KINEMATIC ANALYSIS OF THE OPEN AND SQUARE STANCE TENNIS FOREHAND

Abstract

165 The purpose of this study was to compare the kinematics of the upper extremity during the forward swing (FS) of players using open and square stance forehands. Seven male teaching professionals (PRO) and eight intermediate (INT) tennis players were filmed (100 Hz) while doing open and square stance forehands. The DLT method was used to get the 3D coordinates of 21 body landmarks, five racket points and the ball. Standard rigid body kinematics were used to compute the linear velocities of the joints, racket and ball, and joints angular displacements and velocities. The square stance produced larger racket velocities at impact (20.7 m/s and 17.4 m/s) than the open stance (19.8 m/s and 15.9 m/s) for both skill levels. The joint angular displacements were very similar for both type of stances and skill level. The PROS' showed greater horizontal adduction of the upper arm than the INT players, which may have contributed to the larger racket linear velocities at impact. Both groups developed greater shoulder angular velocities at impact using the square stance (8.2 and 5.0 rad/s) than in the open stance (7.3 and 4.6 rad/s). The primary angular motions used to accelerate the racket were rotation of the shoulders, horizontal adduction of the upper arm and wrist flexion. In conclusion, the results of this study indicate that there are only minor differences in the FS of the open and square stance forehands. The square stance was superior to the open stance in developing greater racket velocities. The lower linear and angular motions during the open stance could be the result of the lack of linear momentum and the limited amount of angular momentum generated during the FS.