Effects of the International Judo Federation Referee Rules on Competition Contents in theAll-Japan Judo Championships: A 2008–2013 Comparison
Keisuke MIYAKE1, Takashi MATSUI2, Takeru SATO3, Yoshihisa ISHIKAWA4, Takayuki YOKOYAMA5,Toshihiro TAKEZAWA6, Kenji KAWABATA7, Hiroyuki AKIMOTO8, Shinichiro SATO9
1

Chukyo University, 2 JSPS Research Fellow (SPD), 3Kogakkan University, 4Nagano National College of Technology,

5

Setsunan University, 6Kanto Gakuen University, 7Hokuriku University, 8Ryotokuji Gakuen, 9Takushoku University

Introduction
The All-Japan Judo Championships (AJJC) is an open-weight tournament for determining the best judoka in Japan.
AJJC has been held under the Kodokan Judo Referee Rules (KDK Rules) since 1951. In 2011, the All-Japan Judo
Federation (AJJF) introduced the International Judo Federation Referee Rules (IJF Rules), which were formulated tofacilitate more dynamic judo (increased wins by Ippon, decreased wins by judges’ decision, and stoppage time).
Previous studies have examined the changes and trends of dynamic Judo for international matches like the Olympics
and World Championships by introducing the IJF Rules2, 3). Although the IJF Rules have facilitated dynamic judo ininternational competitions, the effects of the IJF Rules on the competition contents in the AJJC are still unknown.
Here, we aimed to clarify whether the introduction of the IJF Rules facilitated dynamic judo in the AJJC.

Methods
The 221 judo matches in the AJJC from 2008 to 2013 were separated into two groups: the KDK Rules’ tournaments(2008–2010) and the IJF Rules’ tournaments (2011–2013). These tournaments’ data were extracted from the AJJC
records by Judo, the official Kodokan journal, and from the match movies recorded by the AJJF. The proportions ofwinning contents (wins by Ippon or superior performance) and winning methods (points from techniques, penalties,
or judges’ decisions), techniques for getting points (Te-waza, Koshi-waza, Ashi-waza, Sutemi-waza, or Katame-waza)
and the match duration and stoppage time (match duration subtracted from net match time) for each match wereanalyzed. A chi-square test, a residuals analysis and an independent t-test were used to perform statistical analyses,
and for each test, statistical significance was assumed at P value < 0.05.

Results and discussionFor the winning contents of the IJF Rules’ and the KDK Rules’ tournaments the proportion of wins by Ippon (39.1%vs. 49.5%) and wins by superior performance (60.9% vs. 50.5%) showed no differences (Fig. 1). The studies byNakamura2) and Sakamoto3) have reported that wins by
Ippon generally occur in more than 50% of the men’smatches in the Olympics or World Championships. In
addition, wins by Ippon have comprised up to 70% of
the matches because of the promotion of dynamic Judo.
Therefore, for the AJJC it is necessary that wins by
Ippon will increase in order to promote dynamic Judo.

Also, the techniques for getting points and the match duration showed no differences between the IJF Rules and theKDK Rules tournaments.
However, the winning methods of the IJF Rules’ and the KDK Rules’ tournaments, the proportion ofpoints from techniques (60.4% vs. 53.6%) and points from penalties (23.4% vs. 15.5%) showed no difference, but
the proportion of wins by judges’ decisions in the IJF Rules’ tournaments was significantly lower than in the KDK
Rules’ tournaments (16.2% vs. 30.9%) (P < 0.05) (Fig. 2). The reason why judges’ decisions decreased can be seenin the increasing existence of “instructional cautions” because the lack of “combative spirit” makes up 70% of all
penalties. This can be undoubtedly seen as an effect of the introduction of the IJF Rules. In addition, the fact that thetiming of assigning penalties by the referees got faster and the instruction not to penalize both judoka at the sametime can be also seen as decisive reasons.
In addition, the stoppage time in the IJF Rules’ tournaments was significantly shorter than in the KDKRules’ tournaments (77 s vs. 105 s) (P < 0.01) (Fig. 3). In 2003, the IJF decided that it is not necessary for the judoka
to come back to the starting line for restarting the fight with “Hajime” to shorten the stoppage time. In addition, thereferees either have to come back to their starting position and moreover, the injury time was also abolished1).
Therefore, the stoppage time could be increased significantly.

Conclusion
Our results revealed that the introduction of the IJF Rules did not affect the winning contents, including wins byIppon, techniques for getting points, and match duration, but decreased the proportion of judges’ decisions andstoppage time in the AJJC. These findings suggest for the first time that the IJF Rules partially facilitated dynamic
judo in the AJJC.

References
1) Isamu Nakamura: Kokusai jūdō no genzai, Junia sensyu ikusei no tame no jūdō kōchingu ron, Dōwasyoin,
178-192, 1st., 2008.
2) Isamu Nakamura et al.: 2003 nen sekai senshukentaikai no kyōgi bunseki: 1995 kara 2001 nen taikai to nohikaku, Jūdō kagaku kenkyū, [Scientific Research on Judo], 9, 1-6, 2004.
3) Michito Sakamoto et al.: Orinpikku jūdō kyōgi no kyōgi bunseki: 1992 nen kara 2000 nen taikai wo taisyō toshite, [Analysis of Olympic Judo: A Trend of the Judo Event 1992 to 2000], Daigaku Taiiku Kenkyū, [Journal ofSport and Physical Education Center University of Tsukuba] , 28, 15-22, 2006.