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This study explored the effects of string type and tension on various factors involved with tennis ball–racquet impact in midsized and oversized racquets. String and racquet material, racquet flexibility, and grip firmness were held constant for each test condition. The dependent variables included postimpact and preimpact ball velocity ratio, racquet head displacement, maximum ball compression, and ball contact duration. It was found that racquet size and string material have varying effects on impact. Although changes in string tension do affect the impact, it is not in a linear fashion. Various string tensions change a racquet's flexibility, thus affecting ball velocity and other factors associated with impact. The results of this study demonstrate the complexity of string and frame interaction.
Jack Groppel is with the Dept. of Physical Education at the University of Illinois at Urbana-Champaign. In-Sik Shin is an assistant professor at Seoul National University in South Korea. Jo Ann Thomas was a master's student at the University of Illinois at the time of this writing. Gregory Welk is a master's student at the University of Iowa.
Direct all correspondence to Jack L. Groppel, 117 Freer Hall, 906 S. Goodwin, University of Illinois, Urbana, IL 61801.