KINETICS OF SOCCER SIDE-FOOT KICKING WITH VARIED EFFORT LEVELS

We aimed to illustrate joint kinetics during submaximal effort of soccer side-foot kicking. Side-foot kicks with three effort levels (50, 75 and 100% effort levels based on maximal effort) of eight male university soccer players were captured at 500 Hz while intial ball velocities were monitored simultaneously. Kinetic differences (angular impulses due to resultant joint moments) were clearly illustrated for hip flexion and knee extension thereby supporting the interpretation that the velocity of the distal end of the leg (foot) is controlled in a context of a proximal to distal segmental sequential system similar to instep kicks. Moreover, among joint moments responsible for out of thigh-shank plane motion, hip external rotation moment was found to be systematically adjusted between three effort levels. Additionally, an inconsistent trend was observed for hip external rotation angular velocity, suggesting some kinematic change in particular for the contribution of hip external rotation likely occured in submaximal side-foot kicks

THE EFFECT OF HIP LINEAR MOTION ON LOWER LEG ANGULAR VELOCITY DURING SOCCER INSTEP KICKING

The influence of the hip linear motion on the lower leg kinetics was examined for soccer instep kicking. Five highly skilled club players volunteered and their kicking motion was three-dimensionally captured at 200 Hz. According to the procedure of Putnam (1991), the interactive moment due to the hip linear acceleration (MHLA) acting on the lower leg was extracted. The MHLA exhibited a large positive moment to increase the lower leg angular velocity during the final phase of kicking. This effective action of the MHLA was mostly caused by the upward acceleration of the hip. As the hip motion is exclusively due to the motion of the support leg, it can be assumed that the effective action of the MHLA is most likely due to the support leg motions such as the knee extension motion during kicking

KINEMATICS OF SIDE-FOOT BALL STOPPING TECHNIQUE IN SOCCER

The present study aimed to illustrate the kinematics of side-foot ball stopping in soccer. Eleven male university soccer players performed side-foot ball stops of an air ball fired from a machine from 10 m away. The ball stopping motion was captured using a 10- camera motion capture system sampling at 500 Hz. The changes of foot and ball linear velocities were computed just before, during and after ball contact. Six joint angular motions of the stopping leg were also calculated. The participants demonstrated a distinct draw back of the foot before ball contact after a gentle forward swing. A rapid knee external rotation was also initiated just after ball contacting, suggesting the knee was passively rotated externally. These kinematic aspects may represent significant motion features required for the side-foot ball stopping technique in soccer

PELVIC ROTATION DYNAMICS OF ACCURACY ENHANCED, SUBMAXIMAL EFFORT INSTEP SOCCER KICKING

The purpose of this study was to clarify the kinetic aspects of the pelvic rotation in accuracy enhanced, submaximal effort soccer instep kicking. Fifteen male soccer players conducted instep kicking in a maximal (MAX) effort and a submaximal (SUB) effort with an emphasis on accuracy. Kicking motions were recorded by a motion capture system with a force platform at 500 Hz. The counter-clockwise pelvic rotation decreased significantly in SUB. Also, the interaction torque on the support leg hip joint decreased significantly in SUB. A previous study reported that the interaction torque was the primary factor in producing pelvic rotation. Thus, controlled pelvic rotation seen in SUB is most likely due to a reduced interaction torque acting on the support leg hip joint. It can be considered that to restrain pelvic rotation is a strategy to slow down the foot swing velocity in accuracy enhanced, submaximal effort instep kicking

KINEMATICS OF SOCCER INSTEP KICKING: A COMPARISON OF TWO-DIMENSIONAL AND THREE-DIMENSIONAL ANALYSIS

The influence of two- and three-dimensional filming procedures on the calculation of soccer instep kicking kinematics was examined in this study. The knee angular velocity calculated three-dimensionally was compared with the data obtained from the following two procedures: 1. the angular velocity vector was computed as a perpendicular component to the sagittal plane (2D projection); 2. the angular velocity was computed only from the two-dimensional coordinates (2D standard). A distorted changing pattern was produced by the 2D standard approach which was most likely caused by computing segmental angular velocities from quasi-planar projection. It is suggested that researchers treat with caution any comparisons in the literature between three-dimensional angular kinematics and those computed two-dimensionally

THE PREDICTIVE MODEL OF INTERVAL TIME BASED ON PACING STRATEGY IN A 400 M HURDLES RACE

The purpose of the present study was to verify the reliability of the prediction equation for interval time (the times between hurdles) established from the hierarchical model in the 400 m hurdles. From 155 data samples of previous studies (record range: 47.42–50.99s), regression equations were established to predict each interval time throughout the race (model #1), during the first and latter halves (model #2) and during the first, middle, and last parts (model #3). Leave-one-out cross-validation was used to avoid overtraining for each regression equation. Models #2 and #3 showed better goodness of fit and generalization for each interval time compared to model #1. These hierarchical models are found to be more reliable compared to the non-hierarchical model. The hierarchical model will help to set the pace distribution to achieve the athlete’s target records accurately

INVESTIGATING KEY FACTORS FOR FEMALE PLAYERS TO GENERATE COMPARABLE INTERACTION TORQUE TO THAT OF MALE PLAYERS

We aimed to clarify the kinetic strategy of female players to achieve comparable motion-dependent interaction torque to that of male players during soccer instep kicking. The kicking leg motion of female and male players was captured at 500 Hz. The interaction torque was decomposed into two components due to the kicking leg and the support leg actions using the procedure of Inoue et al., (2013). Female players exhibited significantly smaller counter-clockwise (positive) interaction torque due to the support leg action while the clockwise (negative) component due to the kicking leg action was significantly suppressed in the latter part of kicking than male players. Our findings suggest coaches and female players should pay more attention to the kicking leg posture during the latter part of the leg swing to maintain their effective action of the interaction torque