specific X-rays and found to be a vertebral subluxation. It is based on the teachings of B. J. Palmer, who advocated the Hole-In-One version of spinal adjustment. It is primarily used by straight chiropractors. Referring to the origins of upper cervical techniques, Dan Murphy, DC, DABCO, wrote: "Over the past 100 years, the practice of chiropractic has branched into dozens of specialty techniques. However, historically, for a third of this time, from the 1930s into the 1960s, the predominant practice of chiropractic involved primarily the upper cervical spine." Extremity manipulating/adjusting Activator methods The Activator Method Chiropractic Technique (AMCT) is a chiropractic treatment method and device created by Arlan Fuhr as an alternative to manual manipulation of the spine or extremity joints. The device is categorized as a mechanical force manual assisted (MFMA) instrument which is generally regarded as a softer chiropractic treatment technique. The activator is a small handheld spring-loaded instrument which delivers a small impulse to the spine. It was found to give off no more than 0.3 J of kinetic energy in a 3-millisecond pulse. The aim is to produce enough force to move the vertebrae but not enough to cause injury. The AMCT involves having the patient lie in a prone position and comparing the functional leg lengths. Often one leg will seem to be shorter than the other. The chiropractor then carries out a series of muscle tests such as having the patient move their arms in a certain position in order to activate the muscles attached to specific vertebrae. If the leg lengths are not the same, that is taken as a sign that the problem is located at that vertebra. The chiropractor treats problems found in this way moving progressively along the spine in the direction from the feet towards the head. Although prone "functional leg length" is a widely used chiropractic tool, it is not a recognized anthropometric technique, since legs are often of unequal length, and measurements in the prone position are not entirely valid estimates of standing X-ray differences. Measurements in the standing position are far more reliable. Another confounding factor is that simply moving the two legs held together and leaning them imperceptibly to one side or the other produces different results. Fuhr claims that properly trained doctors show good interexaminer reliability. In 2003, the National Board of Chiropractic Examiners found that 69.9% of chiropractors used the technique, and 23.9%