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Acupuncture points (Chinese: 腧穴; pinyin: shùxué, also called acupoints (Chinese: 穴位; pinyin: xuéwèi or Japanese: つぼ tsubo) are locations on the body that are the focus of acupuncture, acupressure, sonopuncture, and laser acupuncture treatments. There are several hundred acupuncture points that are distributed along meridians (connected points across the body which affect a specific organ or other part of a person) as well as numerous other "extra points" that are not associated with a particular meridian.
Most of the current research into acupuncture point locations and mechanisms is taking place in China. Traditional Chinese medicine's acupuncture theory predates use of the scientific method, and has received various criticisms based on scientific thinking. There is no known anatomical or histological basis for the existence of acupuncture points or meridians. Acupuncturists tend to perceive TCM concepts in functional rather than structural terms, i.e. as being useful in guiding evaluation and care of patients.  Neuroimaging research suggests that certain acupuncture points have distinct effects that are not otherwise predictable anatomically.
This article is part of the branches of CAM series.
Acupoints used in treatment may or may not be in the same area of the body as the targeted symptom. The Traditional Chinese Medicine (TCM) theory for the selection of such points and their effectiveness is that they work by stimulating the meridian system to bring about relief by rebalancing yin, yang and qi (also spelled "chi" or "ki"). This theory is based on the paradigm of TCM and has no analogue in western medicine.
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. There are nearly 400 basic acupoints recognized by the WHO on the meridians. 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.
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.
Categories of body acupuncture points
Certain acupuncture points are ascribed different functions according to different systems within the TCM framework.
Five Transporting Points system describes the flow of qi in the channels using a river analogy, and ascribes function to points along this flowline according to their location. This system describes qi bubbling up from a spring and gradually growing in depth and breadth like a river flowing down from a mountain to the sea.
Jing-well points represent the place where the qi "bubbles" up. These points are always the first points on the yang channels or last points on the yin channels and with exception of Kid-1 YongQuan all points are located on the tips of fingers and toes. The Nan Jing and Nei Jing described jing-well points as indicated for "fullness below the heart" (feeling of fullness in the epigastric or hypochondrium regions) and disorders of the zang organs (yang organs).
Ying-spring points are where the qi "glides" down the channel. The Nan Jing and Nei Jing described ying-spring points as indicated for heat in the body and change in complexion.
Shu-stream points are where the qi "pours" down the channel. Shu-stream points are indicated for heaviness in the body and pain in the joints, and for intermittent diseases.
Jing-river points are where the qi "flows" down the channel. Jing-river points are indicated for cough and dyspnoea, chills and fever, diseases manifesting as changes in voice, and for diseases of the sinews and bones.
He-sea points are where the qi collects and begins to head deeper into the body. He-sea points are indicated for counterflow qi and diarrhea, and for disorders resulting from irregular eating and drinking.
Five Phase Points ascribe each of the five phases - wood, fire, earth, metal and water - to one of the Five Transporting points. On the yin channels, the jing-well points are wood points, the ying-spring points are fire, shu-stream points are earth, jing-river points are metal, he-sea points are water points. On the yang channels, the jing-well points are metal, ying-spring are water, shu-stream are wood, jing-river points are fire and he-sea points are earth points. These point categories are then implemented according to Five Phase theory in order to approach the treatment of disease.
Xi-cleft points are the point on the channel where the qi and blood gather and plunge more deeply. These points are indicated in acute situations and for painful conditions.
Yuan-source points are points on the channel from where the yuan qi can be accessed.
Luo-connecting points are located at the point on the channel where the luo meridian diverges. Each of the twelve meridians have a luo point that diverges from the main meridian. There are also three extra luo channels that diverge at Sp-21, Ren-15 and Du-1.
Back-shu points lie on the paraspinal muscles either side of the spine. Theory says that the qi of each organ is transported to and from these points, and can be influenced by them.
Front-mu points are located in close proximity to the respective organ. They have a direct effect on the organ itself but not on the associated channel.
Hui-meeting points are a category of points that are considered to have a "special effect" on certain tissues and organs. The hui-meeting points are:
Additionally, there are microsystems of acupoints that are typically not located on the meridians. For example, auriculotherapy uses the external ear microsystem exclusively, utilizing thousands of points that are not on a meridian, but located on the surface of the external ear. The Korean system of hand acupuncture is a microsystem that utilizes acupoints on the hand. There are other common and uncommon acupoints that are called extra points, meaning that they are neither on a meridian nor part of a microsystem. Extra points are referred to more often by name, though some of the more commonly known have a letter/number combination for reference. A popular extra point is Yintang, located at the midpoint between the eyebrows.
Evidence from neuroimaging studies
Acupuncture appears to have distinct effects on cortical activity, as demonstrated by MRI (magnetic resonance imaging) and PET (positron emission tomography). Researchers from the University of Southampton, UK and Purpan Hospital of Toulouse, France, summarize the literature:
Investigating Acupuncture Using Brain Imaging Techniques: The Current State of Play: George T. Lewith, Peter J. White and Jeremie Pariente. "We have systematically researched and reviewed the literature looking at the effect of acupuncture on brain activation as measured by functional magnetic resonance imaging and positron emission tomography. These studies show that specific and largely predictable areas of brain activation and deactivation occur when considering the traditional Chinese functions attributable to certain specific acupuncture points. For example, points associated with hearing and vision stimulates the visual and auditory cerebral areas respectively." 
This section focuses on the efficacy of specific distal points, i.e. body acupoints that according to TCM theory are indicated for treating conditions whose symptoms manifest in areas of the body that are distant from the acupoint's location. Current biomedical knowledge does not predict that such points should be efficacious. An example is P6, located near the wrist and used to treat nausea.
The Cochrane Collaboration, a group of evidence-based medicine (EBM) reviewers, reviewed the use of P6 for nausea and vomiting, and found it to be effective for reducing post-operative nausea, but not vomiting . The Cochrane review included various means of stimulating P6, including acupuncture, electro-acupuncture, transcutaneous nerve stimulation, laser stimulation, acustimulation device and acupressure; it did not comment on whether one or more forms of stimulation were more effective. EBM reviewer Bandolier said that P6 acupressure in two studies showed 52% of patients with control having a success, compared with 75% with P6 acupressure. One author of an article published in the Scientific Review of Alternative Medicine disagreed .
One randomized controlled trial studied a classical TCM treatment for breech birth (i.e., buttocks-first orientation of the baby, which is much riskier than head-first). The study showed that moxibustion at acupoint BL 67 (aka UB 67), located at the tip of the fifth toe, was more effective than placebo at reducing the incidence of breech birth. An EBM review by Cochrane said that that more data were needed before recommendations on clinical effectiveness could be made.
Criticism of TCM theory
Clinical use of acupuncture points frequently relies on the conceptual framework of Traditional Chinese Medicine (TCM), which some scholars have characterized as pseudoscientific. Proponents reply that TCM is a prescientific system that continues to have practical relevance. See section in main article on acupuncture: Criticism of TCM theory.
Martial arts applications
There are several types of pressure points, each of which is applied differently, and each one creates different effects. Some of the principles are discussed below:
Pain: Some points are painful, because of the prevalence of nerves in the area. For example, being prodded in the throat is painful. The body has a pain withdrawal reflex, whereby it reacts to pain by moving away from it. Martial artists make use of this, sometimes without being aware of it. Applying pressure next to the collar bone, from above, will cause the person to move downwards (away from the pain), whereas poking them in the gap between the jaw and neck (just below the ear) will make their body want to move upwards. Pressure to the shoulder causes that side of the body to move back. A rub to the back down will cause the body to move forth. Some points react more violently to pain from changes in the pressure (rubbing) rather than constant pressure. All pressure points can cause pain but that may not be their true purpose.
Muscular: Here a direct attack is made on a muscle, which will contract. Examples include: (I) a punch to the solar plexus, which impacts the diaphragm and thus affects the person's breathing ("getting the wind knocked out of you"); and (II) an attack to the outer thigh, which could cause the person to fall as their leg loses power (a "dead leg" or "charley horse").
Pressure: The baroreceptor in the carotid artery is pressure-sensitive, allowing the body to control the bloodflow into the brain. Pressure against this region will 'trick' the body into thinking that blood pressure is too high, and thus will constrict and lower blood pressure - which can cause blackout. Striking veins and arteries can also cause them to shut or tear, both of which will definitely cause black-out and possible death if not treated immediately.
Break: There are certain areas which are likely to lead to a break if struck properly. This includes the "loose rib", the philtrum and the top of the skull (soft-spot).
Hyper-Extension There are joints that, when struck, can be hyper-extended and even completely torn apart. This is a technique which can cause permanent damage and disfiguration to one's opponent, usually focusing on the elbow and the knee. There are two types:
brute force: This takes advantage of the vulnerability of the strike point, thereby causing the damage; and
Golgi organs: A relatively gentle strike to the Golgi tendon at the back of the elbow, for example, causes a reflex which immediately relaxes that tendon, allowing the elbow to more easily bend in the wrong direction. If this is immediately followed by a solid strike to the elbow joint, the elbow can be broken with significantly less effort than through brute force.
Brain shake: The brain is actually a very vulnerable organ, which is why it is encased in the skull. The brain floats in fluid and balances on a very flexible spine. Certain techniques can actually shake the brain in a way which causes black out. The most commonly taught technique involves a strike just below the occipital ridge, at the correct angle in the correct direction. Other areas that are succeptable to such techniques are the temples and the top of the skull.
Energy: Some believe that there are energy channels which flow around the body through acupuncture meridians, and an attack will impact the flows, and thus impact the body. This is called "chi", "ki" or "qi" in East Asian cultures. These techniques are said to be capable of causing blackout, serious injuries or death when used by a sufficiently skilled martial artist.
^ Felix Mann: "...acupuncture points are no more real than the black spots that a drunkard sees in front of his eyes." (Mann F. Reinventing Acupuncture: A New Concept of Ancient Medicine. Butterworth Heinemann, London, 1996,14.) Quoted by Matthew Bauer in Chinese Medicine Times, Vol 1 Issue 4 - Aug 2006, "The Final Days of Traditional Beliefs? - Part One"
^ "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." Acupuncture. National Institutes of Health: Consensus Development Conference Statement, November 3-5, 1997. Available online at consensus.nih.gov/1997/1997Acupuncture107html.htm. Retrieved 30 January 2007.
^ Pariente J, Lewith GT; White PJ (Sep 2005). "[http://ecam.oxfordjournals.org/cgi/content/full/2/3/315 Investigating acupuncture using brain imaging techniques: the current state of
play.]". Evid Based Complement Alternat Med - Oxford University Press2 (3). PMID 16136210. Retrieved on 2007-03-06.
^ The Complete Guide to Sensible Eating: Third Edition, by Gary Null, ISBN 1-888363-61-4.
^ Cited from an excerpt from Acupressure's Potent Points by Michael Reed Gach, Ph. D.