Le judo : une éducation pour faire face à l'incertain ? Le cas des compétitions sans catégories de poids pour les enfants au Japon

Etude des conditions d'organisation et de la signification culturelle des compétitions de judo pour les enfants sans catégorie de poids de Kan Nai, emblématiques d'une éducation que le Japon souhaite réhabiliter

Dynamic Control of Upper Limb Stretch Reflex in Wrestlers

Purpose The objective of this study was to clarify the characteristics of the upper limb stretch reflex in wrestlers. Methods Ten wrestlers and 11 control subjects participated in the study. The experiment was divided into two sessions. In the extension perturbation session, participants either relaxed or flexed the elbow when they felt a perturbation (abrupt elbow extension induced by a dynamometer). This was done 30 times by each subject for both sessions. In the flexion perturbation session, participants also relaxed or extended the elbow when they felt a perturbation (abrupt elbow flexion). During the tasks, the stretch reflex was monitored by recording the surface electromyographic (EMG) activities of the right biceps and triceps brachii. The EMG reflex components were divided into three periods based on the time after the perturbation: M1=20 - 50ms, M2=50 - 80ms, and M3=80 - 100ms. The averaged background EMG activity just before the disturbance was subtracted from the EMG activity in each period. The resultant value was integrated to obtain reflex magnitudes of M1 - M3. Result For the triceps brachii, in the relaxation task, the wrestler group showed a significantly smaller value for M2 than did the control group. In the extension task, the wrestler group showed a significantly larger value for M3 than did the control group. There was no difference in M1 between the two groups. For the biceps brachii, there was no significant difference between any reflex components. Conclusion Our results suggest that high level wrestlers have specific characteristics of the long latency stretch reflex in the triceps brachii that are modulated in a situation-specific manner

A KINEMATIC COMPARISON OF THE JUDO THROW HARAI-GOSHI DURING COMPETITIVE AND NON-COMPETITIVE CONDITIONS

The purpose of this study was to compare the kinematics of kuzushi/tsukuri (KT) phases of the harai-goshi throw under competitive and non-competitive conditions. A third degree black belt subject served as the tori (thrower) for both conditions. Two black belt participants ranked as first degree and fourth degree served as the uke (faller) for the competitive and non-competitive conditions, respectively. Two video cameras (JVC 60 Hz) and a three dimensional motion analysis system (Vicon-Peak Performance Technologies, Inc., Englewood, CO) were used to collect and analyze peak velocity for the center of mass (COM) of uke and tori and peak angular velocity of tori's trunk (TAV). Data were smoothed using a 4th order zero lag Butterworth filter with a cut-off frequency set by the Peak software optimization technique. All variables were normalized by time as a percentage of the KT phase. In general, the COM directional velocity patterns were similar between conditions. Uke's defensive efforts during the competitive condition created differences in timing and magnitude of peak COM and TAV velocities. During competition, tori created larger peak COM velocities onto uke which indicated greater throwing power. Peak velocities for tori's COM were larger during the non-competitive condition since uke's resistance was minimal. Findings of the competitive condition suggested that mediolateral COM movement towards tori's pulling (left) hand can be an ideal set-up movement prior to execution. Tori's TAV was also greater during the competitive condition. Two distinct TAVs were observed, a counterclockwise TAV created by tori turning their hips during the entrance of the throw and a clockwise TAV created by the shoulders turning to complete the 180 degree body turn with the simultaneous leg sweep. It is thought that the counterclockwise rotation aids in producing a pre-stretch of trunk muscles which helps to create greater trunk rotation powe