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

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

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

RELATIONSHIP BETWEEN 100 M RACE TIMES AND START, STROKE, TURN, FINISH PHASES AT THE FREESTYLE JAPANESE SWIMMERS

The purpose of this study was to examine the relationships between the race performance and elapsed time in each phase composing the race. The races of Japanese top 113 male and 117 female swimmers in the 100 m freestyle event were analysed. For analysis, races were divided into four phases: start, turn, finish, and first and second half of stroke phases. Statistically significant correlations between the total race time and the times of the four phases were obtained (

MOTION CHARACTERISTICS AFFECT EVALUATION BY JUDGES IN HIP-HOP DANCE: KINEMATIC ANALYSIS OF STEP MOVEMENT

The purpose of this study was to extract motion characteristics closely related to high evaluation by judges, through a comparison of “side-step” movement between eight expert and eight non-expert dancers. Their step motions were captured and the head trajectory relative to the centre of mass, face inclination, and time lags among neck, trunk, hip and knee angles were calculated. As a result, a quarter cycle of phase delay between the neck motion and other body parts were observed for the expert dancers. This delay resulted in a large displacement of the head relative to the centre of mass and a large range of motion of the face inclination. The face inclination was highly correlated with the judging score (r = 0.869). Thus, it is assumed these motion characteristics are the most important element of the side-step movement that induces a better impression of judges

A COMPARISON OF GAIT REGULATION STRATEGIES BETWEEN SUCCESSFUL AND FAILED POLE VAULT PERFORMANCE

This study aimed to investigate the difference in gait regulation strategy of pole vault approach runs between successful and failed trials. Five male junior pole vaulters completed full vaulting to 90-95% personal best height. These trials were categorized into successful and failed trials. Step length and the distance from toe to the planting box were obtained using a two dimensional direct linear transformation procedure. In successful trials, standard deviations of the toe-box distance (SDTB) at the last step and take-off of were significantly smaller than those of failed trials (p < 0.05). We observed a clear difference in gait regulation strategy between successful and failed trials, thereby suggesting that to minimize the fluctuations of the tm-box distance immediately before the take-off is a key gait regulation strategy for successful pole vault performance

HIGH-LOADING ABSORPTION CHARACTERISTICS OF NATURAL AND ARTIFICIAL TURFS

The present study was designed to illustrate shock attenuation characteristics of natural turf as a target property for long pile artificial turf (3-g turf) and to compare the property with that of existing 3-g turf systems. A recently proposed new high loading test was conducted to detect the initial state of shock attenuation property of natural turfs with two different bases (sod and sand base) and of 3-g turfs with three different infills (sand, rubber and sand/rubber). Clear differences between these turfs were observed as the natural turfs are having a higher impact damping and a larger hysteresis with plastic surface deformation. Those features would be beneficial in lowering a high load imparted to the human body but might limit player’s performance