The modern era of tennis has seen large changes in racket design and playing style. As regulators of the game, the International Tennis Federation have assumed a role of constant investigation. Recently, impact models have been used to assess the characteristics of various rackets. Whilst existing models are powerful, they are limited in terms of impact position and racket and ball movement. Realistic shot characteristics of 13 elite level players at the 2006 Wimbledon Qualifying Tournament were obtained. Two high speed cameras running at 1,000 frames per second were used to record ball and racket movements within a fully calibrated 2x2x2 in control volume to an accuracy of ±2.5 mm. It was found that players tend to hit a point on the racket stringbed which generates little to no frame vibration. Forehand shots had an outbound ball spin of 800 - 2,200 rpm, ball velocities in the region of 25 - 40 ms'. The results from the player shot analysis were used in the design of a repeatable impact methodology. Nine hundred laboratory based racket/ball impacts were analysed in 3D. A custom racket mount simulated grip torque. The experimental outputs were interpreted using a multi-variate fitting technique. The experimental results were used in model validation. A predictive impact model was developed. When validated against the laboratory and player testing results, the model showed good correlation. The model was used to investigate the effects of shot weighting, movement and accuracy on post-impact ball behaviour. It was found that: Increasing swing action weighting increases the velocity of tip impacts. Increasing weight towards the edge of the racket reduces the penalty for hitting off the racket's longitudinal axis. A `chopping' action generates ball spin. The model developed in this study can be incorporated into existing shot prediction software used by the International Tennis Federation.

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There is an increasing awareness of the necessity to evaluate the effects of tennis equipment in combination with players and the corresponding need for new methods of testing to be developed. This research has investigated the effectiveness of a range of objective measurements of player performance and their ability to quantity the effects of equipment modification and player fatigue. The hypothesis of this research was that if different designs of tennis equipment affect a player differently in terms of either accelerated/reduced fatigue or increased/reduced likelihood of injury, then there must be some changes in either the impact dynamics in terms of shock loading and vibration transmission, or through kinematic changes in terms of swing motion and biomechanics. Furthermore, it was hypothesised that using state-of-the-art instrumentation technologies in conjunction with a controlled experimental protocol, it may be possible to measure some of these changes.

Children's access to many sports is restricted because of social and equipment costs, in addition the equipment is not frequently designed to suit a child's physique and capabilities. Generally the design of sports equipment for children proceeds by taking adult equipment and scaling it down. Unfortunately this often means that the range of equipment is limited for a population whose dimensions are constantly changing and whose strength to size ratio does not vary linearly (Beak et al. 2000). The use of inappropriate equipment can significantly affect learning skills and cause the development of bad habits which may take years to correct and can be a major detractor to further participation (Sleap 1981 ). It is apparent that little science has been applied to equipment design for children and if wider participation is to be encouraged then well-designed and manufactured equipment that matches child development and growth rates needs to be produced. The intentions of this study were: • To determine the effect of equipment properties on children's, aged between 7 and I 0 years old, ability to generate effective strokes in two example sports: golf and tennis. • To determine whether any relationships existed between children's physical characteristics (e.g. height, strength etc ), equipment properties and performance. • To apply any fitting guidelines established to a group of subject to test their validity. In each sport 3 major equipment properties were examined and a sample of30 children, aged between 7 and I 0 years old of varying ability, were tested in each of the studies. Sixteen anthropometric measures, age, experience and grip strength were taken from each child. This information was examined with the performance data using multiple regression methods to determine whether any fitting relationships existed between child characteristics, performance and club or racket properties. In golf it was found that the club head mass, shaft flexibility and shaft length all significantly affected the distance achieved with 7 -iron clubs, whilst in tennis the racket length, mass and balance all had a significant effect on the power and placement of forehand tennis strokes. Nomograms were constructed for the tennis and golf fitting equations to provide a graphical representation of the fitting so that manufacturers, tennis coaches, club fitters and professional golfers can quickly determine correct club or racket characteristics for a child. The main conclusion of this study is that children should be considered as individuals instead ofbeing grouped into age or height categories. Children should be fitted to equipment in terms of their size, strength and ability if effective equipment that is more suited to their needs can be constructed.

Despite anecdotal evidence of changes to tennis ball characteristics and play properties, little research has been directed towards understanding the causes and effects of tennis ball degradation. Improved racket technology and player fitness have contributed to an increase in the speed of the game, yet balls have seen few advancements over the same period. There are several obvious factors contributing to tennis ball degradation: natural pressure loss in pressurised balls, changes to the cloth covering due to court and racket impacts, and precipitation and environmental factors. As recent tennis research has focused on the new balls, there is a need to investigate other ball conditions present in the game of tennis. This thesis provides a structured investigation into the causes and effects of ball degradation, an objective assessment of the effects of degradation on ball performance, and incorporates subjective perceptions of all aesthetics and play properties noted by players. Particular attention is given to ball fuzziness. Excessive fuzziness can occur from manufacturing variability, court and racket interactions, and environmental conditions - though there is currently no standardised method to assess ball surface condition. An objective measure of ball fuzziness has been developed and used in the analysis of nearly 4000 individual ball images. The effects of court and racket impacts, precipitation, natural pressure loss, and repeated impacts have been analysed for their effects on ball degradation. An assessment of ball performance utilised ball impact and aerodynamic data to determine significant differences between balls and develop an improved ball trajectory model.