From Wikipedia: https://en.wikipedia.org/wiki/Zhan_zhuang
Zhàn zhuāng, literally: "standing like a post", is a training method often practiced by students of neijia(internal kung fu), such as Yiquan, Xing Yi Quan, Bagua Zhang and Taiji Quan. Zhan Zhuang is sometimes translated Standing-on-stake, Standing Qigong, Standing Like a Tree, Post-standing, Pile-standing, or Pylon Standing. It is commonly called a form of Qigong, despite the differences from other Qigong methods in Zhan zhuang's orientation.[1]