The Backspin Backhand Drive In Tennis To Balls Of Varying Height
AbstractModern tactics dictate that while the forehand drive is seldom hit with backspin, the backhand must be able to be hit with topspin or backspin depending on the height of bounce of the ball and/or tactical requirement of a particular rally. No studies have clearly identified the mechanical characteristics of the backspin stroke, although data are available on topspin (Elliott et al., 1989), flat (Pecore, 1979; Young, 1970) and one versus twohanded (Groppel and Ward, 1979) backhand drives. Three-dimensional (3D) high speed cinematography was used to compare backspin backhand techniques of 13 high performance players hitting low (hip height) and high (shoulder height) bouncing balls. The Direct Linear Transformation method was used for 3D space reconstruction from 2D images recorded from laterally placed phaselocked cameras operating at 200 fps. Players modified their technique for a low backspin backhand to hit a high bouncing ball by: 1. adopting a more upright trunk (67°) and larger front knee angle (175°) than was recorded for the lower stroke (61 ° and 156°) respectively. 2. adopting a more closed shoulder alignment in the transverse plane (line joining the two acromion processes was 20° beyond a perpendicular to the net) than was recorded for the lower stroke, where the shoulder alignment at impact was perpendicular to the net. 3. hitting the ball with a larger 3D shoulder joint angle (60°) than was .recorded for the lower stroke (54°). 4. impacting the ball with a less inclined approach trajectory of the racket (16 °) and more vertical racket-free (83°) than was recorded for the lower impact (-25° and 78° respectively). 5. reducing the racket velocity at impact from 20.6m s-l for the lower stroke to 19.5 m s-l for the high stroke. 6. modifying the role of rotation of the upper arm (outward rotation) and forearm (supination). Although not quantitatively measured in this study, it was evident when reviewing the film that outward rotation of the upper arm and forearm supination both would seem to play an integral role in the generation of racket-head velocity for the higher backhand. A comprehensive anaiysis of the mechanics of these strokes will be presented in this paper.
Coaching and Sports Activities
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