Evaluation of the Associations Between Spinal Manipulative Therapy Dosage and the Related Spinal Stiffness Modulation in Participants With Chronic Thoracic Pain

Spinal manipulative therapy (SMT) is based on the premise that clinicians can identify spine mechanical changes and accordingly determine the dosage of its biomechanical parameters: preload force, rate of force application and peak force. In recent years, our research team showed, using an apparatus to deliver specific dosage SMTs, that SMT-related neurophysiological responses depend on the dosage of these parameters. Beside determining the SMT dosage, clinicians have to select the spinal level to be treated which is partly done by applying a light pressure to each spinous process (spinal stiffness assessment). This study consist of a randomized controlled trial including 75 participants with chronic thoracic pain who will be randomized in one of three groups. Based on their group assignment, participants will receive a specific dosage SMT delivered at T7 three times over 2 weeks. These SMT dosages are distinct regarding their speed and/or their peak force in order to generate either a high vertebral displacement or a high muscle reflex response. T6, T7 and T8 spinal stiffness will be measured just before and after treatment and clinical status will be assessed at each session beginning through questionnaires. Session four will include the questionnaires and the spinal stiffness measurement procedure. Both SMT and spinal stiffness measurement will be performed using an apparatus aiming at simulating force-time profiles. Surface electromyography electrodes and accelerometers will be positioned over the upper back skin in order to measure the muscle response and vertebral displacement during SMT and spinal stiffness measurement procedures.