In 1964, George J. Goodheart invented Applied Kinesiology through his unique interpretation and application of Muscles: Testing and Function written by two physical therapists Kendall and Kendall.
George J. Goodheart, a chiropractor, originated AK in 1964 and began teaching it to other chiropractors. An organization of Goodheart Study Group Leaders began meeting in 1973, selected the name "The International College of Applied Kinesiology" (ICAK) in 1974, adopted bylaws in 1975, elected officers in 1975, and "certified" its charter members, called "diplomates" in 1976. ICAK now considers 1976 to be the date it was founded and 1973 to be the date that its first chairman took office.
While it is primarily used by chiropractors, it is now also used by a number of other practitioners. In 2003 it was the 10th most frequently used chiropractic technique in the United States, with 37.6% of chiropractors employing this method and 12.9% of patients being treated with it, and has also been used by naturopaths, medical doctors, dentists, nutritionists, physical therapists, massage therapists, and nurse practitioners. Some basic AK based techniques have also been used/misused by nutritional supplement distributors, including multilevel distributors.
Applied kinesiology is presented as a system that evaluates structural, chemical, and mental aspects of health by using a method referred to as manual muscle testing alongside conventional diagnostic methods. The essential premise of applied kinesiology that is not shared by mainstream medical theory is that every organ dysfunction is accompanied by a weakness in a specific corresponding muscle, the viscerosomatic relationship. Treatment modalities relied upon by practitioners include joint manipulation and mobilization, myofascial, cranial and meridian therapies, clinical nutrition, and dietary counseling.
A manual muscle test in AK is conducted by having the patient resist using the target muscle or muscle group while the practitioner applies a force. A smooth response is sometimes referred to as a "strong muscle" and a response that was not appropriate is sometimes called a "weak response". This is not a raw test of strength, but rather a subjective evaluation of tension in the muscle and smoothness of response, taken to be indicative of a difference in spindle cell response during contraction. These differences in muscle response can be indicative of various stresses and imbalances in the body. A weak muscle test is equated to dysfunction and chemical or structural imbalance or mental stress, indicative of suboptimal functioning. It may be suboptimal functioning of the tested target muscle, or a normally optimally functioning muscle can be used as an indicator muscle for other physiological testing. A commonly known and very basic test is the arm-pull-down test, or "Delta test," where the patient resists as the practitioner exerts a downward force on an extended arm. Proper positioning is paramount to ensure that the muscle in question is isolated or positioned as the prime mover, minimizing interference from adjacent muscle groups.
"Nutrient testing" is used to examine the response of various of a patient's muscles to assorted chemicals. Gustatory and olfactory stimulation are said to alter the outcome of a manual muscle test, with previously weak muscles being strengthened by application of the correct nutritional supplement, and previously strong muscles being weakened by exposure to harmful or imbalancing substances or allergens. Though its use is deprecated by the ICAK, stimulation to test muscle response to a certain chemical is also done by contact or proximity (for instance, testing while the patient holds a bottle of pills). Studies of AK for nutrient or allergy testing have had positive and negative conclusions (see "Scientific Research" below.)
"Therapy localization" is another diagnostic technique using manual muscle testing which is unique to applied kinesiology. The patient places a hand which is not being tested on the skin over an area suspected to be in need of therapeutic attention. This fingertip contact may lead to a change in muscle response from strong to weak or vice versa when therapeutic intervention is indicated. If the area touched is not associated with a need for such intervention, the muscle response is unaffected.