Neurophysiologic Effects of Spinal Manipulation
in Patients With Chronic Low Back Pain
SOURCE: Musculoskelet Disord. 2011 (Jul 22); 12: 170
Brian C Clark, David A Goss Jr,
Stevan Walkowski, Richard L Hoffman,
Andrew Ross, and James S Thomas
Ohio Musculoskeletal and Neurological Institute (OMNI),
236 Irvine Hall,
Athens, OH 45701, USA.
Low back pain (LBP) is one of the most common reasons for seeking medical care and accounts for over 3.7 million physician visits per year in the United States alone. Ninety percent of adults will experience LBP in their lifetime, 50% will experience recurrent back pain, and 10% will develop chronic pain and related disability [1-4]. According to the most recent national survey more than 18 million Americans over the age of 18 years received manipulative therapies in 2007 at a total annual out of pocket cost of $3.9 billion with back pain being the most common clinical complaint of these individuals .
Over the past decade there has been growing scientific evidence supporting the clinical efficacy [6-10] and effectiveness [11,12] of manual therapies in treating LBP. While clinical evidence supporting the efficacy and effectiveness of manual therapies has emerged, less scientific evidence has been offered to explain the effects and mechanisms underlying these treatments. The lack of a mechanistic underpinning hinders acceptance by the wider scientific and health-care communities, and it also limits the development of rational strategies for using manipulative therapies.
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Many scientists and clinicians have long-postulated that manual therapies exert their biologic effects on segmental components of the central nervous system (e.g., supraspinal, spinal, etc.) [13-22]. For example, more than 25 years ago it was noticed that deep somatic or visceral pain leads to increases in muscle tone/spasm in the surrounding musculature , and many authors have speculated that an increased stretch reflex gain underlies the increased muscle tone in painful muscles as is commonly observed in LBP [16-18,24]. Interestingly, the limited animal  or human  data that exists does not support this common clinical assertion. However, the reflex activity of human back muscles has received little attention [26-30], and to our knowledge, no studies have quantified the effects of spinal manipulation (SM; the most common manual therapy used to treat LBP [31,32]) on the stretch reflex excitability of the low back muscles despite this being such a commonly touted mechanism of action.