A recent study appearing in the Journal of Manipulative and Physiological Therapeutics has examined spinal manipulative therapy and tactile allodynia (or hypersensitivity to touch). The results present a possibility laden with meaning for chiropractic: that “manually assisted lumbar spinal manipulation therapy modulates systemic oxidative stress, which possibility contributes to the analgesia and recovery of peripheral nerve functionality .”
The study in question was a rat model (which is a common biological model for human-related studies). The study, which had all its animal ethics approved by the University Universidade Federal do Rio Grande do Sul, used 30 adult male rats. They were housed in a room with stable temperature, and fed a stable, regular diet, and were split into a variety of groups in terms of knee immobilization vs. no immobilization, and sham intervention vs. spinal manipulation.
Using sensitive research equipment, researchers investigated “nociceptive changes after immobilization or after the therapy. A positive response was indicated by an abrupt withdrawal of the paw, and the intensity of the stimuli that provoked the withdrawal response was automatically recorded (in grams).” They also looked at recovery of nerve function post nerve injury. (The original article, referenced below, has full details of mechanical thresholds and sciatic, peroneal and tibial indices if you wish to read more).
After initial measurements, subjects were administered either spinal manipulation or a sham intervention. Adjustments and measurements were performed at significant points in the study before blood samples were taken at the conclusion of the process in order to determine oxidative stress levels.
The study yielded some enlightening results: Spinal manipulation was found to have “improved the immobilization-induced allodynia [sensitivity to touch] and recovered the peripheral nerve functional indices impaired after knee mobilization .” It was discovered that the rats that received spinal manipulation had no significant rises in lipid hydroperoxides (a measurement of oxidative stress) and nitric oxide metabolites (a free-radical indicator) in comparison to the rats who did not. These presented with elevated oxidative stress levels.
The rats that were immobilized and received spinal manipulation also showed modulated antioxidant catalase enzyme activity and modulated reactive oxygen species [ROS] rates. Reactive oxygen species are by-products of metabolism that have important roles in cell signalling but they increase dramatically during stress.
Simply put, it seems that spinal manipulation may assist in modulating systemic oxidative stress. Oxidative stress is thought to be the imbalance of free radicals and antioxidants in the body. When these are in balance, free radicals can do their job properly, the body can better fight pathogens and infections. When they are out of balance, free radicals can actually damage DNA and proteins along with fatty tissue .
The authors of the study also floated the possibility that spinal manipulation and its potential to improve oxidative stress may also contribute to positive impacts on the experience of pain and the recovery of nerve function.
The study was complex in terms of the measurements, variables, and the number of sham vs intervention groups, and was not without its limitations in terms of measuring all oxidative stress measures. Indeed, further research would have to be done in order to apply the rat model to humans more conclusively. However, the findings were far from insignificant. The authors remarked that:
“This study is the first to establish that AAI 4 therapy [the spinal manipulation used] induces recovery of the sciatic, peroneal and tibial nerve function indices decreased by 4 weeks of immobilization. Also, this is the first study showing the effect of the AAI 4 on ROS [reactive oxygen species].”
They concluded that, although it is too early to definitively demonstrate some aspects of the study, the results did show that the therapy may have a protective role on ROS. They said “it’s modulatory effect on systemic oxidative stress may be associated with the antinociceptive effect of [Manually Assisted Spinal Manipulation Therapy], recovery of peripheral nerve functionality and motor performance.”
Overall, the authors felt that the study supported their hypothesis that “AAI 4 on lumbar spine segments ameliorates the mechanical hyperalgesia, recuperates free walking pattern, and stabilizes the ROS activity induced by knee immobilization.”
At this point, we can only speculate what lumbar spinal adjustments may do in terms of recovery, pain, and oxidative stress in humans. But the results are looking promising. If indeed future human studies echo this protective effect in terms of oxidative stress, and the positive effect on pain and recovery, then this will have been very good news indeed.
Spinal Manipulation, Oxidative Stress and Pain: New study offers up potential links