This is a general name given to postures which one holds in place for prolonged periods of time - anywhere between 2 minutes and 2 hours.[34] These postures are related to postures used in actual fighting, and are sometimes identical to them. Initially, these postures are taught as static training stances. After a short amount of time though, the practitioner would be taught how to move the muscles and connective tissues on a minute level from the inside of the body, making these stances very dynamic internally, and more challenging to train. The most common Zhan Zhuang among all Xing Yi schools is San Ti Shi (it is the stance demonstrated by Sun Lutang in the picture at the beginning of the article). Other common stances are: Hun Yuan Zhuang, Wu Ji Zhuang, Fu Hu Zhuang, Xiang Long Zhuang and their many variants. There are many reasons for training Zhan Zhuang. Among them are, in general:- It is the simplest method to work on the training of one's Intent (Yi).- They are used to develop one's martial structure.- One can learn the bodily alignments of the art and perfect them in a more relaxed state.- Correct breathing can be trained more methodically while holding Zhan Zhuang.- There are certain health benefits involved in such training.Some teachers consider Zhan Zhuang to be the most important practice in Xing Yi, while others neglect to train and teach them altogether. The use of the Santi Shi Zhan Zhuang as the main training method in Xing Yi dates back to Li Luoneng - the founder of modern version of the art. In Dai XinYi, the central and most important training method is called 'Squatting Monkey' - a dynamic movement exercise rather than a dynamic posture held in place. In the Geng Jishan/Deng Yunfeng/Rose Li tradition, the phrase Santi is sometimes replaced by "central equilibrium stance".Since the 1980s, Zhan Zhuang had become more and more popular in other martial arts; many of whom, such as some schools of Chen style Taiji, borrowed these methods from Xing Yi schools. Other martial arts sometimes had their own Zhan Zhuang methods beforehand. Today, the posture Hun Yuan Zhuang in particular has become a mainstay of many styles; its spread probably owing to the growing popularity of Yi Quan.