Author(s): NAMIMATSU, D., KIMURA, A., Institution: HOSEI UNIVERSITY, Country: JAPAN, Abstract-ID: 2680

INTRODUCTION:
Scoring success depends on how quickly an athlete can respond to an opening in their opponent’s defense and execute a technique to the target in karate kumite (Mori et al., 2002).
Kizami-tsuki is one of the most frequently used scoring techniques (Chaabène et al., 2014). Therefore, the time required to execute kizami-tsuki is a major factor influencing match outcome.
The time of Kizami-tsuki is the sum of the reaction and movement time. Skilled athletes generally demonstrate shorter reaction and movement times than novices (Layton et al., 1993). Individual differences in these time components among skilled athletes and the mechanisms by which time components are reduced remain unclear, although skilled athletes demonstrate superior performance.
Skilled athletes with similar reaching times may include reaction-dominant types with shorter reaction times and longer movement times, as well as movement-dominant types showing the opposite pattern. This study aimed to clarify individual differences in reaction and movement time among skilled karate athletes during the kizami-tsuki technique, and to examine how skilled athletes shorten these times.
METHODS:
Eleven competitive college karate players conducted a kizami-tsuki toward a sandbag ten times. They were instructed to reach the fist to the target as quickly as possible when the light came on. Whole-body movement and ground reaction forces were measured using a motion capture system (VICON MX, Vicon Motion Systems) and two force plates (Custom FP, Bertec Inc., Ohio, USA), respectively. Reaction and movement times were computed from the motion capture data. These times were converted to Z-scores for normalization, with subjects being classified as either the reaction-dominant or movement-dominant types.
Additionally, the velocities of the center of mass (COM) and fist were calculated from the motion capture data to investigate biomechanical factors associated with movement time. Pearson correlation coefficients were used to examine the relationships between movement time and peak COM and fist velocities.
RESULTS:
A reaction-dominant type was 3 participants, and a movement-dominant type was 8 participants. Movement time was not significantly correlated with fist velocity (r = −0.14, p = 0.67) but showed a significant positive correlation with COM velocity (r = 0.64, p = 0.03).
CONCLUSION:
The results indicate the presence of reaction-dominant and movement-dominant types among skilled athletes. These findings suggest that the process for reducing reaching time is not uniform.
In addition, athletes with high COM and fist velocities did not necessarily show shorter movement times due to factors such as having more time to reach peak velocity and performing preparatory movements.
Rapid velocity generation and movements without preparatory actions may contribute to shorter movement time in kizami-tsuki.
The findings of this study may contribute to the development of athlete-specific performance evaluation and training design.