Developmental differences of kinematic and muscular activation patterns in instep soccer kick

Kinematic and neuromuscular activity differences amongst soccer players in different age groups were examined in this study. Thirty male soccer players evenly divided into three age groups (Group 1: age 12-13; Group 2: age 14-15; Group 3: age 16-17) were asked to perform instep kicks towards a target 11 m away. Their anthropometrics, instep kick kinematics, resultant ball velocities, both legs isokinetic strength, and electromyography (EMG) during kicking were compared amongst the three age groups. There were significant differences in height, body mass, body mass index, ball velocities, and isokinetic strength values amongst three age groups. Also, kicking kinematics including angular and linear velocities of hip, knee, ankle, and toe were significantly different (p < 0.05) amongst groups in several kicking phases. Furthermore, the activities of m. rectus femoris, m. vastus medialis, m. biceps femoris were significantly different amongst groups (p < 0.05). The ball velocities and leg strength parameters increased with age, neuromuscular activations, and kinematic parameters differed especially in leg-coking and forward swing phase of instep soccer kick. It should be concluded that an increase of resultant ball velocity of the instep kick is closely associated with chronical age, the development of leg muscle strength, and the neuromuscular activity of the kicking leg.