Hironari Shinkai

Ball impact dynamics of instep soccer kicking.

PURPOSE The purpose of this study was to reveal the foot-ball interaction during ball impact phase of soccer instep kicking. METHODS Eleven soccer players performed maximal instep kicks. The behavior of kicking foot and ball during ball impact was captured using two ultrahigh-speed cameras at 5000 Hz. Foot motion was described three dimensionally, and the motion of the center of gravity of the ball (CGB) was estimated by the spherical shell model in which the ball deformation was taken into account. The peak ball reaction force acting on the foot was estimated from Newtons equation of motion in which the peak CGB acceleration in sagittal plane was calculated from its velocity slope near the peak ball deformation. RESULTS During ball impact (9.0 +/- 0.4 ms), the foot was passively abducted and everted. Moreover, an unknown feature--slight dorsal flexion before distinctive plantarflexion--was quantified in most trials. The CGB velocity exceeded that of the foot when the ball was maximally deformed (6.2 +/- 0.6 cm). The magnitude of peak ball reaction force reached 2926 +/- 509 N, which corresponds to approximately twice as that of the mean force (1403 +/- 129 N). From the changes of the foot velocity, the CGB velocity, and the ball deformation, the ball impact phase can be divided into four phases. CONCLUSIONS The ultrahigh-speed video and methodology in this study documented complex three-dimensional foot motions to impact in soccer instep kicks, dynamic foot-ball interaction, and larger peak ball reaction force on the foot that previously estimated. It can be considered that effectual duration to accelerate the ball is roughly three fourths of visually determined ball contact time.

Dynamics of the support leg in soccer instep kicking

Abstract We aimed to illustrate support leg dynamics during instep kicking to evaluate the role of the support leg action in performance. Twelve male soccer players performed maximal instep kicks. Their motions and ground reaction forces were recorded by a motion capture system and a force platform. Moments and angular velocities of the support leg and pelvis were computed using inverse dynamics. In most joints of the support leg, the moments were not associated with or counteracting the joint motions except for the knee joint. It can be interpreted that the initial knee flexion motion counteracting the extension joint moment has a role to attenuate the shock of landing and the following knee extension motion associated with the extension joint moment indirectly contributes to accelerate the swing of kicking leg. Also, appreciable horizontal rotation of the pelvis coincided with increase of the interaction moment due to the hip joint reaction force on the support leg side. It can be assumed that the interaction moment was the main factor causing the pelvis counter-clockwise rotation within the horizontal plane from the overhead view that precedes a proximal-to-distal sequence of segmental action of the swing leg.

Myth and fact of ball impact dynamics in football codes

Kicking is important in all the football codes and impact is the most crucial component of the skill. However, only a few studies have documented the foot to ball impact phase adequately due to low sample rates and methodological issues. This paper reviews these studies in an attempt to better understand foot-ball impact and explores the veracity of impact-related coaching cues. In soccer, the use of ultrahigh-speed video, a new smoothing procedure and ball modelling to calculate the centre of mass of the ball during deformation has allowed for detailed analysis of impact. A number of studies have identified four phases during foot-ball contact. First the foot acts to deform the ball (phase I), followed by ball acceleration until foot and ball speeds are similar (phase II). The ball then begins to reform while still accelerating (phase III). The last phase shows little interaction between foot and ball suggesting no influence on ball speed. Also using ultrahigh-speed video in the punt kick, but with methods largely focusing on average rather than instantaneous analyses of impact, differences in impact characteristics have been found between seniors and juniors, preferred and non-preferred legs, and kick distances and kick types. The four phases evident in soccer kicking were also present in the punt kick and might have similar underlying mechanisms. Differences exist between player perceptions of what is happening at impact and what actually occurs. Coaching advice to extend the time in contact to produce greater ball velocity was not correct but maintaining a firm foot in the punt kick for distance is an appropriate cue. Further, impact phase analysis has been shown to have useful practical applications. A unique impact location on the foot was found in producing a knuckle ball, and using the difference between this and the instep kick as a cue, the technique was successfully learned by a university level player. Finally footwear design to improve resultant ball performance was explored, looking at existing footwear products, application of ball to foot impact research and potential theories applicable to footwear.

Ball impact dynamics during soccer instep kicking

Understanding the characteristics of the collisions between a ball and the player’s body or between a ball and any equipment is important for performance enhancement in ball sports. In soccer, the most typical, important collision is that of ball impact during kicking. Coaches and players believe that to manipulate the foot and the ball motion during ball impact is an essential task to produce a faster resultant ball velocity and a precise ball flight path. For example, a longer contact time between the ball and the foot during ball impact phase has been thought of as an important factor of highly skilled footballers who can produce a faster ball velocity with good ball impact quality. However, to date, the number of studies that have adequately illustrated the dynamics of the foot and the ball in the ball impact phase is limited (Tsaousidis and Zatsiorsky 1996, Tol et al. 2002) because as Nunome et al. (2006) reported, the contact time between foot and ball is very short (typically less than 10 ms) in soccer instep kicking.