Judo looks gentle. Two people in soft cotton jackets bow before they grab hold, then fall in a controlled arc onto a padded mat. That surface impression is exactly why so many parents, gym-seekers, and casual observers assume judo is the safe, low-contact alternative to boxing or wrestling.
The surface impression is wrong in one important way. Judo is a full-contact combat sport with real forces, real falls, and real injury data behind it, and its reputation for gentleness describes its etiquette, not its physics.
Judo is a Japanese combat sport and martial art founded in 1882 by educator Jigoro Kano, built around throwing an opponent to the ground (nage-waza) or controlling them there through pins, chokes, and joint locks (katame-waza). It has been a full Olympic sport since 1964 and is practiced under standardized international rules by federations in more than 200 countries.
- What it is: a grappling combat sport centered on throws, pins, chokes, and armlocks, with strikes preserved only in choreographed forms, not live sparring or competition.
- Origin: developed in Japan starting in 1882 by Jigoro Kano, who combined older jujutsu schools under a philosophy of efficient movement and mutual benefit.
- Core technique domain: nage-waza (throws) and katame-waza (pins, chokes, and joint locks), organized under the Kodokan's classical technique lists.
- Ranking in one line: student ranks (kyu) count down toward black belt, then dan grades count up from 1st, with 6th to 8th worn on a red-and-white belt and 9th to 10th on solid red.
- Competition status: a permanent Olympic sport since 1972 after a one-off 1964 debut, governed internationally by the International Judo Federation.
- Who it tends to suit: people who want a structured, high-feedback grappling sport with a clear belt path and a strong falling and control curriculum, more than people looking for a purely low-impact hobby.
A Discipline Built From Older Systems: History and Founding
Jigoro Kano was born October 28, 1860, in Kobe, Japan, and died May 4, 1938. A graduate of Tokyo Imperial University, he founded judo at the Kodokan in 1882, a school he opened at the Eisho-ji temple in Ueno, Tokyo, with 9 disciples training on 12 mats. The exact founding date within 1882 is not reliably documented in any source worth trusting, so it is more honest to say "1882" than to pin it to a specific day, and this article will not invent one.
Kano did not invent judo's techniques from nothing. He drew chiefly from two older jujutsu schools, Tenjin Shin'yo-ryu and Kito-ryu, and reorganized their throws and grappling methods around a teaching system with graded ranks and standardized practice. The choice of the word "judo," using "do" (way or path) instead of the older "jutsu" (technique), was deliberate. Kano wanted his system read as an educational and moral discipline built through combat training, not simply a fighting method passed down for its own sake, as detailed in the IJF Hall of Fame entry on Jigoro Kano.
Kano's influence went well past his own dojo. He became the first Asian member of the International Olympic Committee (IOC) in 1909, led Japan's first Olympic delegation to the 1912 Stockholm Games, and returned as a delegation leader in 1928, 1932, and 1936. In 1911 he founded Japan's first national sports body, the Japan Amateur Athletic Association. The Kodokan itself grew alongside his career: from 12 mats in 1882 to 40 by 1887, 107 by 1894, and 314 by 1898. Today's Kodokan headquarters in Bunkyo, Tokyo, has 1,206 mats, a physical record of how far the school scaled in under a century and a half, a growth curve documented by the University of Tsukuba's institutional history of Kano, who taught there in an earlier form of the institution.
- Growth on paper: 12 mats (1882) to 1,206 mats at today's Kodokan headquarters.
- Growth in reach: 1909 IOC membership, four Olympic delegations, a national sports federation founded in 1911.
- Growth in who trained: women admitted from 1926, with Keiko Fukuda, who reached 6th dan in 1972 and 8th dan in 1994, becoming the first woman in judo's history to hold 9th dan from a recognized judo body, awarded in 2006, two years before her death.
The 1886 Tokyo Police Tournament
Judo's early legitimacy rests heavily on one contest: a tournament in 1886 that pitted the Kodokan against the rival Totsuka-ha Yoshin-ryu jujutsu school, organized so Tokyo's police could decide which system to adopt for officer training. The Kodokan won decisively enough that it shaped how Japanese institutions viewed judo for a generation.
What the exact score was is genuinely contested. One account has the Kodokan winning every match but one, which ended in a draw. Another puts the record at 13 wins and 2 draws. Popular retellings tend to round this into a suspiciously clean "won every single match," which overstates what the sources actually agree on. What both versions agree on is the direction and scale of the result: a near-total win that established the Kodokan's reputation over its established rival.
A near-clean sweep and a genuinely clean sweep tell almost the same story, but only one of them is actually documented.
The Technique System: Throws, Holds, and What's Left Out of Competition
Judo sits within the broader family of grappling arts, sports and systems built around clinching, throwing, and ground control rather than striking. Its own technique catalog divides into three broad categories, and only two of them show up in live practice. Nage-waza (throwing techniques) covers everything used to put an opponent on the ground: te-waza (hand techniques), koshi-waza (hip techniques), ashi-waza (foot and leg techniques), and sutemi-waza (sacrifice throws, where the thrower drops their own body to generate throwing power). Katame-waza (grappling techniques) covers what happens once the fight reaches the ground: osaekomi-waza (holding or pinning techniques), shime-waza (strangulation techniques, or chokes), and kansetsu-waza (joint-locking techniques). Competition joint locks have been restricted to the elbow only since 1925, a rule that still holds today.
Short answer: judo removes striking from live sparring and competition, but preserves it inside kata. Atemi-waza (striking techniques, including strikes, kicks, and thrusts at vulnerable points) exist in the classical curriculum and are practiced in choreographed forms, never in randori (free practice) or shiai (competition), where the safety risk would be unacceptable.
The classical reference list of throws, the Gokyo no waza, organizes 40 throws into 8 groups of five. The Kodokan's fuller modern technique list is commonly cited at 67 throws, though a single primary Kodokan document listing exactly that number was not something this article could independently pin down, so treat that figure as widely repeated rather than beyond dispute. Two principles hold the whole system together, and Kano treated them as more than slogans: Seiryoku Zen'yo, maximum efficient use of energy, mind, and body, is the idea that a throw should work by redirecting an opponent's force and balance rather than overpowering them, and Jita Kyoei, mutual welfare and benefit, is the idea that training partners improve together rather than at each other's expense. Both principles explain why judo reads differently from a pure fighting system built only around winning individual exchanges.
| Category | Japanese term (plain gloss) | Examples | When used |
|---|---|---|---|
| Throws | Nage-waza (throwing techniques) | Hand, hip, and foot/leg throws, plus sacrifice throws | Randori and shiai (competition) |
| Pins | Osaekomi-waza (holding techniques) | Hold-downs scored for sustained control on the mat | Randori and shiai |
| Chokes | Shime-waza (strangulation techniques) | Collar chokes, arm chokes | Randori and shiai, adult competitors |
| Joint locks | Kansetsu-waza (joint-locking techniques) | Armlocks targeting the elbow only | Randori and shiai, elbow-only since 1925 |
| Strikes | Atemi-waza (striking techniques) | Strikes, kicks, and thrusts at vital points | Kata only, never randori or shiai |
Kime-no-kata and the Self-Defense Curriculum
A common claim about judo is that it is "just a sport" with no real self-defense content, since competition strips out strikes and restricts joint locks to the elbow. That claim skips over a large part of the curriculum. Kime-no-kata, developed at the Kodokan around 1888, is judo's dedicated self-defense form: 20 techniques, 8 practiced kneeling and 12 standing, that explicitly include atemi-waza against both armed and unarmed attacks. The Kodokan later added a second, modernized self-defense kata, Kodokan Goshin Jutsu, in 1956.
The competition ruleset is a deliberately narrowed subset of a broader curriculum, trimmed for safety in live sparring rather than because the wider system never addressed striking defense. That distinction matters for anyone evaluating judo specifically for self-defense: the striking and weapon-defense material exists, it is just taught through kata rather than tested in randori or shiai.
Rules and Competition Today
Judo's competitive rules worldwide are set by the International Judo Federation (IJF), founded July 11, 1951, in London and headquartered today in Budapest, Hungary. The IJF's own member-federation directory lists more than 200 national federations, organized under five continental unions: the African Judo Union, the Judo Union of Asia, the European Judo Union, the Oceania Judo Union, and the Pan American Judo Confederation. The IOC formally recognizes the IJF as judo's Olympic governing body, as shown in the IOC's own profile of the International Judo Federation.
Scoring in judo is simpler to describe than it looks from ringside. Ippon is the highest score and ends the match immediately, awarded for a throw landing an opponent largely on their back with force and control, for a pin held long enough, or for a submission from a choke or armlock. Waza-ari is a lesser score, awarded for a throw or pin that falls short of full ippon criteria. Under current rules, waza-ari scores accumulate without automatically converting into an ippon, a change explained further below.
Judo debuted at the Olympics for men at the 1964 Tokyo Games, the first martial arts events in Olympic history. That debut is remembered as much for who won as for the sport's arrival: Anton Geesink of the Netherlands, already the first non-Japanese World Champion after his 1961 title, took gold in the open category, a result that ended the assumption that Japan would automatically dominate a sport it invented. Judo was then dropped from the 1968 Mexico City program and returned permanently from 1972 Munich onward. Women's Olympic judo followed later, debuting at the 1992 Barcelona Games. The first World Judo Championships were held in Tokyo in 1956, men only, open weight, before weight classes and women's divisions expanded the format over the following decades.
Weight Categories and Match Format
Current IJF senior and junior weight categories run seven per gender. Men compete at -60, -66, -73, -81, -90, -100, and +100 kg. Women compete at -48, -52, -57, -63, -70, -78, and +78 kg. Standard match duration for seniors, juniors, and cadets is 4 minutes, a figure equalized between men and women in the 2017 rule change; before that, men's and women's matches ran different lengths.
Yasuhiro Yamashita of Japan is a useful reference point for what elite technical judo looks like inside these categories: a four-time World Champion and 1984 Olympic gold medalist, remembered specifically for competing through injury without losing the technical precision that defined his throws. Kayla Harrison of the United States, the first American to win Olympic judo gold, later became a two-time Olympic champion, showing the same weight-class structure producing champions well outside Japan decades after Geesink's breakthrough.
The Rule-Change History: How Judo's Scoring Got to Where It Is
Judo's competition rules have never been static, and tracking the changes is the clearest way to understand why matches look and score the way they do today. Each shift responded to a specific problem: safety, stalling, or a scoring system that had grown too complicated to referee consistently.
The earliest restriction came in 1899, when Kodokan contest rules first excluded finger, toe, wrist, and ankle locks from competition, narrowing legal submissions toward the arm. That narrowing tightened further in 1925, when the elbow became the sole legal joint-lock target in competition, a restriction that still defines legal armlocks in judo today. Ground fighting itself was also curtailed around 1925, partly in response to concerns, discussed further in the lineage section below, that unrestricted newaza (ground technique) was pulling competitive judo away from Kano's broader vision of the art.
By the 1970s, the problem had shifted from what techniques were legal to how matches were being won, or not won. In 1974, the Kodokan and early international rule bodies introduced Yuko and Koka, smaller scoring categories below waza-ari, alongside the Shido passivity penalty, giving referees graded ways to reward partial technique and punish stalling instead of forcing every exchange toward an all-or-nothing ippon. In 2003, the IJF created the Golden Score overtime format and simplified penalty tiers, replacing open-ended repeated periods with a clearer sudden-score structure once regulation time expired in a tie.
| Year | Change | Governing body | Practical consequence |
|---|---|---|---|
| 1899 | Contest rules first restrict joint locks, excluding fingers, toes, wrists, and ankles | Kodokan | Narrowed legal submissions toward arm-based locks |
| 1925 | Elbow becomes the sole legal joint-lock target in competition | Kodokan | Set the armlock restriction still in force today |
| 1974 | Yuko and Koka scoring categories added, plus the Shido passivity penalty | Kodokan / early international rule bodies | Gave referees graded ways to reward partial technique and penalize stalling |
| 2003 | Golden Score overtime format created; penalty tiers simplified | International Judo Federation (IJF) | Replaced open-ended extra periods with a clearer sudden-score overtime |
| April 2017 | Yuko folded into waza-ari; two waza-ari no longer auto-equal ippon; match duration equalized at 4 minutes | International Judo Federation (IJF) | Made waza-ari cumulative rather than auto-converting, changing close-match strategy |
| Circa 2010-2013 | Direct leg-grab attacks progressively restricted | International Judo Federation (IJF) | Pushed competitors back toward upper-body gripping and classical throws |
The biggest overhaul in recent memory landed in April 2017. The IJF removed Yuko as a live scoring category, folding those actions into waza-ari, and eliminated the old rule where two waza-ari automatically equaled an ippon. Waza-ari scores became cumulative without auto-converting into a match-ending ippon, which changed end-game strategy in close matches considerably: a fighter ahead on a single waza-ari can no longer be caught out by an opponent quietly stacking a second one into an automatic win. The same 2017 package equalized men's and women's match duration at 4 minutes, as confirmed in the British Judo Association's account of the IJF rule overhaul.
Separately, the IJF progressively restricted direct leg-grab attacks in competition starting around 2010, a change that was firmly entrenched by roughly 2013. No primary IJF document pins that restriction to a single date, so "around 2010" is the honest framing rather than a falsely precise year. The practical effect was to push competitors back toward upper-body gripping and classical throws instead of wrestling-style single and double-leg attacks. Whether Yuko survives today in any residual tiebreaker role is a genuinely unsettled question in current discussion of the rules, and this article will not assert an answer beyond describing the 2017 change itself; readers who need the current wording should check the IJF's official rules portal directly, since rule text has continued to move since 2017.
Every scoring reform in judo's history solves a real problem on the mat and creates a new one for someone to argue about at the next congress.
Ranking and Belt Progression
Judo's ranking system runs on two separate counting directions, which trips up a lot of newcomers reading a promotion chart for the first time. Kyu grades, the student ranks, count down: 6th kyu through 1st kyu, with 1st kyu closest to black belt. Dan grades then count up from there: 1st through 5th dan wear the standard black belt, 6th through 8th dan wear a red-and-white panel belt, and 9th and 10th dan wear solid red, by convention rather than strict rule.
The Kodokan clarified in 1963 that the dan scale stops at 10th, even though a higher grade is theoretically definable within the system's own logic. In the entire history of judo, only 15 people have ever reached 10th dan, which gives some sense of how rare the top of the scale actually is compared to how often black belt itself gets treated as the finish line.
Kyu and Dan: Two Different Counting Systems
Dan grades are internationally consistent in structure, but kyu-level belt colors and even the number of kyu grades vary meaningfully by country. A yellow-belt chart from one national federation will not necessarily match another country's system exactly, so treat any single belt-color chart you find online as a regional convention rather than a universal standard. If you are tracking a specific student's progress, the federation that issued the rank is the only reliable source for what a given color or kyu number means in that country.
Lineage and Branches: What Grew Out of Judo, and What Judo Grew Out Of
Judo did not stay a single, fixed system once it left the Kodokan, and understanding its offshoots clears up one of the most common points of confusion between judo and other grappling sports.
Kosen judo emerged from Japanese technical-college judo competitions starting in 1898, under rules that allowed far more ground fighting than mainstream Kodokan practice, including pulling guard to start a match on the ground, a tactic that would be penalized in standard judo competition. Kano himself reportedly noted in 1926 that this style produced strong competitors at some cost to the broader self-defense skill set the Kodokan curriculum was built around, and the Kodokan's 1925 restriction of ground fighting was, in part, a response to that concern.
A second, more consequential branch came through Mitsuyo Maeda, a Kodokan judoka who reached godan (5th dan) in January 1912 and emigrated to Brazil. Maeda gave his first Brazilian demonstration in Santos in September 1914, and in 1917 he began teaching a 14-year-old named Carlos Gracie. Carlos, together with his brothers, including Helio Gracie, is credited as a founder of Brazilian Jiu-Jitsu, a distinct branch that grew out of judo and pushed further into ground control and submission grappling than mainstream competitive judo allows.
Judo grew out of jujutsu. Brazilian Jiu-Jitsu grew out of judo. Neither step erases the one before it.
A third branch developed independently in Russia. Vasili Oshchepkov, Kodokan-trained and the third European ever to reach nidan (2nd dan), in 1917, began combining judo with other regional grappling systems starting in 1929, contributing to what became sambo. None of these three branches replaced judo; they diverged from it at different points and for different reasons.
The lineage deserves stating plainly, since the terms get flattened together constantly in casual conversation. Jujutsu (or jiu-jitsu) is the older umbrella family of Japanese unarmed combat systems that judo itself grew out of in 1882. Brazilian Jiu-Jitsu is a separate branch that grew out of judo afterward, through Maeda's teaching starting in 1917. The lineage runs jujutsu, to judo, to Kosen judo and Maeda's teaching, to Brazilian Jiu-Jitsu. Judo is not an older or newer version of either; it is a distinct point on that timeline with its own rules, its own throw-first emphasis, and its own governing bodies.
Training Reality: Randori, Ukemi, and What the Injury Data Actually Shows
Ukemi Comes Before Throws
Every serious judo curriculum teaches ukemi, breakfalling, before or alongside throws themselves. The four basic falls, rear, side, front, and rolling, exist because a beginner who cannot fall safely will get hurt learning to be thrown long before they get hurt in an actual contest. This ordering is one of the clearest structural differences between judo and sports where falling itself is not a taught skill.
Once ukemi is solid, students move into randori, judo's live sparring practice, which ranges from fully cooperative drilling to competitive-intensity live grappling depending on the partners, the coach, and the day's goal. Randori is where the gap between judo's calm dojo etiquette and its physical demands becomes obvious to anyone training it for the first time.
The popular claim is that a sport built around bowing, cooperation, and controlled falls must be gentle in the sense of low-impact and low-risk. What the evidence actually shows is more specific and less comforting. A 2024 peer-reviewed systematic review found time-loss injury rates of 1.1% to 4.1% of competitors, and medical-attention injury rates ranging from 2.5% all the way to 72.5%, depending heavily on competition level and how each study defined an injury, according to a peer-reviewed systematic review of judo tournament injury epidemiology. A large French cohort covering 316,203 competitors across 21 seasons found that only 1.1% sustained injuries needing more than a week of recovery, a reassuringly low figure at that scale, while a separate study of 673 judoka at World Championship level recorded 47.2 injuries per 1,000 athlete-exposures, a far higher rate that reflects how much harder elite competition pushes bodies than a typical club session.
Calm etiquette on the mat and low physical risk are two different things, and judo only reliably delivers one of them.
Two more details cut against the "gentle equals safe" assumption specifically. Standing exchanges (tachi-waza) account for 50% to 84.9% of recorded injuries across studies, not the ground grappling that looks more chaotic to an outside observer. And while head injuries show up more often in raw counts, most are minor; the more serious, time-loss injuries cluster around the knee and shoulder instead, the joints doing the real work in every grip fight and every throw attempt.
| Popular claim | What the evidence shows |
|---|---|
| Judo is gentle, so it is safe and low-contact | Time-loss injury rates run 1.1% to 4.1% of competitors, and medical-attention injury rates range from 2.5% to 72.5% depending on level and study design |
| Ground work is where judoka get hurt | Standing exchanges account for 50% to 84.9% of recorded injuries, not ground work |
| Injuries are rare at any level | A large recreational-to-club cohort found 1.1% needing over a week off, while an elite World Championship study found 47.2 injuries per 1,000 athlete-exposures |
| Head injuries are the real danger | Head injuries are common in raw counts but mostly minor; knee and shoulder injuries dominate the more serious, time-loss cases |
None of this means judo is unusually dangerous compared to other combat sports; the injury literature simply does not support treating it as a soft alternative to grappling sports with more visible intensity. Coaches who run a genuine falling curriculum before live randori are managing exactly the risk this data describes.
Equipment: The Judogi
Judo is practiced in a judogi, a heavy woven cotton uniform built to survive repeated gripping and throwing. It has three parts: the uwagi, a reinforced jacket cut to withstand grip fighting without tearing; the obi, a belt colored by rank and tied to hold the jacket closed under load; and the zubon, drawstring trousers reinforced at the knees for repeated ground contact. The weave and reinforcement points exist specifically because so much of judo's grip fighting happens through the fabric itself, not just the body underneath it.
Judo Compared: Wrestling First, Then Brazilian Jiu-Jitsu
Short answer: judo is not wrestling and not jiu-jitsu; it shares grappling ancestry with both but differs in what contact points count and where a match can be won. Wrestling is the closer structural comparison, since both sports are fundamentally throw-and-takedown arts scored on getting an opponent down with control.
Grip, Mat, and Scoring: Where Judo and Wrestling Diverge
The clearest difference starts with what fighters are allowed to grab. Judo is a gi-based grappling art: competitors fight for grips on the judogi itself, on sleeves, collars, and lapels, and a huge share of match strategy is decided before a throw ever starts, in that grip fight. Wrestling, in both its freestyle and folkstyle forms, is gripless in the jacket sense; wrestlers grip skin, wrists, legs, and body directly, which produces a faster, more continuous style of engagement without the pauses a gi grip fight can create.
Scoring diverges just as sharply. A clean judo throw landing an opponent largely on their back can win the match outright as ippon; smaller throws score waza-ari, which, as covered above, no longer automatically stack into a match-ending score. Wrestling takedowns score points based on exposure and control, but rarely end a match outright the way ippon does; wrestling matches are typically decided on accumulated points, near-falls, and, in folkstyle especially, riding time rather than a single decisive score.
| Dimension | Judo | Wrestling (freestyle/folkstyle) |
|---|---|---|
| Grip | Fighters grip the judogi (the jacket), fighting for sleeve, collar, and lapel control | Fighters grip skin, wrists, legs, and body directly; no jacket to hold |
| Scoring a takedown | A clean throw can win outright as ippon; smaller throws score waza-ari | Takedowns score points on exposure and control, rarely ending a match outright |
| Where a match is won | On the feet (throws) or on the ground (pins, chokes, armlocks) | On the feet (takedowns) or on the ground (control and exposure, no submissions) |
| Ground game | Time-limited; referees stand fighters back up if action stalls | Extensive control-based ground wrestling with riding time and near-fall scoring |
| Submissions | Chokes and elbow armlocks can end a match by tap | No submissions in either freestyle or folkstyle |
Judo's relationship to Brazilian Jiu-Jitsu is closer historically than its relationship to wrestling, since BJJ descends directly from Kodokan judo through Maeda's teaching, but the two sports have grown apart in what they reward. BJJ competition allows extended ground fighting toward submission with far fewer time restrictions on newaza than judo permits, while judo keeps its center of gravity on the standing throw. Ronda Rousey, the first American woman to medal in Olympic judo, taking bronze in 2008, is a useful illustration of how the two connect in practice: her judo throws, grip fighting, and off-balancing carried over directly when she moved into mixed martial arts. What carried over is specific and describable; it is a different claim from saying judo, or any single art, "works" on the street or in a cage in some general sense, which is not a claim this article will make.
The English-Speaking Judo World
Judo took root across English-speaking countries on different timelines, and none of them center the sport's global story the way Japan does, but each built durable federations that still run today. Judo was introduced to Australia as early as 1906, and Judo Australia was founded in 1952 as the sport's national governing body. In the United Kingdom, the British Judo Association was founded in 1948, giving England, Scotland, and Wales a unified structure not long after judo had already spread through military and university circles. Judo Canada was incorporated in 1956, coordinating a federation that spans a country large enough that regional clubs often operate with real independence. In the United States, national competition and Olympic qualification run through USA Judo, and American judoka have produced some of the sport's most visible recent champions, including Kayla Harrison's back-to-back Olympic titles.
What ties these federations together is affiliation with the IJF's continental structure and a shared belt and rules framework, even as local club culture, competition calendars, and kyu-belt conventions vary from country to country within that shared frame.
Who Judo Suits, and How to Choose a School
Judo tends to reward people who like a visible, gradable path more than people who want an unstructured hobby. If you want a kids' program built around a clear belt sequence, a strong falling curriculum before contact starts, and referees and coaches trained specifically in age-appropriate throwing progressions, judo clubs affiliated with a national federation are built for exactly that. Ask a prospective school how much time a new student spends on ukemi before live throwing starts; a school that rushes this step is cutting a corner the injury data above suggests you should care about.
If you are an adult grappler coming from wrestling or BJJ and want to round out a standing game, judo's gi-based grip fighting and throw mechanics fill a gap those sports leave open, and most clubs welcome cross-training visitors for open randori sessions once you can fall safely. If your interest is self-defense specifically, ask whether the school teaches Kime-no-kata or Kodokan Goshin Jutsu alongside sport judo; not every competition-focused club prioritizes the kata curriculum, and the self-defense material described earlier in this article only helps you if your school actually teaches it.
For competitive-minded adults, look for a club that runs regular open randori and sends athletes to sanctioned local tournaments, since the jump from cooperative practice to real competitive pressure is large and worth testing well before a first serious match. Whatever your reason for walking in, the belt path, the graded rank structure from kyu through dan, gives a concrete way to measure progress that few grappling sports match for clarity.
