Browsing by Author "Alvarez Ruf, Joel"
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Publication Brain’s Energy After Stroke: From a Cellular Perspective Toward Behavior(2022) Mariman, Juan José; Lorca, Enrique; Biancardi, Carlo; Burgos, Pablo; Alvarez Ruf, JoelStroke is a neurological condition that impacts activity performance and quality of life for survivors. While neurological impairments after the event explain the performance of patients in specific activities, the origin of such impairments has traditionally been explained as a consequence of structural and functional damage to the nervous system. However, there are important mechanisms related to energy efficiency (tradeoff between biological functions and energy consumption) at different levels that can be related to these impairments and restrictions: first, at the neuronal level, where the availability of energy resources is the initial cause of the event, as well as determines the possibilities of spontaneous recovery. Second, at the level of neural networks, where the “small world” operation of the network is compromised after the stroke, implicating a high energetic cost and inefficiency in the information transfer, which is related to the neurological recovery and clinical status. Finally, at the behavioral level, the performance limitations are related to the highest cost of energy or augmented energy expenditure during the tasks to maintain the stability of the segment, system, body, and finally, the behavior of the patients. In other words, the postural homeostasis. In this way, we intend to provide a synthetic vision of the energy impact of stroke, from the particularities of the operation of the nervous system, its implications, as one of the determinant factors in the possibilities of neurological, functional, and behavioral recovery of our patients.Item Control postural en personas con antecedente de accidente cerebrovascular de la clínica UDD en comparación con personas sin antecedente de accidente cerebrovascular: un estudio transversal(Universidad del Desarrollo. Facultad de Medicina, 2022) Alvarez Martínez, Gabriel; Espinoza Orellana, Francisca; Herrada Michaud, Florencia; Mazo Valenzuela, Javiera; Alvarez Ruf, JoelAntecedentes: Los accidentes cerebrovasculares (ACV) que dañan las áreas de integración de la respuesta motora o sus vías de conducción generan alteraciones del control motor y, consecuentemente, del control postural. Estos cambios son evaluables mediante el uso de una plataforma de fuerza. Aun cuando existen numerosos estudios enfocados en analizar el control postural mediante plataforma de fuerza en personas con ACV, estos se han realizado casi exclusivamente en el extranjero. En Chile, los estudios de este tipo se han limitado a otras patologías neurológicas que afectan el control motor. Objetivo: Comparar la ponderación de los sistemas sensoriales en el control postural durante la mantención de posición bípeda en personas adultas con antecedente de ACV en comparación con personas sin ACV. Método: Estudio de tipo cuantitativo, diseño observacional analítico transversal. Se evaluó mediante una Wii Balance Board™ la señal del centro de presión de 7 personas con ACV atendidas en la Clínica UDD, comparando con personas sin ACV. Se incluyó a personas con antigüedad de ACV mayor de 6 meses, capaces de adoptar la posición bípeda independiente y seguir instrucciones. Se excluyeron personas con alteraciones cognitivas (puntaje MMSE >24) o visuales no compensadas. Resultados: La mayoría de las variables estudiadas tuvo diferencias estadísticamente significativas entre ambos grupos (ACV y control) y entre las diferentes condiciones. Conclusión: Las personas con ACV atendidas en la Clínica UDD poseen un control postural disminuido y una ponderación sensorial distinta a la de personas sin ACV.Item Guía teórico práctica de análisis biomecánico del movimiento(Universidad del Desarrollo. Facultad de Medicina, 2016) Vega Gana, Eduardo Antonio; Alvarez Ruf, Joel; Troncoso Trujillo, Alejandro; Robles Cruz, Diego; Santibáñez Arellano, TomásEl espíritu tras el diseño y confección de este proyecto de apoyo a la docencia es la intención de facilitar el proceso de aprendizaje de nuestros estudiantes de Análisis Biomecánico del Movimiento. La génesis de este documento se ubica en la necesidad de integrar múltiples fuentes y algunas de las áreas de las Ciencias del Movimiento Humano más pertinentes para aproximarse al campo del Control Motor y la Biomecánica. Se justifica en la escasa disponibilidad de literatura en español propia del campo de estudio y la aún más escasa disponibilidad de textos de estudio con un enfoque integrativo. Por medio de esta Guía Teórico Práctica esperamos en los futuros Kinesiólogos y profesionales de la salud UDD potenciar la capacidad de asombro, la curiosidad y compromiso con el entendimiento del movimiento y la funcionalidad de las personas, a través de la presentación, explicación, análisis y discusión de diferentes fenómenos del movimiento humano presentes en las tareas cotidianas. A través de diferentes actividades de seminario y laboratorio se pretende ayudar a la comprensión e integración de los principios neuromecánicos presentes en variados fenómenos del movimiento humano. Así también, el estudiante encontrará actividades de análisis y evaluación del movimiento humano que aportarán a la construcción de las bases de su razonamiento kinésico. El texto resultante constituye un documento original y novedoso, pues recopila información de múltiples áreas de las Ciencias del Movimiento Humano y proporciona un hilo conductor desde la perspectiva de la Biomecánica con orientación Clínica pertinente para la formación de Kinesiólogos en Chile.Item Surface Electromyography in Clinical Practice. A Perspective From a Developing Country(2020-10) Manzur-Valdivia, Hachi; Alvarez Ruf, JoelSurface electromyography (sEMG) has long been used in research, health care, and other fields such as ergonomics and brain-machine interfaces. In health care, sEMG has been employed to diagnose as well as to treat musculoskeletal disorders, pelvic floor dysfunction, and post-stroke motor deficits, among others. Despite the extensive literature on sEMG, the clinical community has not widely adopted it. We believe that in developing countries, such as Chile, this phenomenon may be explained by several interacting barriers. First, the socioeconomics of the country creates an environment where only high cost-effective treatments are routinely applied. Second, the majority of the sEMG literature on clinical applications has not extensively translated into decisive outcomes, which interferes with its applicability in low-income contexts. Third, clinical training on rehabilitation provides inadequate instruction on sEMG. And fourth, accessibility to equipment (i.e., affordability, availability, portability) may constitute another barrier, especially among developing countries. Here, we analyze socio-economic indicators of health care in Chile and comment on current literature about the use of sEMG in rehabilitation. Then we analyze the curricula of several physical therapy schools in Chile and report some estimations of the training on sEMG. Finally, we analyze the accessibility of some available sEMG devices and show that several match predefined criteria. We conclude that in developing countries, the insufficient use of sEMG in health might be explained by a shortage of evidence showing a crucial role in specific outcomes and the lack of training in rehabilitation-related careers, which interact with local socioeconomic factors that limit the application of these techniques.Item Understanding the effect of window length and overlap for assessing sEMG in dynamic fatiguing contractions: A non-linear dimensionality reduction and clustering(2021) De la Fuente, Carlos; Martinez-Valdes, Eduardo; Priego-Quesada, Jose Ignacio; Weinstein, Alejandro; Valencia, Oscar; Kunzler, Marcos R.; Alvarez Ruf, Joel; Carpes, Felipe P.The Short-Time Fourier transform (STFT) is a helpful tool to identify muscle fatigue with clinical and sports applications. However, the choice of STFT parameters may affect the estimation of myoelectrical manifestations of fatigue. Here, we determine the effect of window length and overlap selections on the frequency slope and the coefficient of variation from EMG spectrum features in fatiguing contractions. We also determine whether STFT parameters affect the relationship between frequency slopes and task failure. Eighty-eight healthy adult men performed one-leg heel-rise until exhaustion. A factorial design with a window length of 50, 100, 250, 500, and 1000 ms with 0, 25, 50, 75, and 90% of overlap was used. The frequency slope was non-linearly fitted as a task failure function, followed by a dimensionality reduction and clustering analysis. The STFT parameters elicited five patterns. A small window length produced a higher slope frequency for the peak frequency (p < 0.001). The contrary was found for the mean and median frequency (p < 0.001). A larger window length elicited a higher slope frequency for the mean and peak frequencies. The largest frequency slope and dispersion was found for a window length of 50 ms without overlap using peak frequency. A combination of 250 ms with 50% of overlap reduced the dispersion both for peak, median, and mean frequency, but decreased the slope frequency. Therefore, the selection of STFT parameters during dynamic contractions should be accompanied by a mechanical measure of the task failure, and its parameters should be adjusted according to the experiment’s requirements.