mnf en
dc.subject Arv en
dc.subject Conductivity tensor en
dc.subject Joint angle en
dc.subject Muscle shortening en
dc.subject Fe modelling en
dc.subject Numerical model en
dc.subject Sfap en
dc.subject Muap en
dc.subject Semg en
dc.subject UCTD en_US
dc.title A finite element model for the investigation of surface EMG signals during dynamic contraction en
dc.type Dissertation en


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