Comparison of hip joint mechanical energetics in table tennis forehand and backhand drives: a preliminary study

Hip joints are highly involved in table tennis. Some authors found both pelvic angular velocity and hip joint torques are related to the racket velocity. Others have also demonstrated how some of the best players have higher ranges of motion of the lower-limb joints. Therefore, the mechanical work generated by the playing-side-hip can be seen as indicator of the playing intensity associated with different strokes. The aim of this study was to quantify the hip joint mechanical work and power during four classical strokes. Motion capture acquisitions were performed on two international players. A biplanar radiographic acquisition was also performed to personalize the biomechanical model. Hip joint velocity and torques were calculated on the dominant side, allowing mechanical power and work to be calculated between the end of backswing and the ball impact. The highest level of mechanical work from the hip joint was found for forehand drive against backspin and forehand topspin drive with pivot. A backhand drive required the lowest hip mechanical work, and the forehand drive against topspin was found to be intermediate. The lower work required from the backhand stroke makes it suitable as a waiting stroke

IS BALL-RACKET CONTACT CONCOMITANT WITH THE MAXIMAL RACKET SPEED IN YOUNG TRAINED TABLE TENNIS PLAYERS?

Previous table tennis studies have broadly assumed the racket to reach its maximal speed at ball-racket impact but only few identified this instant experimentally. Hence, there remains a lack of information regarding the validity of this hypothesis and therefore a need to develop a strategy to identify ball-racket contact that can be implemented into future experimentations. A 3D motion capture system was used to measure racket movements of seven young talents (12.6 ± 0.8 years old) -a category that had not been tested yet- during topspin forehand and backhand drives. Ball-racket impacts were identified with a synchronized microphone. Maximal racket speed and sound peak occurrences were compared, and racket parameters (speed, orientation) were calculated at both events. Differences emerged when examining participants individually for forehand drives and over the whole cohort for backhand drives, with consequences on both racket orientation and speed between the two events. As it was shown that ball-racket contact is not always concomitant with the maximal racket speed, futures studies should add supplementary equipment such as a synchronized microphone to identify the exact impact time

Physiology, biomechanics and injuries in table tennis: A systematic review

Objectives Table tennis is a widely practiced sport, often described as a reaction sport. Therefore, players need to practice extensively that may expose them to overuse injuries. For optimizing training with limitation of the injury risk, the knowledges of table tennis physiology, biomechanics and epidemiology are of primary interest. Methods For that purpose, a literature review has been made through a systematic search on three scientific databases. Overall, table tennis physiology is complex due to intense and intermittent efforts. It results that some technological challenges still need to be addressed to accurately quantify this physiology. Besides, current rules changes may modify the table tennis physiological requirements. Results Findings in neurophysiology tend to define table tennis as an anticipation sport rather than a reaction sport and higher occulo-motor skills were found in table tennis population with respect to average population. Regarding biomechanics, some rare studies have been done but none had investigated the energy flow between the upper- and the lower-body, which would be interesting to understand how the energy generated by the footwork contributes to racket velocity. Conclusion Finally, epidemiological studies lack of details on injury locations and diagnosis. These data could be of high interest to improve medical and training care

Bioceramic powders for bone regeneration modified by high-pressure CO2 process

Non-stoichiometric nanocrystalline apatites present enhanced bioactivity compared to stoichiometric hydroxyapatite. The purpose of this work was to modify the calcium phosphates (CaP) generally used to prepare bioactive ceramics in the aim of obtaining a biomimetic apatite powder. Hydroxyapatite (HA) powder, amorphous tricalcium phosphate (amTCP) powder and a blend of these two were modified by means of an innovative, simple, “green” carbonation process, involving water and high-pressure CO2 (80 bar). This process induced a modification of the CaP, which is sensitive to the environment in which it is located and, in particular, to the pH variations that occur during the treatment phase (decrease in the pH) and during the degassing phase (return to neutral pH). FTIR and Raman spectroscopy, XRD and SEM analyses showed that, depending on the type of initial CaP powder, high-pressure CO2 treatment led to the formation of different types of calcium phosphate phases. This process allowed partial dissolution of the initial powder, mainly of TCP when present, and precipitation of a new CaP phase. HA and HA/amTCP powders were transformed into a mixture of OCP and immature carbonated apatite (PCCA) phases, including OCP maturation/transformation into PCCA. In the case of amTCP powder, a DCPD phase was also present due to the high TCP solubility and an earlier precipitation during the degassing step. This work shows the great potential of such an innovative low-temperature and high-pressure process to transform HA, HA/TCP and TCP powder into bioactive biphasic ceramics composed of OCP and PCCA similar to bone mineral

Biomechanical analysis of the golf swing: methodological effect of angular velocity component on the identification of the kinematic sequence

The golf swing is a complex whole-body motion for which a proximal-to-distal transfer of the segmental angular velocitiesfrom the pelvis to the club is believed to be optimal for maximizing the club head linear velocity. However, previous experimental resultsabout such timing (or kinematic sequence) are contradictory. Nevertheless, methods that were used in these studies differed significantly,in particular, those regarding the component of the angular velocity vector selected for the identification of the kinematic sequence.Hence, the aim of this study was to investigate the effect of angular velocity vector component selection on the identified kinematicsequence. Methods: Thirteen golfers participated in this study and performed driver swings in a motion capture laboratory. Seven meth-ods based on different component selection of segmental angular velocities (vector norm, component normal-to-sagittal, frontal, trans-versal and swing planes, segment longitudinal component and a method mixing longitudinal and swing plane components) were tested.Results: Results showed the critical influence of the component chosen to identify the kinematic sequence with almost as many kine-matic sequences as the number of tested methods for every golfer. Conclusion: One method seems to show the strongest correlation toperformance but none of them can be assessed as a reference method for the identification of the golf swing kinematic sequence. Re-garding the limited time lag between the different peak occurrences and the uncertainty sources of current materials, development ofsimulation studies would be more suitable to identify the optimal kinematic sequence for the golf swin

Influence of the projection plane and the markers choice on the X-factor computation of the golf swing X-factor: a case study

Study of variability induced by the methology choice on the X-factor computation of the golf swing. Based on optoelectronic measurements. Variability of the choice of upper limb, plane of projection and instant of computation

Personalized biomechanical modeling of hip injuries on pivot sports : application to table tennis.

La pratique du tennis de table à haut niveau nécessite des charges et volumes d’entrainement importantes. Dans cette optique, la Fédération française de tennis de table a instauré des programmes d’entraînement intensifs dès le plus jeune âge. Il s’en est suivi une amélioration des résultats au niveau international mais une augmentation du nombre de joueurs avec des pathologies de hanche. Dans ce contexte encore très mal documenté dans la littérature, la possibilité de pouvoir modéliser de façon personnalisée le geste sportif est une piste essentielle qui permettrait de comprendre si les évolutions néfastes observées sont génétiques ou liées à un geste traumatogène. L’objectif de la thèse était alors de réaliser une analyse biomécanique personnalisée des mécanismes lésionnels de la hanche pour les joueurs de tennis de table. La capture du mouvement couplée à l’analyse stéréo-radiographique et un examen clinique de la hanche ont permis d’évaluer de nombreux paramètres biomécaniques et morphologiques qui ont permis de dégager des différences entre les joueurs qui présentaient des douleurs au niveau des hanches et ceux qui n’en présentaient pas. Certains paramètres étaient différents entre les cohortes mais ils ne permettaient pas de savoir s’ils étaient la cause de ces douleurs, ou une adaptation induite de celle-ci. Néanmoins, il sera intéressant de suivre ces paramètres dans le temps et chez les nouveaux joueurs, pour prévenir l’apparition de pathologies.High-level table tennis requires high workloads and training volumes. With this in mind, the French Table Tennis Federation has introduced intensive training programs from an early age. This has led to an improvement in international results for elite French players but an increase in the number of players with hip pathologies. In this context, which is still poorly documented in the literature, the possibility of being able to model the sporting gesture in a personalized way is an essential way to understand whether the harmful developments observed are genetic or related to a traumatic gesture. The objective of the thesis was then to carry out a personalized biomechanical analysis of the lesion mechanisms of the hip for table tennis players. The motion capture coupled with stereo-radiographic analysis and a clinical examination of the hip resulted in the evaluation of numerous biomechanical and morphological parameters that revealed differences between players with hip pain and those without hip pain. Some parameters were different between cohorts, but they did not indicate whether they were the cause of these pains, or an induced adaptation of it. Nevertheless, it will be interesting to follow these parameters over time and in new players, to prevent the appearance of pathologies

Modélisation biomécanique personnalisée des mécanismes lésionnels de la hanche sur les sports de pivot : application au tennis de table.

High-level table tennis requires high workloads and training volumes. With this in mind, the French Table Tennis Federation has introduced intensive training programs from an early age. This has led to an improvement in international results for elite French players but an increase in the number of players with hip pathologies. In this context, which is still poorly documented in the literature, the possibility of being able to model the sporting gesture in a personalized way is an essential way to understand whether the harmful developments observed are genetic or related to a traumatic gesture. The objective of the thesis was then to carry out a personalized biomechanical analysis of the lesion mechanisms of the hip for table tennis players. The motion capture coupled with stereo-radiographic analysis and a clinical examination of the hip resulted in the evaluation of numerous biomechanical and morphological parameters that revealed differences between players with hip pain and those without hip pain. Some parameters were different between cohorts, but they did not indicate whether they were the cause of these pains, or an induced adaptation of it. Nevertheless, it will be interesting to follow these parameters over time and in new players, to prevent the appearance of pathologies.La pratique du tennis de table à haut niveau nécessite des charges et volumes d’entrainement importantes. Dans cette optique, la Fédération française de tennis de table a instauré des programmes d’entraînement intensifs dès le plus jeune âge. Il s’en est suivi une amélioration des résultats au niveau international mais une augmentation du nombre de joueurs avec des pathologies de hanche. Dans ce contexte encore très mal documenté dans la littérature, la possibilité de pouvoir modéliser de façon personnalisée le geste sportif est une piste essentielle qui permettrait de comprendre si les évolutions néfastes observées sont génétiques ou liées à un geste traumatogène. L’objectif de la thèse était alors de réaliser une analyse biomécanique personnalisée des mécanismes lésionnels de la hanche pour les joueurs de tennis de table. La capture du mouvement couplée à l’analyse stéréo-radiographique et un examen clinique de la hanche ont permis d’évaluer de nombreux paramètres biomécaniques et morphologiques qui ont permis de dégager des différences entre les joueurs qui présentaient des douleurs au niveau des hanches et ceux qui n’en présentaient pas. Certains paramètres étaient différents entre les cohortes mais ils ne permettaient pas de savoir s’ils étaient la cause de ces douleurs, ou une adaptation induite de celle-ci. Néanmoins, il sera intéressant de suivre ces paramètres dans le temps et chez les nouveaux joueurs, pour prévenir l’apparition de pathologies

À la recherche d’un critère de performance pour les athlètes d’escrime fauteuil

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À la recherche d’un critère de performance pour les athlètes d’escrime fauteuil

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