Effect of Aging on the Lower Limb Kinematics in Karate Practitioners: Comparing Athletes and Their Senseis

With the life expectancy increasing, older adult population has gained the attention of many researchers. Aging is known to lead to a general decline in bodily functions, which affect the quality of life. The aim of this study was to analyze how the aging process affects veteran active karate practitioners, in the kinematic and temporal structure of the frontal kick. Nine black belt karate practitioners over 50 years old and 24 black belt karate practitioners, aged between 20 and 30 years old, all male, performed the frontal kick mae-geri. Results showed that knee is the structure that holds most differences between young and veterans, both for linear and for angular variables during the mae-geri performance. Statistical differences were found in linear velocity for the knee; linear acceleration of the knee, hip, and RASIS; maximum angular velocity for knee and hip; maximum angular acceleration for ankle and hip; and in the range of motion of knee. The temporal variables show differences, between groups, in maximum linear velocity, maximum linear acceleration, and maximum angular acceleration. However, no differences were found between groups for the time before contact in the maximum linear and angular acceleration, which allow us to remark both the effects of the aging process and the effect of training. This study corroborates the ability of older people to achieve benefits from sports practice, achieving higher efficiency than the younger adults in task execution, but using different motor control strategies.info:eu-repo/semantics/publishedVersio

Takahasi semigroups

Takahasi's Theorem on chains of subgroups of bounded rank in a free group is generalized to several classes of semigroups. As an application, it is proved that the subsemigroups of periodic points are finitely generated and periodic orbits are bounded for arbitrary endomorphisms for various semigroups. Some of these results feature classes such as completely simple semigroups, Clifford semigroups or monoids defined by balanced one-relator presentations

Gold in the Lousal mine, Iberian Pyrite Belt, Portugal

Recent exploration boreholes in the Lousal Mine, located within the Portuguese sector of the Iberian Pyrite Belt (IPB) yielded marked concentrations in gold/electrum in a section of core consisting of banded metasediments with massive pyrite. Preliminary research indicates that the gold is associated with native bismuth and bismuthinite and is clearly late in the paragenetic sequence occurring in fine chalcopyrite (± covellite)-bismuthinite-gold filled veinlets within the dominant and more massive pyrite. The pale yellow gold grains are fine, seldom reaching more than 6 ..m in length and half of that in thickness. EPMA results indicate that silver concentrations in gold grains can be as high as 27 wt.%. The results show similarities with conclusions drawn from the IPB on the Spanish side where gold of Co-Bi geochemical association is found as electrum with abundant to common Co and Bi minerals. These associated with pyrite and/or chalcopyrite are characterized by an abundance of sedimentary facies and show that the gold association formed at high temperature (>300 °C) during the initial phases of massive sulphide formation

Caracterización de los patrones cinesiológicos de la patada frontal, mae­-geri, en practicantes expertos de kárate y en sujetos no practicantes

[ES] Actualmente, los entrenadores e investigadores necesitan comprender bien los parámetros cinesiológicos del movimiento ya que son una herramienta importante de soporte de las metodologías de entrenamiento y enseñanza, y para mejorar el rendimiento de los gestos motores. El objetivo de este estudio fue (i) identificar los patrones cinemáticos y del control neuromuscular de ejecución de la patada frontal (mae­geri) en un objetivo fijo, realizada por 14 karatecas cinturón negro, (ii) y comparar con la ejecución del mismo gesto técnico realizada por 16 participantes sin práctica o experiencia en kárate, siendo posible el uso de esos datos en análisis del entrenamiento y del proceso de aprendizaje del kárate. Se verificó que la actividad cinemática y neuromuscular de ejecución de esta patada sucede en un espacio temporal de 600ms. La actividad muscular y cinemática evidencia la existencia de una norma secuencial temporal de intervención segmentar con un sentido próximo‐distal, donde los músculos estudiados tienen dos momentos distintos de actividad (períodos 1, 2). En el análisis electromiográfico (EMG), el grupo de karatekas presenta una mayor intensidad de activación (root mean square – RMS) y de pico de actividad en el músculo RectusFemoris (RF1) y VastusLateralis (VL1), y menor tiempo de contracción en ambos períodos en las relaciones entre los músculos RectusFemoris‐BicepsFemoris e VastusLateralis‐BicepsFemoris.En la realización de esta acción motora, los movimientos segmentares de flexión de muslo, de extensión de la pierna y de flexión plantar del tobillo fueron realizados con menor amplitud angular (range of action – ROA) por los karatekas, reflejando diferentes posicionamientos de los segmentos entre grupos. En conclusión, existe un patrón cinesiológico general, semejante entre practicantes y no practicantes de kárate. En el grupo de karatecas el entrenamiento induce una especialización de la actividad muscular, reflejada en los resultados del EMG y de la cinemática de movimiento, produciendo una mejor acción balística en la ejecución del mae­geri, que en asociación con una velocidad máxima de los segmentos distales, alcanzada cerca del momento del impacto, puede traducirse en un impacto más potente.[EN] Presently, coaches and researchers need to have a better comprehension of the kinesiological parameters that should be an important tool to support teaching methodologies and to improve skills performance in sports. The aim of this study was to (i) identify the kinematic and neuromuscular control patterns of the front kick (mae­geri) to a fixed target performed by 14 experienced karate practitioners, and (ii) compare it with the execution of 16 participants without any karate experience, allowing the use of those references in the analysis of the training and learning process. Results showed that the kinematic and neuromuscular activity during the kick performance occurs within 600 ms. Muscle activity and kinematic analysis demonstrated a sequence of activation bracing a proximal‐to‐distal direction, with the muscles presenting two distinct periods of activity (1, 2), where the karateka group has a greater intensity of activation – root mean square (RMS) and electromyography (EMG) peak – in the first period on RectusFemoris (RF1) and VastusLateralis(VL1) and a lower duration of co‐contraction in both periods onRectusFemoris‐BicepsFemoris and VastusLateralis‐BicepsFemoris (RF‐BF; VL‐BF). In the skill performance, the hip flexion, the knee extension and the ankle plantar flexion movements were executed with smaller difference in the range of action (ROA) in the karateka group, reflecting different positions of the segments. In conclusion, it was observed a general kinesiological pattern, which was similar in karateka and non‐karateka practitioners. However, in the karateka group, the training induces a specialization in the muscle activity reflected in EMG and kinematic data, which leads to a better ballistic performance in the execution of the mae­gerikick, associated with a maximum speed of the distal segments, reached closer to the impact moment, possibly representing more power in the contact.[PT] Actualmente, treinadores e investigadores necessitam de compreender bem os parâmetros cinesiológicos do movimento porque são uma ferramenta importante de suporte das metodologias de treino e ensino, e para melhorar a performance dos gestos motores. O objective deste estudo foi (i) identificar os padrões cinemáticos e de controlo neuromuscular da execução do pontapé frontal (mae­geri) num alvo fixo e realizado por 14 karatecas cinto negro, (ii) e comparar com a execução do mesmo gesto técnico realizada por 16 participantes sem qualquer prática ou experiência de karate, tornando possível o uso desses dados na analise do treino e do processo de aprendizagem do karate. Verificou‐se que a actividade cinemática e neuromuscular na execução deste pontapé acontece num espaço temporal de 600ms. A actividade muscular e cinemática evidencia a existência de um padrão sequencial temporal de intervenção segmentar com um sentido próximo‐distal, onde os músculos estudados têm dois distintos momentos de actividade (períodos 1, 2). Na análise electromiografia (EMG), o grupo de karatecas apresenta uma maior intensidade de activação (rootmeansquare– RMS) e de pico de actividade no musculo RectusFemoris (RF1) eVastusLateralis (VL1), e menor tempo de cocontração em ambos os períodos nas relações entre os músculos RectusFemoris‐ BicepsFemorise VastusLateralis‐ BicepsFemoris.Na realização desta acção motora, os movimentos segmentares de flexão da coxa, de extensão da perna e de flexão plantar do tornozelo foram realizados com menor amplitude angular (range of action – ROA) pelos karatecas, reflectindo diferentes posicionamentos dos segmentos entre grupos. Em conclusão, existe um padrão cinesiológico geral, semelhante entre praticantes de karate e não praticantes de karate. Todavia, no grupo de karatecas o treino induz uma especialização da actividade muscular, reflectida pelos resultados do EMG e da cinemática do movimento, o que conduz a uma melhor acção balística na execução do mae­geri, em associação com um máximo de velocidade dos segmentos distais, alcançado próximo do instante do impacto, o que poderá traduzir‐se num impacto mais potente

Characterization of kinesiological patterns of the frontal kick, mae-geri, in karate experts and non-karate practitioners

Presently, coaches and researchers need to have a better comprehension of the kinesiological parameters that should be an important tool to support teaching methodologies and to improve skills performance in sports. The aim of this study was to (i) identify the kinematic and neuromuscular control patterns of the front kick (mae-geri) to a fixed target performed by 14 experienced karate practitioners, and (ii) compare it with the execution of 16 participants without any karate experience, allowing the use of those references in the analysis of the training and learning process. Results showed that the kinematic and neuromuscular activity during the kick performance occurs within 600 ms. Muscle activity and kinematic analysis demonstrated a sequence of activation bracing a proximal-to-distal direction, with the muscles presenting two distinct periods of activity (1, 2), where the karateka group has a greater intensity of activation – root mean square (RMS) and electromyography (EMG) peak – in the first period on Rectus Femoris (RF1) and  Vastus Lateralis (VL1) and a lower duration of co-contraction in both periods on Rectus Femoris-Biceps Femoris and Vastus Lateralis-Biceps Femoris (RF-BF; VL-BF). In the skill performance, the hip flexion, the knee extension and the ankle plantar flexion movements were executed with smaller difference in the range of action (ROA) in the karateka group, reflecting different positions of the segments. In conclusion, it was observed a general kinesiological pattern, which was similar in karateka and non-karateka practitioners. However, in the karateka group, the training induces a specialization in the muscle activity reflected in EMG and kinematic data, which leads to a better ballistic performance in the execution of the mae-geri kick, associated with a maximum speed of the distal segments, reached closer to the impact moment, possibly representing more power in the contact