Language：English   Publishing type：Research paper (scientific journal)   Publisher：HUMAN KINETICS PUBL INC  

The objective of this study was to investigate the factors affecting ball velocity at the final instant of the impact phase (t(1)) in full instep soccer kicking. Five experienced male university soccer players performed maximal full instep kicks for various foot impact points using a one-step approach. The kicking motions were captured two dimensionally by a high-speed camera at 2,500 fps. The theoretical equation of the ball velocity at t(1) given in the article was derived based on the impact dynamics theory. The validity of the theoretical equation was verified by comparing the theoretical relationship between the impact point and the ball velocity with the experimental one. Using this theoretical equation, the relationship between the impact point and the ball velocity was simulated. The simulation results indicated that the ball velocity is more strongly affected by the foot velocity at the initial instant of the impact phase than by other factors. The simulation results also indicated that decreasing the ankle joint reaction force during ball impact shifts the impact point that produces the greatest ball velocity to the toe side and decreasing the ankle joint torque during ball impact shifts the impact point that produces the greatest ball velocity to the ankle side.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The differences between the assessments performed with and without the point cluster technique (PCT) for knee joint motions during the high-risk movements associated with non-contact anterior cruciate ligament (ACL) injuries have not been reported. This study aims to examine the differences between PCT and non-PCT assessments for knee joint angles and moments during shuttle run cutting. Fourteen high school athletes performed a maximal effort shuttle run cutting task. Motion data were collected by an 8-camera motion analysis system at 200 Hz, and ground reaction force data were recorded using a force plate at 1000 Hz. In both PCT and non-PCT approaches, the knee joint angles were calculated using Euler angle rotations, and the knee joint moments were obtained by solving the Newton-Euler equations using an inverse dynamics technique. For the extension/flexion angle, good agreement was measured between PCT and non-PCT assessments. The abduction angle obtained in the non-PCT assessment was smaller than that obtained with the PCT. An internal rotation angle was obtained in the PCT assessment, whereas a small external rotation angle was obtained in the non-PCT assessment. For the knee joint moments, good agreement between PCT and non-PCT assessments was observed for all the components. The differences in the knee joint angles were attributed in part to the differences in the position of the medial femoral epicondyle. The results suggest that the ACL injury risk during shuttle run cutting is estimated lower in the non-PCT assessment than in the PCT assessment. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jbiomech.2011.05.001

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

CiNii Article

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TAYLOR & FRANCIS LTD  

The first objective of this study was to investigate the influence of foot angle and impact point on ball velocity and rotation immediately after impact in the side-foot soccer kicking. The second objective was to calculate impact force during the ball impact phase. Five experienced male university soccer players performed side-foot kicks with one step approach in varying foot angle and impact point. The kicking motions were captured three-dimensionally by two high-speed video cameras at 2500 fps. Impact on the area from the center of mass of the foot to the medial malleolus produced the greatest ball velocity. Varying the foot angle with the same impact point did not affect the ball velocity. Also, Impact on the surrounding area of the metatarsal with large foot angle produced the greatest ball rotation. Even if the impact point was the same, the ball rotation increased with the foot angle. Time change of the impact force was calculated from the ball deformation, based on the Hertz contact theory. As an example, in a trial with a ball velocity of 16.3 m/s, a peak ball deformation was approximately 4 cm and a peak impact force was approximately 1200 N.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Sports Industry  

The objective of this study was to measure ball deformation and impact force during the ball impact phase in side-foot soccer kicking, using a three-dimensional analysis technique. Firstly, to examine the method for measuring the three-dimensional position of the center of the ball while the kicking foot contacted the ball, the motion of ball rolling on the ground was captured three-dimensionally at 250fps. The position of the center of the ball was calculated as the point located at 11cm (=radius of the ball) from three markers fixed on the ball surface. It was suggested that in cases when the distances between each marker were more than 8cm, the position of the center of the ball was validly calculated. Also, five experienced male university soccer players performed side-foot kicks using a one-step approach. The kicking motions were captured three-dimensionally by two high-speed cameras at 2500fps. The contact point between the kicking foot and ball was calculated as the intersection point of the perpendicular line dropped from the center of the ball to the medial aspect of the kicking foot. The ball deformation was calculated by subtracting the distance between the center of the ball and the contact point from the radius of the ball. Furthermore, the impact force was calculated from the ball deformation, based on the Hertz contact theory. It was considered that the ball deformation and the impact force measured with these approaches were valid.

DOI： 10.5997/sposun.17.2_13

CiNii Article

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Other Link： https://jlc.jst.go.jp/DN/JALC/00382736283?from=CiNii