Author(s): OGISO, G., KITAMURA, M., KAMIBAYASHI, K. , Institution: DOSHISHA UNIVERSITY, Country: JAPAN, Abstract-ID: 787

INTRODUCTION:
In basketball, there has been extensive discussion about the effectiveness of changing defense systems mid-game. Such "changing defense" employs various defensive tactics during a game, such as man-to-man defense and zone defense, with the aim of catching their attacking opponent by surprise.
In fact, this strategy is commonly utilized not only at world tournaments such as the Olympics and the World Cup but also at the university level in Japan. However, the decision to implement changes in defense during a game often relies on subjective judgments of coaches and managers. Although there are numerous references to the changing defense in instructional books, including Smiths book [1], its effectiveness remains unclear without rigorous game analytics.
Therefore, this study aimed to quantitatively evaluate the effectiveness of changing defense on the opponents offensive performance in university mens basketball games held within the Kansai region (south-central part) of Japan.
METHODS:
The analysis focused on closely contested games (defined as games with difference up to 8 points at the end of the third quarter and 12 points at the end of the game) in the first division of the 2021/22 Kansai region (south-central part of Japan) Student Basketball League. A total of 35 games met the analysis criteria. From the game video, we identified which of the four main defensive systems was employed for each ball possession: man-to-man defense, zone defense, press defense, or mixed defense. In addition, the number of passes and elapsed time to a shot were examined for each possession. Turnover percentage, free throw rate, and points per possession extracted from the four factors [2], as well as shot clock duration (evaluated as time taken to shoot) and the number of passes were averaged for the opponents offenses against man-to-man defense, the opponents first offense after a change from man-to-man defense to a different defensive system, and the opponents second and third offenses after changing the defense.
RESULTS:
The results revealed a statistical advantage associated with the changing defense: immediately after the changing defense, the opponents offense had more time to shoot, and the free throw rate dropped. In addition, it was numerically evident to induce opponents turnovers and reduce the expectation of scoring immediately after the changing defense.
CONCLUSION:
The findings of the present study indicated the effectiveness of changing defense in limiting the opponents offensive performance, especially immediately after the change.

REFERENSES
1. Smith, Dean, and Bob Spear. Basketball, multiple offense and defense. (1982).
2. Oliver, Dean. Basketball on paper: rules and tools for performance analysis. U of Nebraska Press, (2011).