足の運動
Ashi no undō 
Leg stretch

 

Shōrin ryū Seibukan kihon renshū

The stance is not naname zenkutsu dachi.
The rear foot can move backward for a better stretch, as long as the front knee is kept above the toes.

 

Ashi no undō is one of the exercises of Shōrin ryū Seibukan kihon renshū.

Ashi no undō is often practiced with the front arm extended directly downward, as in this gedan zuki,
except with a lower stance. The fist is then pushed downward while keeping the torso upright,
sinking the hips to stretch the legs.

Shimabukuro Zenshin 島袋善俊

Zenpō Shimabukuro and Dan Smith, Shorin ryū Seibukan: Kyan's Karate