While strikes and use of weapons are included in some pre-arranged forms (kata), they are not frequently trained and are illegal in judo competition or free practice.

Judo has also spawned a number of derivative martial arts around the world, such as Brazilian jiu-jitsu, Krav Maga, sambo, and ARB.

[11] Jigoro Kano had an academic upbringing and, from the age of seven, he studied English, shodō (書道, Japanese calligraphy) and the Four Confucian Texts (四書, Shisho) under a number of tutors.

[13] In 1877, as a student at the University of Tokyo, Kano learned that many jujutsu teachers had been forced to pursue alternative careers, frequently opening Seikotsu-in (整骨院, traditional osteopathy practices).

[14] After inquiring at a number of these, Kano was referred to Fukuda Hachinosuke (c. 1828–1880),[15] a teacher of the Tenjin Shin'yō-ryū of jujutsu, who had a small nine mat dōjō where he taught five students.

[23] Central to Kano's vision for judo were the principles of seiryoku zen'yō (精力善用, maximum efficiency, minimum effort) and jita kyōei (自他共栄, mutual welfare and benefit).

Accordingly, he changed the second character to dō (道), meaning "way", "road" or "path", which implies a more philosophical context than jutsu and has a common origin with the Chinese concept of tao.

Each technique has three distinct stages: Nage-waza are typically drilled by the use of uchi-komi (内込), repeated turning-in, taking the throw up to the point of kake.

This term covers a variety of forms of practice, and the intensity at which it is carried out varies depending on intent and the level of expertise of the participants.

At one extreme, is a compliant style of randori, known as Yakusoku geiko (約束稽古, prearranged practice), in which neither participant offers resistance to their partner's attempts to throw.

A related concept is that of Sute geiko (捨稽古, throw-away practice), in which an experienced judoka allows himself to be thrown by his less-experienced partner.

In 1899, Kano was asked to chair a committee of the Dai Nippon Butoku Kai to draw up the first formal set of contest rules for jujutsu.

Wins were by two ippons, awarded in every four-main different path of winning alternatives, by "Throwing", where the opponent's back strikes flat onto the mat with sufficient force, by "Pinning" them on their back for a "sufficient" amount of time, or by "Submission", which could be achieved via Shime-waza or Kansetsu-waza, in which the opponent was forced to give himself or herself up or summon a referee's or corner-judge's stoppage.

Then the Olympic Games are so strongly flavored with nationalism that it is possible to be influenced by it and to develop "Contest Judo", a retrograde form as ju-jitsu was before the Kodokan was founded.

[70] Dutchman Anton Geesink won the first Olympic gold medal in the open division of judo by defeating Akio Kaminaga of Japan.

Penalties may be given for: passivity or preventing progress in the match; for safety infringements (for example by using prohibited techniques), or for behavior that is deemed to be against the spirit of judo.

[71] There are currently seven weight divisions, subject to change by governing bodies, and may be modified based on the age of the competitors: A throw that places the opponent on their back with impetus and control scores an ippon (一本), winning the contest.

[73] Ippon is scored in ne-waza for pinning an opponent on his back with a recognised osaekomi-waza for 20 seconds or by forcing a submission through shime-waza or kansetsu-waza.

After three shidos are given, the victory is given to the opponent, constituting an indirect hansoku-make (反則負け – literally "foul-play defeat"), but does not result in expulsion from the tournament.

It is represented by well-known coaches such as Alexander Retuinskih and Igor Yakimov, and mixed martial arts fighters such as Fedor Emelianenko, Oleg Taktarov, Khabib Nurmagomedov, and Karo Parisyan.

Cuban Judo is characterized by an explosive and high athletic style that puts an emphasis on body conditioning and calculated planning mixed with raw power.

It's a hybrid of the original Kodokan Judo and the traditional Azerbaijan style of wrestling called Azeri, whose techniques consist of unorthodox grips and positioning during counter-attacks.

Oshchepkov went on to contribute his knowledge of judo as one of the three founders of Sambo, which also integrated various international and Soviet bloc wrestling styles and other combative techniques.

Oshchepkov was executed during the political purges of 1937 and judo was banned for decades until its inclusion in the 1964 Olympics, where sambists won 4 bronze medals.

[102] An adoption of Kano jiu jitsu (a common name for judo at the time) in Brazil attributed to Mitsuyo Maeda's students,[103] most notably the Gracie family.

To maximise safety in nage waza (throwing techniques), judoka trained in ukemi (break falls) and practiced on tatami (rice straw mats).

[citation needed] The application of joint manipulation and strangulation/choking techniques is generally safe under controlled conditions typical of judo dōjō and in competition.

[114] The modern use of the blue judogi for high level competition was first suggested by Anton Geesink at the 1986 Maastricht IJF DC Meeting.

In Japan, both judoka use a white judogi and the traditional red obi (based on the colors of the Japanese flag) is affixed to the belt of one competitor.

Outside Japan, a colored obi may also be used for convenience in minor competitions, the blue judogi only being mandatory at the regional or higher levels, depending on organization.