Unlike other combat sports, kickboxing is hardly an unified discipline: it developed under several forms in very disparage countries and time periods, often with little to no direct contact to each other, which resulted in a myriad of circuits that only gain the appellative of kickboxing by sharing a vaguely similar punch-and-kick ruleset. To blur the lines even more, many traditional martial arts contain elements that would fit this definition as well, like Karate, Muay Thai, Taekwondo and some more, with some of them having contributed actively to their nearest kickboxing style. In synthesis, it is more correct to talk about kickboxing forms, just as "wrestling" can convey a variety of fighting systems instead of an overarching sport.
The term "kickboxing" was a Gratuitous English term created in The Sixties by Osamu Noguchi, a Japanese promoter that codified most of the aspects we associate with modern kickboxing. The discipline he would go to promote was shaped by Tatsuo Yamada, a karateka who became fascinated with the full contact nature and liberal rules. With their influence and that of several publicized challenge matches between karatekas and nak muay, Japan saw the creation of a Kickboxing Association and the rise of a new, exciting professional sport whose popularity exploded right then and didnt burn off completely until The '80s. Even then, the seed remained deeply planted, and when Akira Maeda and his collaborators broke off from Professional Wrestling to entertain the idea of real fighting, the return of kickboxing was one of its consequences. With the help of Maeda, a modernized organization named K-1 blossomed, attracting fighters from around the world and exploding in its own boom of fighting culture, dream matches and bone-breaking kicks.
At the same time, United States witnessed a similar evolution. Although some minor martial artists had attempted to create something similar, it was again a disenchanted karateka from The '70s, Joe Louis, who had the idea (inspired by his training under Bruce Lee) to combine elements of karate and boxing. His creation was initially conceived as a form of full contact karate, with the term kickboxing being an exotic term that ended up sticking; it was not until the founding of the Professional Karate Association (PKA) and the World Kickboxing Association (WKA) that their road became bifurcated and took separate directions. Other acronyms like IKF and ISKA appeared around this time, keeping shaping it as a niche but tough competition circuit. It is interesting to note that, despite its revolutionary beginning, American kickboxing would differ from foreign forms for its conservative ruleset, which forbad kicks around the waist and barely allowed striking tools other than fists and feet. This would be a point of evolution when one of its main stars, Benny "The Jet" Urquídez, made contact with muay thai fighters.
Meanwhile, the rest of the world was taking its own notes. Dutch martial artists influenced by Jon Bluming discovered in mid-80s the remnants of the Japanese circuit and its Thai neghbours, and after deciding it was the coolest thing around, they put their efforts in learn whatever they could found and recreate with their own arts what they could not. A long tradition of kickboxers started there, marked by but not limited to a legendary rivalry between Thom Harinck's Chakuriki team and Jan Plas's Mejiro Gym. With the rise of K-1 in Japan along with their branch of Mixed Martial Arts, they decided to give back more than what they had taken and joined them in the journey.
Nowadays, the main styles or forms of kickboxing are the following ones. Note again that, as mentioned before, traditional martial arts can muay thai and karate can be considered kickboxing modalities as well.
- Full contact or American kickboxing: born in the United States, this style is, as mentioned before, conservative and based on karate competitions. Its fighters wear long trousers with shin pads and boxing gloves, as well as protective helmets if they are amateur or under 16. On the ring, they can use only punches and kicks (usually with the foot, although the shin is sometimes legal too), and kicking about the waist is forbidden altogether. Clinch-fighting is similarly forbidden, but sweeps can be allowed depending on the ruleset. There is also a variation named semi-contact, with a slightly more closed ruleset, where gaining points is the main way to win.
- International or freestyle kickboxing: popular in European countries outside Netherlands, it is essentially a customized version of American kickboxing. Its ruleset is similar, except that it allows kicking to the legs and disallows sweeps.
- Oriental or K-1/Japanese kickboxing: created by the Japanese and adored by the Dutch, it is the originator of the kickboxing name. Fighters here wear mainly boxing shorts, although trousers and even full karategi used to be legal, often causing a surprising visual diversity. This style is substantially open: fighters can hit with punches, kicks, knees to any part except by the groin, and a limited amount of clinching is allowed (throws and sweeps were legal in the past). Back in the 80s, its main promotion K-1 was essentially the Mecca of kickboxing, so this modality is probably what most non-American fans see when they think about the sport.
- Shootboxing: an unique Japanese variation created by former kickboxer Caesar Takeshi, who had connections to the Japanese wrestling environment that gave birth to Mixed Martial Arts. The most open of all the kickboxing forms, shootboxing allows punches, kicks, knees, elbows, clinching, throws, sweeps and even submission holds (as long as they are finished standing), and their fighters are clad in pro wrestling-esque long tights. This used to be a very niche sport compared to the other forms, but it has become bigger through the years, and nowadays it is a significant pool of talent.