Letteratura scientifica selezionata sul tema "Spatially distributed sequential stimulation (SDSS)"

Abstract Purpose The low power output and fatigue resistance during functional electrical stimulation (FES) limits its use for functional applications. The aim of this study was to compare the power output and fatigue properties of spatially distributed sequential stimulation (SDSS) against conventional single electrode stimulation (SES) in an isokinetic knee extension task simulating knee movement during recumbent cycling. Methods M. vastus lateralis and m. vastus medialis of eight able-bodied subjects were stimulated for 6 min on both legs with both setups. In the SES setup, target muscles were each stimulated by a pair of electrodes. In SDSS, four small electrodes replaced the SES active electrodes, but reference electrodes were the same. Torque was measured during knee extension movement by a dynamometer at an angular velocity of 110°/s. Mean power (Pmean) was calculated from stimulated extensions for the first 10 extensions, the final 20 extensions and overall. Fatigue is presented as an index, calculated as the decrease with respect to initial power. Results Pmean was significantly higher for SDSS than for SES in the final phase (9.9 ± 4.0 vs. 7.4 ± 4.3 W, p = 0.035) and overall (11.5 ± 4.0 vs. 9.2 ± 4.5 W, p = 0.037). With SDSS, the reduction in Pmean was significantly smaller compared to SES (from 14.9 to 9.9 vs. 14.6 to 7.4 W, p = 0.024). The absolute mean pulse width was substantially lower with SDSS (62.5 vs. 90.0 µs). Conclusion Although less stimulation was applied, SDSS showed a significantly higher mean power output than SES. SDSS also had improved fatigue resistance when compared to conventional stimulation. The SDSS approach may provide substantial performance benefits for cyclical FES applications.

Abstract Background In this work, we share the enhancements made in our system to take part in the CYBATHLON 2020 Global Edition Functional Electrical Stimulation (FES) Bike Race. Among the main improvements, firstly an overhaul, an overhaul of the system and user interface developed with User-centered design principles with remote access to enable telerehabilitation. Secondly, the implementation and experimental comparison between the traditional single electrode stimulation (SES) and spatially distributed sequential stimulation (SDSS) applied for FES Cycling. Methods We report on the main aspects of the developed system. To evaluate the user perception of the system, we applied a System Usability Scale (SUS) questionnaire. In comparing SDSS and SES, we collected data from one subject in four sessions, each simulating one race in the CYBATHLON format. Results User perception measured with SUS indicates a positive outcome in the developed system. The SDSS trials were superior in absolute and average values to SES regarding total distance covered and velocity. We successfully competed in the CYBATHLON 2020 Global Edition, finishing in 6th position in the FES Bike Race category. Conclusions The CYBATHLON format induced us to put the end-user in the center of our system design principle, which was well perceived. However, further improvements are required if the intention is to progress to a commercial product. FES Cycling performance in SDSS trials was superior when compared to SES trials, indicating that this technique may enable faster and possibly longer FES cycling sessions for individuals with paraplegia. More extensive studies are required to assess these aspects.

Spatially distributed sequential stimulation (SDSS) has demonstrated substantial power output and fatigue benefits compared to single electrode stimulation (SES) in the application of functional electrical stimulation (FES). This asymmetric electrode setup brings new possibilities but also new questions since precise placement of the electrodes is one critical factor for good muscle activation. The aim of this study was to compare the power output, fatigue and activation properties of proximally versus distally placed SDSS electrodes in an isokinetic knee extension task simulating knee movement during recumbent cycling. M. vastus lateralis and medialis of seven able-bodied subjects were stimulated with rectangular bi-phasic pulses of constant amplitude of 40 mA and at an SDSS frequency of 35 Hz for 6 min on both legs with both setups (i.e. n=14). Torque was measured during knee-extension movement by a dynamometer at an angular velocity of 110 deg/s. Mean power, peak power and activation time were calculated and compared for the initial and final stimulation phases, together with an overall fatigue index. Power output values (Pmean, Ppeak) were scaled to a standardised reference input pulse width of 100 μs (P_mean,s, P_peak,s). The initial evaluation phase showed no significant differences between the two setups for all outcome measures. P_peak and P_peak,s were both significantly higher in the final phase for the distal setup (25.4 ± 8.1 W vs. 28.2 ± 6.2 W, p=0.0062 and 34.8 ± 9.5 W vs. 38.9 ± 6.7 W, p=0.021, respectively). With distal SDSS, there was modest evidence of higher P_mean and P_mean,s (p=0.071, p=0.14, respectively) but of longer activation time (p=0.096). The rate of fatigue was similar for both setups. For practical FES applications, distal placement of the SDSS electrodes is preferable.

Cette thèse vise à surmonter les limites de la stimulation électrique fonctionnelle (SEF) grâce à une approche novatrice et multimodale, qui explore aussi bien le développement d'électrodes transcutanées, que les stratégies de stimulation, ainsi que les perspectives d'optimisation biomécanique. Une première étude compare l'efficacité des électrodes textiles intégrées dans les vêtements, utilisées avec une lotion hydratante, par rapport aux électrodes conventionnelles à hydrogel auto-adhésives. L'évaluation porte sur des aspects tels que le confort de la stimulation, la cohérence temporelle, l'efficacité, et le comportement de l'impédance électrique dans des conditions isométriques. Les participants à l'étude ont effectué des tests avec les deux types d'électrodes, nous permettant d’évaluer des paramètres tels que les intensités minimales générant une contraction musculaire ou une sensation de brûlure, et l'intensité maximale tolérable. Les résultats indiquent que les électrodes textiles, lorsqu'elles sont complétées par une lotion, sont comparables aux électrodes à hydrogel en termes de confort, de consistance et d'efficacité. Une seconde étude examine l'impact de la stimulation séquentielle distribuée spatialement (SSDS) à intensité moyenne ou haute, sur la réduction de la fatigue chez les personnes souffrant d'une lésion de la moelle épinière. L'étude révèle que la SSDS est significativement plus efficace à moyenne intensité. En outre, une étude de cas a été réalisée pour évaluer les différences de puissance et fatigue produites lors d’un exercice de cyclisme électrostimulé utilisant la SSDS. Il s'agissait de stimuler les quadriceps de quatre participants paraplégiques moteurs complets. L’étude a montré que la SSDS génère non seulement plus de puissance que la configuration à une seule électrode, mais également sans avoir d'impact significatif sur le niveau de fatigue. La dernière étude se concentre sur l'optimisation des propriétés biomécaniques du cyclisme et de la séquence de stimulation afin d'obtenir une puissance de sortie maximale avec une stimulation appliquée minimale. Un modèle musculaire précis et facile à utiliser, associé à des fonctions de transfert de couple basées sur le Jacobien, a été adopté pour déterminer la position assise optimale, l'angle du tronc, la longueur du bras de manivelle et les séquences de stimulation. En outre, l'impact de la fonction force-vitesse du muscle sur la détermination de la position assise optimale et des séquences de stimulation a été étudié. Les modèles de simulation ont montré un effet insignifiant de la fonction force-vitesse sur la position assise optimale de six sujets sains simulés. Nous pensons que les contributions de cette thèse augmenteront l'efficacité de la SEF en tant que technique de rééducation fonctionnelle
This thesis aims to overcome the limitations of functional electrical stimulation (FES) through a multifaceted novel approach that concentrates on developing transcutaneous electrodes, stimulation strategies, and biomechanical optimization perspectives. The first study investigates the effectiveness of garment-embedded textile electrodes, used with a moisturizing lotion, against conventional self-adhesive hydrogel electrodes. The evaluation encompasses aspects such as stimulation comfort, temporal consistency, efficiency, and electrical impedance behavior under isometric conditions. Participants in the study underwent tests with both electrode types, evaluating parameters like motor threshold intensity, burning sensation intensity, and maximum tolerable intensity. The results indicate that textile electrodes, when supplemented with lotion, perform comparably to hydrogel electrodes in terms of comfort, consistency, and efficiency. The next study investigates the impact of spatially distributed sequential stimulation (SDSS) at high and moderate intensities on reducing fatigue in individuals with spinal cord injury. The study, focusing on the quadriceps muscle group, found that moderate-intensity SDSS is significantly more effective than high-intensity SDSS. Additionally, a case study was conducted to assess the differences in power generation and fatigue levels between FES cycling using SDSS and a single electrode setup. This involved stimulating the paralyzed quadriceps muscles of four participants over multiple days during motor-assisted FES cycling. The results indicated that SDSS not only generated more power compared to the single electrode setup but did so without significantly impacting fatigue levels. The last study focuses on the optimization of the cycling biomechanical properties and stimulation pattern to achieve maximum output power with minimum applied stimulation. In this work, an easy-to-use and precise muscle model in conjunction with Jacobian-based torque transfer functions was adopted to determine the optimal seating position, trunk angle, crank arm length, and stimulation intervals. Furthermore, the impact of muscle force-velocity factor in finding the optimal seating position and stimulation intervals was investigated. The simulation models showed the trivial effect of the force-velocity factor on the resulting optimal seating position of six healthy simulated subjects. We believe that the contributions of this thesis will increase the efficacy of FES as a rehabilitation technique