Dissertations / Theses on the topic 'Biomechanics of tennis'

Electrical and Computer Engineering
M.S.E.E.
The purpose of this study is to create a gesture recognition system that interprets motion capture data of a tennis player to determine which biomechanical aspects of a tennis swing best correlate to a swing efficacy. For our learning set this work aimed to record 50 tennis athletes of similar competency with the Microsoft Kinect performing standard tennis swings in the presence of different targets. With the acquired data we extracted biomechanical features that hypothetically correlated to ball trajectory using proper technique and tested them as sequential inputs to our designed classifiers. This work implements deep learning algorithms as variable-length sequence classifiers, recurrent neural networks (RNN), to predict tennis ball trajectory. In attempt to learn temporal dependencies within a tennis swing, we implemented gate-augmented RNNs. This study compared the RNN to two gated models; gated recurrent units (GRU), and long short-term memory (LSTM) units. We observed similar classification performance across models while the gated-methods reached convergence twice as fast as the baseline RNN. The results displayed 1.2 entropy loss and 50 % classification accuracy indicating that the hypothesized biomechanical features were loosely correlated to swing efficacy or that they were not accurately depicted by the sensor
Temple University--Theses

Table tennis playing involves complex spatial movement of the racket and human body. It takes much effort for the novice players to better mimic expert players. The evaluation of motion patterns during table tennis training, which is usually achieved by coaches, is important for novice trainees to improve faster. However, traditional coaching relies heavily on coaches qualitative observation and subjective evaluation. While past literature shows considerable potential in applying biomechanical analysis and classification for motion pattern assessment to improve novice table tennis players, little published work was found on table tennis biomechanics. To attempt to overcome the problems and fill the gaps, this research aims to quantify the movement of table tennis strokes, to identify the motion pattern differences between experts and novices, and to develop a model for automatic evaluation of the motion quality for an individual. Firstly, a novel method for comprehensive quantification and measurement of the kinematic motion of racket and human body is proposed. In addition, a novel method based on racket centre velocity profile is proposed to segment and normalize the motion data. Secondly, a controlled experiment was conducted to collect motion data of expert and novice players during forehand strokes. Statistical analysis was performed to determine the motion differences between the expert and the novice groups. The experts exhibited significantly different motion patterns with faster racket centre velocity and smaller racket plane angle, different standing posture and joint angular velocity, etc. Lastly, a support vector machine (SVM) classification technique was employed to build a model for motion pattern evaluation. The model development was based on experimental data with different feature selection methods and SVM kernels to achieve the best performance (F1 score) through cross-validated and Nelder-Mead method. Results showed that the SVM classification model exhibited good performance with an average model performance above 90% in distinguishing the stroke motion between expert and novice players. This research helps to better understand the biomechanical mechanisms of table tennis strokes, which will ultimately aid the improvement of novice players. The phase segmentation and normalization methods for table tennis strokes are novel, unambiguous and straightforward to apply. The quantitative comparison identified the comprehensive differences in motion between experts and novice players for racket and human body in continuous phase time, which is a novel contribution. The proposed classification model shows potential in the application of SVM to table tennis biomechanics and can be exploited for automatic coaching.

Le tennis elbow est une pathologie fréquente affectant le membre supérieur. Cette pathologie s'observe également dans un large éventail d'activités manuelles allant de la manipulation d'outils de maçonnerie à la manipulation d'une souris d'ordinateur. Malgré son prévalence élevée, les mécanismes sous-jacents au développement du tennis elbow demeurent paradoxalement largement méconnus et n'offrent pas de consensus scientifique. Toutefois, les outils, les instruments ou les objets manipulés, formant une interface avec la main, sont soupçonnés d'être en partie responsables de l'apparition de cette affection. Cependant, le manque de moyens d'investigation biomécanique sur la main ramène cette assertion au statut d'hypothèse. Dans ce travail de thèse, l'idée que les caractéristiques physiques de la raquette (i.e. taille et forme du manche ; inertie de la raquette) puissent avoir une influence sur le risque d'apparition du tennis elbow a été testée. Pour cela, nous avons mené une démarche structurée en trois étapes. Tout d'abord, une approche expérimentale contrôlée nous a permis de quantifier les efforts exercés au niveau de l'interface main-manche lorsque l'on serre simplement ce dernier. Pour cela, un instrument de mesure des forces a été développé (i.e. ergomètre à 6 poutres couplé à une nappe de pression Tekscan). Cela nous a permis de définir une taille et une forme de manche optimale pour les forces de serrage. Dans un second temps, ce manche optimal (i.e. de section circulaire et de périmètre égal à 17,9% de la longueur de la main) a été testé au cours de frappes de tennis
Lateral epicondylalgia (LE) have been reported to occur at least once in a range of 40% to 50% of tennis players and in a large number of workers using hand tools. Despite high prevalence, the mechanisms underlying the development of tennis elbow are paradoxically misunderstood and suffer from a lack of scientific consensus. The characteristics of the handled tools (e.g. the grip size and the shape) are believed to be partly responsible for the occurrence of these disorders. However, the available material and technique for investigation and the proceedings studies did not gave evidence for this hypothesis. In this work, the idea that the size and shape of a tennis racket handle can affect the risk of developing tennis elbow was tested in three main steps. First, a controlled experimental approach was performed in order to quantify the forces exerted at the interface hand / handle when squeezing simply a handle. A special force ergometer has been developed to measure the forces at the hand/handle interface. This study enabled us to define an optimal size and shape (i.e. circular perimeter equal to 18% of the length of the hand) to perform a maximal squeezing force. In a second step, the optimal handle was tested during tennis strokes. Our results show that with and without fatigue, the grip force was lower for the optimal handle compared to bigger or smaller handle. Finally, in a last step, a biomechanical model of the hand was used to assess the impact of the tennis racket grip size on the forces applied on muscles affected by tennis elbow during a simulation. Our results suggest that the optimal grip size reduces muscle tensions of hand extensor muscle

Les joueurs de tennis sont confrontés à un problème fondamental : comment améliorer la vitesse de leur service tout en limitant le plus possible les risques de pathologies chroniques ? L'objectif de ce travail est d'analyser, d'identifier et de comprendre les facteurs biomécaniques responsables de l'amélioration de la performance et de l'apparition des blessures articulaires chroniques lors de la réalisation du service au tennis. A partir de captures de mouvement en 3D chez des joueurs professionnels, la première étude s'attache à analyser les relations entre les valeurs de moments cinétiques segmentaires et la vitesse de balle au service. Grâce à une approche combinant captures de mouvement en laboratoire et suivi épidémiologique, la seconde étude explore l'influence du niveau d'expertise sur les contraintes articulaires du membre supérieur lors de la réalisation du service et sur l'apparition de blessures articulaires chroniques. La troisième étude identifie des facteurs "pathomécaniques" du service en comparant les mouvements de joueurs "sains" avec ceux de joueurs "blessés". La quatrième étude s'intéresse aux relations pouvant exister entre la vitesse de balle, les contraintes articulaires et le transfert de l'énergie mécanique lors du service. Enfin, la dernière étude porte sur l'influence de la fatigue musculaire sur la biomécanique, les risques de blessures et la performance du service lors d'un match de tennis prolongé. L'ensemble de ce travail démontre qu'il est à la fois possible d'améliorer la performance sportive et de limiter les risques de blessures grâce à la réalisation d'un geste de service "juste" sur le plan biomécanique

Elite tennis players are required to perform on a variety of tennis court surfaces which differ in mechanical characteristics, such as friction and hardness, influencing their performance and risk of injury. To understand the influence of surfaces on performance and injury risk, three studies were conducted to investigate tennis players' perceptions and biomechanical responses during tennis-specific movements on different court surfaces. In study 1, tennis players perceptions of acrylic and clay courts were identified following a thematic inductive analysis of semi-structured interviews (n = 7) to develop a series of visual analogue scales (VAS) to quantify perceptions during studies 2 and 3. Perceptions of predictability of the surface and players' ability to slide and change direction emerged, in addition to anticipated perceptions of grip and hardness. Study 2 aimed to examine the influence of court surfaces and prior clay court experience on perceptions and biomechanical characteristics of tennis-specific skills. Perception, kinematic, insole pressure and mechanical data were collected on an acrylic and a clay court. In agreement with findings reported in study 1, lower mechanical friction and hardness on the clay court were perceived and accompanied by less predictability and greater difficulty to change direction whilst being easier to slide. As result of sliding, players' adopted an altered technique on the clay court compared to the acrylic leading to reductions in loading provide evidence to explain lower injury risks previously reported on clay courts. Prior clay court experience did not influence players' perceptions. However, biomechanical response to the clay surface differed, such that players with high clay court experiences contacted the ground with an everted foot, believed to contribute to controlling sliding. Differences in perception-response relationships were reported between experience groups suggesting players with greater clay court experience are better able to choose an appropriate response to improve their performance. Friction properties of the surface may change during play on clay courts due to player movements and sliding on the court. Therefore there may be areas of expected and unexpected changes to friction to which players must respond to. Study 3 aimed to examine the influence of changes in friction and players awareness of these changes on perceptions and biomechanical response. Compared with study 1 and 2, players found it more difficult to identify differences in perceived grip during study 3, possibly due the smaller mechanical friction differences reported. Unexpected reductions in friction produced greater initial ankle inversion angles compared to the expected decreases in friction, increasing players' risk of injury. Lower horizontal and vertical loading rates were reported on the lower friction conditions where further sliding was reported; suggesting a reduced injury risk by allowing longer time spent applying the forces. This thesis has identified key perception variables that enabled a holistic understanding of perceptions and their interaction with biomechanical response. Mechanical friction was an important factor influencing players' ability to slide. Sliding on clay resulted in altered loading characteristics, pressure distributions and kinematics potentially reducing players' injury risk. Tennis players' experience of clay courts does not influence their perceptions of the surface but the response that players adopt, which lower their risk of injury and increase performance. It is important when playing on a clay court that friction properties are maintained across the court during a tennis match as much as possible to reduce injury risks, due to the influence of unexpected changes to friction on perceptions and response.

De nos jours, la plupart des fabriquants de chaussures proposent des chaussures pour les jeunes joueurs de tennis qui sont des modèles réduits de celles des adultes. Cependant, les enfants ne sont pas des adultes-miniatures et ont des besoins spécifiques. Entre 8 et 12 ans, les enfants sont sujets à des poussées de croissance qui diminuent la flexibilité du membre inférieur et augmentent les forces de tension sur les sites d’insertions des tendons sur les os. De plus, la pratique du tennis à haute intensité, avec la répétition d’accélérations et décélérations, place d’importantes forces de tension au niveau de l’insertion du tendon d’Achille sur le calcaneus et d’importantes forces de compression sous le calcaneus. La combinaison de ces 2 facteurs augmente le risque de subir l’une des principales blessures de sursollicitaton chez les enfants : la maladie de Sever. Par conséquent, l’objectif de ce travail de thèse était de définir les caractéristiques d’un chaussant adapté au joueur de tennis enfant en terme de volume chaussant confortable et de limitation des blessures. Premièrement, une chaussette équipée de capteurs de pressions textiles a été conçue et la fiabilité de sa mesure a été validée. Ensuite, cet outil innovant a été utilisé afin de corréler la mesure de pression et la perception du confort sur 8 zones du pied, permettant ainsi de déterminer le volume intérieur de la chaussure optimal pour le joueur de tennis enfant. Deuxièmement, les effets aigus du drop de la chaussure sur la biomécanique des joueurs de tennis enfants ont été examinés et il a été montré que la réduction de 12 mm à 6 mm permettait de réduire les forces de réaction du sol et donc potentiellement les blessures liées à l’impact. Enfin, l’influence à long-terme de la réduction du drop de la chaussure sur la biomécanique et les douleurs au talon reportées par les jeunes joueurs de tennis a été investiguée. La réduction progressive du drop de la chaussure a induit un changement de patron de pose du pied, arrière vers avant-pied, pour la moitié des participants et a permis de supprimer leurs douleurs au talon. De futures études sont nécessaires pour examiner les adaptations structurelles du membre inférieur liées à l’utilisation de chaussures partiellement minimalistes
Nowadays, most of tennis footwear manufacturers propose children tennis shoes that are scaled-down from adult shoes. However, children are not adult-miniature and have specific needs. Between 8 and 12 years old, children experience growth spurts that decrease the lower limb flexibility and increase the tensile forces on tendons insertion sites onto bones. In addition, the practice of tennis in high-intensity, with the repetition of accelerations and decelerations, places high tensile forces at the Achilles tendon insertion site onto the calcaneus and large compressive forces under the calcaneus. The combination of these 2 factors increase the risk to experience one of the main overuse injuries in children: Sever’s disease. Therefore, the aim of this thesis work was to define the features of a suitable footwear for children tennis players in terms of fitting comfort and limitation of injuries. Firstly, a sock equipped with textile pressure sensors was designed and its measurement reliability was validated. Then, this innovative device was used to correlate pressure measurement and comfort perception on 8 foot locations, allowing to determine the optimal inner-shoe volume for children tennis players. Secondly, the acute effects of shoe drop on the biomechanics of children tennis players were examined and it was shown that reducing from 12 mm to 6 mm allowed to reduce ground reaction forces and thus potentially impact-related injuries. Finally, the long-term influence of shoe drop reduction on the biomechanics and heel pain reported by children tennis players was investigated. The gradual reduction in shoe drop induced a switch from a rear- to forefoot strike pattern in half of the participants and allowed to remove heel pain for them. Future studies are needed to examine the lower-limb structural adaptations linked to the use of partial minimalist shoes

Le développement et la médiatisation du sport de haut niveau, notamment en fauteuil roulant, ont changé l 'image du handicap et favorisé le développement d'infrastructures permettant la pratique handisport, reconnue comme bénéfique pour la santé physique et psychique des personnes handicapées...Dans ce contexte, en partenariat avec un joueur de tennis fauteuil de haut niveau, l'objet de ces travaux a été d'étudier l'influence des réglages du fauteuil roulant sur son comportement en match, afin de l'optimiser pour le sport concerné. Ces travaux se concentrent d'abord sur les résistances au mouvement, en particulier dans les paliers des roues, lors du roulement en ligne droite et en rotation. La méthode consiste à créer d'abord un modèle mécanique représentatif du mouvement pour ensuite le valider avec une série d'expérimentations et l'exploiter. L'étude du sportif en mouvement sur son fauteuil a nécessité l'adaptation d'un modèle volumique à une personne assise, avec estimation des paramètres inertiels par mesures rapides. Ce modèle a été appliqué à l'étude de la propulsion à vitesse maximale, pour vérifier l'influence de la position du siège sur ce mouvement. Enfin une étude expérimentale des paramètres influant sur la rotation du fauteuil a mis en avant la forte influence de la position du centre de gravité du sujet sur la rotation, corroborée par un modèle mécanique.Les résultats issus de ces travaux ont permis de mieux comprendre les influences des réglages sur le comportement du fauteuil, de modifier certains réglages pour le sportif et d'orienter la conception d'un nouveau fauteuil. Ces études ont par ailleurs eu des retombées sur les fauteuils conventionnels et entre temps, notre sportif est devenu N°1 mondial
The development of Paralympics has done a lot for a more positive image of handicap and has opened up new opportunities for the practice of disability sport, known to be highly beneficial for the physical and psychological health of disabled people. Conducted in close partnership with a high level tennis player, this study focuses on the influence of the wheelchair settings on its behavior in order to adapt this behavior to wheelchair tennis playing. The study first highlighted the forces of resistance to straight line or rotating wheelchair movements, thanks to mechanical models validated by experiments. Then, the inertial parameters of the seated player's body segments were assessed by adapting a volumic model to the sitting position, and his propulsion at maximal velocity was studied, in order to understand the effect of the seat fore-and-aft position on this movement. Then, an experimental study proved the major influence of the center of gravity position on free rotation, which was modelized too.In a nutshell, this research work has led to a better understanding of the effects of the wheelchair settings on its behavior, its results have allowed to modify various settings on our partner's wheelchair and can be used as a basis for future wheelchair conception/design. They have also proved useful for conventional wheelchairs and in the meantime, our tennis player partner has become wheelchair tennis world champion…

O movimento pendular é dotado de qualidades dinâmicas, estratégicas e biomecânicas que o tornam padrão de excelência para o ensino do tênis. Ele reduz em até uma ordem de grandeza o esforço físico dispendido e elimina os riscos de tendinites do tipo \"cotovelo de tenista\". Transfere, dentro da maior eficiência, o impulso do chão sobre os pés para os quadris, tórax, braço e raquete. Naturalmente mantém o braço esticado e o punho rígido. Maximiza a velocidade da raquete e minimiza a indicação de endereçamento da bola. Estes são as conclusões do presente trabalho, buscando-se uma comparação direta das qualidades do movimento pendular frente as práticas de movimentação difundidas atualmente para o tênis de campo. São utilizadas conceituações dinâmicas e biomecânicas simples, fundamentadas na anatomia das inserções musculares, dos centros de gravidade e de rotação dos segmentos do corpo envolvidos nos movimentos. Os resultado indicam um aumento de eficiência com a utilização da movimentação pendular, atingindo-se um ganho médio de 10% em velocidade da raquete com uma redução do impulso no solo de cerca de 20%.
The pendular movement for the practice of optimized tennis has been under study as a graduate project at the Escola de Engenharia de São Carlos, Universidade de São Paulo-Brazil since 1977. The proposed procedure is based on the Newton\'s Laws of dynamics. The pendular movement incorporates dynamic, strategic, and biomechanical qualities that lends itself to a standard of excellence for tennis coaching. It reduces the dispended physical effort by one order of magnitude as well as eliminating the risk of tendinitis, among them the well known \"tennis elbow\". It also transfers the impulse received from the ground through the feet to the hip, torax, arm and raquet with the maximum efficiency. It keeps the arm naturally extended and the wrist rigid. It also maximizes the velocity of the raquet and reduces to a minimum the chances of the opponent anticipating the addressing of the ball. The characterisics of the pendular movement are compared to the other fundamental movements, the vertical, the rigid and the free movement. Simple dynamic and biomechanical concepts are utilized, based on the anatomy of muscular tendon insertions, on the centres of gravity and rotation of the body segments involved in the movement.

Orientador: Ricardo Machado Leite de Barros
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Educação Física
Made available in DSpace on 2018-08-21T20:35:16Z (GMT). No. of bitstreams: 1 Vieira_ClaudioLuisRoveri_M.pdf: 12894696 bytes, checksum: 4dbae6a7ceccc03d7fd333f49daecb76 (MD5) Previous issue date: 2011
Resumo: O objetivo do presente estudo é propor um conjunto de métodos para análise de movimentação de jogadores de tênis de campo a partir de vídeos pré calibrados com uso de câmeras fixas, bem como em vídeos televisivos. Primeiramente, foi proposto e validado um método para rastrear automaticamente jogadores de tênis de campo a partir de vídeos coletado in loco e de câmeras fixas e previamente calibradas. O percentual de rastreamento automático foi de 99,98%. As distâncias percorridas pelos dois jogadores durante um set de uma partida de tênis também puderam ser calculadas. A reconstrução das coordenadas bidimensionais da quadra foi validada calculando a repetibilidade intra-operador (0,009 m), a repetibilidade inter-operador (0,007 m), o erro relativo (comprimento e largura 0,03% 0,06%). O erro de medição alcançada para a posição do jogador foi de 0,36 m. Para ambas as coordenadas houve uma regressão linear significativa (R2 > 0,99, p <0,05) das posições obtidas pelos métodos de rastreamento automático e manual. Além disso, as distâncias percorridas por ambos os jogadores puderam ser extraídas como exemplo de aplicação do método. O segundo método proposto foi o de detecção automática de rallies em vídeos televisivos de tênis. O método desenvolvido foi baseado na extração de histograma, filtragem de percentuais estatísticos e semelhança com um quadro de referência. Três vídeos de partidas de tênis representando três diferentes pisos foram utilizados para avaliar o método proposto. O percentual médio de acerto dos cortes foi de 81%. A duração dos rallies obtidos com o método proposto são comparáveis ao método manual e adequado para determinar a duração dos mesmos para todos os vídeos de amostra. O terceiro método proposto foi o de calibração dinâmica em vídeos televisivos de tênis de campo. O percentual de automatização na identificação das linhas e geração das matrizes homográficas foi de 99,98%. Os testes estáticos, variando ±2 pixels por pontos de calibração, mostraram erros de medição satisfatórios (2,26 cm). Os testes dinâmicos, no qual foram reprocessados 522 quadros usando de 4 a 8 pontos de calibração, também revelaram um erro de medição satisfatório (23 cm). O quarto método proposto foi o de rastreamento automático de jogadores de tênis em vídeos televisivos. A determinação da posição do jogador foi baseada na identificação da sub-região de maior correlação com o modelo do uniforme do jogador dada uma região de interesse (ROI) através do uso da matriz homográfica. O percentual de automatização foi de 99,62% e o tempo de processamento foi de 0,86 segundos por quadro processado. As incertezas (RMS) envolvidas na determinação da posição dos jogadores foram de aproximadamente 45 cm para o lado da quadra mais próxima à câmera e 64 cm para o lado da quadra mais afastada da câmera. As distâncias percorridas, velocidades e áreas de ocupação de ambos os jogadores foram calculadas como exemplo de aplicação do método. Em conclusão, a metodologia desenvolvida e aplicada ao tênis de campo em vídeos televisivos mostrou ser viável, com alto nível de automatização e erro de medição similar aos métodos baseados em câmera fixa
Abstract: The aim of this study is to propose a set of methods for tennis players motion analysis from pre calibrated video using fixed cameras as well as on broadcast tennis videos. First, it was proposed and validated a novel automatic method for tracking tennis players from precalibrated videos using two fixed cameras. The percentage of automatic tracking was 99.98%. The two-dimensional coordinates reconstruction of the tennis court was validated by calculating the intra-operator repeatability (0.009 m), inter-operator repeatability (0.007 m), relative error (0.03% length and 0.06% width). The accuracy reached for the player's position was 0.36 m. For both coordinates, the linear regression was significant (R2 > 0.99, p <0.05) from the positions obtained by automatic and manual tracking methods. The covered distance performed by the players during a set of a tennis match was calculated. The second proposed method was the automatic detection of rallies in broadcast tennis videos. The method developed was based on the histogram extraction, statistical filtering and key frame similarity comparison. Three videos of tennis matches representing three different court surfaces were used to evaluate the proposed method. The average hit rate of the scene cuts was 81%. The rallies duration obtained by the proposed method was valid whether compared with the manual annotation and suitable to determine the rally duration for all sample videos. The third proposed method was proposed a dynamic calibration (frame by frame) in broadcast tennis video based on the automatic tennis court lines intersections detection. The percentage of automation of lines intersections identification and homographic matrix generation was 99.98%. The static test, based on varying by ± 2 pixels the calibration points, revealed a satisfactory accuracy (2.26 cm). The dynamic test, which have been reprocessed 522 frames using 4-8 calibration points, also showed satisfactory accuracy (23 cm). The fourth method presented was the automatic tracking of tennis players on broadcast tennis videos. The identification of the players' position was based on the sub-region of higher correlation with the players' clothes model in a region of interest (ROI) constructed by using the homographic matrix. The percentage of automation was 99.62% and the processing time was 0.86 seconds per frame processed. The errors (RMS) involved in determining the position of the tennis players were about 45 cm to the side of the court closest from the camera and 64 cm to the side of the court farthest from the camera. The covered distances, velocities and occupancy areas for both players were automatically extracted. In conclusion, the proposed methods developed and applied on broadcast tennis videos revealed to be feasible, with a high level of automation and accuracy similar to methods based on fixed cameras
Mestrado
Biodinamica do Movimento e Esporte
Mestre em Educação Física

O forehand e o backhand são as técnicas de movimentos mais utilizados no tênis. São golpes técnicos de complexa execução, pois dependem de uma perfeita sincronização temporal entre o movimento da raquete e a trajetória da bola. A literatura especializada demonstra que o posicionamento dos pés é fundamental para gerar potência nestes golpes e registra basicamente dois tipos de forehand quanto ao posicionamento dos pés: forehand open stance (FOS) e forehand square stance (FSS). A técnica de backhand, desde o início da prática da modalidade, apresenta duas maneiras de ser executada: com uma mão (BK1) ou com duas mãos (BK2) segurando o cabo da raquete. Pesquisas científicas específicas nesta modalidade esportiva têm se tornado razoavelmente freqüentes nas últimas duas décadas. O objetivo deste estudo é descrever as características biomecânicas a partir de parâmetros dinâmicos, cinemáticos e eletromiográficos segundo variáveis e músculos relacionados experimentalmente em função da utilização das quatro técnicas descritas acima. Através do conhecimento destas características biomecânicas, pretende-se ainda estabelecer uma relação de dependência quanto às influências no desempenho técnico esportivo. A amostra foi composta por dez indivíduos do sexo masculino, que possuíam domínio das técnicas analisadas. Ao analisarmos os resultados que reúnem as variáveis Biomecânicas estudadas, percebemos que é possível aceitar parcialmente a hipótese inicial de nosso estudo: as técnicas FOS e BK2 demandam maior ativação muscular quando comparadas com as técnicas FSS e BK1, respectivamente. Observando-se ainda os resultados de eletromiografia, verificamos a predominância de valores mais elevados de ativação muscular para as técnicas FOS e BK2 durante a fase pós-impacto, confirmando-se, portanto a hipótese inicial. Porém, durante a fase pré-impacto, os valores mais elevados de ativação muscular foram observados nas técnicas FSS e BK1, contrariando desta maneira a hipótese inicial. Concluímos, portanto, distintos comportamentos entre as duas técnicas de forehand e backhand, principalmente ao analisarmos as fases pré e pós-impacto, o que nos permitiu uma análise técnica detalhada dos gestos esportivos estudados, dada a complexidade estrutural dos mesmos
The forehand and the backhand are the most common movements in tennis. They are technical strokes of complex execution because they depend on perfect temporal synchronization between the racket\'s movement and the ball\'s trajectory. The tennis literature on the subject shows that the feet\'s positioning is crucial to generate power during these strokes. Two kinds of forehand are identified: the forehand open stance (FOS) and the forehand square stance (FSS). The backhand, since its origin, has appeared in two forms: the one-handed grip (BK1) and the two-handed grip (BK2). Scientific research on the subject has been conducted regularly during the two decades. Hence, the aim of this study is to describe the biomechanical characteristics within dynamic, kinematic and electromyographic parameters, and according to variables and experimentally related muscles in relation to the four different tennis techniques. In addition, through knowledge of these biomechanical characteristics, this thesis intends to identify the influences on technical sports performance. The sample was composed of males (n=10) that have mastery of the forehand and backhand strokes. After analyzing the results that evolve Biomechanics variables studied, we realized that it\'s possible to partially accept the initial hypothesis of our study: the forehand open stance and backhand strokes with both hands demand greater muscle activation when they are compared with forehand square stance and backhand stoke with just one hand, respectively. Still, observing the results of electromyography, we verified the predominance of the highest values of muscle activation for forehand open stance and backhand strokes with both hands during the post-impact phase, it\'s, thus, confirming the initial hypothesis. However, during the pre-impact phase, the highest values of muscle activation were observed in the forehand square stance and backhand strokes with one hand, counteracting, in this way, the initial hypothesis. We concluded, therefore, distinct behaviors between the two forehand and backhand strokes, mainly to analyze the pre and post-impact phase, which allowed us a detailed technical analysis of the sportive gestures studied, owing to its structural complexity

A repetitividade dos golpes em uma partida de tênis pode sobrecarregar a musculatura do punho e predispor a lesões, como a epicondilite lateral. A presente pesquisa propõe o uso de visão computacional para a obtenção de imagens tridimensionais reconstruídas, valores de forças atuantes em grupos musculares e articulações específicas e posições, velocidades e acelerações. O objetivo deste estudo é propor um método para descrever as características biomecânicas dos movimentos do punho durante a prática do tênis de campo, segundo as técnicas de punho rígido, a partir de parâmetros dinâmicos e cinemáticos, segundo variáveis físicas e antropométricas. Um indivíduo do sexo masculino, que possuí domínio das técnicas analisadas, realizou cinco sequências do movimento forehand em um laboratório de análise do movimento. Foi utilizado um sistema de aquisição de imagens (Qualisys Motion Capture Systems) que permitiu a reconstrução tridimensional dos movimentos dos segmentos. A partir de dados obtidos, através do sistema, verificou-se que os torques encontrados nos três eixos de movimento do punho, correspondentes aos movimentos de pronação, desvio ulnar e flexão de punho, apresentam magnitudes de 1.11 Nm, 3.98 Nm e 7.68 Nm, respectivamente. Verificou-se o maior valor de torque em torno do eixo z (flexão do punho), que será sustentado pela musculatura extensora de punho. A sobrecarga repetitiva dessa musculatura pode desencadear a epicondilite lateral.
The repeatability of the hitting in a tennis match can overload the muscles of the wrist and predispose to injury, such as lateral epicondylitis. This research proposes the use of computer vision for obtaining reconstructed three-dimensional images, active forces values in specific joints and muscle groups and positions, velocities and accelerations. The objective of this study is to propose a method to describe the biomechanical characteristics of the movements of the wrist during the practice of court tennis, using static wrist techniques, from kinematic and dynamic parameters, according to physical and anthropometric variables. A male person, who possess mastery of the techniques analyzed, held five forehand motion sequences in a laboratory analysis of the movement. It was used an image acquisition system (Qualisys Motion Capture Systems) that allowed the three-dimensional reconstruction of the movements of the segments. From the data obtained, through the system, it was found the torques in the three axes of motion of the wrist, corresponding to the movements of pronation, wrist flexion and ulnar deviation, which presented magnitudes of 1.11 Nm, 3.98 Nm and 7.68 Nm, respectively. It was found the greatest value of torque around the z axis (wrist flexion), which will be sustained by the extensor muscle of wrist. Repetitive overload of this muscle can unleash the epicondylitis.

碩士
國立成功大學
體育健康育與休閒研究所
96
The purpose of this study is to investigate effect of foot insole on lower extremities biomechanics during the cutting movement of forehand volley in tennis. Six male tennis players without history of lower limb injury volunteered for this investigation. Subjects perform three cutting angles movements (0°, 30° & 60°) to hit a dropping ball with a racket. Subjects are asked to wear a tennis shoe (Adidas 012508, size US: 9.5) under two conditions: with its insole and an adhesive insole. Eight-cameras vedio system (Motion Analysis Corp., Santa, Rosa, CA, US) was used to collect the data (different condition in cutting angles and insole) of 3D kinematics. One force platform (Kitsler, Type 9281B, 1000Hz) was used to determine the ground reaction force (GRF). During the experiment, both the motion analysis system and the Kitsler’s force platform are activated at the same time. The result shows that there is no significant difference in the kinematics parameters of the ankle during early stance. Because the movement during early stance is belong to a task-oriented skill, which would lead to different modifications by the subjects. Highest medio-lateral and vertical forces occurred while performing 0° cutting angle with adhesive insole, that increases the stop ability during early stance. The eversion angle, and angular velocity, plantarflexion angle and angular velocity increase with an increase in cutting angle with normal insole during late stance. According to the results, the subjects perform higher cutting angle with normal insole seem to have higher chance to get Achilles tendon injury. The risk factors of adhesive insole with 60° cutting angle are smaller than normal insole. Therefore, the subjects perform 60° cutting angle with adhesive insole has more ankle stability than normal insole during the late stance. Most tennis injuries in lower extremity seem to be caused by push-off during the late stance, and the reduction of foot slipping inside the shoe would improve the ankle stability.

M.Tech.
This study was conducted to determine whether Chiropractic treatment was beneficial in improving a male tennis player’s serve speed. Thirty participants were recruited and placed into a single group. Participants were between the ages of 18 and 40 years and selected based on the inclusion criteria being met. Participants had to be injury-free at the time of the research study and fall within a specified skill level (Provincial colours must have been attained at some stage in the participants tennis career). The participants were treated six times over a 3-week period and fifteen serve speed measurements were taken before the first consultation, and following the third and six consultations. A full case history, full physical examination, cervical spine regional examination and shoulder regional examination were conducted at the first consultation to locate joint restrictions and myofascial trigger points in the associated musculature of these areas. Diversified Chiropractic techniques were employed in the treatment of any restrictions found and trigger points were treated using either dry needling or ischaemic compression techniques. The results were interpreted by an outsourced statistician and the data was analysed using the ANOVA model and a Box Cox transformation was applied to transform the scale to normality. This yielded data onto which a parametric approach could be applied. According to the analysis, the treatment applied to the participants produced significant increases in their serve speed over the three sessions, although some increases were more prominent than others. This study concluded that Chiropractic treatment was effective in increasing the serve speed of a male tennis player and the study provides evidence that the effects of Chiropractic treatment could enhance performance in a sporting environment, perhaps even on a sustainable timeline with maintenance treatment.

Sports scientists and trainers generally agree that the multidimensional training in tennis should start during early childhood in order to ultimately reach a professional playing standard. Evidence suggests that motor skills, including power, strength, agility, speed and explosive power, as well as mental strength and a highly developed neuromuscular coordinating ability are strongly correlated with the level of tournament performance. Turner&Dent (1996) found that 27% of all tennis injuries in junior players occur in the shoulder region. The shoulder girdle is prone to injury because of its ability to maximally accelerate and decelerate the arm while the arm maintains it maintains precise control over the racquet at ball contact. The purpose of this study was to determine whether the occurrence of shoulder injuries could be minimized in tennis players by following a specific exercise programme, focusing on the shoulder girdle. A total of 42 tennis players participated in this study. They were all aged between 14 and 18 years. Both males and females were used for the purpose of this study. All the players were training at the SA Tennis Performance Centre and the International Tennis Federation at the University of Pretoria. They were all elite tennis players practising daily and scheduled for standard major tournaments throughout the year. Each subject completed a questionnaire of his or her tennis and medical history. The players were then divided into a control group and an experimental group. Both groups completed a series of physical scientific tests, consisting of posture analysis, body composition, flexibility, functional strength of the upper body; and isokinetic power and endurance of the shoulder muscles. These tests were executed every 3 months over a 9-month period and the results of each battery of tests were used to adjust and upgrade the new programmes. The experimental group did specific preventative shoulder exercises 5 times a week in addition to their usual gymnasium programme twice a week, while the control group followed a normal strengthening programme twice a week. A medical doctor immediately evaluated any muscle stresses or pains throughout the year. At the end of the year the data was compared to determine the difference in injury occurrence between the two groups. There was a significant difference (p<0.05) in the distribution of the lean body mass with the Lean body mass at T1 being lower than the Lean body mass at T3 in the control group. In the experimental group the fat percentage showed a significant decrease (p<0.05) from T1 to T3. The distribution of the muscle percentage at T1 was significantly different (p<0.05) from the distribution of the muscle percentage at T3 in the experimental group with the muscle percentage at T1 being lower than the muscle percentage at T3. There was a significant difference between the control and experimental group for 1RM bench press (p<0.05) with the 1RM bench press measurements at T3 being lower for the control group than for the experimental group. Also, the 1RM bench press at T1 was lower than the 1RM bench press at T3 in the experimental group. The experimental group showed a significant increase from T1 to T3, peaking at T3 with the 1RM bench press. Results of the tests done to determine isokinetic muscle strength showed that a statistical significant correlation (p<0.05) was found with regard to the strength of the internal rotators of the non-dominant shoulder at T3, with the experimental group having a higher measurement than the control group. The internal rotators and external rotators of both the dominant and non-dominant shoulders were lower at T1 than at T3 in the experimental group (p<0.05). The external rotators of the non-dominant shoulder at T1 were lower than the external rotators of the non-dominant shoulder at T3 in the control group. Results of the tests done to determine flexibility showed a statistically significant difference with the internal rotators and external rotators of the dominant as well as the non-dominant shoulders being lower at T1 than at T3 in the experimental group. Also, the external rotators of the non-dominant shoulder of the control group were lower at T1 than at T3. Results of the tests done to determine posture showed that in the control group, 54.5% of the players had scoliosis at T1 as opposed to 40.9% at T3. In the experimental group 55% had scoliosis at T1 compared to the 30% at T3. In the experimental group, 55% of the players’ shoulder heights were not level at T1, compared to 30% at T3. 63.6% of the control group’s non-dominant shoulders were higher than the dominant shoulder at T1, compared to the 40.9% of subjects at T3. Among the subjects in the experimental group, 50% had a higher non-dominant shoulder and 5% a higher dominant shoulder at T1, compared to 25% and 5% respectively in the control group, at T3. Results of the tests done to determine the occurrence of injuries, showed that the subjects with no injuries in the control group stayed stable from T1 (54.5%) to T2 (54.5%) whereafter it increased to 59.1% at T3. The experimental group stayed stable from T1 (55.0%) to T2 (55.0%) where after it increased to 85% at T3. In the control group the percentage grade 1 and 2 injuries was 13.6% at T1, increasing to 18.2% at T2, and decreasing to 13.6% at T3. In the experimental group 15% of the subjects had grade 1 injuries at T1. This percentage increased to 30% at T2 where after it decreased to 15% at T3 again. The percentage of subjects with grade 2 injuries in the experimental group remained stable at 10.0% from T1 to T2. None of the subjects had grade 2 injuries at T3. In the control group 9% had grade 3 injuries at T1, with none at T2 and T3. In the experimental group the percentage of subjects with grade 3 injuries remained stable at 5.0% from T1 to T2. None of the subjects had grade 3 injuries at T3. In the control group 4.5% of subjects had grade 4 injuries at T1. This stayed more or less stable at T2 (4.6%) and increased to 9.1% at T3. In the experimental group 10.0% had grade 4 injuries at T1. None of the subjects had grade 4 injuries at either T2 or T3. In the control group 4.5% had grade 5 injuries at T1, none had it at T2, and 4.5% had it at T3. In the experimental group none of the subjects had grade 5 injuries at T1, T2 or T3. In the control group none of the subjects had grade 6 injuries at T1 or T3. At T2, however, 4.6% had grade 6 injuries. In the experimental group 5.0% of the subjects had grade 6 injuries at T1 and none had this type of injury at T2 or T3. In conclusion, the results indicate that a specifically designed exercise programme can help to diminish the risk of shoulder injuries in tennis players. It can also improve bi-lateral muscle strength in opposing muscle groups which are used in tennis.
Thesis (DPhil)--University of Pretoria, 2007.
Biokinetics, Sport and Leisure Sciences
unrestricted

碩士
國立臺灣師範大學
體育學系在職進修碩士班
98
The purpose of this study was to investigate the kinematical variations between the movements of forehand drive in straight and diagonal line when receiving topspin and backspin services of elite table tennis male players. Five collegiate elite table tennis male players in Taiwan were served as the participants. Ten Vicon Motion Capture systems MX13+ (250 Hz) were used to collect the movements of forehand drives, and the Vicon Nexus 1.4 soft ware was used to calculate the kinematic parameters. All the variables were tested by Friedman two-way analysis of variance nonparametric statistical test which was calculated by SPSS 17.0, and the post-hoc comparison were calculated by the Excel software, the significant levels as α = .05. The results as follows: The duration time of each phase of the forehand drives were different. The duration time of backswing were significant less while receiving the backspin than receiving the topspin. The duration time of swing forward movement in diagonal line was less than in straight line. In the swing velocity at contact point and the peak velocity of swing, the drive of receiving backspin was faster than receiving topspin. The center of gravity (COG) of receiving backspin drive in straight line was the lowest among the four movements while in the end of backswing, the contact point and the fastest swing point. The relative sagittal distance between the racket and the COG at contact of forehand drive in diagonal line were more than the distance of the straight line. The racket tilt angle was less when receiving the topspin than the backspin. The shoulder axis (upper trunk) rotation of receiving backspin in diagonal line was the greatest among the four different drives, and it was the least while receiving topspin in straight line drive. There were significant differences in the upper and the lower limb joints angle and angular velocities among the four different drives.

碩士
國立臺灣師範大學
體育學系
99
The purpose of this study was to investigate the kinematical variations among the backhand drive in diagonal and straight line when receiving backspin and topspin services. Eight male collegiate elite table tennis players(age: 23±5yrs, hight: 172.5±.6.2cm, weight: 67.1±11.2kg, experience: 13.2±2.7yrs) in Taiwan were served as the participants. Ten Vicon Motion Capture systems MX13+ (250 Hz) were used to collect the movements of backhand drives, and the Vicon Nexus 1.4 & Visual 3D soft ware were used to calculate the kinematic parameters. All the variables were tested by Friedman two-way analysis of variance of non-parametric statistical test which was calculated by SPSS 19.0, and the significant levels as α = .05. The results as follows: The elite collegiate male table tennis players performed backhand drive with the similar height and the similar percentage duration time in diagonal and straight line when receiving backspin and topspin services. It’s not only need lower COM, but also needed the greater racket velocity, swing trajectory angle and racket tilt angle of the contect point in receiving backspin than topspin services. In backswing phase, the rotation angle of shoulder and hip axis were greater in receiving backspin than receiving the topspin services. In the swing phase, the shoulder and the hip axis rotation angles in returning drives to the diagonal were greater than to the straight line. In the joint angle and angular velocity of the upper and lower extremities, due to different spin and direction variations, the main trend showed that the drives for receiving backspin was greater than the topspin; driving return in diagonal were greater than the straight line. Base on the results of this study, we recommen that the table tennis players should increase the preparation movement and ball initial velocity to perform the drives to receive the backspin serves than receive the topspin serves. The players should increase the trunk rotation angle, trunk angular velocity and the angular velocities of the upper and the lower limbs to perform the diagonal line drives in the table tennis game.

碩士
中國文化大學
運動教練研究所
88
The purpose of this study was to investigate a biomechanical analysis of flat serve in tennis which was made use of two dimensional photography (2-D) to record the tennis service actions . Nine collegiate players of Chinese Culture University were served as subjects. Their mean age, height, and competition age were respectively 20 years, 176cm and 9 years. A camera (60 HZ) was used to film the service actions and Peak performance 2D film analysis system was used to investigate the kinematics data. The results were concluded as follows: 1.The stance of the subjects, 77% preferred the foot-up style and 23% preferred the foot-back style. The foot-up style characterized by a greater height off ground at impact, whereas the foot-back traveled a greater distance into the court with the first step. The foot-up style hit the ball at a greater height relative to their standing height (1.58+0.072) when compared to the foot-back style (1.53+0.014). 2.A peak ball toss height is influential the downward velocity at impact. The maximum downward mean velocity of 4.28 m/sec and the minimum downward mean velocity of 2.10 m/sec at the moment of impact so that the player would have more shorter time to hit a ball. 3.A mean minimum elbow angle of 49.5 degrees and knee angle of 142.2 degrees for all subjects didn*t fully flex the joints during the back swing of the serve. 4.When the hip was at its maximum vertical velocity. The racket moved down the back with a negative mean velocity of 3.88+0.56 meter/sec. The motions of upper extremities are general sequence in a proximal-to-distal fashion and whip- like movement .

碩士
台北巿立體育學院
運動科學研究所
95
The Ability of master the outcome of the service is very important to players who want to be successful in tennis. Although the serve consist of the coordination of the upper and lower limb, most of the injuries occur frequently on upper limb because of the direct impact force . The purpose of this study was to compare the impact force and the muscle torque on the upper extremities during the impact phase of the serve. The kinetics and kinematics data were obtained by two high speed cameras, a inverse dynamics program was used to calculate the impact force and the muscle torque on the upper extremities. Five right-handed collegiate tennis player’s service motion data were recorded. The results are showing that the wrist joint had the greatest kinematics data during the impact phase. The result is similar to other studies which had already illustrated that wrist joint generates most of the racket speed. The greatest impact force was obtained at the shoulder joint 0.12sec prior to impact, wrist joint had the second highest impact force during impact, while elbow joint is having the insignificant impact force compares to the wrist and shoulder joint. For the net muscle torque of the upper extremities, although there’s no significant difference between different joint, the elbow had the greatest muscle torque during the impact. Base on the outcome of this study, we would like to suggest the players to develop a optimal weight training program for upper limbs and also try to use more lower body strength during the service motion training to reduce the possibility of injury, also it’s necessary for both players and coaches to understand the importance of the relaxation and the medical treatment after training.

碩士
國立臺灣師範大學
體育學系在職進修碩士班
99
The purpose of this study was to combine the kinematics, kinetics and surface EMG methods to analyze six elite collegiate table tennis players in Taiwan (age: 21 ±4.69 yr, height: 173.5 ±4.59 cm, weight: 67 ±5.80 kg, experience: 12 ±4.52 yr.) when they were performing the forehand and backhand drives techniques while receiving the top spin and the under spin services. Ten VICON MX13+ Motion Capture systems (250 Hz), two KISTLER Force Plates (1500 Hz) and Noraxon Wireless EMG system (1500 Hz) were used to collect the kinematics of the dominate upper limb muscle groups, which were the wrist flexor, wrist extensor, biceps brachii, triceps brachii, pectoralis major, anterior deltoid and posterior deltoid. The EMG data were analyzed by using the Acknowledge software (1000Hz)., kinetics data and surface EMG signal. The Vicon Nexus 1.52 was used to calculate the kinematics and the kinetics data, the Noraxon software was to analyze the EMG signal parameters. All the variables were tested by Friedman two-way analysis of variance nonparametric statistical test, and the post-hoc comparisons were calculated by the Excel software. The Wilcoxon matched-pairs signed-rank nonparametric statistical test was to test the different variables between forehand and backhand drives, the significant level was at α =.05. The results were as follows: there was a significant difference that the forehand drive was greater than backhand drive in the following variables, the return initial velocity of the ball, racket swing velocity, the velocity of center of gravity, racket upswing displacement and the height of center of gravity at the contact point. There was greater racket tilt angle and a lower center of mass when return backspin serve. In ground reaction forces, there was a significant correlation between anteroposterior impulse and horizontal racket anteroposterior velocity. In EMG, The anterior deltoid, pectoralis major, flexor carpi radialis and extensor carpi ulnaris in forehand drives, the posterior deltoid, triceps and extensor carpi ulnaris in back hand drives exerted the greater muscular amplitude during the swing forward phase. There were co-contractions between Biceps Brachii and Triceps Brachii, Flexor carpi radialis and Extensor carpi ulnaris in forehand drives during upswing phase, while a less co-contraction in backhand. The muscular strategy and the patterns of the forehand and backhand drives in elite table tennis players were not the same.

碩士
中國文化大學
體育學系運動教練碩博士班
105
Abstract Purpose: The purpose of this study was to observe the influence of two different table tennis shakehand grips on biomechanics during backhand flick. Methods: Fourteen collage male table tennis athletes who are shakehand-griped players participated in this study. They were asked to successfully perform three trials of backhand flick using two types of shakehand grips: the western and eastern grips, respectively. The ball velocity was measured by a speed gun and eleven infrared cameras were used to record the movement of the trajectory of reflective marks attached on players’ body. The collected data was analyzed by a MATLAB software and then being contributed to a paired sample t-test. Results: There are significant differences in four variables which are the ball velocity (the western grip is faster than the eastern grip), angle of shoulder joint at the beginning of backswing (the eastern grip has greater external rotation angle than the western grip), angle of shoulder joint at the end of backswing (the western grip has greater internal rotation angle than the eastern grip) and wrist angular velocity at the end of swing (the western grip has higher velocity than the eastern grip). Conclusion: This study showed that the western grip showed significantly greater biomechanical merits than the eastern grip during backhand flick. It is recommended that the instructors can introduce the western grip to players to improve the performance on increasing ball velocity.

碩士
國立臺灣師範大學
體育學系
100
In striking, a table tennis play’s footwork is very important. If an athlete has good footwork, and strikses the ball at an appropriate position, he will give the ball with good speed, strength, spin, curve and location, whith will improve his skill level. The purpose of this research was to analyze the biomechanic parameters about two footsteps “side step” and “cross step” with two distance ”far” and “near”. The subjects were eight elite collegiate male table tennis players. The mark trajectories of body motion were collected by the VICON Motion Capture System（300Hz）. In the same time, the ground reaction forces（GRF） data were collected by three KISTLER force plates（1500Hz）. Using Visual 3D software to calculate the kinematic and kinetic data. Collecting the EMG data by the Noraxon wireless EMG system（1500Hz）and calculate the data by MyoResearch XP Master Edition software. All the paremeters were tested by Friedman two-way analysis of variance nonparametric statistical test by SPSS 19, the significant level as α＝.05. The results are：1.There is more horizontal displacement about the”Side step”（far：1.047±0.093m； near：0.533±0.108m）, closing the ball much more after moving than the “cross step”. In the same time, there is higher body COG（far：0.534±0.015H； near：0.528±0.022H） when moving that might effect the timing of striking. 2.There is less time from start to the ready striking position to strike by the ”cross step” （far：0.782±0.161s；near：0.718±0.061s）.In the same time, it costs more time to strike after the ready striking position（far：0.259±0.029s；near：0.209±0.039s）. 3.Farther moving need exciting more lower limb muscles, that bring more GRF and joint force. 4.There is significant difference when comparing the total IEMG from start to striking, but there is no significant difference when comparing the IEMG in a unit of time with some muscle. Suggestion：Stable striking with “side step”; nevertheless if one have to reach the ready striking position in a short time, excuting the “cross step”. Including the two steps to the day-to-day practice may enhance a trainee’s proficiency. Training lower limb muscles would strengthen the muscle strength and endurance.

碩士
中興大學
生物產業機電工程學系所
95
Playing tennis, most people often injured for not warming up enough or having an improper way to hit the ball. The common injured condition is muscle strain in elbow using backhand stroke. In order to find out some injuring factors, the objectives of this study were to simulate and analyze biomechanics of upper extremities for backhand stroke. The study utilized commercially available software, ADAMS and LifeMOD, to build a human body model. The motion data of tennis’s backhand stroke was recorded by high-speed video cameras, and was applied for the motion simulation. Following the published methods, the joints’ parameters were tested in the research. The results showed 105 and 104 for stiffness and damping, respectively, associated with weighted factor of 10 at wrist would result in better correlation of joints’ movement as well as better moment. Thus, based on the factors found in the research, the simulation model would be able to represent the real action and would be applied for calculating moments at the joints.

碩士
國立體育學院
運動傷害防護研究所
93
Purpose: The purposes of this study were to compare the differences of the following factors in tennis players using single-handed backhand stroke with and without brace by 4, 8cm distal to lateral epicondyle: (1). maximal muscle activities, (2) range of motion (ROM) among the trunk, shoulder, elbow and wrist, and (3). relative joint positions opposed to neutral positions among the trunk, shoulder, elbow and wrist when each tested muscle achieves maximal contract. Methods: The subjects were ten collegiate tennis players. Surface electrodes were placed on six forearm muscles. Twelve strokes among three tested conditions were recorded on high-speed camera and synchronized with electromyographic signals. Results: The results showed that no significant differences were found on maximal muscle activities, ROM and relative positions of the trunk, shoulder, elbow and wrist among three tested conditions. Ball velocities and maximal muscle activities of Extensor Carpi Radialis (ECR) and Flexor Carpi Radialis (FCR) were correlated, p=0.000 and 0.025 respectively. The correlation appeared to be negative on ECR and positive on FCR, r2=0.062 and 0.015 respectively. Conclusion: The correlation between ball velocities and muscle activities of ECR and FCR might relate to the wrist stability, since they were the major stabilizers of the wrist during backhand strokes. From the consistence of muscle activities, ROM and relative positions of joints, they made no differences between bracing at different position and non-bracing. The effects of braces do not seem to be obvious for the expert tennis players.

碩士
國立臺灣師範大學
體育學系
97
Purpose: Kinematics data and EMG data was collected from elite tennis players to determine the effects of the split step on the poaching action used in doubles tennis. Specifically the timing of the split step was examined to see if it affected the success rate of the poaching action. Methods: The subjects who participated in this study are: Eight male players (age 21 ± 2.33 years; height 182.06 ±2.73cm； weight 74.62 ± 6.23kg) and eight female players (age 20.9 ± 2.10 years; height 169.12 ± 3.52cm; weight 60.38 ± 5.73kg) who have no injury within six months and are ranked in the top 32 players of the country. The ball velocity and direction was controled by other players during the experiment. Two high-speed FASTEC Inline cameras were synchronized to collect 2D kinematics data. Nine Vicon Motion Capture System cameras and an EMG system were synchronized to collect 3D kinematics data. A dependent t-test was used to test the kinematic difference between forehand and backhand poaching. Conclusion: The following are the results of kinematics data : 1. The results of this research clearly show that the success rate of the forehand poaching for both male and female is much greater than the backhand poaching. Interestingly the speed of the split step is the same for both. 2. The change in the height of male’s center of gravity (CG) was greater on their backhand. This occurred at the time of the split step. For females, the greatest change in the height of the center of gravity (CG) occurred when their lead foot was planted on their forehand. The speed of the lateral movement of the center of gravity (CG) for female from the time the leading foot leaves the court to the moment the trailing foot is planted and the ball is struck, is faster on their backhand side. For male, the speed of the entire stroke for both forehand and backhand is the same. This is true for both male and female. Reaction time for male is fast for their forehand. The following are the results of electromyography (EMG) data : 1. The crouch of the split step takes longer than the jump. It is during the crouch that the muscle stores the energy needed for the jump. So the split step is an important step that prepares the leg muscles for the springing action needed in the footwork of the poaching action. 2. At the time of the crouch in the split step, the EMG activity of muscles is directly related to whether the player will hit a forehand or backhand stroke.

Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia
O desporto é um estilo de vida saudável, que traz inúmeros benefícios para aspessoas. Todavia, por vezes leva o corpo humano a conhecer os seus limites,principalmente em termos físicos.As vibrações são um elemento presente em praticamente todos os desportos.No ténis, as Vibrações Mão-Braço são as mais perigosas, pois podem originar lesões aonível dos membros superiores, com maior incidência nos ombros, pulsos e cotovelos.A preocupação pela saúde das pessoas, a curto, médio e longo prazo, faz comque os estudos na área das vibrações no desporto, se direcionem para a tentativa dadiminuição de lesões e de problemas relativos à saúde causados pela prática desportiva.Por exemplo, a nível do ténis, existem estudos apoiados em diferentestécnicas, para o constante desenvolvimento das características das raquetes, e doconhecimento do corpo humano. No entanto, a revisão das investigações leva a concluirque grande parte dos estudos existentes é direcionado para a raquete. Os movimentosmais estudados são a direita e a esquerda. O serviço é uma das pancadas que exige maisfisicamente do atleta, contudo até agora pouco estudada.Do mesmo modo, o estudo da fadiga muscular, e os seus tempos e métodosde recuperação, utilizando a eletromiografia e a termografia, retratam uma área quenecessita de ser mais explorada.Assim, este estudo visa abranger todos os estudos associados a análise daexposição dos tenistas a situações que possam potencializar o aparecimento de lesões. Oprincipal objetivo é apresentar um conjunto de análises que possam ajudar os treinadores,e os atletas, a definirem estratégias de treino de forma a reduzirem, ou evitarem, oaparecimento de eventuais lesões.
Sport represents a healthy lifestyle, which has several benefits for the humanbeing. However, sometimes it leads the human body to face its limits, mainly in a physicalway.Vibrations are an element that’s felt in almost all sports. In tennis, the handarm vibrations are the most dangerous because they can cause injuries at the level of theupper limbs, with greater incidence in shoulders, wrists and elbows.The concern for people’s health, in short, medium and long term, makes thestudies related to vibration in sports to focus on the attempt to reduce injuries andproblems related to health caused by sport’s practice.In tennis, for example, there are studies supported by different techniques,aiming the constant development of racket characteristics and knowledge about thehuman body. However, the investigation’s review leads to the conclusion that a large partof the existing studies are directed towards the racket. The most studied movements arethe right and left ones. The service is one of the stokes that physically demands more fromthe athlete but, so far, has not been much studied.Likewise, the study of muscle fatigue and its recovery times and methods,using electromyography and thermography, portray an area that needs to be furtherexplored.Thus, this study aims to cover all studies associated with the analysis of tennisplayers exposure to situations that may enhance the appearance of injuries. The mainobjective is to present a set of analyzes that can help coaches and athletes to definetraining strategies to reduce, or prevent, the appearance of possible injuries.

abstract: Every year, 3 million older people are treated for fall injuries, and nearly 800,000 are hospitalized, many of which due to head injuries or hip fractures. In 2015 alone, Medicare and Medicaid paid nearly 75% of the $50 Billion in medical costs generated by falls. As the US population continues to age, more adults are beginning to deal with movement related disorders, and the need to be able to detect and mitigate these risks is becoming more necessary. Classical metrics of fall risk can capture static stability, but recent advancements have yielded new metrics to analyze balance and stability during movement, such as the Maximum Lyapunov Exponent (MLE). Much work has been devoted to characterizing gait, but little has explored novel way to reduce fall risk with interventional therapy. Targeting certain cranial nerves using electrical stimulation has shown potential for treatment of movement disorders such as Parkinson’s Disease (PD) in certain animal models. For human models, based on ease of access, connection to afferents leading to the lower lumber region and key brain regions, as well as general parasympathetic response, targeting the cervical nerves may have a more significant effect on balance and posture. This project explored the effects of transcutaneous Cervical Nerve Stimulation (CNS) on posture stability and gait with the practical application of ultimately applying this treatment to fall risk populations. Data was collected on each of the 31 healthy adults (22.3 ± 6.3 yrs) both pre and post stimulation for metrics representative of fall risk such as postural stability both eyes open and closed, Timed-Up-and-Go (TUG) time, gait velocity, and MLE. Significant differences manifested in the postural stability sub-metric of sway area with subject eyes open in the active stimulation group. The additional 8 metrics and sub-metrics did not show statistically significant differences among the active or sham groups. It is reasonable to conclude that transcutaneous CNS does not significantly affect fall risk metrics in healthy adults. This can potentially be attributed to either the stimulation method chosen, internal brain control mechanisms of posture and balance, analysis methods, and the Yerkes-Dodson law of optimal arousal. However, no adverse events were reported in the active group and thus is a safe therapy option for future experimentation.
Dissertation/Thesis
Masters Thesis Biomedical Engineering 2019