Biomechanics of Kuzushi-Tsukuri and Interaction in Competition

Abstract: In this paper it is performed the comparative biomechanical analysis of the Kuzushi (Unbalance) -Tsukuri (the entry and proper fitting of Tori's body into the position taken just before throwing) phases of Judo Throwing techniques. The whole effective movement is without separation, as already stated by old Japanese biomechanical studies (1972 -1978), only one skilled connected action, but the biomechanical analysis is able to separate the whole in didactic steps called Action Invariants. The first important finding singled out is the existence of two classes of Action Invariants the first the General one' connected to the whole body motion is specific of shortening distance in the Kuzushi Tsukuri Phase. The second one, the Specific Action Invariants is connected to the superior and inferior kinetic chains motion and right positioning connected both to Kuzushi and Tsukuri phases. Some interesting findings derive from this analysis: among throwing techniques, couple techniques could be independent from Kuzushi; instead physical lever groups need all two action invariants to be performed successfully and as complex motor skill they are more difficult to perform than the first ones. Complexity in motion is connected to the energy consumption, and to the skill ability of athletes. This biomechanical comparative analysis is useful from the didactic point of view, clarifying the basic mechanical steps of all throws, and showing also hidden connections, similarities and differences among throwing Judo techniques. The last part of the paper concerns the study on Interaction in Competition, performed by the author, showing 20 years results on Judo Biomechanics.