The Metrics of the Rules of Judo

IJF Rules Wordle
Image From

Judo, like any sport is subject to rules that define the sport and what is and is not acceptable, the rules are the skeleton that the sport builds around. The rules of Judo are relatively simple when compared to some other sports. The sport closest to my heart is Rugby Union which has 196 (or 77 if you cut and paste just the words) pages of rules (admittedly spaciously formatted) compared to Judo’s 29 pages.

The image above shows the focus of the IJF rules based on word density, which can give us an indication perhaps of the importance each of these words has on the sport of Judo. It is good to see that “contestant” and “contestants” are right up there with “Referee”. This places the player(s) the number one priority in the 13,000 (approx) words that make up the Judo rules. So lets look at Rugby Union and see how their notoriously complicated rules stack up against Judo.

IRB Rules
Wordle of the IRB Rules.

You can quickly see that “Player” and “Ball” standout in the (approximately) 39,000 words that make up the IRB Rugby Union rules. What perhaps is interesting is the prominence of the word “Penalty” in the rugby union rules compared to Judo. In our wordle it is difficult to find Penalty (it is visible) or Shido. Does this suggest that penalties are a bigger part of the game of Rugby than the game of Judo? Also interesting is the prominence of the word “referee” in both images, Referee is more prominent in Judo than Rugby, does this suggest that in our rules the Referee is a bigger factor?

Two other interesting words to consider is the word “Area” in Judo, does this suggest that much of the rules of Judo are about the contest area? In Rugby, the word “Scrum” stands out, which is not surprising given the rule changes made to protect the players from serious injuries in that part of the game.

Another look at this data shows us the top five words in the IJF rule book:

IJF Tules Top 5 WordsThis table shows us again the importance of the word Referee and adds to our investigation by showing the distribution of the top 5 words throughout the rule book.

As one might expect, the word referee is more wide spread throughout the rules whilst contestant for example is more focussed in one area.

You might also suggest from this table that the use of the words contestant and area do not coincide very often, suggesting that these items are very seperate within the rules of Judo.

If we look a little more deeply we can see the following:

Total words: 13080
Unique words: 1577
Words that occur once: 654
Words that occur twice: 245
Highest word frequency: 1380
Average words frequency: 8.29

List top 10 words not in the stop word list

Word: Count

referee: 177
contest: 171
contestant: 158
shall 142:
area: 129
contestants: 103
article: 101
judges: 63
competition: 62
position: 55

If we merge “referee” and “judges”, they total 240 occurances and if we merge “contestant” and “contestants”, which comes to 261 occurances. Players (contestants) come in higher than referees, but only by a small margin. From this the  words “position” and and “area” both are of interest due to their relevance in awarding of penalties, calling of Matte etc. What is interesting here is that Shido and Matte do not occur often enough to rank in the top ten words. Susprising perhaps, given the amount of Matte and Shido calls by referees observed in modern Judo.

The obvious next step(s) is to analyse the use of these keywords in the text and draw some conclusions. This is of course beyond the scope of what we want to look at in this article, so lets examine words that matter to players perhaps? So lets look at “Shido”, which is you have been following this site for a while or observe much Judo contest you will know is a major factor in modern Judo in terms of scores, strategy and so forth.

This suggests to us that the word “shido” is being used primarily in relation to a contestant, nothing too exciting there.

The Word Shido only occurs 8 times within the rules of Judo, however we know from observation that Shido occurs frequently within a contest, so these rules are ones that perhaps all players, coaches, referees should learn thoroughly?

It is interesting that a word that only occurs 8 times (out of almost 13,000 words) accounts for around half the scores in Jud(at least according to the research of people like Sikorski et al. (1987) and my own research of the Beijing 2008 Olympic Judo).

So What about Ippon?

Summary: 32 entries found.

End of Contest 20 . Ippon 21 . Waza-ari awasete Ippon
Ippon 21 . Waza-ari awasete Ippon 22 . Sogo-Gachi 23 .
the following actions : i Ippon : shall raise one arm
to shoulder height . iii Waza-ari-awasete-ippon : First waza-ari , then
: First waza-ari , then ippon gesture . iv Yuko :
Article 13 – Osaekomi time Ippon : total of 25 seconds
shall be extended until either ippon or equivalence is announced or
shall be extended until either ippon is scored or the referee
a When one contestant scores ippon or waza-ari-awasete-ippon Articles 20 and
one contestant scores ippon or waza-ari-awasete-ippon Articles 20 and 21 .
Where one contestant has scored ippon or equivalent , he shall
case where both contestants score ippon or sogo-gachi simultaneously the referee
has been no score of ippon or equivalent , the winner
result . Article 20 – Ippon The referee shall announce ippon
Ippon The referee shall announce ippon when in his opinion an
declared the winner . Simultaneous ippon See Article 19 f
. Appendix Article 20 – Ippon Simultaneous techniques : when
. Should the referee announce Ippon during ne-waza in error and
avoided the necessary criteria for ippon , the referee may nonetheless
the referee may nonetheless award ippon or any other score he
authorise the referees to award ippon when the effect of a
altogether . Article 21 – Waza-Ari-awasete-ippon Should one contestant gain a
referee shall announce waza-ari awasete ippon . Appendix Article 21 –
. Appendix Article 21 – Waza-Ari-awasete-ippon Article 22 – Sogo-gachi compound
the four elements necessary for ippon see Article 20 a and
Waza-ari Although the criteria for ippon of largely on the
other three elements necessary for ippon : Examples : i Partially
continue until the announcement of ippon or waza-ari or equivalent in
equivalent in the case of waza-ari-awasete-ippon or toketa or matte .
Sweeping hip throw Hiki-wake Draw Ippon Full point Joseki Head table
An arm-lock technique Waza-ari Almost Ippon Waza-ari-Awasete Two waza-ari score Ippon
Ippon Waza-ari-Awasete Two waza-ari score Ippon Yoshi Continue Yuko Almost waza-ari

Ippon occurs 32 times, 4 times more often than Shido, yet Shido is a much more prevalent score in Judo, what does this suggest about the rules?

This is a very basic example investigation of the rules of Judo, mainly to serve as a demonstartion that it is possible and how we might approach analysis of the rules beyond looking purely at the rules in terms of action on the match. The question is can analysis of the rules as a text document provide insights into Judo that can have a positive efeect on the sport?

Perhaps you have more time (and experience) at examining text and might be able to find some interesting findings in the IJF rule book. Please let me know if you do.


Attack rates in Judo.

The following post is another summary of the work done by Dave Elmore of Wolverhampton University, who is a colleague of mine on the University of Bath Foundation degree. This piece of research was done as part of the Bath course and Dave has kindly allowed me to share it here. For those not aware of the course at Bath, it is a fantastic learning opportunity for any person dedicated to Judo. It covers everything from the Origins and HIstory of Judo to the latest scientific research and modern Judo waza, not to forget Kata also. Applications for the 2010 intake are open now, so please do visit the website and consider signing up.

Scores at 2008 Prague Judo World Cup

What the chart above shows us very simply is when scores were achieved in matches at this event, broken into 30 second segments. This chart is based on the toal number of score across categories. You can see that during the 21-90 second mark the number of scores is reaches a peak, then drops off; followed by another peak at 271-330 seconds.

This data can be interpretted in a number of ways as players, coaches, physiologists and analysts. Tactically, we can look at this and suggest that our training programmes need to prepare our Judo athletes to expect higher work rates at these two peaks. Strength and Conditioning be it in the gym or in the Dojo could be modelled around the structure shown in the chart.

Of course there is more to the story than this, we need to look deeper before making radical changes to our training regimes.
For example, we need to look at the weight category that your Judo athletes are competing in, below are chart is from the -60kg and +100kg categories, does it tell a different story?

Scores Vs. Time 2008 Prague Judo World Cup

The above chart shows some differences between weight categories that are interesting. The +100kg category shows a marked drop off in scoring after the peak at 151-180 seconds. The -60kg players appear to show a more consistent scoring pattern across the duration of the matches. This may be purely due to the physical characteristics of the players in these weights, we do not know.

Both the charts above include all scores in the matches, which is interesting but argueably less interesting that when the decisive, winning score occurs in a match. Luckily, we have this information too.

Winning Scores vs. Time

The chart above suggests that there is a period of risk after around one minute, around three minutes and finally near the end of the match. The numbers of scores in these “hot spots” increases as the match goes on. The “dips” may indicate periods where players are resting? Perhaps we can train players to attack in the dips, where the majority of players are not scoring? This is one perspective of the data at least. Again this is data covering all attacks and all categories, lets look more closely at the data for individual categories.

Judo -60kg winning scoresThis chart shows when the scores that won the matches occured in the -60kg category of the 2008 Prague World Cup. From this we can infer that the period from 211 seconds through 300 seconds is the “hotspot” at which point you are at the greatest risk of being scored against (or of course you have the greatest opportunity for scoring). Players can be trained (potentially) using methods that capitalise on this identified “hotspot”.

Here, for the first time we also see shat scores are occurring when. Shido is sadly the most common score. Let us now look at a entirely new category, the -81kg category.

picture-4This chart of the -81kg category of the 2008 Prague World Cup shows a very different shape to matches. Here there appears to be a steady increase in scoring up to the 181-210 mark, at which there is a sharp decline. There are a variety of ways this information might be used; perhaps if your athletes can be trained to withstand the onslaught leading up to the 211 seconds mark they might profit from planning their own barrage later in the match?

What is also interesting in this category is the large gap between Shido and Ippon scores and Wazari, Yuko and Koka scores. There is also what looks like a clear relationship between the Ippon and Shido scores, the peaks are consistently at the same places. What does this suggest? Why is there a difference between this category and the -60 fighters?

Perhaps at this point it is worth considering the overall scoring rate again, but look at the individual scores rather than an amalgamated chart:

Scores vs. Time

This chart shows some interesting data that might be of interest. For example, the jump in Shido scores at 271-300 might show the penalties that accrue as a player ahead on points defends their lead at the end of a match. It is also clear that Shido is the top socre in this event, followed by Ippon, Wazari, Yuko and lastly Koka.

Perhaps it is data like this that served as proof to the IJF to scrap the Koka in international competition, seeing as it is clearly the least frequest score. Perhaps now that Yuko incorporates (some) Koka a future investigation might have Yuko more frequent than Wazari?

In terms of player preparation, can we apply what the data shows us? Should we be teaching/training Koka Judo? Is it an effective use of training time? Even at the “golden score” (301-420) stage of the fight Koka is infrequent. Should more time be dedicated in training to preventing or generating Shido?

The data from this study is fascinating, and it is interesting to consider the implications it might have in modern Judo preparation and competitive tactics and strategy. This sort of study and our own analysis of it in terms of our own specific situations may highlight potential changes in training or performance Judo that we can implement.

To close, I would like to thank Dave Elmore once more for sharing the data he collected with me and allowing me to share it online. Dave is doing great work which is not only statistical in nature. here in the UK he is perhaps better known for his work in the Advanced Aprenticeship In Sporting Excellence JUDO (and blog). If anyone is interested in enrolling for this course in September 2009 here is a document which gives more information and contact info: what-is-aase-word-doc.


An examination of BJA Dan grades (Part 2)

In this the second part of our examination of the British Judo Association (BJA) Dan grade register we shall look at the dates grades were awarded.

Dan grades awarded from 1960 to 2008

In this chart we see the number of dan grades awarded per year of all levels between 1960 and 2008. You will see there is a sudden jump in the early 1970s, followed by a steady growth (with peaks) ever since.

From the data we are not able to determine the reason for the sudden jump, common sense suggests that this has more to do with recording of data rather than actual changes in the grading structure.

The average (mean) number of Dan grades awarded per year is 237.16 (+/- 125.98).

The Average Growth year on year is 7.4 (+/-  49.24).

It is perhaps interesting that there is a visible increase in the number of Dan grades being awarded, when the “old wives tale” is that Judo is on the decline.

In this second chart we can see which months the Dan grades were awarded, which shows us that March, June and November are when a majority of grades are awarded.

This perhaps suggests the times of regular gradings. January and December we would expect to be less due to the Christmas season. What is surprising is that August is the month with the least grades awarded, it is summer, but personally I would have expected December and January to be lower. perhaps quite a few people grade just prior to the end of the year and after a Christmas break?

Of course, as mentioned in part one of this examination, this data is not complete. One big weakness is that we do not have a record of prior gradings, just the most recent. The data presented is a “snapshot” only of the BJA Dan grade register as of late March 2009.

An examination of BJA Dan Grades (part one).

So far, a majority of the information shared on this site has been about performance Judo and the metrics associated with competition Judo. This is, of course, just a subset of the Judo world, so this article is not about elite performance Judo rather about the demographics of a Judo association.

Future Black Belt
Picture by MikeOliveri

The British Judo Association (BJA) maintains a record of all Dan grades (Black belts and above) within their orgainsation. They also make this  information partially available via their website at which means that I was able to peruse that data and make some basic analysis.

Before we begin, we should consider that the website of the BJA is not kept up to date, the Dan grade register should not be considered accurate. Also, the information is not made available in a easy to access format, you can reach only one record at a time. So to conduct any analysis of the information the first step was to scrape the BJA website and pull the data into a MySQL database where queries could be run. The data scraping process can introduce errors into the information.
Finally, the register provides no information on past grades or if the people listed are alive, deceased, members or retired. There are anomalies in the data such as the total number of entries in the database not equalling the number of grades at each level, this is caused by inconsistencies/errors in the data. This data was collected on March 26th 2009.

Simple descriptive statistics about the BJA dan grade register.

Male Dan Grades:        9941 (84.22%)
Female Dan Grades:        1862 (15.78%)

If we focus on female Dan grades, we can compare this to the general population of the BJA by referring to the BJA 2007/08 Annual Report.

A quick analysis of this data shows the following:

Male:        20226 (75.56%)
Female    :      6541 (24.44%)

Now if we compare these two basic percentages, we see right away that despite women being approximately a quarter of the Judo population, less than 16% are Dan grades. We do not have enough information to make any inferences as to why this is, but we can suggest there is an issue here that needs addressing by the BJA. Why is their an imbalance between male and female when compared to the wider Judo population. Is it a case of institutional sexism, or are there other forces at work, like for example maternity.

The general population also includes children, so we should not read too much into this difference in percentages. However, it does perhaps suggest that the BJA (and Judo more widely) should research this area and try and determine if there is an actual difference and if so, why it is occurring and when.

It would also be interesting to compare these participation levels to other sports such as Tennis, Dance, Rugby, Wrestling, TKD or Karate. We might find that Judo participation levels by females and at the Dan Grade may be good rather than poor. The percentage of girls aged 14-15 that do not participate in any active sports, on a weekly basis, is around 15% to 20%  (Balding, J. (2004). Young people in 2003. Exeter: Schools Health Education Unit.), so how would this fit with our numbers?

The Dan grade register data also has information such as area, club and date of the grading, analysing this information shall be the subject of later posts. You may also wish to take a look at the data yourself, the part that formed the basis of this post is available at it has the data and some nice charts too.

The anatomy of an elite level Judo match (Craig Fallon at 2003 European Judo championships).

Craig Fallon
Photo by M Lee

Recently a colleague of mine sent me a study he conducted some time back observing British fighter Craig Fallon in action at the 2003 European Championships. Dave Elmore analysed all the fights Craig had on the day against Paischer, Uematsu, Morokhovets, Nazaryan and Khergiani. He carefully recorded the time spent in the following categories:

  • Adjusting Judo Gi
  • Gripping
  • Ne – Waza (grappling)
  • Hajime
  • Matte
  • Attacking – Tachi – Waza
  • Defending Tachi – Waza

Dave is the Judo Development officer at the University of Wolverhampton in the UK. He also runs the very good Advanced Apprenticeship Judo Blog. He looked at the data on a fight by fight basis and also overall, which produced the following chart:

As you can see from the chart, very little time was spent by Craig Fallon attacking in Tachi Waza. A majority of the matches was taken up with Ne Waza, Kumi Kata and adjusting Judo suits. Of the 19 minutes and 23 seconds spent in the competition, only 33 seconds of that time was actual attempts at throwing. Now there are lots of reasons for this, not least of all the speeed at which attacks happen. What stands out is the percentage of time that Craig spent fighting for a grip (29.41%), which shows the importance kumi kata perhaps.

31.30% of Craig Fallon’s time was spent in Ne Waza, it would be interesting to conduct a wider study looking at an entire category or event to see if this is a feature of Craig Fallon’s Judo or of light weight Judoka, or not.

The amount of time spent adjusting the Judo suits is also an eye opener, not an area of Judo that I have seen recorded before and as the chart shows quite a large part of the fight was spent just getting dressed (26.57%). Again this may be a feature of the fighting style of Craig and his opponents, it would be interesting to see if this amount of time is consistent across weights and genders.

If these numbers were to be proven to be standard across Judo, then it would have implications for coaching. Kumi Kata is growing in acceptance as an important skill that must be practised, this study supports this idea. This study could be used to justify increasing the amount of time drilling and practising kumi kata in club training sessions.

The amount of time spent adjusting the Judo Gi may also be important in terms of recovery time between segments of action during a match. Further study might provide suggestions to train for shorter bursts of action, or perhaps more grip related training similar to that shown on the Judo-Sport blog recently (via

Dave has kindly provided me with his data and I shall be looking at it in more detail and will post a follow up in a future article.

A quick test of notation reliability.

I am, as some are aware, presently researching the attack rates of athletes in the 2008 Olympic Judo tournament in Beijing. To do this I am notating the attacks made by each athlete and analyzing the results. As with many forms of analysis there are issues to be addressed around the calidity of the data. One of which is how accurate your recording is, in this post I would like to invite you to help my project by notating a short video from YouTube and emailing me your result, this will be helpful so I can see what the variations in the data are. I shall post the findings of this experiment afterwards.

Notation Methodology:

Take a sheet of paper, draw a line down the middle of the page and notate as follows:

On the paper based hand notation form each attack will be recorded as a vertical line “|” if the
opponent does not touch the floor with another part of the body other than the feet. A “+” will be
recorded if the attack does cause the opponent to touch the floor with another part of their body but
no score is given. The form has two columns, one for each player, the “|” is placed in the
appropriate column for each player. If a score was given, no “|” is marked,  a letter indicating the
score is written instead. These are K for Koka,  Y for Yuko, W for Wazari, I for Ippon and P for a
penalty. When Matte was called, the recorder moves down one line on the notation form. If no
attack has been made a horizontal line is recorded “-”, is neither player has attacked, then both
columns have a “-” recorded. Each period between the referee’s “Hajime” call and “Matte” call is
termed a segment and recorded on a separate line on the form.

If you could forward your notation to me ( that would be terrific, it will be interesting to see how many people participate and also how much the data varys between people. I shall keep your data anonymous of course.

Many Thanks,


Ages of medalists at 2009 Judo World Cup events.

Airborn combatIn this post we shall briefly look at the ages of the Judoka competing at the latest Judo World Cup events in Europe. The two events are the 2009 – World Cup – Prague, and the World Cup Warsaw – 2009. Prague was a womens event, Warsaw a mens event.


  • Ages and results were obtained from the JudoInside website for both events.
  • Data was analyzed for medalists only
  • Statistics between winners and silver and bronze medalists is compared.


  • 24.95    Average Age of medalist
  • 34    Max oldest medalist
  • 17    Min youngest medalist

Winners/Gold Medalist:

  • FEMALE:  Average age: 25.14(+-5.67)    Max: 34    Min: 19
  • MALE: Average age: 26.2(+-4.66)    Max: 32    Min: 21

Non-Winners/Silver and Bronze:

  • FEMALE: Average age: 25.15(+-3.62) Max: 31 Min: 17
  • MALE: Average age: 24.4(+-3.62) Max: 33    Min: 20


The sample size for here is very small, a mere 52 data points (of a possible 56).The analysis is in no way comprehensive.

Target age of players to compete in these events:
The ideal target age to be ready to compete in these events is between  19.47 and 30.81 for women and 21.54 and 30.86 for men. How this relates to the 2012 games is a matter of debate, but these target ages suggest either that athletes winning in London will be approximately 28, or that the older athletes competing today will be retired by London 2012, thereby keeping average ages down.

The age span is quite large 17-34, with average winners age being 25-26 years of age. This perhaps indicates younger athltetes need to spend several years at this level before winning. This could be tested by a further examination of ages for those who did not make the medals potentially.

Talent ID:
For countries looking for players to medal at London 2012 this brief analysis could suggest that they need to be focusing on players who are presently around 22 years of age. For the next Olympic games in 2016 a further talent squad could/should be identified who are approximately 18 years old. This could be extended to 2020, 14 years old now.

Statistical Summary of Judo at 2006 Commonwealth Judo Tournament.

The text below is the result of the pilot study that was the inspiration for my BSC. research project at University of Bath on the Beijing Olympic games Judo event. The study looks at the attack rate of players in the 2006 Commonwealth Judo tournament and their success rate. I have posted it previously on but have decided to add it here as it is in keeping with the subject of this site.

Summary of the 2006 Commonwealth Judo Tournament.

At the 2006 Commonwealth Tournament, a study of the attacks,
scores and durations of bouts was made. Eighty-nine bouts were successfully notated. The results
have been collated and analysed and this document is a summary of the findings.
Full details on the study and methodology are being developed so to make them available to
everyone. The hope is that this will encourage others to conduct similar studies.
Descriptive Statistics
Total Fights 89
Total Scores 139(no penalties)
Total Attacks 1305
Total Penalties 100
Total Segments 732
Total Match Time 259Minutes 101.45Recovery time in fights
Total Actual Time 360Minutes 1.14Recovery per fight
Total Possible Contest Time 432Minutes 0.14Between segments
Fights won by Blue 47 53%
Fights won by White 42 47%
Fights won by person who attacks most 61 69%
Fights won by person who attacks least 28 31%
69 33%
21 10%
61 29%
58 28%
Total: 209
Scores per fight (AVG) 1.56
Attacks per fight (AVG) 14.66
Penalties per fight (AVG) 1.12
Segments per fight(AVG) 8.22
Of Actual time on mat 72%
Of time allocated 83%
Scores per segment 0.19
Attacks per segment 1.78
Penalties per segment 0.14
Ippons Scored
Wazaris Scored
Yokus Scored
Kokas scored
(incl Penalties)
Findings for players and coaches:
By averaging out the results of the data collected, we are able to describe an average Judo bout at
the Commonwealth Tournament level.  An average fight at commonwealth level consists of the
Each match is approximately four minutes long, and consists of eight “segments” of action.
Each segment of approximately 30 seconds in duration, with 14 seconds between each segment.
Within each segment we can expect 1-2 attacks only before Matte is called.
We can expect a score every 7-8 segments, this score will be Ippon 1/3rd of the time. The other
two thirds of the time it will be divided almost equally between Koka & Yoku. Wazari will be
scored infrequently (only 10% of the overall scores).
Given this description of an average match, we are able to develop coaching strategies and
training sessions to best simulate commonwealth level Judo. Sessions could be developed
following approximately the following format.
Endurance drill:
Athlete attacks at near maximal level for 30 seconds.
They then recover for 14 seconds
The above two steps are repeated 8 times.
This drill helps develop the athletes ability to give maximum effort for entire match for difficult
Tactical Drill:
Athlete fights for grip for 10 seconds
Coach calls “NOW”, and athlete must make one large attack
Athlete then continues to grip fight for 10 seconds
Coach calls “NOW”, and athlete must make one large attack
Athlete recovers for 14 seconds
Repeat above steps eight times.
This drill trains the athlete to make maximum use of the available time. Minimising risk of
passivity attacks whilst keeping energy expenditure minimal.
Active defence Drill:
Athlete is attacked constantly for 30 seconds, they must only defend.
At 10 seconds the coach shouts “NOW”, the athlete must make some form of positive attack.
At 20 seconds the coach shouts “NOW”, the athlete must make some form of positive attack.
At 30 seconds the coach shouts “NOW”, the athlete must make some form of positive attack, this
attack must be “terminal”, concluding on the floor or outside safety area.
Recover for 14 seconds
Repeat above steps eight times.
This document is a very basic analysis of a small amount of information from the 2006
Commonwealth Tournament. It is hoped that this documents shows how this form of study and
analysis can provide interesting insights which can be applied to training programme
Further analysis of the data is under way and a more detailed document will follow.
The use of simple mean averages provides generalised information which provides only an
indication of general trends in the data analysed. This needs to be considered when developing
training programmes.
For example, the four minute figure mentioned in this document is a mean average of all the
fights recorded. The range of durations went from a few seconds to over twelve minutes spent on
the mat.
Similarly, the mean averaged number of segments, covers all stages in a competition. Initial
examination of the data showed a visible change in contest structure in the later stages of a
category. This included more segments, hence more attacks, but with each segment being sorter.
Your athlete may be better served by drills that followed this pattern over the average format of a
Commonwealth level Judo match
Full details of this research are available via the
website and/or by contact the author, Lance Wicks, directly at the email
address: Fellow researchers are invited to contact Lance
Wicks to source the data and digital copies of the notation forms, etc.
It is hoped that this research will act as a catalyst, encouraging further
research within the sport by researchers both with and without experience.
Kia Kaha, Kia Toa, Kia Manawanui
Be brave, Be Strong, Be Perservering
(Old New Zealand Maori Saying)
(c)2006, Lance Wicks.

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JudoMetrics: Re-stating my assumptions.

Recently I have been involved in two conversation threads related to, but seperate from this site. The first was about my BSc. research project notating the attack rate of Judo athletes in the Beijing Olympic Judo Tournament. The second is a thread about Talent Identification in Judo and generally. Also there have been a couple of posts in the Judo Blogosphere about Malcolm Gladwells “Outliers” book that helped inspire this post.

In both conversations my response has been that if we can identify the factors needed, then we should be able to predict future results. As per Max Cohen in the movie Pi, I decided to “re-state my assumptions” as I think it will help set the context for this website better for visitors.

Assumption 1: If we can identify the right metrics, we can predict results.

So, what I mean is if we knew what caused a player to win a Judo match, then we could track this for two players before (or during) a match and predict the victor.

Evidence: If player 1 has beaten player 2 ten times in ten matches, then we could fairly comfortably predict that player 1 will beat player 2 in their next match. If player 3 has won all their pre-liminary fights by Ippon we can start predicting that Player 4 will lose to player 3 by Ippon.

The “ah yes, but…“:

The problem is that Judo is very complex, (argueably) more so than other sports. In Rugby Union for example, the team that retains possesion and territory will generally win. It is not always the case, but it is a performance metric that works in a sport where there are (again argueably) more variables to consider than in Judo. There are 30 players not 2 (more if you count subsitutions), there is weather conditions etc. Yet the simple metrics of possesion and territory can give a pretty good prediction of results.

So rather than say it is not possible to predict Judo using metrics, I argue that it is possible and that we just have yet to research well enough to find the metrics that matter.

Whether we ever are able to measure enugh worthwhile information to predict results of individual matches… we shall see. Also, whether we will be able to use these metrics for anything other than academic use is questionable also. I am not sure that we can coach players to fight certain ways as the statistics say it will result in a victory. So perhaps Judo metrics will never be an “applied science”.

Personally, I suspect that performance metrics will prove useful.
Assuming we can discover the right things to measure and we are able to interpret the results appropriately. “Knowledge is power” they say, we already know that countries like Germany and France are compiling information/knowledge about the players their players will meet, in terms of throws they use etc. It is not that big a leap from this to them also collecting statistics on throw frequencies and scoring ratios etc.

I suspect that we could increase our success in Judo if we were able to analyze more knowledge (metrics) about players from other countries.

Talent ID and Judo Metrics

I believe that we can predict the result of matches through Judo metrics, I also believe that we can/could predict who would be a good Judoka; if we can assess enough variables. We may not be able to predict accurately, but we could identify likely candidates. We have some evidence to support this via the soviet era sport and more recently in China.


It may well be the case that JudoMetrics is as realistic science as Psychohistory and it may well be “bunkum“, but IMHO it is worth researching further, at least to a point where we have a better view of it and can decide if it is the future or snake oil. It may be that on this site I am pursueing an idea as mad as Max Cohen’s in Pi…  time will tell.

The International Judo Federation (IJF) Ranking system.

This weekend (25 January 2009), the first of the events of the IJF ranking system will be held. The new system of ranking is important as it shall decide who can attend the London 2012 Olympic Judo tournament. In this post we shall take a good look at the system…

IJF Ranking Points System.
IJF Ranking Points System.

As you can see from the table, athletes are awarded ranking points depending on the position they reach and the event they are competing in.

So, win the World Championships and get 500 points, win one of the new masters events and get 400. Third in my native OJUs and you’ll get 32 points.

Come 30th April 2012, the players ranked in the top 22 for men, or top 14 for women (per category) are the qualifiers for the London Olympics.

The system gets more complicated from here on in, only the top 5 results per year are counted. So if you were to win the 2009 World Cup, Grand Prix, Grand Slam, Masters,World Championships and the OJUs; you would receive 1400 points. However, these points will not actually be worth 1400 in 2012, they will in fact only be worth 350 points as the points “degrade” by 25% per year (The dividing line is the beginning of the month in which the tournament ‘s first
competition day, was held).

Now the rest of the places in the games will be chosen by the Continental unions. Each continental union gets half the number of National Federations affiliated to each that union. So the EJU which has 50 member states and would receive 25 places for athletes who do not make the top 22/14.  These will be decided basically by the top points scorer in the continent, until the fill quota is used, with a maximum of two athletes per category being qualified by this method.

The new system starts with all athletes having zero points. So this weekend is the first opportunity for them to start qualifying for 2012.
It is however based on the result in the tournament not on the athletes you beat. If you happen to have the easiest draw in history at the World Championships it is worth just as much as if you fight all the top athletes in your category. Will this work well is to be decided, I have not seen what research was done in deciding on this system.

Personally, I am more in favour of a system like the ELO system used in Chess (and online gaming like Xbox Live). The ELO system takes into consideration the probabilities involved in one athlete beating another. If a player who is much lower on the ELO ranking beats a higher ranked player, they receive a larger number of ranking points than if they beat someone below them. It is my intention, if I can obtain all the draw sheets, to run the ELO system and monitor the rankings to see if it ranks athletes over the 4 years differently.

A site devoted to developing metrics for Judo by Lance Wicks.