Gutai

The Gutai Archive (Japanese)
Material on Shimamoto
Fluxusgenova.org historical essay on Fluxus, mentioning formative influence of "Gutaj" [sic] group
UNESCO biographical information on Atsuko Tanaka: "...

Gutai [Gutai Bijutsu Kyokai; Jap.: Concrete Art Association].
Japanese group of artists, active between 1954 and 1972. It was formed by 18 young avant-garde artists, led by Jiro Yoshihara, one of the founders of Japanese abstract painting.

Gutai
The Gutai was a Japanese artistic movement that was founded by Jiro Yoshihara in 1954. The group was preoccupied with beauty that is born from things that are damaged or decayed.

Gutai (concrete) (1954-72)
The Gutai Bijutsu Kyokai (Gutai Art Association), a Japanese avant-garde group, was founded in 1954 in Osaka by Yoshihara Jiro, Kanayma Akira, Murakami Saburo, Shiraga Kazuo, and Shimamoto Shozo.

The British painter William Green, for example, rode a bicycle over his canvas, while one of the Gutai Group in Japan painted with his feet as he hung from a rope.

Other names for this movement are l'art informel (similar to action painting) and abstraction lyrique (related to American Lyrical Abstraction). The Cobra group artists are also related to Tachisme, as is Japan's Gutai group.
See more at Wikipedia.

He'd ride over the canvas on a bike, whereas other similar artists like those in the Gutai Group from Japan painted with their feet as they hung from ropes.

See also: Movement, Painting, Expressionism, Expression, Abstract expressionism