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Jpn J Biomechanics Sports Exercise 11(1):25-37, 2007

Three dimensional motion analysis of direct free kick in relation to the rotational axis of soccer balls

Satoshi SHIMONO1), Mitsuhisa SHIOKAWA2), Kazufumi TAKAHASHI3), Sachio USUI4)

1)Graduate School of Education, Hiroshima University,
2)Faculty of Health and Welfare, Prefectural University of Hiroshima,
3)Contemporary Society and Culture, Kinjo Gakuin University,
4)Graduate School of Integrated Arts and Sciences, Hiroshima University

Abstract

In soccer, the topspin-kick skill, which deflects the trajectory of a ball vertically in a direct free kick, has recently attracted widespread attention. The purpose of this study was to clarify the mechanism of the topspin-kick motion by focusing on the fact that the rotational axis of a ball which generates topspin leans to the left. We instructed 7 subjects skilled in soccer to kick the ball with their right foot with various angles of rotational axis. The shooting motions were recorded using an optical motion capture system. The following results were found using multiple linear regression analysis applied to the variables of the impact phase.
1)Movements of the foot to impact
The main factors are to turn the swing direction of the foot upwards to impact and to turn the toe upwards to impact to make the rotational axis of the ball lean to the left.
2)Motions of the kicking leg
To position the greater trochanter of the kicking leg backward has a beneficial effect on turning the swing direction of the foot upwards to impact. Also, dorsiflexion of the ankle joint and inclination of the shank of kicking leg to the left have a beneficial effect on turning the toe upwards to impact.
3)Motions of the supporting leg
With individual differences, the motions of the supporting leg to make the rotational axis of the ball lean to the left include planter flexion of the ankle joint, flexion of the knee joint, inclination of the shank to the left, keeping the pivoting foot further to the side from the ball and increasing the approach angle.
It is concluded that these results are expected to give useful information for soccer players to improve their topspin-kick skill.

Key Words: direct free kick, topspin, rotational axis

Submittted for Publication : Mar. 29, 2006,

Accepted for Publication : Jan. 15, 2007

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