Traditional tai-chi chuan (taijiquan) is a Chinese martial art that uses the 'six harmonies movement' system of internal martial arts. It is so named for the expression of yin and yang within those movements. While all traditional martial arts use the "tan-tien", "yi", "chi" and "jin", to augment power and maximise strength, the internal arts additionally and uniquely use these constructs to formulate the 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 connected movement in which all the parts of the body move as one unit while presenting an alignment to any applied forces at all times ("peng-jin"). The combination of intention (yi), relaxation (sung) and "chi" creates a 'ground path' that enables forces to pass though the body without encountering resistance and allows the body to function more efficiently.
In tai-chi this type of movement is referred to as 'reeling silk' because of its similarity to the motion of the silk worm and it 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.
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. Full use of the "tan-tien" to control movement is expressed in two ways; as circular movement with the axis being through the centre of the "tan-tien" or as a snake like movement, the two can also be combined. These are regarded as the three movement principles of tai-chi. The midriff plays a multiple role connecting the internal to the external by being a focal point for the mind, the controller of the breath, the centre 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. The movement requires a complex intimate connective interaction between "tan-tien", "kua" and "ming-men" in order to fully connect the midriff to the legs/ground and spine/upper body.
Tai-chi is popularly characterised by its slow movements which appear to the observer as graceful, well ordered and totally unique. Slowly performing these 'silk reeling' techniques enables 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.
There are strict parameters that define classical tai-chi movement but these are difficult to fully comprehend and harder still to achieve and as a result some aspects are often missed or omitted. Circular movement is accomplished by rotating the "tan-tien" to affect three dimensional movement. Moving in this way requires a considerable amount of practice. A helpful initial exercise is to use the hands to rotate the abdominal area on each axis (training from the outside in). Gradually a feeling of moving from the inside is developed, and eventually this feeling can be clearly expressed in movement. This movement then has to be transferred through the body using the connective tissue and a gravity based association with the ground. Add to this the fact that the movement is powered by the lower body with the upper body being a relaxed conduit and the complexity of achieving the baseline skill begins to become apparent.
In order to simplify the processes and make the art widely accessible it has become common practice in many modern systems to teach a sequence of movements without first teaching how to move 'internally'. What is taught is well-coordinated 'normal' movement performed in a slow relaxed fashion in conjunction with some generic martial parameters. Once this becomes ingrained into the movements through repetition it is very difficult to change. While there are still benefits derived from slow relaxed exercise it negates the development of the full range of "tan-tien" skills. It is not the sequence of movements or the external appearance (to the untrained eye) that defines the quality of six harmonies movement but rather how those movements are achieved. Some of the most respected masters of the art regard rectifying this as the biggest challenge currently facing tai-chi. Considering the time, effort, knowledge and understanding required to re-program the body movements in order to learn the internal movement system it is not surprising that few teachers can move this way, let alone pass that knowledge on. For students who engage in the art at a superficial level this is unlikely to be important but for those who wish to investigate its traditional completeness it is a significant impediment.
There are many facets to tai-chi but its real strength is its depth 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.