Xing Yi Quan (Hsing-I Chuan) is the oldest of the Neijia, the orthodox internal Chinese martial arts (predating the creation of both Taiji Quan and Bagua Zhang). It is also the most aggressive and linear, its primary strategy is relentless attack using sudden bursts of whole-body power with combinations of simultaneous advancing, blocking and striking. The energy of Xing Yi is likened to that of a canon ball knocking down and running over a target.
Xing refers to form or shape and Yi refers to the mind or intent. Quan means fist, but denotes a method of unarmed combat (boxing, or fist method). Xing Yi Quan is commonly referred to as Mind Form or Mind Intention boxing. The name illustrates that the form the body takes is an external manifestation of the internal state of mind. The mind visualizes a shape and the body takes that shape. The mind visualizes the opponent and the state of combat, and creates the shape that will give strategic advantage. The body then takes that shape.
Master Wang Shujin in san ti shi
The martial goal of Xing Yi training is to reduce the time gap between the mind creating the correct shape and the body taking that shape.
San Ti
Correct shape is primarily achieved through the most basic and important exercise in Xing Yi: San Ti Shi (heaven-earth-and-man stance, or three-bodies-power stance). San Ti is a stance that teaches correct body posture and correct mind posture. In training the stance is held for extended periods of time, which increase with the practitioner’s skill level. San Ti also builds the leg muscle and tendon strength necessary to prevail in combat. San Ti requires a great amount of concentration, awareness and sensitivity. It is a method of martial foundation training (jibengung), as well as a powerful meditation and chi gung method.
Master Han explains San Ti practice:
Forms
Xing Yi strategic forms are divided into two groups: the five element fists (Wu Xing) and the twelve animal fists.
The twelve Xing Yi animals are: The bear and eagle (often used in combination), the snake, tiger, dragon, rooster, horse, swallow, sparrowhawk, monkey, the turtle and the Tai (Phoenix). The animal forms follow the spirit and tactics of the various animals and do not copy the physical movements as predominantly as is the case in shaolin animal systems.
The five element fists (Wu Xing Quan) are based on the Taoist five element theory, which is applied widely in Chinese culture and especially in Chinese medicine.
Five Element Theory
The system of five elements is used for describing interactions and relationships between phenomena. The five elements are metal, water, wood, fire and earth. The Wu Xing is a cyclic arrangement of the five elements. There are two cycles: a creative cycle and a destructive cycle. These cycles work on the same principal as the simple children’s hand game paper-rock-and-scissors, where paper covers rock, rock breaks scissors and scissors cut paper.
Creative cycle • Wood feeds Fire • Fire creates Earth (ash) • Earth bears Metal • Metal collects Fire and Water • Water nourishes Wood.
Destructive cycle • Wood parts Earth • Earth absorbs Water • Water quenches Fire • Fire melts Metal and burns Wood • Metal chops Wood.
The Five Elements of Xingyiquan:
Splitting (Pi) Metal Like an axe chopping up and over. Pounding (Pào) Fire Exploding outward like a cannon while blocking. Drilling (Zuān) Water Drilling forward horizontally like a geyser. Crossing (Héng) Earth Crossing across the line of attack while turning over. Crushing (Bēng) Wood Arrows constantly exploding forward.
Xing Yi practitioners use the Five Elements as an interpretative framework for reacting and responding to attacks. The Five Element Fist theory is a general combat formula which assumes at least three outcomes of a fight; the constructive, the neutral, and the destructive. Xingyiquan students train to react to and execute specific techniques in such a way that a desirable cycle will form based on the constructive, neutral and destructive interactions of Five Element theory. Where to aim, where to hit and with what technique—and how those motions should work defensively—is determined by what point of which cycle they see themselves in.
Each of the elements has variant applications that allow it to be used to defend against all of the elements (including itself), so any set sequences are entirely arbitrary, though the destructive cycle is often taught to beginners as it is easier to visualise and consists of easier applications. The Five Elements forms are usually taught before the Twelve Animals because they are easier and shorter to learn.
History
Although the exact origin of Xing Yi Quan is uncertain, the earliest written records of Xingyiquan can be traced to the 18th century. Legend, however, credits the invention of Xingyiquan to the renowned Song Dynasty (960-1279 AD) general Yue Fei. According to the book Henan Orthodox Xing Yi Quan written by Pei Xirong the art was originally based on spear fighting techniques:
“...when Yue Fei was a child, he received special instructions from Zhou Tong. Extremely skilled in spearfighting, he used the spear to create fist techniques and established a skill called Yi Quan (intention Boxing). Meticulous and unfathomable, this technique far outstripped ancient ones."
The spear is primarily a linear thrusting and piercing weapon which makes use of small angles and techniques of simultaneous advance, defence and attack. It is therefore very likely that spear technique was indeed the predecessor of Xing Yi Quan.
Yue Fei synthesised and perfected existing Shaolin principles into his own style of gongfu which he popularised during his military service. Yue Fei is usually identified as the creator of Xing Yi because of his considerable understanding of the art (as shown in the work The Ten Theses of Xingyiquan, credited to Yue) and his cultural status as a Chinese war hero.
After Yue Fei's death, the art was lost for half a millennium. Then, during the Ming and Qing Dynasties, Yue Fei's boxing manual was discovered by Ji Jike of neighbouring Shanxi Province. Ji Jike revived the art and it started to evolve into the Style as it is known today.
Sun Lu Tang in San Ti
Some historians attribute the stylistic influence of spear technique to Ji Jike himself, who was known as the "Divine Spear" for his extraordinary skill with the weapon. Ji Jike called his art Liu He, The Six Harmonies. The six harmonies signify the use of whole-body power and the integration of perception, intent (yi), energy (qi), and power (li).
Xing Yi Quan remained fairly obscure until the 19th century. It was Li Luoneng and his successors—which include Guo Yunshen, Li Cunyi, Zhang Zhaodong, Sun Lutang, and Shang Yunxiang—who would popularise Xing Yi Quan across Northern China. Sun Lutang exchanged knowledge with Fu Chen Sung, who subsequently took this branch of Xing Yi Quan to southern China
Xing Yi Quan (Hsing-I) 
Five Element Theory
Creative cycle
Destructive cycle
