Fundamental Study on Teaching for the Soccer Basic Skill (I)

Electromyographic Study on Instep Kicking with Swing Speed and Ball Speed as Criteria

Abstract

With five players from the Kansai Student Soccer League and one untrained player as subjects, control of ball speed when kicked at various speed by the instep kick was studied from the point of view of muscle action.
Speed of the swinging leg before contact with the ball and subsequent velocity of the ball were measured, and at the same time the activities of 14 muscles in the leg, trunk, and arm on the kicking side were recorded. The kick form was also recorded by 16mm cinematography.
With all of this information, the role of skill in the relation between swing speed and ball speed was investigated.
1) Correlation between swing speed and ball speed was high in proportion to the level of skill of the player. The more skillfull the player, the steeper the slope of the regression line. This means that the correlation coefficient reflected consistency in skill and the slope of the regression line revealed the level of skill.
2) To maximize swing speed, active hip flexion and knee extension during the forward swing appeared to be important factors. Thus the activities of muscles crossing these two joints would control the ball speed.
3) Maintaining activity in the knee extensors and hip flexors up to the point of ball impact, and also fixating the foot in plantarflexion, were important in effectively transmitting the momentum acquired during the forward swing into the ball.
4) In kicks in which ball speed was relatively low for a given swing speed, the maintenance of muscle activities up to the point of impact was lacking. This was especially prominent in the ankle and knee musculature of the untraind player.
5) In the skilled players, the movement of hip flexion was momentarily delayed just as the foot was in impact with the ball. This could be considered a “whipping action” as the momentum of the thigh was transmitted into the forefoot.
6) Active knee extension, delay in the hip flexion motion at ball impact, and fixation in ankle plantarflexion were all lacking in the untrained player. After five months of practice, however, the correlation between swing speed and ball speed in this player increased, as well as the slope of the regression line. This player's form and muscle activity also came to more closely resemble that of the skilled players.