A Dynamic Test for Comparison of Rebound Characteristics of Three Brands of Tennis Balls

The purpose of this study was to compare Dunlop, Spalding and Wilson pressurized tennis balls for rebound when fatigued at trial intervals of 0, 800, 1,600, 2,400, 3,200 and 4,000 bounce impacts. Eighteen yellow tennis balls, six each from Wilson, Dunlop and Spalding pressurized tennis cans were equally divided and randomly placed in a control or experimental group. The control group was not subjected to any fatigue. The experimental group was fatigued by use of a Lobster tennis ball firing machine. Both groups were filmed with a camera and strobe light assembly after each fatigue interval. The experiment was designed to indicate, with the use of a fatigue curve, which brand of balls fatigued the most and what number of bounce impacts were required to show fatigue. Four primary statistical analyses were used to analyze the rebound data: a one-way analysis of variance, a three-factor re­ peated measures analysis of variance, an analysis of covariance repeated measures with the covariate held constant, and two-factor repeated measures analysis of variance. Once a significant F was found, a Newman-Keuls Multiple range test was employed to further investigate the difference, The following findings were produced from this study: 1. No statistical significant difference was found between the main effects of control versus experimental balls; however, there was a significant interaction between balls and trials. The analysis revealed that the interaction occurred between trial 1 when the balls were new and trial 2 when the experimental balls had received 800 bounce impacts. 2. Relative to brands of balls, Spalding tennis balls rebound significantly higher than Wilson tennis balls, both when the balls were new and throughout the trials. No other significant difference was found between brands. 3. Relative to trials, a significant difference was found across trials. Tennis balls rebounded significantly higher at each trial interval 1 through 5 than at the last trial (trial 6) when the experimental and control group were analyzed together. This indicates that tennis balls may remain out of their pressurized cans for 172.5 hours before there is a significant lowering in rebound height. A separate analysis of the experimental group data revealed that fatigued tennis balls actually rebounded significantly higher than new balls until after 172.5 hours or 3,200 bounce impacts. The control group revealed a significant decrease in rebound height after the fifth trial or 172.5 hours when this group was analyzed separately. When the three brands of balls were equated statistically at the start (trial 1), no statistical significant difference was found across trials. This indicates the different brands of balls fatigued at the same rate and time.