Rodney T. Imamura1, Misaki Iteya 2, Alan Hreljac1 and Rafael F. Escamilla1
1- California State University Sacramento, Department of Kinesiology and Health Science, Sacramento, CA, USA
2 - Tokyo Gakugei University, Japan
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 toriís trunk (TAV). Data were smoothed using a 4th order zero lag utterworth 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.
Ukeís 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 toriís COM were larger during the noncompetitive condition since ukeís resistance was minimal. Findings of the competitive condition suggested that mediolateral COM movement towards toriís pulling (left) hand can be an ideal set-up movement prior to execution. Toriís 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 power.
Key words: Biomechanics, Harai-goshi, kinematics, judo, throw, velocity.