Category Archives: general

A new Olympic qualification cycle begins, Rio2016

On May 31st 2014, the qualification period for the Rio2016 Judo tournament began. This is the start for the nations and athletes of the final build-up to the pinnacle event in Judo, the Olympic Games. judobase_bannerAnd this site will be following along closely and exploring the numbers. The qualification system for Rio2016 is similar to that of London2012, in simple terms the 22 men and top 14 women in the world get entry into the games. Then a quota system is used to select players from the ranking list from a wide variety of nations. As with the last Olympic cycle, the IJF Senior World Ranking List is the most important element in an athletes qualification chances.


As with the last cycle we expect to see players approach qualification in different ways. Teams struggled with qualification last cycle and no doubt will again. Although we hope that they have a better understanding of the system than last time around. Only the British have an excuse for not understanding it as last time round they did not need to qualify players; this time the Brazilians have that advantage.


The WRL also affects the seeding at each event, and for the games itself. As such, it is really important for athletes to monitor the WRL and manage their entries to try and get as high on the list as they need to be. The next 6 months will be interesting to see how the better teams have chosen to distribute the athletes. We have seen many of the big names getting rehab since London and many have obviously been taking time out and getting set for the trials and traumas that follow.


I personally am very interested in how strategic entry into events affects the WRL. So, stay tuned as this site will try and be very active for the next two years leading up to Rio2016. A new resource is available to us now also, the newly launched IJF site contains the absolute best data direct from the IJF on every event (its a IJF only ).



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.


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.

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.

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.