Variability of impact kinematics and margin for error in the tennis forehand of advanced players |
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| Authors: | Duane V Knudson John R Blackwell |
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| Institution: | (1) Department of Kinesiology, California State University, 95929-0330 Chico Chico, CA;(2) University of San Francisco, USA |
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| Abstract: | The kinematics of the racket and ball near impact in tennis forehands were studied to document typical variation in successful
and unsuccessful shots, in order to determine biomechanically meaningful differences in advanced players and confirm models
of groundstroke trajectories. Seven tennis players (six males and one female) were videoed from the side at 180 Hz as they
performed 40 forehand drives on an indoor tennis court. Vertical plane kinematics of the racket and ball near impact were
analysed for sub samples of successful and unsuccessful shots for each subject. Most racket kinematic variables were very
consistent (mean CV< 6.3%) for successful shots, so bio mechanically meaningful differences in angles and velocities of the
racket and ball (3° and 2 m s−1) near impact could be detected between successful and unsuccessful shots. Four subjects tended to miss long and three subjects
missed shots in the net that were reflected in initial ball trajectories. Mean (SD) initial trajectories for long shots were
9.8° (1.4°), while netted shots were 0.7° (1.1°) above the horizontal. The initial ball trajectories and margins for error
for these subjects were smaller than those previously reported (Brody, 1987) because players tended to select mean ball trajectories
close to one error than another, differing amounts of topspin, or incorrect lift and drag coefficients for tennis balls had
not been published when this model was created. The present data can be used to confirm if recent models (Cookeet al., 2003; Dignallet al., 2004) more closely match actual performance by advanced players. |
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| Keywords: | angle biomechanics consistency error model velocity |
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