Study title: The biomechanics of spinal manipulation Authors: Herzog W, Faculty of Kinesiology, University of Calgary, Canada Publication information: Journal of Bodywork and Movement Therapies 2010; 14: 280-286. BACKGROUND INFORMATION Biomechanics, in general, is the science of internal and external forces and their impact on biological systems. As all readers know, but may not often think about, spinal ma-nipulation is a mechanical event. Clinicians exert a force of a certain magnitude, in a specific direction, at a specific target site (or area) to affect changes in a joint. This causes a deformation of the spine and surrounding soft tissues. In high-velocity, low-amplitude (HVLA) manipulations commonly employed by chiropractors, force magnitudes and rate of force development are high. Each patient’s spine differs in terms of tissue stiff-ness, joint mobility, and so on – presenting significant challenges to those who study the biomechanics of this treatment intervention. Despite the emergence of advanced research techniques and ideas, we still know relatively little about the biomechanics of spinal manipulation. In this paper, Dr. Herzog describes the current state of knowledge on selected topics in this area, discussing the forces delivered to patients, the effects of those forces, and the stresses placed upon the vertebral artery (this aspect will not be reviewed in detail here). Dr. Shawn Thistle is the founder and president of Research Review Service Inc., an online, subscription-based service designed to help busy practitioners to integrate current, relevant scientific evidence into their practice. Shawn graduated from CMCC and holds an Hon-ours Degree in Kinesiology from McMaster University. He also holds a certificate in Contemporary Medi-cal Acupuncture from McMaster University, and is a Certified Active Release Techniques (ART®) Pro-vider. For more information about the Research Review Service, visit www.researchreviewservice.com. SUMMARY External Forces Applied by Chiropractors During HVLA Manipulations The following patterns emerge from studies measuring forces applied during manipula-tion using thin pressure pads and other similar devices: peak and preload forces vary dramatically depending on the location of treatment application; treatment forces vary highly between clinicians; the average forces delivered by males and females are about the same as are forces between novice and experienced practitioners; clinicians who adjust with greater force tend to do so consistently; thrust times typically range from 100ms in the cervical spine to 150ms in other regions. Effects of HVLA Spinal Manipulation The article discussed specificity of the manipulation, reflex response in adjacent muscle contributing to treatment effect, and the role of cavitation. CONCLUSIONS AND PRACTICAL APPLICATIONS This paper provided a brief snapshot on the literature dealing with some selected issues surrounding the biomechanics of SMT. This review did not include a summary of the section on internal forces during SMT (specifically to the vertebral artery), as there are more detailed reviews elsewhere. As mentioned, the literature in this area is still develop-ing. As new research emerges, prudent clinicians will adapt their techniques, views and patient education language/materials appropriately. • For a full review, including a detailed discussion of external forces during, and effects of, HVLA manipulation, study methods, strengths and weaknesses, and additional references, please visit www.canadianchiropractor.ca. This brief review is a sample of the content posted weekly on Research Review Service and is one of over 60 reviews available per year of the latest scientific literature in chiropractic. RRS is approved for 4.0 CEUs/year by CMCC. 86 • CANADIAN CHIROPRACTOR | SEPTEMBER 2010 www.canadianchiropractor.ca Shawn Thistle, BKin (Hons), DC, CSCS
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