563- How Spinal Adjustments Impact Multifidus Muscle Firing in Acute Low Back Pain

Welcome to The Evidence-Based Chiropractor, where each week we deliver the latest chiropractic research and marketing strategies, all in the time it takes to get to your office. Now here's your host, Dr. Jeff Langmaid.

Hello and welcome to The Evidence-Based Chiropractor. I'm your host, Dr. Jeff Langmaid. On today's episode, we're talking all about spinal adjustments. Fantastic study that really showcases what happens with the multifidus, what happens with those motor units, how do they fire more steadily, less steadily, what happens when people have acute low back pain and get adjusted. Fantastic study. Before we dive in, a few shoutouts. One, Care Plan Pro. If you are looking to help more people and make more money and don't wanna feel like you're selling timeshares, Care Plan Pro and our playbook training is built for you. It is not only the systems that I teach, I use, but it also is the software that makes it easy to present care and to ultimately have automated follow-up. It's all going on right now. If you're on the email list, you're seeing everything about this. Care Plan Pro. And when I say care plans, if you recommend more than one visit at a time, it is a care plan, whether it is 2 visits or 52 visits. It's all about packaging it in a way where people can understand what you actually mean, and you don't need to feel cheesy or sleazy making sure that people get the care that they need. Additionally, Leander Tables, $750 off their Series 950 is still going on. And Shockwave Centers of America, $500 off and a free cart. Big savings for being a listener here on this podcast. But as I said at the top, today we're talking research. The study title, Spinal Manipulation in Acute Low Back Pain Patients Is Associated with Reduced Motor Unit Firing Variability Without Altering Bilateral Coordination: A Single Motor Unit EMG Study of the Lumbar Multifidus. That is a mouthful. We're going to talk about what all of that means, clinical pearls, how it can impact your practice, and much more.

Yeah.

On today's episode. So to set this study up correctly, imagine you are a patient. You've had low back pain for a few days. It's 6 out of 10. And somebody comes to you and says, hey, do you mind if a radiologist puts tiny wires straight through into the deepest muscle of your back and then a chiropractor adjusts you while the wires are still in? Most people would probably say, I'm going to think about it. But they found some individuals in Norway who said yes. And because they said yes, we get to peek at something almost nobody in our profession has ever seen. And that is what individual motor units in the deep lumbar multifidus, my favorite muscle, are actually doing before and after an adjustment. Not surface EMG, not a guess, the actual firing pattern of single motor neurons. So after one side-lying high-velocity, low-amplitude adjustment, those motor units Did not fire faster. You might say, well, is faster better? Well, they also did not fire slower. They fired steadier, less jitter, less noise, cleaner signal. We're going to talk about what that means. It's a pretty small study, so it's limited in what we can extrapolate, but it's a really good one to start the conversation around what happens. So first, let's start with the why. We all know spinal adjustments are recommended in guidelines for both acute and chronic low back pain. But if we're really honest, the mechanism is still a little bit fuzzy. We talk about mechanism of action all the time, and it's— the breadth and depth is like so wide, it's hard to just like nail down to this one thing, which is a great thing. But it also makes it so that there's a lot of stuff that goes on, right? The facet joint gets gapped, there's breaking up of adhesions, synovial folds, improvements of reflexes of the tight muscles, better proprioception, pain modulation. So when the researchers have gone looking for, well, the classic muscle relaxes after an adjustment, the results have been mixed because there's so much stuff that happens very, very quickly. Part of that problem is the tool. So most of this work historically has used surface EMG and surface electrodes over the low back. They mostly kind of hear the big erector spinae and a lot of crosstalk. They can't isolate muscles and certainly they cannot isolate The deep multifidus. And the multifidus is the muscle that we really care about. It is the segmental stabilizer, the key segmental stabilizer. And we know it gets inhibited and can start to atrophy early in low back pain. So this team had built a method. Under CT guidance, an interventional radiologist places custom, like fine, fine wire, like thin as a human hair, think about it, electrodes into the deepest part of the multifidus. At the painful level on both sides. Then they check via CT after the patient moves around so they know they're really in the right target. And then with that, they were able to really identify in single motor units what happened. So part of this, you can trace all the way back in 2015, which there was a group that showed that in healthy people, motor units in the multifidus share a strong, what they called common drive. Both on the same side and across left and right. Think of it as both sides of the spine basically getting the message from the nervous system. And then in 2019, looking at acute low back pain patients, they found the cross-side information was weaker. The 2 sides were less in sync. And then those 2019 recordings were only before half of the experiment. In the same sessions back in March and April of 2007, Yeah. The same patients were adjusted and the recordings kind of kept going. This 2026 paper is the first analysis of the after data, if you want to think about it that way. So the patients serve as their own control, same wires, same day. So in this study— so that's a long story short is over 10 years ago, people started to measure this. However, this is the first study that measures before and after.

Mm-hmm.

deep into the affected tissue and really starts to say what actually happens at a single motor neuron level. So they had 3 predictions. One, the adjustment would make the motor neurons fire more steadily. 2 is that would improve left-to-right coordination, so the message being equal to both sides. And 3, it would help motor units take turns, what they call rotation. So keep those in mind as we kind of go through some of these findings. So They found a little bit under a dozen individuals, acute nonspecific low back pain, median age 38, and their pain had been going on for a median of just a few days with a max of 3 weeks. So these were acute, right? Not chronic. Medium pain, 6 out of 10. No leg pain, no neuro symptoms, nothing scary on MRI. 4 of them had one-sided pain, 5 had pain on both sides. The adjustment, as we highlighted, side-lying, high— think of it like a diversified, basically. A chiropractor delivered this, same chiropractor every time, and they used a finger pull contact on the spinous process, and that's how it was delivered. So prediction 1, steadier firing. Yes, they measured how much the gap between one firing and the next one bounced around. After the adjustment, that jitter, the variability, dropped by about 5 milliseconds. That's after adjusting for posture, voluntary activity. That's a true prediction, so to speak. Prediction 2 was better left-to-right coordination. In this case, the answer was no. And prediction 3, motor units taking turns, that was not seen. So the adjustment didn't turn the multifidus up or down, it just made the signal clearer. And if we slow down and start to unpack what firing variability means, that, that's the important component here. A motor unit is one motor neuron plus all of the muscle fibers it controls. When it's been holding you upright, it fires in rhythm, tap, tap, tap, tap, tap. In a perfect world, the space between those taps is very even. In the real world, it wobbles a lot. Tap, Tap, tap, tap. So the researchers measured that wobble tap to tap. Think about it that way. So if you picture like a drummer keeping time, a really good drummer is super steady. They're keeping the same BPM, beats per minute, right? A nervous drummer, an experienced drummer speeds up and slows down so that the tempo on average might be identical, but one sounds like tight to the music and one sounds pretty sloppy. So after the adjustment, the multifidus drummer, so to speak, Got tighter. And you might say like, okay, 5 milliseconds on its own, that sounds tiny, but you have to know what the size of the yardstick it is, right? So going from sitting to standing changes this variability by about 15 milliseconds. So the adjustment effect was roughly a third of what a full postural change does. And it moved patients' numbers closer to what the team had previously recorded in pain-free people. That is really a big take-home message. And why would this steadier firing matter? Well, other research has linked more motor noise with experimental muscle pain, neck pain, and even stress. In the motor system, noise doesn't like buy you anything. It can mean, you know, shakier force input, lower max force. And the authors even speculate it could tie into poor endurance that we see in people who have low back pain. And that finding sort of smoothed out after the adjustment.

Wow.

And that is really, really impactful. And the authors even take it a bit further, talking about what didn't change. In pain-free people, the left and right multifidus get the same signal about equally. In these back pain patients, the cross-side information was weaker before the adjustment. It was still weaker after. So one adjustment didn't sync those up. And if you take that one step further, they've wondered whether weaker left-to-right coordination is caused by pain or a preexisting pattern that sets people up for pain.

Hmm.

And because it didn't budge after the care and treatment delivered in this, they lean towards the second. Maybe it's a trait, not a state. So they're careful to say this is early, this is pretty limited data, but I think it's really, really impactful and important to say, hey, we know that steady muscle firing is quote unquote normal. We know in people that have low back pain, abnormal firing is normal when you're having back pain. And now we know, and we start to see that when an adjustment is delivered, individuals with back pain and abnormal firing, that aberrant firing becomes more regular, more consistent, and more normal, more akin to individuals that have no back pain at all. So I liked this study because it starts to highlight— I mean, these are like, this stuff's a little geeky, but it gets deep into the adjustment itself. When you deliver that adjustment, you are literally changing How the multifidus fires. Yes, they're gapping. Yes, you're gapping the facets. You're impacting the peripheral nervous system, the central nervous system, biochemical marker changes. You're reducing adhesions. You're potentially gapping synovial folds and ensuring that they're moving more fluidly from a biomechanical perspective. However, we also know now that you are actually influencing the input and output that's going on at a motor unit. And for individuals that have—

Yeah.

Fear avoidance behavior. They're not moving correctly. You do— let's say you're using SFMA, DNS. You go through your movement assessments, you have somebody go through a squat. They either can't even complete the squat, or, you know, the movement is just not good. It's jacked up top to bottom. Wow. Being able to stabilize the firing of the primary stabilizer in the lower lumbar spine and clearing it out, as a matter of speaking, making it fire, influencing it to fire more regularly, more systematically. Is a great— you know, this is another step in my mind towards, man, you start to pair this with— you deliver that adjustment, then you get somebody going through movements, exercises, stretches, whatever it might be, whatever they need, but you tag movement onto the back end of that adjustment when things are firing more regularly. I cannot help believe that that would improve your results, it would improve the outcomes, and potentially even speed up the process of the recovery that that patient is going to get. So I thought this was a super cool study. It does go deep into a lot of technical jargon and aspects. However, I will drop a link down below. You can check it out at your own leisure. And as we wrap up today's episode, big shout out as well to NovoPulse and their OA Recovery Program. You can bring an OA Recovery Program in with no capital outlay, no big money out. You'll get the hardware, the software, all the marketing. Check out the NovoPulse OA Recovery Program. I'll drop that down below.

Awesome.

As well as the Rehab Fix Hybrid Program. Dr. Grant Elliott's been doing this a long time. He's done it himself, he's coached others. If you're looking to make more money and expand beyond the 4 walls of your practice, help people that are beyond the circle of practice, the Hybrid Program allows you to not abandon what you built brick and mortar, but actually lean in and expand your brick and mortar to an online hybrid program as well. Grant knows this world better than anybody else. I'll drop a link down below to connect with him and his team. Thank you so much for tuning in. If you have not left a rating or review for this podcast, I would love it if you would take a moment and do so. It helps more and more docs find out about it. Other than that, I hope you— thank you for being a chiropractor. I hope you have a fantastic week in practice, and I will talk to you soon.

Thank you for joining us on this episode of The Evidence-Based Chiropractor. If you want to grow your practice, come back for next week's episode. If you want to grow faster, visit theevidencebasedchiropractor.com. Visit TheChiropractor.com and join our MD Marketing membership today.

The Chiropractor.