Sōchin is an advanced black belt kata.
This is one of the kata that can be selected for the 3rd Dan Black Belt examination. (Video tutorial below)
Sōchin (壯鎭) Kata (powerful calm)
Some karate historians beleive Sōchin may have derived from Dragon style kung fu, and was taught in the Naha district of Okinawa by Seisho Arakaki. Some say Yoshitika funakoshi ( Master Gichin Funakoshi's son), learned the kata from Master Kenwa Mabuni, then developed the kata and introduced it into the Shotokan syllabus.
Sōchin translates as 'powerful calm' or 'tranquil force'. This Shotokan kata is very explosive and dynamic, with lots of examples of contraction and expansion, slow powerful movements followed by bursts of explosive fast techniques. Sōchin is known for the fudo dachi stance, that is used throughout the kata, indeed many karateka refer to the stance as Sōchin dachi and not fudo dachi (immovable stance).
Fudo dachi is a very strong stance, rooting the karateka to the ground, fudo dachi is strong in all directions with the back leg in the kiba dachi position and the front leg in the zenkutsu dachi position.
Sōchin is a very physical kata and develops extremely strong legs and explosive techniques. Using the hips in Sōchin is very difficult as the stance needs to be held correctly, so after the 2nd move (tate shuto), there are two explosive straight punches, where the hips and legs must be utilised whilst keeping the fudo dachi stance strong.