The three internal martial arts
Tai chi chuan
The chief characteristic of tai chi is a deep relaxation of the body, so that the chi can circulate freely. When the tai chi explosive force (Jing) is used it is soft like a whip, but with deep penetrating power. Tai chi strategy in fighting is defensive, preferring to wait for the opponent to attack, and then using the oncoming force against the attacker. A strategy such as this enables even elderly tai chi practitioners to overcome a much younger assailant, not by contending strength against strength, but by using the mind allied to their skill and experience. All defensive movements are circular in nature. The tai chi defender endeavours to 'stick' to the attacker by using the acute sense of touch acquired through training.
Tai chi has a large array of kicks, but tends to use them to support the hands in self-defence applications. At close quarters tai chi commands an extensive array of throwing and grappling manoeuvres.
Hsing yi requires that you be relaxed and natural. When both defending and attacking the movement is relaxed until the last instant, when the body stiffens momentarily as the hsing yi Jing is emitted. Hsing yi Jing is like a piece of bamboo, flexible but possessing shocking force. This force is characterised as being heavy like a cannon ball.
Hsing yi fighting strategy is much more assertive than that of tai chi - direct in its actions and preferring to move offensively as a form of defence, instantly countering every attack with one of its own, frequently at the same time. The mind and body move as one with a consistent forward momentum, hencc the art's name 'mind fist'. Dodging, slipping and side-stepping are also used at a higher level. The 'mind fist' possesses several kicks, but tends to keep them low and blend them with an explosive barrage from the hands.
The basic arsenal of the various hsing yi styles encompasses the use of straight and circular punches, palm strikes, elbow, shoulder, head butt, kicking both high and low, and throwing and grappling.
Pa kua chang
The movements of pa kua are not as forceful as hsing yi or as soft as tai chi. Spiralling and whip-like power emanate from pa kua techniques. Always circular in appearance, its footwork is lightning fast, complex and evasive, patterned on the imaginary movements of a dragon. (The dragon was thought to be as light as a bird, with the elusive quality of a snake.) More defensive than hsing yi, a circular defencc is quickly followed by a powerful circular attack with one of a vast array of hand, foot or body attacks, or throws. Pa kua strategy is to move to the side or rear of an opponent and attack the aggressor in their most vulnerable position. Throwing manoeuvres are used extensively, while striking techniques are aimed at vital points.
Pa kua has many kicking manoeuvres hidden within the pa kua chang form (72 in total). Occasionally kicks are aimed at the head, usually when the attacker least expects it and with lightning speed.
Pa kua chang literally means 'eight diagrams palm' and is aligned with the ancient Taoist philosophy of the I Ching (Yi Jing) or 'Book of Changes'. The basis of this philosophy is the dynamic inter-connections between all things in existence, both animate and inanimate. The basic eight manoeuvres of pa kua chang can be ascribed to the eight core trigrams of the Yi Ching. These eight trigrams are considered as the prime movers in existence, which in turn have eight actions each, making 64 actions. These 64 have also eight actions, and so on. It is a mathematical philosophy of great complexity which attempts to place Man and his actions in context with the cosmos.
Source: Yang Tai Chi Chuan, by John Hine.