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Introduction: According to the literature, eccentric exercise has been considered a precursor of neuromuscular changes generated by post-exercise damage, mainly causing an alteration in the muscle cell membrane. Muscle fiber conduction velocity (MFCV) has been one of the physiological variables that have allowed to quantify this alteration. Some investigations have shown a decrease in the MFCV after eccentric exercise protocols; however, few studies have confirmed these findings. This review aimed to describe the recent scientific evidence that reports changes in the MFCV after eccentric exercise protocols. Material and method: From 265 articles, 6 articles were selected from EBSCO and MEDLINE platforms with a temporal filter of 10 years (between 2010 and April 2020), using inclusion/exclusion criteria predetermined. Firstly, the information from eccentric exercise effect on MFCV, and exercise protocols were described. Secondly, the techniques used to record electromyographic signals and some criteria to determine the MFCV were reported. Results: Modifications of MFCV can be observed after eccentric exercise in almost all selected articles. At the same time, a decrease of this variable was observed in four studies, associated with the biceps brachii and two portions of the quadriceps muscles. However, one article describes an increase of the MFCV in the vastus lateralis quadriceps. Conclusion: The articles suggest that eccentric contractions could modify the MFCV behavior of some muscles. However, evidence is still lacking to describe the real cause of these changes.

Resumen Introduccion El fenomenos de caidas frecuentes (CF) es un problema de salud para la poblacion adulta mayor, por lo cual el diseno de herramientas objetivas en la valoracion del riesgo de CF es necesario, en este sentido la utilizacion de parametros biomecanicos puede ser de utilidad en el diseno de estas. El objetivo de este trabajo estuvo en describir las diferencias biomecanicas registradas durante la transferencia de sedente a bipedo (TSB) entre sujetos con y sin historia de caidas frecuentes. Material y metodo Se evaluo una muestra de 60 sujetos adultos mayores, divididos en 2 grupos de 30. El primero de ellos formado por sujetos sin historia de caidas frecuentes (SHCF) y el otro con historia de caidas frecuentes (CHCF). En ambos grupos se evaluo la velocidad del centro de masa, la magnitud de flexion anterior de tronco, los momentos articulares y de soporte de la extremidad inferior y el tiempo de ejecucion durante la TSB. Resultados Los sujetos CHCF generaron menor velocidad vertical (p Conclusiones Existen diferencias en los parametros biomecanicos registrados durante la TSB entre ancianos CHCF y SHCF. Los resultados indican que la funcion de los musculos extensores de cadera podrian tener un importante rol en la ejecucion de la TSB en sujetos CHCF. Las variables biomecanicas registradas durante la TSB deben ser consideradas como herramientas utiles para diferenciar entre sujetos CHCF y SHCF, pudiendo ser consideradas en el diseno de herramientas para determinar el riesgo de caidas frecuentes.

The phenomenon of frequent falls (FF) is a health problem in the older population, and is a reason why tools need to be designed for the objective assessment of the risk of FF. In this sense the use of biomechanical parameters could be of use in designing these. The aim of this work was to describe the biomechanical differences registered during a sit to stand transfer (STS) between subjects with and without a history of frequent falls.A sample of sixty voluntary older adults were assessed, divided in two groups of thirty subjects. The first group was composed of older adults without history of frequent falls (WoHFF) and the other group with history of frequent falls (WHFF). In both groups the velocity of the mass centre, the anterior flexion of the trunk, the joint and support moments of the lower extremity and the time of execution during the TSB was assessed.The subjects WHFF generate a slower vertical velocity (P0.001), lower slope (P0.001), greater anterior trunk flexion (P0.0001), lower support moment (P=0.001) and took longer in executing the STS (P=0.0001) than the group WoHFF.Differences exist in the biomechanical parameters registered during the STS between the elderly WHFF and WoHFF. The results indicate that the function of the hip extensor muscles could have an important role in the execution of the STS in subjects WHFF. The biomechanical parameters assessed during the STS should be considered as useful tools to distinguish between subjects WHFF and WoHFF, and should be considered in the design of tools to determine the risk of frequent falls.

The momentum of the upper body (UB) during transfer sit-to-stand (STS) could be sensitive to the deterioration of dynamic postural control, and also the risk of falls. The aim of this study is to quantify the differences in the momentum development on UB during the STS in a sample of fall and no-fall elderly subjects. MATERIAL AND MEHODS: The sample consisted of twenty three voluntary elderly subjects (n=23), six elderly adults with antecedents of frequent falls (more than two within a year period) and seventeen without histories of frequent falls. Through a motion analysis system we registered the kinematics of UB during STS, from which we calculated the momentum of UB. The determined analysis variables were: the maximum values of the vertical (P(V)M) and horizontal (P(H)M) lineal momenta, the minimum (L(Max)) and maximum (L(Min)) values of the angular momentum and maximum trunk flexion (thetaM(UB)).No difference was observed in P(H)M, L(Max) and L(Min) (P0.05) between both groups. However, a significant difference was found for the variable P(V)M (P=0.03) and thetaM(UB) (P=0.03) between both groups.We can conclude that, for the sample studied, the frequent fall condition relates to a smaller capacity to develop vertical momentum and increase flexion of the upper body.