No description available.

A subject-specific, torque-driven, 3D computer simulation model with eight segments was developed to investigate the effects of different variables belonging to the racket and player on the wrist and elbow loadings in one-handed tennis backhand groundstrokes. Wobbling masses were included to represent soft tissue movement. The string-bed was represented by nine-point masses connected to each other and the racket frame with elastic springs. There were twelve rotational degrees of freedom: three at the shoulder, two at the elbow, two at the wrist, three at the grip and two between the racket handle and racket head. Seven pairs of torque generators were used to control (via activation profiles) the joint angle changes in the model. An elite player was chosen to perform consistent and high standard backhand topspin strokes and a Vicon System was used to record the performances.

Assessment of wielded implement performance is important to a variety of human endeavours and often critical to success in a sports context, particularly so in the game of tennis. Tennis racket design and manufacture is a multimillion business involving 10 major international companies. Tennis participation is currently estimated at around 60 million individuals worldwide. Thus the importance of optimum racket performance to maximise competitive advantage and minimise the risks of injury is clear. This thesis presents work to enable advances in tennis racket performance with respect to player feel perception, measurement of physical phenomena and the correlation of these aspects within real play contexts. To investigate feel perception a methodology was adapted from the existing literature. Interview testing was conducted to elicit a comprehensive range of tennis specific vocabulary. The end goal was to create a perception relationship map or 'feel map'. The inductive analysis was used to link all the related clustered themes identified from the vocabulary to sub and base themes describing the relationship. Further analysis introduced higher level general dimensions that unified common base themes. The resulting feel maps were created from both English and German sample groups, with a view to subsequent comparison. To complete the map and broaden its application a wide scale questionnaire was distributed to a tennis playing population. The responses provided data indicating percentile use of selected vocabulary within the tennis community and the relative importance players associate with assorted perception groups. Visual representations of the data were introduced to the map for quick and easy use and an associated lexicon compiled to provide a reference for more detailed information. The feel maps and lexicon provide users with a versatile tool in the form of a 'perception relationship model'. The map itself can act as an overall research guide for future work in the field. The addition of percentile use and relative importance data mean the map can be used to create more informed and subtle player test questionnaires or as a design aid, with interdependency links indicating which additional factors should be considered or exploited for their influence on the characteristic areas in question. Interestingly the general dimensions of highest relative importance were sound and grip respectively. This may be due to the basic level of interaction between player and racket which ultimately has to be perceived either through the grip or from the sound. A perception test questionnaire was also created with the use of the feel map and later used to study the correlation between objective and subjective measures. To best attain objective measures from the racket an innovative instrumentation system was created. Two alternative systems were designed and tested, the first based on wired instrumentation and data capture the second based on wireless technologies as these became available. Both systems were required to take measures of grip pressure and acceleration with 6 degrees of freedom. The first system utilised uniaxial accelerometers mounted on an aluminium bracket, and a triaxial accelerometer inserted inside the butt of the racket arranged to allow measurement and calculation of acceleration from the required 6 degrees of freedom. The system could be adapted to include either TekScan multi-cell full grip coverage force measurement, or 2 single point higher sample rate single cell grip force sensors. All data was fed via 15 m of cable to data acquisition systems. This restricted the participants' freedom of movement and encumbered the racket and thus the systems application, making it unsuitable for extensive perception or fatigue testing. The second system utilised a compact data logger with an integrated on board tri-axial accelerometer small enough to be mounted within the racket handle. A revised mount overcame the need for the aluminium throat bracket, moving the uniaxial accelerometers into a bulbous addition to the butt of the racket. The system was capable of capturing 8 channels simultaneously which allowed for the 6 accelerometers and two single cell grip force sensors to be located under the grip. The system was more difficult to adapt and maintain than the wired system, but improved freedom and reduced added weight to the racket made the system far more suitable for the planned perception and fatigue testing. Fatigue testing conducted with the wireless device investigated the effect of full body fatigue on players' performance by monitoring the resultant effects in the racket. The protocol was based on the multistage fitness test, designed to progressively increase in difficulty until volitional fatigue. Heart rate data indicated that the protocol was successful in fatiguing the participants to a point at or near their VO2max. Unfortunately, with the wireless system in its early stages of development, the device failed mid way through testing. The limited data set that was collected indicated that technique was affected by fatigue. Further research is required to confirm this finding and to make comparisons between racket types during the fatiguing process. The wireless device was adapted to make it more durable and reliable before the planned perception testing was conducted. A protocol was developed to investigate the affect of changing racket moment of inertia on player perception and physical measures. The test questionnaire developed from the feel map was used to evaluate player perception ratings of various elements of racket feel, and the wireless instrumentation system was used as part of methodology designed to compile a set of comparable physical data. A detailed analysis of the results revealed that there was some evidence of correlation between the perceptions of power, balance, flexibility and control and the moment of inertia of the racket. In a design optimisation context, however, more definitive correlations would be more useful. These would be expected to be found with future testing utilising a wider range of racket properties. The research proves to a large extent the original hypothesis that through the use of non invasive instrumentation and improved player perception elicitation techniques it is possible to substantially and usefully improve the objective and subjective assessment of tennis racket performance in play to enable investigation of better design characteristics and fatigue related injury phenomena.

No description available.

The aim of this thesis was to better understand the tribological mechanisms that occur during typical player movements, build further on this understanding and develop a robust, portable device to assess the friction characteristics of tennis surfaces that relate to playing performance and safety. To understand the tennis player’s response and adaptability to a tennis court surface, including friction in the shoe-surface interface, a series of friction experiments were carried out on three categories of tennis surface, grass, clay and hardcourt. For grass, parameters such as moisture, level of wear and height were found to have an effect on the shoe-surface friction. For clay, influence of clay particle size and the infill volume was established. In terms of biomechanical conditions, it was found that the shoe orientation during a slide affects the friction. It was demonstrated that matching applied pressures is a useful approach for shoe friction testing and analysis. Through video analysis, shoe landing and sliding were found to be two possible ‘risk’ movements. Material characterisation, combined with friction and temperature measurements have provided empirical knowledge into the manner in which shoes and surfaces behave. During a slide on hardcourts, temperature changes were found to be different along a shoe outsole. The front part experienced higher change of temperature compared to other positions. Three types of bespoke tread samples were produced and tested, resulting a ‘holed sample’ the optimal to use. These samples resulted relatively easy to manufacture and generate frictional results compared to tennis shoes. The final robust portable device resulting from this study, measures the friction characteristics of the shoe-surface interface representative of match-play tennis. The device can be used in two configurations to replicate a shoe landing and a sliding movement. The test shoe consists of a commercial rubber with a bespoke tread design with mechanical properties that match typical values to a tennis shoe. This device will aid the International Tennis Federation (ITF) and the sports surface research community to gain understanding of player-shoe-surface frictional interactions, and allow courts to be monitored around the world.

Over the last 20-30 years the subject of spin in tennis has become increasingly important. A great deal of work has been done to establish the effects which, increased levels of spin have, on shots. The most prominent effect of increased spin in a tennis shot is the resulting deviation in flight which allows players to, amongst other things, strike the ball harder with top-spin in the knowledge that it will still fall inside the court due to the extra aerodynamic downward force. With such significant advantages available racket manufacturers are naturally keen to maximise spin generation. That being said, very little research has been performed into the subject of spin generation in tennis and the affecting factors. This thesis details the development of a finite element model which is to be used to allow a greater understanding of spin generation and how varying properties such as string density (the number of strings in a string-bed), gauge and orientation affect its magnitude. The primary aim, or goal, of this research is to create an FE model which can be used to model oblique impacts and measure the resulting spin. Whilst considerable focus was placed on developing novel, modelling techniques to create the FE model, a great deal of emphasis was also placed on its validation. The validity of the model was examined under static loading conditions, such as that experienced during stringing. The dynamic performance was also validated using a combination of modal analysis and high speed video of dynamic impacts. Each of the validation methods provided assurance of the models performance, with all error margins less than 5%. The two areas of the FE model which required the most attention were the interaction properties (specifically coefficient of friction (COF)) and material properties. Previous studies have sought to obtain a single value for the COF of a tennis racket/ball system but this study examines how the COF varies as the strings interact first, with themselves and secondly with the ball. Each of the validation methods (dynamic and static) were deemed successful as they provided concise data which could be readily compared with the results produced by the FE model. Having validated the model s performance, with respect to predicting outbound spin, a number of oblique impact angles were modelled to allow a greater understanding of how the mechanisms of spin generation change with the inbound trajectory of the ball. This analysis showed that for the impact conditions studied the contact time of the impact was reduced from 6.2 milliseconds to 5.7 milliseconds when the angle was increased from 32 degrees to 40 degrees. Furthermore, a number of novel string-beds were modelled, with varying string orientations (between 30 degrees and 60 degrees relative to the rackets frame) and subjected to a similar analysis procedure, with their results providing the concluding section of the thesis.

Although there currently exists an in-depth empirical understanding of parents experiences and involvement in youth sport, there is an absence of published field-based intervention research specifically with sport parents (Harwood & Knight, 2015). In order to address this gap in the literature, this thesis developed a psychosocial parent education programme for British Tennis. The first study identified the education and support needs of tennis parents operating within British high performance centres (study one). Adopting a grounded theory design, data were collected through informal chats, observations, and formal interviews with parents, coaches, and ex-youth players (n=29) during a six-month period of fieldwork. Findings revealed how parents education and support needs occur across multiple levels of functioning (i.e., social, organisational, developmental, and intra-interpersonal) and are influenced by the developmental stage that parents operate in. This theoretical framework was then used as the basis for a group-based tennis parent education programme (study two). Using a qualitative organisational action research framework seven workshops were run over a 12-week period for parents with children between the ages of 5 and 10 years. Participant diaries, social validation feedback forms, and post programme focus groups (n=19) revealed perceived improvements in parents knowledge, affect, and skills across a range of learning objectives. In an attempt to improve accessibility and extend participation, the final study utilised a convergent parallel mixed methods design to examine the effectiveness of an online education programme for British tennis parents (n=38) and their perceptions of engaging in the programme (study three). Quantitative findings revealed positive directional changes in tennis parent efficacy, general parent efficacy, emotional experiences, and achievement goal orientations after completing the programme. Qualitative data provided complementary and unique insights into what worked, how, and why. Taken together, the studies within this thesis are the first to demonstrate the effectiveness of face-to-face and online sport parent education programmes. Findings also extend and advance existing recommendations and guidelines in relation to the design, development, implementation, and evaluation of education programmes for sport parents. In particular, studies illustrate the importance and value of providing sport parents with accessible, proactive, structured, and developmentally appropriate education and support which addresses their stage-specific needs.

L'objectif de ce travail de doctorat étati d'examiner les modalités d'entrainement permettant de développer la vitesse de balle post impact en coup droit au tennis, tout en évaluant les risques potantiels d'hypersollicitation de l'épaule qui pourraient en résulter. Les résultats de nos différentes études ont montré que la puissance maximale développée lors d'un lancer de medecine-ball (MB) à 2 mains sur le côté expliquait 25% de la variation de la vitesse maximale de balle en coup droit et qu'elle était atteinte en utilisant une masse de MB de 5,7% du poids de corps du joueur. Toutefois, les relations entre les distances obtenues lors de ce type de lancer et la vitesse de balle en coup droit sont faibles. En revanche, les lancers de MB sur le côté à une main ont démontré une relation significative avec la vitesse maximale de balle en coup droit. Un entrainement de six semaines basé sur l'utilisation de ce type de lancers a augmenté la vitesse de balle de 11% mais la précision des coups tendait à diminuer. Finalement, un entraînement incorporant des frappes de balle avec une raquette lestée d'environ 12% a également amélioré la vitesse maximale de balle en coup droit (5%), tout en conservant la précision des coups. Enfi, la comparaison de la coordiantion musculaire entre lesles deux types de lancers de MB et la frappe en coup droit a montré que les muscles du tronc et du membre supérieur testés présentaient des modèles d'activité musculaire et des niveaux de sollicitations similaires. Ainsi, les craintes concernant un potentiel de blessure ne sembleraient pas justifiées. Ainsi, les résulats de ces tudes ont contribué à la périodisation de la préparation physique pour l'amélioration de la performance en coup droit chez le joueur de tennis compétiteur amateur / This work aimed at exploring the training modalities to develop maximal post impact ball velocity fo the tennis forehand drive, while assessing the potential risk of upper limb oeruse. The results of our studies showed that maximal power developed during a two-handed side medecine-ball(MB) throw explained 25% of the variation of maximal forehand ball velocitiy, and was achieved when using a MB mass of 5,7 % of player's body weight. However, the relationship between throwing distances and maximal ball velocity of forehand drive was weak. By contrast, a significant relationship was found between the performance for the one-handed side MB throw and the maximal velocity of the forehand drive. A six-week trainig program based on one-hand MB throws increased the ball velocity by 11%, but the shot accuracy tended to be reduced. In the same way, a six-week training program including forehand drives with an overweighted racketr about 12 % allowed the maximal forehand ball velocity to be improved (5%), without alteration in theshot accuracy. Finally, the comparison of muscular coordination between both MB throws and the forehand drive demonstrated that the trunk and upper limb muscles presented similar activity pattern and levels. The potentials for injury risk would thus not justify. In conclusion, the finding of this work contributed to the periodization of the strength and conditioning training in order to improve the forehand drive performance in nonprofessional competitive tennis players.