Chiropractic Adjustments and Their Effect on the Autonomic Nervous System | Podcast Ep. 229

Foreign hello and welcome to the Evidence Based Chiropractor. I am your host, Dr. Jeff Langmaid. And today we are going to talk about a really interesting research study that came out just last year. In 2019, it was released in Spine. And basically they looked at what happens when you adjust the symptomatic people, what happens when you adjust asymptomatic people. And they're really trying to get to the heart of how does an adjustment work? Title of the paper is Neurophysiological Effects of High Velocity and Low Amplitude Spinal Manipulation in Symptomatic and Asymptomatic Humans. We're gonna break this down and talk about context for how it matters with the conversations that you're having with your patients each and every day. On today's episode, we are talking about a study that was released by Spine. It's actually a literature review, technically SPE it was released in 2019 and it was titled Neurophysiological Effects of High Velocity and Low Amplitude Spinal Manipulation in Symptomatic and Asymptomatic Humans. Basically, they looked at 18 studies covering about 1,000 people and they were trying to delineate what happens when you adjust somebody who's symptomatic and what happens when you adjust somebody that is. That is asymptomatic. Now they kind of set the stage by talking about some previous animal studies that indicated spinal manipulation basically can increase the discharge frequency of proprioceptive afferents. And those are our muscle spindles and Golgi tendon organs. So we've talked about how an adjustment or a manipulation can ultimately affect Golgi tendon organs as well as muscle spindles. In the past we've also talked about how there can be basically changes in biochemical markers, how pain sensitivity can be altered, how increase in pain pressure thresholds can ultimately change, and subsequently substance P, neurotensin, oxytocin, interleukin and cortisol levels all have the potential to be affected. We've explored all of that and more in previous episodes. Now this literature review takes that into accord and much more. So a couple things that they talk about that we had not really discussed is increased skin conductance and decreased skin temperature pointing towards activation of the sympathetic nervous system. We've talked around that, but I would say not really about that in the past. So ultimately this gets down to are there effects on the autonomic nervous system? This is a really clutch and key question. Now say it right off the bat that this paper on its own and nothing that I've seen really affects. Press this button, get this outcome right in terms of the autonomic nervous system. But there definitely seems to be some impact or influence via an adjustment. So they say for blood pressure, one study reported a significant reduction of the systolic blood pressure after an adjustment. So that's pretty interesting. And then they talk about. Two studies found no effect of upper thoracic adjustments on heart rate variability. Okay, so now we're getting into some interesting things. They found an adjustment to the upper or lower cervical spine did not affect heart rate in healthy adults or adults with acute neck pain. So, okay, now we're starting to get into some interesting stuff here. You know, what has sympathetic effect, what doesn't? They say, quote, A sympathetic response to an adjustment was reported when measuring skin conductance, another common measure for sympathetic activity. Skin conductance measured in the lower limb increased after a lumbar adjustment in healthy participants. Okay, so this is starting to get interesting. And in their discussion, they point out there's some evidence that adjusting affects the autonomic nervous system, as identified by more than one study, showing a significant effect for heart rate variability as well as skin conductance. The direction of the autonomic effects might depend on the location of the adjustment, as well as if the patient is in pain versus being asymptomatic. So that starts to get really, really interesting. Right. When we see that the adjustment is associated with an increase in the sympathetic to parasympathetic ratio. And now we start to break down when it's applied to the lower cervical or the upper thoracic spine, there might be a different impact, different influence than to the lumbar spine or to the upper cervical spine. Now, this study doesn't sort of nail that down in terms of the final verdict, but it's showcasing that previous studies have indicated there are differences. So upper cervical spine was associated with a decrease in the LF to HF ratio, indicative of a decreased sympathetic to parasympathetic ratio, and that was in the upper cervical spine. Now, alternately, an adjustment to the upper cervical spine might affect the parasympathetic autonomic nervous system via the brainstem, where the preganglionic parasympathetic fibers originate. Okay. And also, they note that things shift towards sympathetic activity when applied to the lower cervical or upper thoracic spine and lumbar spine and towards parasympathetic activity when applied to the upper cervical spine. So this starts to get really, really interesting. Now, there's no real final conclusions. What I'd say from this paper but it points to the fact that there is some effect on autonomic system. There is some effect, at least on parasympathetic to sympathetic ratios. And that the research currently points to the fact that there is gonna be differences based upon where you adjust. So in the upper cervical spine, as they're talking about, there seems to be a shift in sympathetic parasympathetic relationships. Now they're pointing to the fact that they think it's brainstem and preganglionic nerve fibers that are, you know, conducting or impacting those changes. Whereas if you're adjusting the thoracic spine or the lumbar spine, there might be some opposite type effect. Really, really interesting stuff as we start to break down, okay, we see patients that come in, most of us all the time, that are having the common symptomatic complaints, right? Neck pain, headache, low back pain, radiculopathy, disc issues, you name it. Very common reasons why a majority of people go in to see a chiropractor. Now, historically, we've also seen and noted that there's plenty of people that asymptomatically get a tune up, visit, get an adjustment every once in a while, and it seems to stave off potential issues. We've talked about that in terms of previous maintenance studies as well as a new maintenance study that we'll touch on coming up in the next week or two. But what this study indicates, which starts to get really interesting, is that asymptomatic patients versus symptomatic patients, that on the symptomatic patient there seems to be a very clear reduction in pain. And there's a complex series of events that basically enable that to happen, right? Pain gating, to a certain extent, impact on the central nervous system, to a certain extent, movement, Golgi, tendon organs, muscle spindles, all of these things increase range of motion, decrease pain and improve function. But when we have a patient who is asymptomatic, how are they affected? Now this paper again, looked at it from the lens of, well, let's take a look as far as the autonomic nervous system, let's take a look in terms of sympathetic to parasympathetic shift. And what they're finding is the changes that are made, the influence that is had can at least in some part be looked at through the lens of what area of the spine is being adjusted. Now this starts to get really interesting to me because it's a really cool area where research can go in the future. Again, I don't think this study comes down with Any do this or don't do that, right? That's not the point of research. The point of research is to answer questions and open up new ones. And this paper does a great job doing that because I'm gonna put it in the clinical context. When you're seeing a patient in your clinic who might be asymptomatic, maybe they're coming to you for performance, maybe they're coming to you for maintenance wellness, however you want to define that, at whatever frequency they are coming in, you know, taking a look really at what's going on in their life, understanding their lifestyle factors and then going through the examination might make a heck of a lot of sense. When we're talking about sympathetic parasympathetic nervous system that really has a psychological component, right? Fight or flight, what's going on physiologically, what's going on mentally, and what's going on with the movement of their joints. And really taking that from a holistic approach, if you're doing a movement assessment, understanding what's going on and is there a psychological issue going on, is there not? These are important things as we talk about. It's hinted at in the biopsychosocial model, but it really should be brought down to the brass tacks of how you're going through your updates, your examinations and not necessarily your evaluations, your quote unquote BIG evaluations every six to 12 visits. But even with your day to day interaction with the patients, understanding where they're at, are they symptomatic, are they asymptomatic, what are their goals? Right. What are they looking to achieve in the practice through your care and what are they currently experiencing, what challenges are they looking to overcome and or where are, what benefits are they looking to achieve? When you start to look at it through that sort of lens from a clinical sense, not from a research sense, it starts to really crystallize how you can apply your craft. How can you apply the craft of what you do as a chiropractor in a way that is going to help that guide that patient towards the outcome that they are looking for. Because that ultimately is what it is all about. It's having a patient centric model in your practice. It's really being what I call relentlessly focused on the patient experience while being evidence informed and evidence based. And evidence informed, evidence based doesn't always mean that it comes down to just what's a randomized control trial in a research paper. It comes down to what's your best clinical experience, what, how is that individual patient presenting and what's the best you can do given those circumstances while leaning into what you know at the literature, but not having that make every single ultimate decision for you and your practice. So really keeping that in mind, I think is a good way to go about clinical practice. Interesting studies like this in spine literature reviews that are really starting to examine how does an adjustment impact a person, whether they're experiencing pain, whether they're not experiencing pain. Really interesting way for things to go. As research continues, I hope to see more of it and I'd encourage you to get out there and continue to explore the research. Continue to tune into this podcast if you've been tuning in for a while. I really, really appreciate it. I'd love rating, review, feedback. You can do that right from your app if you're listening in itunes on an iPhone. If you're not, you can just head on over to itunes, leave rating or feedback there. And if you're a new listener, welcome. This is a podcast where each and every week we dive into the intersection of research and marketing in the time it takes to get to practice. So try to keep every episode 15 minutes, 20 minutes or less, but really appreciate everybody tuning in listening. I have just a ton of gratitude if you're a doc out there right now as well who's just getting back into the swing of practice after all this Covid craziness. Kudos to you. If I can help whatsoever, please feel free to reach out to me, jeff the evidencebasedchiropractor.com I know this last couple months has been super, super difficult on a lot of docs out there. So if I can help you in any way, please feel free to reach out to me. Keep up the fantastic work. Keep up the great mental mindset of keeping with your practice of staying up to date with the research and applying that in the best way that you can for the people in your community. I'll be here doing my best to support you on that journey and if there's any way I can help you more again, please feel free to reach out to me, jeff the evidencebasedchiropractor.com and stay safe, stay healthy, have a fantastic week in practice and I'll talk to you soon.

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