The rebound accuracy of tennis impacts was studied by measuring the vertical angles of approach and rebound of tennis balls projected in a vertical plane at a clamped racket. Three identical oversized tennis rackets were strung with nylon at 200, 267, and 334 N of tension. Ten impacts were filmed at 200 Hz for each string tension with the ball impacting the strings centrally and 8 cm off-center. A two-way ANOVA revealed significant (p < .01) main effects for string tension, impact location, and the interaction of string tension and impact location. Treatment-Contrast Interactions demonstrated one significant (p < .01) difference: The decrease in rebound accuracy from a string tension of 200 to 334 N was significantly different for central versus off-center impacts.
Duane Knudson is with the Department of HPER, Baylor University, P.O. Box 97313, Waco, TX 76798-7313.