Person: Rodríguez Falces, Javier
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Rodríguez Falces
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Javier
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Ingeniería Eléctrica, Electrónica y de Comunicación
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ISC. Institute of Smart Cities
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0000-0002-9150-8955
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8624
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Publication Open Access Evaluation of the electromyography test for the analysis of the aerobic-anaerobic transition in elite cyclists during incremental exercise(MDPI, 2019) Latasa Zudaire, Iban Alexander; Córdova Martínez, Alfredo; Quintana Ortí, Gregorio; Lavilla Oiz, Ana; Navallas Irujo, Javier; Rodríguez Falces, Javier; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren(1) Background: The aim of this study was to investigate the validity and reliability of surface electromyography (EMG) for automatic detection of the aerobic and anaerobic thresholds during an incremental continuous cycling test using 1 min exercise periods in elite cyclists. (2) Methods: Sixteen well-trained cyclists completed an incremental exercise test (25 W/1 min) to exhaustion. Surface bipolar EMG signals were recorded from the vastus lateralis, vastus medialis, biceps femoris, and gluteus maximus, and the root mean square (RMS) were assessed. The multi-segment linear regression method was used to calculate the first and second EMG thresholds (EMG(T1) and EMG(T2)). During the test, gas exchange data were collected to determine the first and second ventilatory thresholds (VT1 and VT2). (3) Results: Two breakpoints (thresholds) were identified in the RMS EMG vs. time curve for all muscles in 75% of participants. The two breakpoints, EMG(T1) and EMG(T2) , were detected at around 70%-80% and 90%-95% of VO2MAX, respectively. No significant differences were found between the means of VT(1 )and EMGT(1) for the vastii and biceps femoris muscles (p > 0.05). There were no significant differences between means of EMG(T2) and VT2 (p > 0.05). (4) Conclusions: It is concluded that the multi-segment linear regression algorithm is a valid non-invasive method for analyzing the aerobic-anaerobic transition during incremental tests with 1 min stage durations.Publication Open Access Correlation between discharge timings of pairs of motor units reveals the presence but not the proportion of common synaptic input to motor neurons(American Physiological Society, 2017) Rodríguez Falces, Javier; Negro, Francesco; Farina, Dario; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta ElektronikoaWe investigated whether correlation measures derived from pairs of motor unit (MU) spike trains are reliable indicators of the degree of common synaptic input to motor neurons. Several 50-s isometric contractions of the biceps brachii muscle were performed at different target forces ranging from 10 to 30% of the maximal voluntary contraction relying on force feedback. Forty-eight pairs of MUs were examined at various force levels. Motor unit synchrony was assessed by cross-correlation analysis using three indexes: the output correlation as the peak of the cross-histogram (ρ) and the number of synchronous spikes per second (CIS) and per trigger (E). Individual analysis of MU pairs revealed that ρ, CIS, and E were most often positively associated with discharge rate (87, 85, and 76% of the MU pairs, respectively) and negatively with interspike interval variability (69, 65, and 62% of the MU pairs, respectively). Moreover, the behavior of synchronization indexes with discharge rate (and interspike interval variability) varied greatly among the MU pairs. These results were consistent with theoretical predictions, which showed that the output correlation between pairs of spike trains depends on the statistics of the input current and motor neuron intrinsic properties that differ for different motor neuron pairs. In conclusion, the synchronization between MU firing trains is necessarily caused by the (functional) common input to motor neurons, but it is not possible to infer the degree of shared common input to a pair of motor neurons on the basis of correlation measures of their output spike trains.Publication Open Access End-of-fiber signals strongly influence the first and second phases of the M wave in the vastus lateralis: implications for the study of muscle excitability(Frontiers Media, 2018) Rodríguez Falces, Javier; Place, Nicolas; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta ElektronikoaIt has been recurrently observed that, for compound muscle action potentials (M wave) recorded over the innervation zone of the vastus lateralis, the descending portion of the first phase generally shows an 'inflection' or 'shoulder'. We sought to clarify the electrical origin of this shoulder-like feature and examine its implications. M waves evoked by maximal single shocks to the femoral nerve were recorded in monopolar and bipolar configurations from 126 individuals using classical (10-mm recording diameter, 20-mm inter-electrode distance) electrodes and from eight individuals using small electrodes arranged in a linear array. The changes of the M-wave waveform at different positions along the muscle fibers' direction were examined. The shoulder was identified more frequently in monopolar (97%) than in bipolar (46%) M waves. The shoulder of M waves recorded at different distances from the innervation zone had the same latency. Furthermore, the shoulder of the M wave recorded over the innervation zone coincided in latency with the positive peak of that recorded beyond the muscle. The positive phase of the M wave detected 20 mm away from the innervation zone was essentially composed of non-propagating components. The shoulder-like feature in monopolar and bipolar M waves results from the termination of action potentials at the superficial aponeurosis of the vastus lateralis. We conclude that, only the amplitude of the first phase, and not the second, of M waves recorded monopolarly and/or bipolarly in close proximity to the innervation zone can be used reliably to monitor possible changes in muscle membrane excitability.Publication Open Access A masked least-squares smoothing procedure for artifact reduction in scanning-EMG recordings(Springer, 2018) Corera Orzanco, Íñigo; Eciolaza Ferrando, Adrián; Rubio Zamora, Oliver; Malanda Trigueros, Armando; Rodríguez Falces, Javier; Navallas Irujo, Javier; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenScanning-EMG is an electrophysiological technique in which the electrical activity of the motor unit is recorded at multiple points along a corridor crossing the motor unit territory. Correct analysis of the scanning-EMG signal requires prior elimination of interference from nearby motor units. Although the traditional processing based on the median filtering is effective in removing such interference, it distorts the physiological waveform of the scanning-EMG signal. In this study, we describe a new scanning-EMG signal processing algorithm that preserves the physiological signal waveform while effectively removing interference from other motor units. To obtain a cleaned-up version of the scanning signal, the masked least-squares smoothing (MLSS) algorithm recalculates and replaces each sample value of the signal using a least-squares smoothing in the spatial dimension, taking into account the information of only those samples that are not contaminated with activity of other motor units. The performance of the new algorithm with simulated scanning-EMG signals is studied and compared with the performance of the median algorithm and tested with real scanning signals. Results show that the MLSS algorithm distorts the waveform of the scanning-EMG signal much less than the median algorithm (approximately 3.5 dB gain), being at the same time very effective at removing interference components.Publication Open Access Sliding window averaging in normal and pathological motor unit action potential trains(Elsevier, 2018) Malanda Trigueros, Armando; Navallas Irujo, Javier; Rodríguez Falces, Javier; Porta Cuéllar, Sonia; Fernández Martínez, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenObjective: To evaluate the performance of a recently proposed motor unit action potential (MUAP) averaging method based on a sliding window, and compare it with relevant published methods in normal and pathological muscles. Methods: Three versions of the method (with different window lengths) were compared to three relevant published methods in terms of signal analysis-based merit figures and MUAP waveform parameters used in the clinical practice. 218 MUAP trains recorded from normal, myopathic, subacute neurogenic and chronic neurogenic muscles were analysed. Percentage scores of the cases in which the methods obtained the best performance or a performance not significantly worse than the best were computed. Results: For signal processing figures of merit, the three versions of the new method performed better (with scores of 100, 86.6 and 66.7%) than the other three methods (66.7, 25 and 0%, respectively). In terms of MUAP waveform parameters, the new method also performed better (100, 95.8 and 91.7%) than the other methods (83.3, 37.5 and 25%). Conclusions: For the types of normal and pathological muscle studied, the sliding window approach extracted more accurate and reliable MUAP curves than other existing methods. Significance: The new method can be of service in quantitative EMG.Publication Open Access Scanning electromyography(InTechOpen, 2012) Navallas Irujo, Javier; Rodríguez Falces, Javier; Stålberg, Erik; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako Gobernua, 1312/2010The study of the anatomy and physiology of the motor unit has important implications in the diagnosis and follow-up of neuromuscular pathologies. Muscle action potentials allow the use of electrophysiological techniques based on electromyography (EMG) to make inferences about muscle structure, state and behaviour. Scanning EMG is one such technique that can record the temporal and spatial distribution of electrical activity of a single motor unit, allowing for deep insight into the structure and function of motor units. In this chapter, we describe the scanning EMG technique in detail, both from a technical and clinical point of view. A brief review of the motor unit anatomy and physiology is provided in Section 2. The technique, the apparatus setup, the recording procedure and the signal processing required are described in Section 3. Key results of studies using scanning EMG are reviewed in Section 4, including findings related to motor unit organisation in normal muscle and how changes due to pathology are reflected using this electrophysiological technique. Finally, Section 5 provides some hints regarding the use of scanning EMG in research.Publication Open Access Actividad electromiográfica (EMG) durante el pedaleo, su utilidad en el diagnóstico de la fatiga en ciclistas(SEMED - FEMEDE, 2017) Córdova Martínez, Alfredo; Nuin, Iván; Fernández-Lázaro, Diego; Latasa Zudaire, Iban Alexander; Rodríguez Falces, Javier; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta ElektronikoaLa fatiga muscular tiene múltiples definiciones, pero con una misión especial cual es la misión protectora, avisando al organismo sobre la debilidad o la aparición de una incapacidad funcional. En esta revisión se hace un análisis de las aplicaciones de la electromiografía (EMG) como técnica para comprender los patrones de activación musculares durante el pedaleo y la aparición de fatiga muscular. Se ha realizado una revisión en la cual se analizan las variaciones de la actividad EMG durante las fases del pedaleo. El movimiento del pedaleo ha sido estudiado exhaustivamente y se ha legado a distinguir 4 fases en el pedaleo que originan la propulsión y el recobro. Mediante el uso de la EMG se pueden describir los patrones de activación típicos, en cuanto al nivel de actividad y el tiempo de activación de los principales músculos de las extremidades inferiores. La actividad muscular y la coordinación pueden variar entre personas a lo largo de un solo ciclo de pedaleo y entre diferentes ciclos de la misma persona. También se examinan los principales factores que pueden influir en estos patrones EMG durante las fases del pedaleo. Asimismo, se describe la influencia de factores como la potencia de salida, cadencia o frecuencia de pedaleo, pendiente y postura, interfaz calzado pedal, nivel de entrenamiento y fatiga muscular, que producen alteraciones en el tiempo de activación y coordinación muscular.Publication Open Access EMG modeling(InTechOpen, 2012) Rodríguez Falces, Javier; Navallas Irujo, Javier; Malanda Trigueros, Armando; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta ElektronikoaThe aim of this chapter is to describe the approaches used for modelling electromyographic (EMG) signals as well as the principles of electrical conduction within the muscle. Sections are organized into a progressive, step-by-step EMG modeling of structures of increasing complexity. First, the basis of the electrical conduction that allows for the propagation of the EMG signals within the muscle is presented. Second, the models used for describing the electrical activity generated by a single fibre described. The third section is devoted to modeling the organization of the motor unit and the generation of motor unit potentials. Based on models of the architectural organization of motor units and their activation and firing mechanisms, the last section focuses on modeling the electrical activity of a complete muscle as recorded at the surface.Publication Open Access Electromyographic, cerebral, and muscle hemodynamic responses during intermittent, isometric contractions of the biceps brachii at three submaximal intensities(Frontiers Media, 2014) Bhambhani, Yagesh; Fan, Jui Lin; Place, Nicolas; Rodríguez Falces, Javier; Kayser, Bengt; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta ElektronikoaThis study examined the electromyographic, cerebral and muscle hemodynamic responses during intermittent isometric contractions of biceps brachii at 20, 40, and 60% of maximal voluntary contraction (MVC). Eleven volunteers completed 2 min of intermittent isometric contractions (12/min) at an elbow angle of 90° interspersed with 3 min rest between intensities in systematic order. Surface electromyography (EMG) was recorded from the right biceps brachii and near infrared spectroscopy (NIRS) was used to simultaneously measure left prefrontal and right biceps brachii oxyhemoglobin (HbO2), deoxyhemoglobin (HHb), and total hemoglobin (Hbtot). Transcranial Doppler ultrasound was used to measure middle cerebral artery velocity (MCAv) bilaterally. Finger photoplethysmography was used to record beat-to-beat blood pressure and heart rate. EMG increased with force output from 20 to 60% MVC (P < 0.05). Cerebral HbO2 and Hbtot increased while HHb decreased during contractions with differences observed between 60% vs. 40% and 20% MVC (P < 0.05). Muscle HbO2 decreased while HHb increased during contractions with differences being observed among intensities (P < 0.05). Muscle Hbtot increased from rest at 20% MVC (P < 0.05), while no further change was observed at 40 and 60% MVC (P > 0.05). MCAv increased from rest to exercise but was not different among intensities (P > 0.05). Force output correlated with the root mean square EMG and changes in muscle HbO2 (P < 0.05), but not changes in cerebral HbO2 (P > 0.05) at all three intensities. Force output declined by 8% from the 1st to the 24th contraction only at 60% MVC and was accompanied by systematic increases in RMS, cerebral HbO2 and Hbtot with a leveling off in muscle HbO2 and Hbtot. These changes were independent of alterations in mean arterial pressure. Since cerebral blood flow and oxygenation were elevated at 60% MVC, we attribute the development of fatigue to reduced muscle oxygen availability rather than impaired central neuronal activation.Publication Open Access Motor unit profile: a new way to describe the scanning-EMG potential(Elsevier, 2017) Corera Orzanco, Íñigo; Malanda Trigueros, Armando; Rodríguez Falces, Javier; Porta Cuéllar, Sonia; Navallas Irujo, Javier; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta ElektronikoaThe motor unit profile, a representation of the trajectories of positive and negative turns of a scanning-EMG signal, is a new way to characterize the motor unit potential. Such characterization allows quantification of the scanning-EMG signal's complexity, which is closely related to the anatomy and physiology of the motor unit. To extract the motor unit profile, an algorithm that detects the turns of the scanning-EMG signal and links them using point-tracking techniques has been developed. The performance of this algorithm is sensitive to three parameters: the turn detection threshold, the maximum tracking interval threshold, and the trajectory purge threshold. Real scanning-EMG signals have been used to analyze the algorithm's behavior and the influence of the algorithm's parameters and to determine which parameter values provide the best performance.