Body acupoints are generally located using a measurement unit, called the cun, that is calibrated according to their proportional distances from various landmark points on the body. Acupoint location usually depends on specific anatomical landmarks that can be palpated. Many of these basic points are rarely used. Some points are considered more therapeutically valuable than others, and are used very frequently for a wide array of health conditions.
Points tend to be located where nerves enter a muscle, the midpoint of the muscle, or at the enthesis where the muscle joins with the bone. Location by palpation for tenderness is also a common way of locating acupoints (see also trigger point). Points may also be located by feeling for subtle differences in temperature on the skin surface or over the skin surface, as well as changes in the tension or "stickiness" of the skin and tissue. There is no scientific proof that this method works and some practitioners disagree with the method.
Body acupoints are referred to either by their traditional name, or by the name of the meridian on which they are located, followed by a number to indicate what order the point is in on the meridian. A common point on the hand, for example, is named Hegu, and referred to as LI 4 which means that it is the fourth point on the Large Intestine meridian.
Acupuncture points often have allusive, poetic names that developed over the course of centuries, often involving synonyms to ensure similar points are located on the appropriate limb. A total of 360 points are generally recognized, but the number of points has changed over the centuries. Roughly 2/3 of the points are considered "yang", while the remaining 1/3 are considered "yin".
Scientific research
Overall there is only preliminary evidence to suggest acupuncture points exist. A 1997 NIH consensus statement has observed that "Despite considerable efforts to understand the anatomy and physiology of the 'acupuncture points', the definition and characterization of these points remains controversial.
Even more elusive is the basis of some of the key traditional Eastern medical concepts such as the circulation of Qi, the meridian system, and the five phases theory, which are difficult to reconcile with contemporary biomedical information but continue to play an important role in the evaluation of patients and the formulation of treatment in acupuncture."
There are several plausible theories for how acupuncture works or what acupuncture points are, but for now none of these theories have been conclusively proven. Acupuncture points may exhibit low electrical resistance and impedance but this evidence is mixed, and limited by poor-quality studies with small sample sizes and multiple confounding factors.
Efficacy of P6 point against nausea
A meta-analysis of 40 trials suggested that stimulation of the P6 acupuncture point (located on the wrist) was effective for prophylactic treatment of postoperative nausea and vomiting, with minimal side-effects. The study also said: "The risks of postoperative nausea and vomiting were similar after P6 acupoint stimulation and antiemetic drugs."
Standardization
In 1993 the World Health Organization published a list of standard acupuncture points.
Source : Wikipedia.
