Lit. Three-fold Keiko
Sanban for short.
Sanbangeiko often forms the basis of Rikishi physical preparation in Keiko. Especially for the Toriteki.
Two Rikishi will practice Sanban for usually 30 minutes. During this period no other Rikishi will step on the Dohyou and they go fighting on in a series of Shoubu as hard as possible.
Sanbangeiko is therefore basically an extended series of Shoubu between two Rikishi.
First matches are easy. However after a couple it becomes extremely hard. 30 minutes is super-hard. Rikishi build Stamina this way and the habit of going hard into your Aite no matter what.