Applied kinesiology

# Overview
Applied Kinesiology (AK) is a controversial method of medical diagnosis.  It purportedly gives feedback on the functional status of the body.  Proponents say that when properly applied, the outcome of an AK test, such as a muscle strength test, will provide for a low risk diagnostic method to help determine the efficacy of therapy for patients.
Applied Kinesiology is classified with alternative medicine, and is therefore different from academic kinesiology, which is the scientific study of human movement and its application.  Applied kinesiology has been called a pseudoscience. 
AK draws together many similar therapies. It attempts an integrated, interdisciplinary approach to health care.  George J. Goodheart, D.C., a chiropractor, originated AK in 1964.  Subsequently, its use spread to other chiropractors, naturopaths, and a few medical doctors.  In 1976, the International College of Applied Kinesiology  was founded.

# Basic Applied Kinesiology
AK practitioners monitor muscles to determine if stress is "on line".  It is not about 'testing' the muscle in a proper sense, the important thing is the ability of the muscle (more precisely: the ability of the autonomic nervous system) to respond in an appropriate way to the gentle pressure. 
AK patients have their muscles tested in many different functional positions, although the arm-pull-down test is the most common.  Typically during the arm-pull-down test, AK patients lie down and raise their dominant arm.  Next, the AK practitioner instructs the patient to resist as the tester exerts downward force on the subject's arm.  The tester subjectively evaluates not the force exerted by the subject to determine the strength of the muscle, but the smoothness of the response.  A smooth response is sometimes called 'a strong muscle' and a response that was not appropriate is sometimes called 'a weak response'. Please note: this is a figure of speech and not about muscle strength.
Because nearly all AK tests are subjective, many regard the practice with skepticism. The AK practitioner applies the pressure, but this practitioner is also the one who decides if one push is stronger than another.  This is considered by some a conflict of interest: the AK practitioner will benefit if AK is perceived by the client as effective, but the AK practitioner is the one who actually determines how effective the practice has been, because he or she subjectively applies pressure to the patient's muscle or muscles. This weakness in the AK system allows for the possibility of fraudulent practice.
The arm-pull-down test is considered by the International College of Applied Kinesiology (I.C.A.K.) to be a very poor form of muscle testing. The arm-pull-down test involves so many different muscles that no specificity as to the muscle with the problem can be ascertained upon testing.
Applied kinesiologists theorize that physical, chemical, and mental imbalances are associated with a lack of smoothness in the muscle response.  So after a mucle that shows a 'weak' response (i.e. a non-appropriate response) many ways are open to find a way to restore the balance - for an imbalance is theorized to be responsible for a 'weak' response.  After some form of treatment/ restoring balance has been applied, the muscle is again monitored, to evaluate the efficacy of treatment.
AK nutrient testing appears to reflect the nervous system's efferent response to the stimulation of gustatory and olfactory nerve receptors by various tested substances. There is considerable evidence in the scientific literature of extensive efferent function throughout the body from stimulation of the gustatory and olfactory receptors.
For example, the tester might repeat the test with a particular substance under the subject's tongue; if the muscle tests weaker than the first test, that substance is determined to be harmful.  The tester may also have the subject touch a particular body part with the opposite hand.  For example, to "localize" testing to the heart, the subject would place a hand over the heart.  A strong arm muscle test suggests a healthy heart, while a weak test suggests a problem. Instead of sublingual testing, some practitioners have the subject simply hold a substance or place the substance near a particular organ. Some AK practitioners go as far as to hold a sealed container of the substance to be tested on the forehead, chest, etc. and then perform the test.
Another commonly used technique in AK is to have the subject wear colored glasses (blue, green, red, etc.) and perform the muscle monitoring while wearing each color of glasses. The color that causes the greatest perceived smoothness of reaction gains might be a color that is in some way beneficial to the client. There are many tests believed to reveal information about the subject's condition.

# Science and AK
There are now several websites  that display much of the Index Medicus Peer-Reviewed research papers regarding applied kinesiology, although they blend articles on AK with articles on academic kinesiology, so they must be examined with caution to avoid confusion. These papers go from 1915 (Journal of the American Medical Association, with a paper called "A method of testing muscular strength in infantile paralysis" by Martin EG, Lovett RW, (which is unrelated to AK) to papers from 2006 from Journals like Physical Therapy, The Journal of Manipulative and Physiological Therapeutics, and the Journal of Electromyography and Kinesiology, many of which do not specifically address AK.
Proponents of AK provide what they believe to be evidence about the methods, clinical efficacy, and neurologic rationales of applied kinesiology examination and treatment. .
However, many studies (below) of Applied Kinesiology have failed to show clinical efficacy. For example, muscle testing has not been shown to distinguish a test substance from a placebo under double-blind conditions, and the use of applied kinesiology to evaluate nutrient status has not been shown to be more effective than random guessing.
The studies, research and reviews of applied kinesiology mentioned above are listed at the National Library of Medicine and National Institutes of Health.     
Scientific studies showed that applied kinesiology tests were not reproducible. 
Robert Todd Carroll has noted that AK is an example of magical thinking.

# American Chiropractic Association statement
According to the American Chiropractic Association, Applied Kinesiology is one of the 15 most frequently used chiropractic techniques in the United States, with 43.2% of chiropractors employing this method.

# Danish Chiropractic Association position
According to a March 26, 1998 letter from the DKF (Dansk Kiropractor-Forening - Danish Chiropractic Association), following public complaints from patients receiving homeopathic care and/or AK instead of standard (DKF defined) chiropractic care, the DKF has determined that applied kinesiology is not a form of chiropractic care and must not be presented to the public as such. AK and homeopathy can continue to be practiced by chiropractors as long as it is noted to be alternative and adjunctive to chiropractic care and is not performed in a chiropractic clinic. Chiropractors may not infer or imply that the chiropractic profession endorses AK to be legitimate or effective, nor may the word/title chiropractic/chiropractor be used or associated with the practice of AK.