Physical attributes of the tennis racket : implications for laboratory testing, on-court performance and player perception
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NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. ----- The game of tennis has evolved substantially in the last thirty years. Technology has enabled rackets to be designed using composite materials, and wooden rackets have given way to rackets made from metal, fibreglass, graphite, kevlar, boron and titanium. The utilisation of these materials has allowed a wide variety of racket designs to become available in the market. Manufacturers, however, often make claims about the performance of their product that are either contradictory or unproven. This thesis presents original contributions to knowledge by exploring the relationships between a tennis racket’s stiffness, string tension and swing-weight on the rebound speed, angle and spin of the tennis ball. The purpose of the thesis is to produce an integrating document that describes and links the published papers that follow. The principal area of study investigates the physical characteristics of the tennis racket when tested in both a laboratory and on-court setting. The thesis is structured around three main themes that are inherent throughout the publications that follow. The first theme describes the measurement of in-racket properties such as string tension and swing-weight. The measurement of string tension after the racket has been strung enables tension to be more accurately reported. It also provides the researcher with the ability to track string tension during the testing period rather than simply reporting the string tension at the beginning of the study. Swing- weight measurements and their affect on swing speed are also described in this chapter. The relationship between swing-weight and swing speed is greater than the relationship between racket mass and swing speed. It was recommended that racket manufacturers report swing-weight on the frame of the racket in terms of its moment of inertia. This would provide consumers with a greater understanding of the racket’s physical properties so that a more informed racket selection can be made. Under the second theme in this thesis, tennis racket performance is measured in a laboratory setting using a series of controlled experiments. Laboratory tests provide the opportunity to accurately investigate the effects of string tension and racket stiffness on ball rebound speed, spin and angle. Since dependent variables may only differ slightly, precise measurements in a controlled environment are necessary. The research conducted was unique in that it measured ball dynamics following an oblique impact. Oblique impacts more accurately model tennis strokes during game conditions where ball spin is considerable. The vast majority of prior research investigated normal impacts which do not model typical strokes in tennis. The research within this section identified a relationship between the elasticity of the collision and the angle of rebound. More elastic collisions resulted in the ball rebounding in a higher path during topspin strokes. The amount of spin was also analysed for varying levels of string tension and racket stiffness. Higher string tensions were found to produce greater ball angular velocity than lower string tensions. This was also true for low racket stiffness. Evidence of tangential elastic strain in the surface of the ball was identified indicating that it was possible for the ball to “overspin” during and after contact. The final theme considers tennis racket performance during on-court testing. This is based on research that simulates game conditions and measures ball rebound speed and placement during these conditions. It also reports on the perceptions of both advanced and elite tennis players to establish whether they can relate the feel of each ball impact back to the string tension of the tennis racket. The findings in these studies indicated that both advanced and elite tennis players are very poor at discerning levels of string tension in tennis rackets during play. This was evident despite a large range of string tensions being tested and significant findings in ball placement being identified. Lower string tensions resulted in more balls landing over the baseline and higher string tensions produced a greater number of net errors. It was concluded that on-court testing procedures produced results that are congruous with laboratory based tests.
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