Spatial distribution of HD-EMG improves identification of task and force in patients with incomplete spinal cord injury

Background: Recent studies show that spatial distribution of High Density surface EMG maps (HD-EMG) improves the identification of tasks and their corresponding contraction levels. However, in patients with incomplete spinal cord injury (iSCI), some nerves that control muscles are damaged, leaving some muscle parts without an innervation. Therefore, HD-EMG maps in patients with iSCI are affected by the injury and they can be different for every patient. The objective of this study is to investigate the spatial distribution of intensity in HD-EMG recordings to distinguish co-activation patterns for different tasks and effort levels in patients with iSCI. These patterns are evaluated to be used for extraction of motion intention.; Method: HD-EMG was recorded in patients during four isometric tasks of the forearm at three different effort levels. A linear discriminant classifier based on intensity and spatial features of HD-EMG maps of five upper-limb muscles was used to identify the attempted tasks. Task and force identification were evaluated for each patient individually, and the reliability of the identification was tested with respect to muscle fatigue and time interval between training and identification. Results: Three feature sets were analyzed in the identification: 1) intensity of the HD-EMG map, 2) intensity and center of gravity of HD-EMG maps and 3) intensity of a single differential EMG channel (gold standard).; Results show that the combination of intensity and spatial features in classification identifies tasks and effort levels properly (Acc = 98.8 %; S = 92.5 %; P = 93.2 %; SP = 99.4 %) and outperforms significantly the other two feature sets (p < 0.05).; Conclusion: In spite of the limited motor functionality, a specific co-activation pattern for each patient exists for both intensity, and spatial distribution of myoelectric activity. The spatial distribution is less sensitive than intensity to myoelectric changes that occur due to fatigue, and other time-dependent influences.Peer ReviewedPostprint (published version

Prediction of isometric motor tasks and effort levels based on high-density EMG in patients with incomplete spinal cord injury

Objective. The development of modern assistive and rehabilitation devices requires reliable and easy-to-use methods to extract neural information for control of devices. Group-specific pattern recognition identifiers are influenced by inter-subject variability. Based on high-density EMG (HD-EMG) maps, our research group has already shown that inter-subject muscle activation patterns exist in a population of healthy subjects. The aim of this paper is to analyze muscle activation patterns associated with four tasks (flexion/extension of the elbow, and supination/pronation of the forearm) at three different effort levels in a group of patients with incomplete Spinal Cord Injury (iSCI). Approach. Muscle activation patterns were evaluated by the automatic identification of these four isometric tasks along with the identification of levels of voluntary contractions. Two types of classifiers were considered in the identification: linear discriminant analysis and support vector machine. Main results. Results show that performance of classification increases when combining features extracted from intensity and spatial information of HD-EMG maps (accuracy = 97.5%). Moreover, when compared to a population with injuries at different levels, a lower variability between activation maps was obtained within a group of patients with similar injury suggesting stronger task-specific and effort-level-specific co-activation patterns, which enable better prediction results. Significance. Despite the challenge of identifying both the four tasks and the three effort levels in patients with iSCI, promising results were obtained which support the use of HD-EMG features for providing useful information regarding motion and force intentionPeer ReviewedPostprint (author's final draft

Identificación de tareas isométricas y dinámicas del miembro superior basada en EMG de alta densidad

La identificación de tareas y estimación del movimiento voluntario basados en electromiografía (EMG) constituyen un problema conocido que involucra diferentes áreas en sistemas expertos, particularmente la de reconocimiento de patrones, con muchas aplicaciones posibles en dispositivos de asistencia y rehabilitación. La información que proporciona puede resultar útil para el control de exoesqueletos o brazos robóticos utilizados en terapias activas. La tecnología emergente de electromiografía de alta densidad (HD-EMG) abre nuevas posibilidades para extraer información neural y ya ha sido reportado que la distribución espacial de mapas de intensidad HD-EMG es una característica valiosa en la identificación de tareas isométricas (contracciones que no producen cambio en la longitud del músculo). Este estudio explora la utilización de la distribución espacial de la actividad mioeléctrica y lleva a cabo identificación de tareas durante ejercicios dinámicos a diferentes velocidades que son mucho más cercanos a los que se utilizan habitualmente en las terapias de rehabilitación. Con este objetivo, se registraron señales HD-EMG en un grupo de sujetos sanos durante la realización de un conjunto de tareas isométricas y dinámicas del miembro superior. Los resultados indican que la distribución espacial es una característica muy útil en la identificación, no solo de contracciones isométricas sino también de contracciones dinámicas, mejorando la eficiencia y naturalidad del control de dispositivos de rehabilitación para que se adapte mejor al usuario.Identification of tasks and estimation of volitional movement based on electromyography (EMG) constitute a known problem that involves different areas in the field of expert systems and particularly pattern recognition, with many possible applications in assistive and rehabilitation devices. The obtained information can be very useful to control exoskeletons or robots used in active rehabilitation processes. The emerging technology of high-density electromyography (HD-EMG) opens up new possibilities to extract neural information, and it has already been reported that the spatial distribution of HD-EMG intensity maps is a valuable feature in the identification of isometric tasks. This study explores the use of the spatial distribution of myoelectric activity and carries out a task identification during dynamic exercises at different velocities which are much closer to the ones commonly used during therapy. To this end, HD-EMG signals were recorded in a group of healthy subjects while performing a set of isometric and dynamic upper limb tasks. The results show that spatial distribution is a very useful feature in the identification not only of isometric contractions but also of dynamic contractions, so it can be very useful to improve the control of rehabilitation devices, making it more natural and permitting to adapt better to the user

Kernel density estimation of electromyographic signals and ensemble learning for highly accurate classification of a large set of hand/wrist motions

The performance of myoelectric control highly depends on the features extracted from surface electromyographic (sEMG) signals. We propose three new sEMG features based on the kernel density estimation. The trimmed mean of density (TMD), the entropy of density, and the trimmed mean absolute value of derivative density were computed for each sEMG channel. These features were tested for the classification of single tasks as well as of two tasks concurrently performed. For single tasks, correlation-based feature selection was used, and the features were then classified using linear discriminant analysis (LDA), non-linear support vector machines, and multi-layer perceptron. The eXtreme gradient boosting (XGBoost) classifier was used for the classification of two movements simultaneously performed. The second and third versions of the Ninapro dataset (conventional control) and Ameri’s movement dataset (simultaneous control) were used to test the proposed features. For the Ninapro dataset, the overall accuracy of LDA using the TMD feature was 98.99 ± 1.36% and 92.25 ± 9.48% for able-bodied and amputee subjects, respectively. Using ensemble learning of the three classifiers, the average macro and micro-F-score, macro recall, and precision on the validation sets were 98.23 ± 2.02, 98.32 ± 1.93, 98.32 ± 1.93, and 98.88 ± 1.31%, respectively, for the intact subjects. The movement misclassification percentage was 1.75 ± 1.73 and 3.44 ± 2.23 for the intact subjects and amputees. The proposed features were significantly correlated with the movement classes [Generalized Linear Model (GLM); P-value < 0.05]. An accurate online implementation of the proposed algorithm was also presented. For the simultaneous control, the overall accuracy was 99.71 ± 0.08 and 97.85 ± 0.10 for the XGBoost and LDA classifiers, respectively. The proposed features are thus promising for conventional and simultaneous myoelectric control.Peer ReviewedPostprint (published version

A novel spatial feature for the identification of motor tasks using high-density electromyography

Estimation of neuromuscular intention using electromyography (EMG) and pattern recognition is still an open problem. One of the reasons is that the pattern-recognition approach is greatly influenced by temporal changes in electromyograms caused by the variations in the conductivity of the skin and/or electrodes, or physiological changes such as muscle fatigue. This paper proposes novel features for task identification extracted from the high-density electromyographic signal (HD-EMG) by applying the mean shift channel selection algorithm evaluated using a simple and fast classifier-linear discriminant analysis. HD-EMG was recorded from eight subjects during four upper-limb isometric motor tasks (flexion/extension, supination/pronation of the forearm) at three different levels of effort. Task and effort level identification showed very high classification rates in all cases. This new feature performed remarkably well particularly in the identification at very low effort levels. This could be a step towards the natural control in everyday applications where a subject could use low levels of effort to achieve motor tasks. Furthermore, it ensures reliable identification even in the presence of myoelectric fatigue and showed robustness to temporal changes in EMG, which could make it suitable in long-term applications.Peer ReviewedPostprint (published version

Analysis of muscle load-sharing in patients with lateral epicondylitis during endurance isokinetic contractions using non-linear prediction

The aim of this paper is to analyze muscle load-sharing in patients with Lateral Epicondylitis during dynamic endurance contractions by means of non-linear prediction of surface EMG signals. The proposed non-linear cross-prediction scheme was used to predict the envelope of an EMG signal and is based on locally linear models built in a lag-embedded Euclidean space. The results were compared with a co-activation index, a common measure based on the activation of a muscle pair. Non-linear prediction revealed changes in muscle coupling, that is load-sharing, over time both in a control group and Lateral Epicondylitis (p < 0.05), even when subjects did not report pain at the end of the exercise. These changes were more pronounced in patients, especially in the first part of the exercise and up to 50% of the total endurance time (p < 0.05). By contrast, the co-activation index showed no differences between groups. Results reflect the changing nature of muscular activation strategy, presumably because of the mechanisms triggered by fatigue. Strategies differ between controls and patients, pointing to an altered coordination in Lateral Epicondylitis.Peer ReviewedPostprint (published version

Identificación de contracciones isométricas de la extremidad superior en pacientes con lesión medular incompleta mediante características espectrales de la electromiografía de alta densidad (HD-EMG)

[Resumen] La actividad mioeléctrica puede ser utilizada para la identificación de tareas motoras. En este estudio se investigaron diferentes características frecuenciales para la identificación de cuatro tareas motoras de la extremidad superior (flexión, extensión, supinación, y pronación) en pacientes con lesión medular incompleta. También se evaluaron los niveles de esfuerzo y la identificación de las tareas durante fatiga. Aunque se obtuvieron buenos resultados, las características frecuenciales mostraron su utilidad únicamente para la identificación de tareas, mientras que no aportaron información adecuada para la identificación de los niveles de esfuerzo o la identificación durante un ejercicio de fatiga.Ministerio de Economía y Competitividad; DPI2014-59049-RGeneralitat de Catalunya; FI 201

Implementación de una metodología basada en el aprendizaje por proyectos como herramienta para aumentar la motivación de los estudiantes en asignaturas transversales de Informática

Es habitual que planes de estudio para titulaciones de grado incluyan una asignatura transversal de informática en el primer año. En los estudios de Náutica encontramos un perfil de alumnado que percibe la asignatura ajena a la profesión escogida, lo que se refleja en una baja motivación. Para dar respuesta a esta realidad, con el objetivo de aumentar la motivación del alumnado y contextualizar la materia en el centro de interés, se ha llevado a cabo una experiencia de aprendizaje basado en proyectos (ABP). El reto planteado consiste en elaborar, en grupos reducidos, un programa funcional que dé respuesta a alguna de las necesidades propias del ámbito de la náutica. Durante el proceso, se elabora un diario para tomar consciencia del proceso de trabajo y de los aprendizajes. Al final, cada grupo presenta el proyecto a sus compañeros. Se ha valorado la satisfacción del alumnado en relación a la metodología docente y su percepción de aprendizaje mediante cuestionarios, comparándolos con un grupo control, que ha seguido una metodología expositiva participativa. Los resultados evidencian que la metodología ABP da lugar a una mayor satisfacción y a una percepción de un aprendizaje más profundo. La experiencia es generalizable a otras titulaciones con poco carácter tecnológico, siendo necesario adaptar el centro de interés. Para facilitar dicha tarea, se hace público el material generado en la presente experiencia docente.The academic plan in the first year of many bachelor degrees normally includes a course that covers the basics of informatics. In the nautical studies there are students that perceive the course of informatics unconnected to the envisioned career, resulting in low motivation. With the goal of boosting motivation and contextualize to the center of interest, we implemented a project-based learning methodology. The methodology proposes projects performed in small groups, with the objective to create a functional computer program that solves a problem in the nautical field. The students are required to elaborate a reflective learning diary to consolidate and extend learning through reflection and to be aware of the learned skills. At the end of the course, the projects are presented in front of the class. The satisfaction of the students and their perception of the learned material was measured using questionnaires and was compared to the control group, which followed an expository methodology. The results show that the project-based methodology yields greater satisfaction of the students and perception of deeper acquired knowledge. The proposed methodology can be easily adapted to other degrees with moderate presence of information and communication technologies, being necessary to adapt the center of interest. To ease this task, we make the resources publicly available.Este trabajo ha recibido el financiamiento del Institut de Ciències de l’Educació, Universitat Politècnica de Catalunya

Implementació i anàlisi de la metodologia Learning by doing a les assignatures d’Informàtica dels estudis de Nàutica

És habitual que els plans d'estudi per a titulacions de grau incloguin una assignatura transversal d'informàtica el primer any. Als estudis de Nàutica trobem un perfil d'alumnat que percep l'assignatura com una matèria aliena a la professió escollida, cosa que es reflecteix en una baixa motivació. Per donar resposta a aquesta realitat, amb l'objectiu d'augmentar la motivació de l'alumnat i de contextualitzar la matèria al centre d'interès, s'ha dut a terme una experiència d'aprenentatge basat en projectes (ABP). El repte plantejat consisteix en elaborar, en grups reduïts, un programa funcional que doni resposta a alguna de les necessitats pròpies de l’àmbit de la Nàutica. Durant el procés s'elabora un diari per prendre consciència del procés de treball i dels aprenentatges. Al final, cada grup presenta el projecte als companys. S'ha valorat la satisfacció de l'alumnat en relació amb la metodologia docent i la percepció d'aprenentatge mitjançant qüestionaris, comparant-los amb un grup control, que ha seguit una metodologia expositiva participativa. Els resultats evidencien que la metodologia ABP dóna lloc a una satisfacció més gran i a una percepció d'un aprenentatge més profund. L'experiència és generalitzable a altres titulacions on la Informàtica té un caràcter merament instrumental, només cal adaptar el centre d'interès. Per facilitar aquesta tasca, s’ha fet públic el material generat en aquesta experiència docent. L’experiència es va presentar a les XXVII Jornadas sobre la Enseñanza Universitaria de la Informática JENUI 2021 (València)

Implementación de una metodología basada en el aprendizaje por proyectos como herramienta para aumentar la motivación de los estudiantes en asignaturas transversales de Informática

Es habitual que planes de estudio para titulaciones de grado incluyan una asignatura transversal de informá- tica en el primer año. En los estudios de Náutica encontramos un perfil de alumnado que percibe la asignatura ajena a la profesión escogida, lo que se refleja en una baja motivación. Para dar respuesta a esta realidad, con el objetivo de aumentar la motiva- ción del alumnado y contextualizar la materia en el centro de interés, se ha llevado a cabo una experien- cia de aprendizaje basado en proyectos (ABP). El reto planteado consiste en elaborar, en grupos reducidos, un programa funcional que dé respuesta a alguna de las necesidades propias del ámbito de la náutica. Durante el proceso, se elabora un diario para tomar consciencia del proceso de trabajo y de los aprendiza- jes. Al final, cada grupo presenta el proyecto a sus compañeros. Se ha valorado la satisfacción del alum- nado en relación a la metodología docente y su per- cepción de aprendizaje mediante cuestionarios, com- parándolos con un grupo control, que ha seguido una metodología expositiva participativa. Los resultados evidencian que la metodología ABP da lugar a una mayor satisfacción y a una percepción de un aprendi- zaje más profundo. La experiencia es generalizable a otras titulaciones con poco carácter tecnológico, siendo necesario adaptar el centro de interés. Para facilitar dicha tarea, se hace público el material gene- rado en la presente experiencia docente.Postprint (published version