552- Exploring the Impact of Lower Limb Adjustments on Squat Strength in Athletes

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 am your host, Dr. Jeff Langmaid. On today's episode, we're talking all about lower limb adjustments and the effects that it has on squat strength. This is a double-blind randomized crossover trial. Drop a link down in the show notes. But before we get started, big shout out to a few partners of ours. The RehabFix Hybrid Program. If you'd like to extend care beyond the four walls of your practice, make more money, help more people, uh, Grant is somebody you want to speak with. RehabFix Hybrid Program, we'll drop a link down below, connect with their team, ask all those questions that you might have. As well as the NovoPulse OA Recovery Program. Osteoarthritis is rampant. If you do not have a specific program to help those individuals, you're probably missing out on opportunity in your practice. The NovoPulse program gives you the software, hardware, and patient attraction tools to make it super easy. Link down below. Big question on today's podcast is, can lower limb manipulation or adjustments improve squat strength? That's what we're going to talk about. The title of the study: Effects of Lower Limb Joint Manipulation on Squat Strength and Ankle Range of Motion: A Sham-Controlled Double-Blind Randomized Crossover Trial. So are we really doing an episode on squats? Yes, we are. Because whether you love squats avoid squats, program them, recommend them, um, or have patients tell you, hey, every time I squat, my ankles feel pretty stuck. Uh, this research hits on something that matters in your practice. So the question was, can a lower limb adjustment, specifically adjustments to the ankle, foot, or tib-fib region, immediately improve squat strength and ankle range of motion? And it's a pretty fantastic question because in chiropractic practice, we talk all the time, just about every week on this podcast as well, about things like mobility, movement quality, joint function, performance, and helping people move better. And when we see a patient who has limited ankle dorsiflexion, a poor squat pattern, heel lift, knee collapse, limited depth, you name it, forward trunk lean, it's natural to think, oh, if I can improve their ankle biomechanics, maybe we can improve the squat. And clinically, that makes sense. This question goes— this study goes one step farther. Not only can manipulation help somebody feel looser, you know, not just can it help improve movement in general. So it's really going, I'm going to say one step further than that, saying, can one session of a high velocity, low amplitude adjustment to the lower limb produce a measurable immediate improvement in one rep max back squat strength? Wow, that's a mouthful. And ankle dorsiflexion. And that's a tougher test. So the answer is not like this massive hype machine, but I think it's really cool to just start walking through this. So the manipulation group in this study improved their squat by about 3.5%. The sham group improved by about 2%. So both groups improved, but the difference between the real adjustment and sham was it didn't reach a level of statistically significant. So before you say it doesn't matter, hold on, you know, that's not the takeaway. The takeaway I'm gonna say is more clinically useful than that. This study gives us a really good opportunity to talk about where adjustments may fit, where they might not fit, and what we can honestly say about performance. And this can be communicated to, you know, active patients, athletes, weekend warriors, everyday people. It can really apply across the board because a single adjustment, not going to surprise you here, might not magically add, you know, pounds and, you know, hundreds of pounds to somebody's squat that same day. But it does not mean that improving lower limb mechanics is irrelevant. So this is where understanding context, dosage, patient selection, and expectations all really, really matter. So the title tells us a lot. It's a mouthful, but it's a strong study design, and we'll talk about what that means. So it's sham-controlled, number one. Again, title: Effects of Lower Limb Joint Manipulation on Squat Strength and Ankle Range of Motion: A Sham-Controlled Double-Blind Randomized Crossover Trial. There's a lot there. So what does sham-controlled mean? That means they didn't just compare people before and after the adjustment. They compared real adjustments against a sham adjustment. So with manual therapy research, expectation is a big deal. Touch really matters, attention matters, and the ritual of the treatment itself matters. So people might feel differently because something was not done. So having a sham comparison really makes the study stronger. Second, it was double-blinded. So the participants were blinded and the outcome assessor was blinded. So the person testing the outcomes was not supposed to know whether the participant had received real manipulation or sham manipulation, and it was randomized. So the participants were randomly assigned, um, and it was crossover. So each participant received both the real adjustment and the sham adjustment at different sessions. So instead of comparing one group to a totally different group of people, each partici— each participant basically was their own comparison. And this is pretty useful when you're looking at strength outcomes because, uh, individual differences can be pretty meaningful. So they enrolled 26 people, uh, 24 were included in the final analysis, uh, and they were resistance-trained adults. So they weren't like brand new lifters. They all had been able to squat at least one time their body weight for one rep max. And they had a history of resistance training that included squats as well. Also, they all had limited ankle dorsiflexion in at least one ankle. So it was not like this general population sample. This was— and it wasn't like low back pain patients. These were asymptomatic resistance-trained people/athletes with ankle dorsiflexion restriction. And that distinction's huge because we often see symptomatic people in our practices, as you know, uh, people with pain, you know, instability, disability, recurring sprains, old injuries, all that. Now this focused on asymptomatic individuals, but they did have that measurable dorsiflexion limitation. So the authors were looking at a few outcomes. One primary outcome: one rep maximum back squat strength. Man, that is difficult to get out. The second outcome was ankle dorsiflexion during the squat and active dorsiflexion range of motion measured with the weight-bearing lunge test. So they wanted to know basically, does lower limb adjustments manipulation help people squat heavier? Does it change how much the ankle dorsiflexes during a heavy squat? And does it improve the ankle range of motion after the treatment? So the intervention was high-velocity, low-amplitude adjustment applied bilaterally to several lower joint limbs. They targeted a variety of different, again, foot and ankle joints. So they adjusted the ankle, the foot, and the upper tib-fib region with the goal of improving the, the entire ankle-foot complex, specifically dorsiflexion, of course. So sham intervention designed to mimic it. They used a drop mechanism on the table. In mock thrusts, but it, but it wasn't a specific joint manipulation. So now, why was this study done? Well, a squat is one of the most common exercises used to develop lower body strength, and you probably either test for it if you're using DNS, SFMA, or prescribe it, whatever it might be. So whether you're working with athletes, weekend warriors, pretty much anybody out there, a squat is not just a gym metric. It really is important in understanding how people are moving functionally. So this paper notes that increases in squat strength have been associated with sports performance measurements, uh, and benefits. And it also connected the squat strength with activities of daily living and lower limb function. So the performance of a squat really matters. So if someone lacks ankle dorsiflexion, they might struggle to hit the depth necessary to actually perform a squat. They might compensate by lifting heels, by collapsing knees inward, leaning forward, shifting load, all the things that you've seen a million times. So the study notes that normal ankle dorsiflexion, when measured with the weight-bearing lunge test, is typically greater than 44 degrees. So participants in this study, remember, they had at least one ankle below that threshold, and the goal was to see if the adjustment could improve that. It's a very reasonable question clinically, because many of us will assess the ankle, will adjust the ankle. So understanding and seeing what the benefit of that is really, really important. And, you know, the real hard question is, well, then could somebody do a heavier 1-rep max? And that's a pretty high bar. 1-rep max is influenced by a lot more than ankle motion alone, as you know. It's motor learning, it's confidence, fatigue, Bracing, strategy, familiarity, you know, strength ceiling, day-to-day variation. So even if the adjustment changes joint feel, it might not be enough to move a true max strength number in a meaningful way. And I think that's why this study is useful. It helps us separate mobility from, you know, the max strength claim, so to speak. So again, 24 participants analyzed, average age 29 years old. 17 males, 7 females. They all trained again. Um, their baseline, uh, one rep max was around 130 kilograms, about 287 pounds. I think that conversion is, is correct. I'm not a kilogram expert. Uh, and these were not beginners. So the restricted ankle motion was at least one on every single individual. And the big results were the— that the one rep max increased after both interventions again. So In the sham intervention, there's about a 2% improvement. In the adjustment intervention, a 3.5% improvement. So you can look at that and say, hey, it looks like the adjustment group did better. Yes, that is true, but it didn't reach the level of statistical significance. So interesting. Why is that interesting? Because there's a variety of things, as we've said. There's a variety of reasons why that might be the case, but it's really exciting and is interesting because it also shows there was a benefit. Maybe not enough benefit to hang your hat on and be able to claim an adjustment's going to help people lift more, but I don't think that's what we're looking for. What we're looking for is how are we impacting people's functional ability. And man, even a short-term, short-duration, small amount increase is a huge step in the right direction because that is massively more meaningful than no change or worse. So anything that we're doing to move positive, of course the ankle is going to move better, as we're going to see in a moment. But man, anything, even a short-term change, low and not going to last forever. Man, that is meaningfully important, especially when you put that as part of adjustment and rehab in a session, right? Everything's going to stack over time. Again, no, no adverse effects as well. So important to note that. So the most interesting part of this study for me was that both groups improved. And that tells us something pretty important. That's when people repeat a 1-rep max, especially in a study environment, they can improve because of the repetition and familiarity. And the author spent some time discussing this as well, because when you ask somebody to do something a second time, they know what they're doing, they know what they're into, they know how you're going to ask a question, they're going to see how it works. So that's, that's interesting, and it's also something we can leverage, because that's why skilled work and training is so important. Now, there also is something called the ceiling effect that's important to keep in mind. Ceiling effect means that there might not be much room for immediate improvement. If somebody's already strong, trained, coordinated, familiar with squatting, and not in pain, one session might not be enough to produce an obvious jump in maximum strength, which makes total sense. If a trained lifter walks into your office with no pain, no injury, and only a dorsiflexion restriction, you know, it— what is more likely to improve than their one rep max? Um, you know, probably the motion, right? So Manual therapy and what we do can help create a better window for movement, but it's not a replacement for training adaptation. So, uh, so that's also really, really important to keep in mind. So I thought this study was really, really interesting, and I liked how it highlighted also the weight-bearing lunge test. Now, this study found no significant short-term improvement in dorsiflexion, uh, after either intervention, and that lined up with some previous studies as well. But there was some differing in other studies compared to today. So it differed from other studies involving chronic ankle instability or multiple intervention sessions, and that distinction is key. Manual therapy effects can be different for people with pain, instability, or altered neuromuscular control. And if a patient has chronic instability, then the adjustment that you deliver might have more room to create a meaningful change in that single session, right? Um, this is a single session study. I don't love single session studies because what we do has compounding benefit quite often. So I I really wish they would've done a single session on this and then extended it to 1 week, 2 weeks, 6 weeks, whatever it might be, whatever would make the most sense so that we could see things over time. They didn't, but that's why this is a cool study to say, hey, we see a glimmer of hope. We see an opportunity where there was, whether it's increased cortical drive or bottom line is increased ability to lift. Okay, how much of that was repetition? How much of that was the adjustment? Let's design the next study to start diving deeper into that. But man, this gives a great jumping point for something to be done exactly like that in the future. So in real practice, many patients are not asymptomatic. They have pain, they have instability, poor control. So those people also might respond a little bit differently than the individuals in this study. And I think research like this helps you and I communicate better with fitness-minded patients. Um, you know, a lot of active patients appreciate that honesty and transparency. Hey, there's studies that suggest you know, one session of adjusting your, your, your foot and ankle, uh, can actually increase max strength compared to a sham treatment. So, you know, let's see if we can improve that a little bit today. Uh, and that you don't need to overstate things. It can be credible, it can be evidence-informed, and it can ultimately be helping people understand the benefits of what you do and how it not only affects that joint, but it does affect their entire neuromusculoskeletal system. There are biochemical marker changes, there are cortical drive changes, there is pain gating, there is segmental changes where that is occurring. All of those things happen when something as seemingly as simple as getting hands-on care and treatment in your practice is delivered. So I think this is a cool study because it gives you the opportunity if you're doing movement assessments, again, DNS, SFMA, however you're doing a movement assessments, man, talk about a cool opportunity, especially for those individuals that might be lifters in your practice to do a little before and after. Do some testing, see how they're moving before. Do some squat testing pre and post adjustment and see what those improvements look like. That can be, especially for somebody who is nuanced and experienced, small changes can yield big, how would I say, big impacts, right? So somebody that is at the peak of their performance, small changes in their ability to move, small changes in their ability to lift can make a really big impact on how they're going about things, which is totally different than a beginner where the sky's the limit, right? But that ceiling as described in this study, somebody is heading towards expert level. They're at least seasoned. Little changes can make massive impacts in output. And this study was a cool one that I hopefully will give us a better opportunity in future studies to dive even deeper on. Now, as we wrap up today's episode, shout out to Leander Tables. If you're looking for a table, $750 off their Series 950, as well as CarePlan Pro. If you're looking to deliver care plans in a way that does not feel salesy and have the software to do it in a way that makes it super easy, head over to careplanpro.ai. Cannot recommend it enough. And check out the podcast from a couple weeks back where we dive deep on that. Otherwise, if you're not left a rating or review, I'd love it if you take a moment and do so. Thank you so much for tuning in. Thank you for being a chiropractor. Have a fantastic week in practice, and I will talk to you soon.

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