Tai-chi chuan (taijiquan) is a Chinese martial art that uses the 'six harmonies' motion system of internal martial arts. It is so named for the expression of yin and yang within those movements. Characterised by the slow movements of the foundation forms, tai-chi is unique among martial arts in that it is more frequently practiced for its health benefits than for the attainment of fighting skills.
Internal martial arts utilise a system of relaxed movement in which all the parts of the body move as one unit while presenting a perfect posture to any applied forces at all times ("peng-jin"). The combination of structure and relaxation creates a 'ground path' that enables energy to pass though the body without encountering resistance and allows the body to function more efficiently.
In tai-chi this movement can be expressed in two ways; as circular movement or as a snake like movement ('opening' and 'closing' the body). The two can also be combined. Pivotal to this type of movement is a part of the body the Chinese call the "tan-tien" which is situated below the navel about a third of the way in from the front to back. This is regarded as being the physical centre of the body. It plays a multiple role connecting the internal to the external by being a focal point for the mind, the controller of the breath, the center of rotation of circular movement, an internal end point of the connective tissues that control 'opening' and 'closing', as well as controlling the alignment and manipulation of the ground path.
In tai-chi this type of movement is often called 'silk reeling' and is widely known as 'six harmonies movement' amongst the internal martial arts. The three internal harmonies of spirit harmonising with intention, intention harmonising with "chi" and "chi" harmonising with strength describe the mind led skill of using the intention to bring power up and/or outwards from the ground or down and/or inwards through gravity to a part of the body. The three external harmonies of hand-foot, elbow-knee and shoulder-hip describe how the body is tied together as a single unit that is controlled by the "tan-tien", such that the corresponding parts are interconnected by tendons, ligaments and fasciae.
Tai-chi is popularly characterised by its slow movements which appear to the observer as graceful, well ordered and totally unique. These 'silk reeling' techniques enable practitioners to focus their attention on the detail of the mechanics of the motion. However, in traditional tai-chi systems only the foundation forms are predominantly comprised of slow movements.
Most modern developments of tai-chi have focused on the simplification and/or shortening of the traditional movement sets in order to make these systems more accessible to the general public. A general trend in modern Yang and Wu styles of tai-chi is a further slowing down of the movements and more upright postures. Chen style with its speed changes and Sun style which is a faster flowing style, are more likely to retain these original characteristics.
A number of competition forms, some of which combine elements of each of the major styles, have been developed by the Chinese Sports Committee. These range in difficulty from beginner to advanced (right) and are judged on perfection of external form rather than ability to internalise the movements.
There are many facets to tai-chi but its real strength is its completeness which brings about benefits to mind, body and spirit. One thing it is not however is easy to master. Nor is it learnt quickly or without hard work but it is extremely rewarding for those who persevere.