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Objectives: To assess the changes in speed, stroke frequency, acceleration, and shoulder range of motion (ROM) associated with different wheelchair axle positions in people with chronic C7 tetraplegia. Methods: This repeated-measures study was conducted at the Chronic Spinal Cord Injury Unit, FLENI Escobar, Argentina. The speed, stroke frequency, acceleration, and shoulder ROM during wheelchair propulsion were measured in nine participants with C7 spinal cord injury (SCI) in four different axle positions (forward and up, forward and down, backward and down, backward and up). Two strokes performed at maximum speed were analyzed on a smooth level vinyl floor in a motion analysis laboratory. Data were analyzed for significant statistical differences using the Friedman test and the Wilcoxon signed rank test. Results: Our study showed significant differences in the speed with axle position 1 (1.57 m/s) versus 2 (1.55 m/s) and position 2 (1.55 m/s) versus 4 (1.52 m/s). The shoulder ROM showed a significant difference in the sagittal plane in position 2 (59.34 degrees) versus 3 (61.64 degrees), whereas the stroke frequency and the acceleration parameters showed no statistically significant differences with the different rear axle positions. Conclusions: Our study showed that modifying the rear axle position can improve the propulsion speed and produce changes in the shoulder ROM in the wheelchair propulsion of individuals with C7 SCI.

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Wheelchair rugby was created as part of the rehabilitation for patients with spinal cord injury. The biomechanical analysis of wheelchair propulsion (WP) in these athletes seems to be a key element to understand the reasons behind musculoskeletal injuries. This case reports study aimed to describe the electromyographic activity and kinematic parameters of the shoulder during the propulsion phases on the wheelchair in two Paralympic rugby players (A1 and A2) with spinal cord injury. Myoelectric activity (three portions of the deltoid, biceps and triceps brachii) and kinematics of the shoulder were assessed during the push (PP) and recovery (RP) phases. These variables were calculated considering ten propulsion cycles by each athlete. The results showed a different muscle activation between players, A1 described a high average amplitude of the anterior deltoid (PP = 58.44 ± 16.35%MVC; RP = 43.16 ± 13.48%MVC) in both propulsion phases, while A2 generated high average activity of triceps brachii (29.28 ± 10.63%MVC) and middle deltoid (46.53 ± 14.48%MVC), during PP and RP, respectively. At the same time, the player with a C7-T1 spinal cord injury (A2) showed a higher range of motion in the three plans, considering both propulsion phases.

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Introducción: El síndrome de túnel de carpo es una neuropatía del nervio mediano muy frecuente en la población. Para los usuarios de sillas de ruedas hay mayor riesgo biomecánico por utilizar reiteradamente la muñeca en la propulsión de este vehículo. Objetivo: Analizar los factores biomecánicos de la silla de ruedas que inciden en el desarrollo del síndrome de túnel del carpo. Métodos: Se realizó una revisión sistemática con términos Mesh en bases de datos como Embase, Pubmed, Google Acedemics, Scielo desde 1988 hasta 2021. Se revisaron más de 200 artículos y por su impacto clínico, se seleccionaron 52 para la revisión. Resultados: El 43 % de los usuarios de silla de ruedas presentan dolor en la muñeca y prevalece como diagnóstico el síndrome de túnel del carpo. La posición de la muñeca en la propulsión genera un aumento de presión en el túnel carpiano lo que condiciona la lesión del nervio mediano. Existen factores de riesgo como el género femenino, las pendientes, el terreno irregular, la vibración, la altura del asiento y el peso del paciente. Entender correctamente las fases de la autopropulsión con sus cuatro patrones, más una prescripción adecuada y los aditamentos necesarios para la silla de ruedas pueden disminuir el riesgo de padecer el síndrome de túnel del carpo. Conclusión: Es importante involucrar de manera activa a los profesionales de la salud en la implementación de estrategias para el entrenamiento, prescripción y uso correcto de la silla de ruedas y con ello prevenir el padecimiento de el síndrome de túnel carpiano.

Introduction: Carpal tunnel syndrome is a very common neuropathy of the median nerve in the population. For wheelchair users, there is a greater biomechanical risk for repeatedly using the wrist to propel this vehicle. Objective: To analyze the biomechanical factors of the wheelchair affecting the development of carpal tunnel syndrome. Methods: A systematic review with Mesh terms was carried out in databases such as Embase, Pubmed, Google Acedemics, Scielo from 1988 to 2021. More than 200 articles were reviewed and due to their clinical impact, 52 were selected for the review. Results: 43% of wheelchair users have wrist pain and carpal tunnel syndrome prevails as a diagnosis. The position of the wrist in the propulsion generates an increase in pressure in the carpal tunnel conditioning the injury of the median nerve. There are risk factors such as female gender, angles, uneven terrain, vibration, seat height and patient weight. Proper understanding the phases of self-propulsion with its four patterns, plus correct prescription and necessary wheelchair attachments can decrease the risk of carpal tunnel syndrome. Conclusion: It is important to actively involve health professionals in the implementation of strategies for training, prescription and correct use of the wheelchair and thereby prevent carpal tunnel syndrome.

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This study aimed (i) to verify if underwater horizontal, vertical and medio-lateral hand displacements (HD), in pull and push phases of the front crawl stroke, can be associated with arm-stroke efficiency (ƞp) and (ii) to compare np and selected kinematic variables between male and female swimmers. Ten male and 10 female swimmers performed an all-out front crawl 25-m test. Data were obtained with six synchronised video cameras (60 Hz) and analysed with a three-dimensional method. Results for males and females were respectively, as follows: (i) horizontal HD: 0.55 ± 0.06 m and 0.61 ± 0.09 m (p = 0.062; d = 0.78); vertical HD: 0.68 ± 0.06 m and 0.58 ± 0.07 m (p < 0.001; d = 1.53); and medio-lateral HD: 0.22 ± 0.07 m and 0.16 ± 0.03 m (p = 0.012; d = 1.11); (ii) ƞp: 0.33 ± 0.02 and 0.32 ± 0.03 (p = 0.48; d = 0.39); (iii) vCOM: 1.77 ± 0.06 m∙s-1 and 1.55 ± 0.10 m∙s-1 (p < 0.001; d = 2.42). Multiple linear regression (p = 0.019) indicated that horizontal and medio-lateral HD were able to predict np. The lower the horizontal hand displacement, the higher the ƞp.

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Self-assembly is a spontaneous process through which macroscopic structures are formed from basic microscopic constituents (e.g., molecules or colloids). By contrast, the formation of large biological molecules inside the cell (such as proteins or nucleic acids) is a process more akin to self-organization than to self-assembly, as it requires a constant supply of external energy. Recent studies have tried to merge self-assembly with self-organization by analyzing the assembly of self-propelled (or active) colloid-like particles whose motion is driven by a permanent source of energy. Here we present evidence that points to the fact that self-propulsion considerably enhances the assembly of polymers: self-propelled molecules are found to assemble faster into polymer-like structures than non self-propelled ones. The average polymer length increases towards a maximum as the self-propulsion force increases. Beyond this maximum, the average polymer length decreases due to the competition between bonding energy and disruptive forces that result from collisions. The assembly of active molecules might have promoted the formation of large pre-biotic polymers that could be the precursors of the informational polymers we observe nowadays.

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Aims: to evaluate how the act of holding a tennis racket influences the application of forces in the handrim during manual wheelchair propulsion at a self-selected comfortable speed and sprint. Methods: A case study was conducted with an experienced wheelchair tennis player who propelled the wheelchair in a straightforward trajectory at two different velocities (self-selected comfortable speed and sprint) in two different conditions (freehand and holding the racket). Kinetic and temporal data of the pushes were obtained with the SmartWheel system attached in substitution to the conventional rear wheel at the dominant side of the player. Results: holding the racket affects the propulsion pattern mainly when an accelerated movement is required (sprint). Compared to the propulsion at a self-selected speed, propelling the chair as fast as possible with the racket in hands resulted in lower total and tangential forces on the handrim, and decreased push time and increased push frequency. Conclusion: Such influence on both kinetic and temporal propulsion impact the mechanical efficiency of the manual wheelchair propulsion, which may, ultimately, affect the sport´s performance. Special attention should be directed to the propulsion training with the racket in maneuvers and motions that are characteristic of the wheelchair tennis match in an attempt to provide the athlete with proper technique for optimal propulsion efficiency and sports performance.(AU)

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INTRODUCTION: Wheelchair configuration is an important factor influencing the ergonomics of the user-device interface and, from a biomechanical point of view, small changes in chair setup may have a positive influence on the demand on the upper limbs during manual propulsion. This study aimed to investigate the influence of the position of the rear wheels' axle and the use of accessories on the activity of upper limb muscles during manual wheelchair propulsion. METHODS: Electromyography signals of the biceps, triceps, anterior deltoids and pectoralis major were collected for 11 able-bodied subjects in a wheelchair propulsion protocol with four different wheelchair configurations (differing in axle position and the use of accessories) on a straightforward sprint and a slalom course. RESULTS: With accessories, moving the axle forward led to a decrease in the activity of all muscles in both the straightforward sprint (significant differences in triceps, anterior deltoids and biceps) and the slalom course (significant difference in anterior deltoids and biceps). However, when propelling the chair without accessories, no difference was found related to axle position. CONCLUSION: Changes in wheelchair configuration can influence the ergonomics of manual wheelchair propulsion. Reducing the biomechanical loads may benefit users' mobility, independence and social participation.

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Resumen: Los andamios fibrilares han recibido un enorme interés como futuros biomateriales con potencial aplicación en el campo de la biomedicina regenerativa. En este sentido, hemos optimizado los parámetros para la síntesis de diferentes concentraciones (6, 7, y 10 %) de andamios de ácido poli-láctico (PLA) por la técnica de hilado por propulsión de gas (AJS). Dichos andamios fueron caracterizados por Microscopía Electrónica de Barrido (SEM) y por espectrometría Infrarroja con Transformada de Fourier (FTIR). Nuestros resultados mostraron que los andamios son fibrilares con diámetros en escalas nanométricas. Asimismo; se estudió la biocompatibilidad celular in vitro al realizar ensayos de adhesión, proliferación y de interacción célula-material al cultivar células troncales mesenquimales derivadas de médula ósea. Nuestros datos indican que las membranas fibrilares de PLA aumentan la respuesta celular, no son citotóxicas al compararse con las películas delgadas de PLA. Por lo tanto; el método de síntesis propuesto tiene potencial para la fabricación de membranas hiladas con una facilidad de procesamiento y podría ser un prometedor biomaterial económico con futuras aplicaciones en la regeneración de tejidos.

Abstract: Fiber scaffolds have received increasing interest as promising biomaterials for potential application in the field of tissue regeneration. In this sense, we optimized the parameters for the synthesis of different concentrations (6, 7, and 10 %) of poly-lactic acid (PLA) scaffolds by air jet spinning technology (AJS). The PLA scaffolds were characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. Our results by SEM micrographs showed that scaffolds have a fibrilar morphology with nanoscale diameter of fibers. Biocompatibility assay was observed through an in vitro experiment based on cell attachment, MTT and cell-material interaction assay when culturing bone marrow-derived mesenchymal stem cells onto the PLA spun membrane scaffolds. Our data indicate that fiber membrane of PLA scaffold increase the cellular response, are not cytotoxic when compared to thin films of PLA. Thus; the proposed synthesis method has potential for easy processing of spun fibrilar scaffolds with good biocompatibility and could be a promising economical biomaterial with future potential applications in tissue regeneration.

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This study examined whether Sanders' model is suitable for estimating accurately the propulsive force generated by the hands' motion in swimming comparing the calculated force obtained using the model and the measured force during an actual propulsive action. The measured and calculated forces were obtained from 13 swimmers who, while tethered, performed a sculling motion in a prone position for the purpose of displacing the body by moving it forward. Kinematic analyses were conducted to obtain the calculated force, while the measured force was obtained via the use of a load cell. The calculated force was lower than the measured force and accounted for only a small part of the variation in the measured force. The forces could not be used interchangeably, and there were fixed and proportional differences between them. Consequently, this study indicates that Sanders' model is not suitable for estimating accurately the propulsive force generated by the swimmer's hands during sculling motion. However, research that integrates analyses from different approaches could result in improvements to the model that would render it applicable for estimating the propulsive forces during movements that are characterised by directional changes of the hands.

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Background: Subjects with spinal cord injury (SCI) propel their wheelchairs by generating a different level of muscle activity given their multiple deficits in muscle strength. Exercise training programs seem to be effective in improving wheelchair propulsion capacity. Functional electrical stimulation (FES) therapy is a complementary tool for rehabilitation programs. Objectives: To determine the accuracy of the synchronization between the FES activation and the push phase of the propulsion cycle by using hand pressure sensors that allow anterior deltoids activation when the hand is in contact with the pushrim. Methods: We analyzed 2 subjects, with injuries at C6 American Spinal Injury Association Impairment Scale (AIS) A and T12 AIS A. The stimulation parameters were set for a 30 Hz frequency symmetrical biphasic wave, 300 µs pulse width. Data were collected as participants propelled the wheelchair over a 10-m section of smooth, level vinyl floor. Subjects were evaluated in a motion analysis laboratory (ELITE; BTS, Milan, Italy). Results: Subject 1 showed synchronization between the FES activation and the push phase of 87.5% in the left hand and of 80% in the right hand. Subject 2 showed synchronization of 95.1% in the left and of hand 94.9% in the right hand. Conclusion: Our study determined a high accuracy of a novel FES therapeutic option, showing the synchronization between the electrical stimulation and the push phase of the propulsion cycle.

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