The purpose of this study was to investigate  the relation between preload and peak forces during Spinal Manipulative  Therapy (SMT). Forces during clinical trials of SMT were measured on the  sacroiliac joint, the thoracic spine, and the cervical spine using a  thin, flexible pressure pad (EMED Inc.). Preload forces were found to  correlate well with peak forces during SMT, suggesting that the force  required to move the joint of interest to the end range of passive  motion (i.e., the preload force required) influences the magnitude of  the treatment thrust. Furthermore, the change in force from preload to  peak (∆F) also correlated well with peak thrusting forces for all SMTs  tested, suggesting that the stiffness of the joint of interest at the  limit of passive range of motion may be related to peak thrusting  forces. Preload and corresponding (∆F) forces were not correlated  highly.

Journal of the Neuromusculoskeletal System. 1993; 1(2): 52-8.

Author information: Herzog W, Kawchuk GN, Conway PJ.  Human Performance Laboratory, Faculty of Physical Education, The University of Calgary, Calgary, Alberta, Canada.