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

Knee osteoarthritis affects approximately 25 million adults. In severe cases, total knee arthroplasty (TKA) is the most common solution. TKA is effective at addressing pain and reducing continued degeneration of articular cartilage. However, effective physical therapy (PT) following TKA is vital for a full functional recovery. Despite the importance of PT, half of patients never achieve a full functional recovery. Decreases in proprioceptive feedback, severe atrophy, and pain inhibition all likely contribute to the variability in effectiveness. Surface electromyography-based biofeedback (sEMGBF) may allow clinicians to address some of these barriers by supplementing proprioceptive feedback and targeting small muscle contractions before eventually increasing the contraction requirement. Using a between group design, we compare the effectiveness of sEMGBF (7) to neuromuscular stimulation (NMES) (6), and a control group (6) in recovery following TKA. Effectiveness was evaluated across 4 metrics (quadriceps strength, range of motion, functional improvement, and quality of life) in a pre-test/post-test fashion. At the statistical level this study suggest that sEMGBF leads to greater improvements in quadriceps strength relative to the NMES and control group. Additionally, visual analysis suggests that sEMGBF may also lead to greater improvements in range of motion, and functional improvement relative to the NMES and control group. The results for quality of life are mixed. Overall, the study provides initial clinical support for the utility of sEMGBF following TKA.

The Master's thesis is focused on monitoring of the core muscles and m. biceps femoris activity in postural stability examination by Dynamic Neuromuscular Stabilization tests using surface electromyography in patients with LBP. Trunk extension test, trunk flexion test and squat test were chosen. The aim of this study was comparing muscle activity timing, symmetry of muscle activation and average activation between healthy subjects and patients with LBP. The changes of muscle activation pattern were observed and average activation was determined. In theoretical part the principles of DNS, surface electromyography and the relationship between postural stabilization and LBP are discussed. Two groups were measured - patients with LBP and a control group, 20 subjects together. The onset times were measured and rank of activation for each test and for each subject was determined. Then the average order for whole group was specified. Measured data were evaluated according to Wilcoxon signed-rank test. In average activation there was analysed change of activation in time. Results were compared between two measured groups. There is significant difference between the two groups in the rank of activation of m. ES l. dx. in trunk extension test and m. EO in squat test. Assymetry in timing of the right and left...

Les hallucinations auditives verbales (HAVs) sont des perceptions langagières en l'absence de stimuli externes appropriés. Elles sont un des symptômes les plus invalidants dans la schizophrénie. Parmi les grands types de modèles explicatifs, deux sont particulièrement intéressants : les modèles à origine perceptive, selon lesquels les voix entendues seraient dues à une imagerie mentale et des représentations auditives trop vives et les modèles à origine productive, selon lesquels la parole intérieure est perturbée de telle sorte que les propres pensées verbales du patient sont attribuées à un agent externe. Pour tester le versant moteur des modèles productifs, une expérience de recueil de traces oro-faciales lors des HAVs à l'aide de l'électromyographie de surface a été conduite auprès de patients schizophrènes. Les résultats montrent une tendance à l'augmentation de l'activité musculaire des orbiculaires de la bouche lors des HAVs par rapport à une condition de repos. Pour tester le versant cérébral des modèles, une expérience d'imagerie cérébrale par IRMf lors de tâches de génération de pensée verbale et de perception auditive a été menée auprès de sujets schizophrènes et sujets contrôles et a évoqué une hyper-activation d'un réseau impliquant le cortex temporal et le cortex cingulaire antérieur qui reste à confirmer. La caractérisation phénoménologique des HAVs vécues par les patients a montré que les HAVs diffèrent de la pensée intérieure typique en ce que les voix entendues peuvent être nombreuses et ne sont pas celle du patient lui-même. Ainsi aucun des deux types de modèles considérés isolément n'est satisfaisant pour expliquer les HAVs. Un modèle intégratif multidimensionnel est proposé qui permettrait de mieux rendre compte de la complexité des HAVs. Il existerait, chez les patients schizophrènes une prédisposition perceptive hyper-active couplée à un système de prédiction défaillant. Les deux dysfonctionnements seraient de plus modulés par des facteurs attentionnels, de stress et par un biais cognitif d'externalisation.

In the field of ergonomics, biomechanics, sports and rehabilitation muscle fatigue is regarded as an important aspect since muscle fatigue is considered to be one of the main reasons for musculoskeletal disorders. Classical signal processing techniques used to understand muscle behavior are mainly based on spectral based parameters estimation, and mostly applied during static contraction and the signal must be stationary within the analysis window; otherwise, the resulting spectrum will make little physical sense. Furthermore, the shape and size of the analysis window also directly affect the spectral estimation. But fatigue analysis in dynamic conditions is of utmost requirement because of its daily life applicability. It is really difficult to consistently find the muscle fatigue during dynamic contraction due to the inherent non-stationary nature and associated noise in the signal along with complex physiological changes in muscles. Nowadays, in addition to linear signal processing, different non-linear signal processing techniques are adopted to find out the consistent and robust indicator for muscle fatigue under dynamic condition considering the high degree of non-linearity (caused by functional interference between different muscles, changes of signal sources and paths to recording electrodes, variable electrode interface etc.) in the signal. In this work, various linear and nonlinear-non-stationary signal processing methods, applied on surface EMG signal for muscular fatigue analysis under dynamic contraction are studied. In present study, surface EMG (sEMG) signals are recorded from Biceps Brachii muscles from eight (N=8) physically active college students during dynamic lifting 7 kg load at the rate of 20 lifts/min till they become fatigue. EMG data is processed in two ways -1. taking the whole EMG response and 2. breaking into three ranges of contraction (0-45)o, (45-90)o and >90o, to study better response region. It is observed that in spectral estimation techniques auto-regressive (AR) based spectral estimation technique gives better frequency resolution than periodogram for small epochs, as AR is based on parametric estimation. Both the previous methods provide only the frequency information in the signal. In order to estimate the time varying nature of frequency content in a signal various time-frequency signal processing techniques are used like – Short Time-Fourier Transform (STFT), Smoothed pseudo Wigner-Ville (SPWD), Choi-William distribution (CWD), Continuous Wavelet Transform (CWT), Huang-Hilbert Transform (HHT) and Recurrence Quantification Analysis (RQA) are used. The last two techniques are used by considering the EMG signal as non-linear and non-stationary signals. Among these techniques, STFT is the simplest time-frequency analysis technique. But tradeoff between time and frequency resolution is the major constraint in STFT, therefore, a window length of 256 samples are considered in this study. In order to tackle time-frequency resolution problem different Cohen-class distribution techniques are used like SPWD and CWD, where the result is severely affected by the presence of interference terms which make its interpretation really difficult. Different adaptive filters are used in SPWD and CWD to suppress these interference terms during analysis. Among these time-frequency analysis techniques continuous wavelet transform provides the most accurate results in comparison to other time-frequency analysis techniques. Similar result is obtained in present study. This fatigue response is further improved using non-linear and non-stationary techniques like HHT and RQA. HHT shows less variation in frequency response than CWT analysis result. Percentage of determinism calculated using recurrence quantification analysis method is found to be more sensitive than mean frequency estimation. Therefore, non-linear and non-stationary signal processing techniques are to be better indicator of muscle fatigue during dynamic contraction.

[ES] La cirugía laparoscopia está considerada uno de los principales avances quirúrgicos en las últimas décadas. Esta técnica ha demostrado numerosas ventajas comparadas con la cirugía convencional abierta y ha sido extensamente usada para procesos quirúrgicos en el área abdominal. Para el paciente, la cirugía laparoscópica supone diversas ventajas, como por ejemplo menor dolor post operativo, tiempos de recuperación menores, menor riesgo de infección, o reducción del trauma. Para el cirujano en cambio, la situación es completamente diferente, esta práctica requiere mayor esfuerzo, concentración y estrés mental que la práctica convencional abierta. Además fuerza al cirujano a adoptar posiciones no-neutras en falanges, manos, muñecas, y brazos. Estas posturas no-neutras son la principal causa de fatiga muscular y aumentan el riesgo de problemas musculo-esqueléticos. Estos problemas han sido ampliamente estudiados por diferentes equipos de investigación, los cuales están tratando de mejorar la experiencia del cirujano en el quirófano. El enfoque utilizado en este estudio es diferente del utilizado anteriormente por la mayoría de estos equipos, los cuales suelen propones soluciones basadas en cambios ergonómicos con la intención de mejorar la geometría del mango de pistola convencional, ya que se considera ergonómicamente deficiente. El problema con este enfoque, es que las deficiencias no se encuentran únicamente en el mango, sino en la utilización de un punto de entrada fijo que fuerza a los cirujanos a mantener posiciones desfavorables. En este trabajo, se introduce el concepto "Libertad Postural" en el ámbito de la cirugía, este se basa en la hipótesis de que, si las herramientas no forzaran la posición de los cirujanos, estos mantendrían posiciones más favorables y cercanas al rango de posiciones neutras durante los procesos laparoscópicos. Los beneficios de este concepto han sido demostrados por medio de análisis de movimiento y de electromiografía de superficie, los cuales indican que la "Libertad Postural" es causante de un claro aumento de las posiciones neutras y de la reducción de la fatiga muscular, y han sido testeados por cirujanos en entornos simulados, los cuales encuentran beneficioso utilizar la "Libertad Postural" como característica base de este nuevo diseño de herramienta laparoscópica. En la sección final de este trabajo se propone un diseño que implementa el concepto de libertad postura con el cual se reduciría la fatiga muscular y los problemas musculo esqueléticos asociados a la práctica laparoscópica. Este diseño tiene la característica de actuar como una nueva sección del brazo, siendo una articulación que soporta los giros y grandes desplazamientos que normalmente tienen que desarrollar los brazos del cirujano. Además, esta solución es económica y fácil de fabricar, lo cual permitiría su uso por cirujanos de todo el mundo. / [CAT] La cirurgia laparoscòpia està considerada un dels principals avanços quirúrgics en les últimes dècades. Aquesta tècnica ha demostrat nombrosos avantatges comparats amb la cirurgia convencional oberta i ha sigut extensament usada per a processos quirúrgics en l'àrea abdominal. Per al pacient, la cirurgia laparoscòpica suposa diversos avantatges, com per exemple menor dolor post operatiu, temps de recuperació menors, menor risc d'infecció, o reducció del trauma. Per al cirurgià en canvi, la situació és completament diferent, aquesta pràctica requereix major esforç, concentració i estrés mental que la pràctica convencional oberta. A més força al cirurgià a adoptar posicions no-neutres en falanges, mans, nines, i braços. Aquestes postures no-neutres són la principal causa de fatiga muscular i augmenten el risc de problemes musculo-esquelètics. Aquests problemes han sigut àmpliament estudiats per diferents equips d'investigació, els quals estan tractant de millorar l'experiència del cirurgià en el quiròfan. L'enfocament utilitzat en aquest estudi és diferent de l'utilitzat anteriorment per la majoria d'aquests equips, els quals solen proposes solucions basades en canvis ergonòmics amb la intenció de millorar la geometria del mànec de pistola convencional, ja que es considera ergonòmicament deficient. El problema amb aquest enfocament, és que les deficiències no es troben únicament en el mànec, sinó en la utilització d'un punt d'entrada fix que força als cirurgians a mantindre posicions desfavorables. En aquest treball, s'introdueix el concepte "Llibertat Postural" en l'àmbit de la cirurgia, aquest es basa en la hipòtesi que, si les eines no forçaren la posició dels cirurgians, aquests mantindrien posicions més favorables i pròximes al rang de posicions neutres durant els processos laparoscòpics. Els beneficis d'aquest concepte han sigut demostrats per mitjà d'anàlisi de moviment i de electromiografía de superfície, els quals indiquen que la "Llibertat Postural" és causant d'un clar augment de les posicions neutres i de la reducció de la fatiga muscular, i han sigut testats per cirurgians en entorns simulats, els quals troben beneficiós utilitzar la "Llibertat Postural" com a característica base d'aquest nou disseny d'eina laparoscòpica. En la secció final d'aquest treball es proposa un disseny que implementa el concepte de llibertat postura amb el qual es reduiria la fatiga muscular i els problemes *musculo esquelètics associats a la pràctica laparoscòpica. Aquest disseny té la característica d'actuar com una nova secció del braç, sent una articulació que suporta els girs i grans desplaçaments que normalment han de desenvolupar els braços del cirurgià. A més, aquesta solució és econòmica i fàcil de fabricar, la qual cosa permetria el seu ús per cirurgians de tot el món. / [EN] Laparoscopic surgery is considered one of the main surgical advances in the last decades, this technique has demonstrated numerous advantages compared to open conventional surgery and it is widely used in abdominal procedures around the world. For the patient, laparoscopic surgery suppose less post-operative pain, shorter recovery time, lower risk of infection, and reduction of the trauma among other benefits. For the surgeon, the situation is completely different, this practice requires more effort, concentration and mental stress than conventional open procedures. It forces the surgeon to adopt non-neutral postures with phalanges, hands, wrists, and arms being this non-neutral postures the main cause of muscular fatigue and high risk of musculoskeletal disorders. The poor ergonomic postures accelerate muscle fatigue and pain because, outside the neutral range, muscles require more energy to generate the same contractile force than in neutral position. This increase of muscular fatigue is associated with the potential to commit errors that may harm the patient during the surgery. Because this problem is widely studied and different research centers are already trying to improve their surgeons experience in the operation room, the approach used during this work is different than most of the ones presented in previous works. Generally, the solutions proposed are based on ergonomic changes in the handle shape of the instrument, because the conventional pistol-grip handle is considered ergonomically poor. But the problem is not only in the shape of the handle but also in the fixed point of entrance that force the positions for the surgeon despite the handle¿s shape. In this work, the concept of postural freedom in laparoscopic surgery is introduced and evaluated. The postural freedom concept is based on the hypothesis that the surgeon involuntarily would maintain neutral postures if the instrument does not force him or her to reach extreme position with the upper limbs. The benefits of this concept has been demonstrated, by means of electromyography and motion capture. It reduces the localized muscular fatigue and increases the number of neutral postures during laparoscopic simulations. In the final section it is proposed a design that implements the postural freedom concept with, according on the results, the potential to reduce the localized muscular fatigue and the musculoskeletal problems associated to the practice. The design proposed here acts as a new section on the arm, being an articulation that support the turns and big displacements that currently suffer the surgeon¿s body. The solution is affordable and easy to manufacture and could be used by surgeons worldwide. / Pace Bedetti, HM. (2019). The effect of "Postural Freedom" in laparoscopic surgery [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/122312 / TESIS

Title: Strategy of postural stabilisation using unstable surface and water barrel. Objectives: The aim of this study is to investigate the level of muscle actiavtion of choosen muscles during lunge on unstable surface or with using water barrel. Investigation of the postural strategy used during lunge orn unstable surface or with the water barrel and creation of methodology for measurment and data analysis. Methods: Into this pilot study, there were picked 5 people (athletes). Data for outcomes where used from 3 athletes. The measurement of level of muscle activation were done by surface electromyography over gluteus medius muscle and musculi multifidii bilaterally.For data procession was used software Origin 2012 Postural stability was measured through force plates by Kistler and gained data were procesed by using software programmes Bioware, MS Excel and Matlab. For data analysis from EMG measurement was used simple comparasion of outcomes. Stabilometry outcomes were analysed by statistical methode t-test. Results: The results indicate greater level of muscle activation during lunge with aquabag than lunge on unstable surface for most of the measured muscles. The only exception, where level of muscle activity was higher, was multifidi muscle on rear leg. Another outcome proved that the postural...

Title: Strategy of postural stabilisation using unstable surface and water barrel. Objectives: The aim of this study is to investigate the level of muscle actiavtion of choosen muscles during lunge on unstable surface or with using water barrel. Investigation of the postural strategy used during lunge orn unstable surface or with the water barrel and creation of methodology for measurment and data analysis. Methods: Into this pilot study, there were picked 5 people (athletes). Data for outcomes where used from 3 athletes. The measurement of level of muscle activation were done by surface electromyography over gluteus medius muscle and musculi multifidii bilaterally.For data procession was used software Origin 2012 Postural stability was measured through force plates by Kistler and gained data were procesed by using software programmes Bioware, MS Excel and Matlab. For data analysis from EMG measurement was used simple comparasion of outcomes. Stabilometry outcomes were analysed by statistical methode t-test. Results: The results indicate greater level of measured trunk muscles activation during lunge with aquabag than lunge on unstable surface. Another thing which was found is that there was higher activation of Gluteus medius muscle on dominant lower extremity when performin lunge on unstable...

This thesis presents an activity mode intent recognition approach for safe, robust and reliable control of powered backbone exoskeleton. The thesis presents the background and a concept for a powered backbone exoskeleton that would work in parallel with a user. The necessary prerequisites for the thesis are presented, including the collection and processing of surface electromyography signals and inertial sensor data to recognize the user’s activity. The development of activity mode intent recognizer was described based on decision tree classification in order to leverage its computational efficiency. The intent recognizer is a high-level supervisory controller that belongs to a three-level control structure for a powered backbone exoskeleton. The recognizer uses surface electromyography and inertial signals as the input and CART (classification and regression tree) as the classifier. The experimental results indicate that the recognizer can extract the user’s intent with minimal delay. The approach achieves a low recognition error rate and a user-unperceived latency by using sliding overlapped analysis window. The approach shows great potential for future implementation on a prototype backbone exoskeleton.

L’objectif de cette thèse a été d’analyser l’effet de l’exercice physique réalisé sur plateforme vibrante (whole-body vibration, WBV) sur l’activité musculaire des membres inférieurs, de développer des outils d’analyse méthodologiques et de proposer des recommandations pratiques d’utilisation. Deux études méthodologiques ont été menées pour identifier la méthode optimale permettant de traiter les signaux d'électromyographie de surface (sEMG) recueillis pendant la vibration et d'analyser l'influence de la méthode de normalisation de l'activité sEMG. Une troisième étude visait à mieux comprendre si les pics sEMG observés dans le spectre de puissance du signal contiennent des artéfacts de mouvement et/ou de l'activité musculaire réflexe. Les trois études suivantes avaient pour but de quantifier l’effet de la WBV sur l’activité musculaire en fonction de différents paramètres tels que, la fréquence de vibration, l'amplitude de la plateforme, une charge supplémentaire, le type de plateforme, l'angle articulaire du genou, et la condition physique du sujet. En outre, l'objectif a été de déterminer l'accélération verticale minimale permettant de stimuler au mieux l'activité musculaire des membres inférieurs. En résumé, les recherches menées au cours de cette thèse fournissent des solutions pour de futures études sur : i) comment supprimer les pics dans le spectre du signal sEMG et, ii) comment normaliser l'activité musculaire pendant un exercice WBV. Enfin, les résultats de cette thèse apportent à la littérature scientifique de nouvelles recommandations pratiques liées à l’utilisation des plateformes vibrantes à des fins d’exercice physique. / The aim of this thesis was to analyze the effect of whole-body vibration (WBV) exercise on lower limb muscle activity and to give methodological implications and practical applications. Two methodological studies were conducted that served to evaluate the optimal method to process the surface electromyography (sEMG) signals during WBV exercise and to analyze the influence of the normalization method on the sEMG activity. A third study aimed to gain insight whether the isolated spikes in the sEMG spectrum contain motion artifacts and/or reflex activity. The subsequent three investigations aimed to explore how the muscle activity is affected by WBV exercise, with a particular focus on the vibration frequency, platform amplitude, additional loading, platform type, knee flexion angle, and the fitness status of the WBV user. The final goal was to evaluate the minimal required vertical acceleration to stimulate the muscle activity of the lower limbs. In summary, the research conducted for this thesis provides implication for future investigations on how to delete the excessive spikes in the sEMG spectrum and how to normalize the sEMG during WBV. The outcomes of this thesis add to the current literature in providing practical applications for exercising on a WBV platform.