| 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 power.
KEY
WORDS: Biomechanics, Harai-goshi, kinematics, judo, throw, velocity.
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