Reliability, validity and responsiveness of chiropractic assessment techniques.

The study involves a single experimental session. The reliability and validity of the two chiropractic analytical tests will be assessed first. Following recruitment and screening, eligible participants will be assessed by two chiropractors using two analytical techniques: compressive prone leg check and sacral leg check. Compressive prone leg check and sacral leg check ascertain the site of vertebral subluxation by evaluating leg length inequality (LLI) and sacral restriction, respectively. Compressive prone leg check involves determining the relative position of the feet in two prone lying positions: knees straight and knees bent to 90 degrees. The sacral leg check involves comparing how high the participant raises each leg in a prone lying position with knees straight and noting the difference. Both the chiropractors will record the outcomes of these assessment tests on separate data collection sheets. The findings of each test will be compared between the two chiropractors to determine the reliability of the tests. The findings will also be compared to automated, computer-based video analysis to establish the validity of the tests. The computer-based video analysis will involve the use of a three-dimensional motion analysis system to record the position and movement of reflective markers placed on the participant's body. To determine whether the compressive prone leg check and sacral leg check are responsive to change caused by a chiropractic intervention, the participants detected with a vertebral subluxation will be randomised to receive either intervention or control intervention. The intervention will be a full spine adjustment session using an activator method technique protocol. The activator method is a standard chiropractic technique protocol that uses a small hand-held spring-loaded instrument called the Activator adjusting instrument to deliver fast, precise and low-force adjustments to the spine. A spinal adjustment is a form of manual therapy which often involves a high-velocity, low-amplitude thrust, which may induce an audible release of the joint. The single spinal adjustment intervention will take five minutes on average. The purpose of having the intervention group is to induce a change in the group, such that the responsiveness of the analytical techniques to detect that change can be evaluated in comparison to computer-based video analysis. Therefore, after the intervention, the participants will be re-assessed by one of the chiropractors using the compressive prone leg check and sacral leg check. Post-intervention computer-based video analysis will also be undertaken. The pre-post change in vertebral subluxation detected by the computer-based video analysis system will then be compared with pre-post change identified by the two analytical techniques. This will be used to determine the responsiveness of the analytical techniques.