A comparison of the ability of different spatial filters to reduce the amount of crosstalk in a surface electromyography (sEMG) measurement was conducted. It focused on the influence of different properties of the muscle anatomy and detection system used on the amount of crosstalk present in the measurements. An analytical model was developed which enabled the simulation of single fibre action potentials (SFAPs). These fibres were grouped together in motor units (MUs). Each MU has characteristics which, along with the SFAPs, are used to obtain the motor unit action potential (MUAP). A summation of the MUAPs from all the MUs in a muscle leads to the electromyogram (EMG) signal generated by the muscle. This is the first model which simulates a complete muscle for crosstalk investigation. Previous studies were done for single fibres (Farina&Rainoldi 1999; Farina et al. 2002e; Farina et al. 2004a) or MUs (Dimitrova et al. 2002; Dimitrov et al. 2003; Winter et al. 1994). Lowery et al. simulated a complete muscle, but only investigated one spatial filter (Lowery et al. 2003a). This model is thus the first of its kind. EMG signals were generated for limbs with different anatomical properties and recorded with various detection systems. The parameters used for comparison of the recorded signals are the average rectified value (ARV) and mean frequency (MNF), which describe the amplitude and frequency components of an EMG signal, respectively. These parameters were computed for each EMG signal and interpreted to make recommendations on which detection system results in the best crosstalk rejection for a specific experimental set-up. The conclusion is that crosstalk selectivity in an sEMG measurement is decreased by increasing the thickness of the fat layer, increasing the skin conductivity, decreasing the fibre length, increasing the interelectrode distance of the detection system, placing the detection electrodes directly above the end-plate area or an increased state of muscle contraction. Varying the contraction force strength or placing the detection electrodes directly above the tendon area has no influence on the crosstalk selectivity. For most of the conditions investigated, the normal double differential (NDD) detection system results in the best crosstalk reduction. The only exceptions are a set-up with poor skin conductivity where NDD and double differential (DD) performed comparably, and the two simulations in which the muscle length is varied, where the DD filter performed best. Previous studies have found DD to be more selective for crosstalk rejection than NDD (Dimitrov et al. 2003; Farina et al. 2002a; Van Vlugt&Van Dijk 2000). Possible reasons for the contradictory results are the high value of skin conductivity currently used or influences of the muscle geometry. / Dissertation (MEng(Bio-Engineering))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted

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. / Dissertation (MEng (Bio-Engineering))--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / MEng (Bio-Engineering) / unrestricted

Title: Measurement of lower extremities spasticity in patients with cerebral palsy Objectives: The aim of the theoretical part of this thesis is to evaluate possibilities of lower extremities spasticity measurement in adult patients with cerebral palsy. The main focus was given to the concept of French professor J.-M. Gracies: Five- step clinical assessment in spastic paresis. This unique concept presents differentiation of three main factors of motor impairment that emerge as a result of a lesion to central motor pathways: stretch sensitive paresis, soft tissue contracture and muscle overactivity. Ability to distinguish these factors is crucial for specific treatment indication. Finding a correlation between the Five-step clinical assessment in spastic paresis and muscle activity in gait measured with polyEMG was the main objective in the practical part of the thesis. Methodology: This thesis has a theoretical-empirical character. The theoretical part is in a form of a research on the topic of spasticity diagnosis, focused on cerebral palsy patients. The empirical part of the thesis has a form of pilot quantitative research, which was attended by 6 participants with cerebral palsy (4 men and 2 women; average age 29 years). There were 2 independent measurement made for each of them. Each...

Title: The effect of progressive static stretching on treatment of spastic paraparesis in patients with cerebral palsy Objectives: The goal of this dissertation is to evaluate the effect of progressive static stretching on treatment of spastic paraparesis in patients with paraparetic form of cerebral palsy (CP). Elements chosen for the treatment were those of the therapeutic concept Guided Self-rehabilitation Contract by French professor Jean-Michel Gracies, which is presented in detail in the theoretical part of the dissertation. Methodology: This dissertation has a theoretical-empirical character. First theoretical part of the dissertation is in a form of a research on the topic of spasticity and diagnosis and treatment of spastic paresis according to the concept of J.-M. Gracies. Second experimental part of the dissertation evaluating the effect of the selected treatment for spastic paresis in people with cerebral palsy, has a form of pilot qualitative research, which was attended by 6 participants. At the beginning of the research each participant has undergone an entrance examination that evaluated spasticity using at first an unique assessing protocol Five step clinical assessment and consequently a surface electromyography. Based on this examination, each participant was instructed to follow...

Title: Measurement of lower extremities spasticity in patients with cerebral palsy Objectives: The aim of the theoretical part of this thesis is to evaluate possibilities of lower extremities spasticity measurement in adult patients with cerebral palsy. The main focus was given to the concept of French professor J.-M. Gracies: Five-step clinical assessment in spastic paresis. This unique concept presents differentiation of three main factors of motor impairment that emerge as a result of a lesion to central motor pathways: stretch sensitive paresis, soft tissue contracture and muscle overactivity. Ability to distinguish these factors is crucial for specific treatment indication. Finding a correlation between the Five-step clinical assessment in spastic paresis and muscle activity in gait measured with sEMG was the main objective in the practical part of the thesis. Methodology: This thesis has a theoretical-empirical character. The theoretical part is in a form of a research on the topic of spasticity diagnosis, focused on cerebral palsy patients. The empirical part of the thesis has a form of pilot quantitative research, which was attended by 6 participants with cerebral palsy (4 men and 2 women; average age 29 years). There were 2 independent measurement made for each of them. Each measurement...