J Manipulative Physiol Ther. 1990 Oct; 13(8): 448-53.

Experimental measurement of the force exerted during spinal manipulation using the Thompson technique.

Hessell BW, Herzog W, Conway PJ, McEwen MC.

Faculty of Physical Education, University of Calgary, Alberta, Canada.

The purpose for conducting this study was to quantify the forces exerted by a chiropractor on a patient during spinal manipulative therapy. Six patients received three treatments each from two chiropractors for a sacroiliac joint fixation. The Thompson technique was used to treat the patients. The force characteristics of the spinal manipulation were analyzed with respect to the following five points: preloading force, peak force, duration of manipulation, impulse of manipulation and point of application of the peak force. The results obtained indicated that all treatments have certain common characteristics; for example, a preload force is always followed by a large thrusting force. The values for the preload force, peak force, duration and impulse were found to have large standard deviations for a given adjuster and between patients. The location of the point of application of the peak force relative to a low back reference system appeared to be very consistent. However, it was not on the posterior superior iliac spines (PSIS) as expected, but always slightly medial to this point. This is the first study to report force results which were measured directly during spinal manipulative therapy in a clinical situation. In further studies, the results of this investigation will be compared to results obtained from a large population of patients and chiropractic adjusters. Differences in the force characteristics between chiropractors will be compared to clinical and objective measures of the rehabilitation process of the patients in order to find an "optimal" way of performing spinal manipulative therapies.