Name: Muscles of the Trunk: Video #19 of Introduction to Functional Anatomy
Uploaded: 2023-04-26T01:00:15.000Z
Duration: 31 min 43 s
Description: Explore the muscle anatomy of the trunk designed for healthcare professionals and students, this lesson covers the origins, insertions, actions, and innervations of key trunk muscles including the abdominals, spinal extensors, and deep stabilizers.

English captions

https://stream.mux.com/hh8J00BwPxG01e02LBFqOKpw9qz1vG27kHSu9ReDQFujps.m3u8

Explore the muscle anatomy of the trunk designed for healthcare professionals and students, this lesson covers the origins, insertions, actions, and innervations of key trunk muscles including the abdominals, spinal extensors, and deep stabilizers.

Understanding the External Obliques

The Role of Rectus Abdominus in Core Stability

Exploring Internal Obliques and Their Functions

The Importance of the Transverse Abdominus

Functions of the Erector Spinae Group

Understanding the Multifidi and Their Stabilizing Role

Quadratus Lumborum: Function and Role in Core Stability

Muscles of the Trunk: Video #19 of Introduction to Functional Anatomy

We're going to go superficial to deep. So let's start with the external obliques. Now your external obliques fiber direction, which way does it go? This way right. The way your fingers would be if you put your hands in your front pockets. So you guys can write external obliques front pockets, to help you guys out a little bit. How many of you guys look at pictures of bodybuilders and fitness models, and you know you've seen a muscle and fitness magazine or a shape magazine, and people get all striated in here right, you see the lines. Which direction do those lines always go? Right because your external obliques are external right, they're the ones that are most superficial that's what we're seeing. So if the fiber direction is this way alright this muscle goes like this, what joint actions is it going to cause? Yeah which rotation is it? If this muscle shortens what's gonna happen to my spine? It's going to rotate this way? Alright if this muscle shortens it's going to twist me this way right, which would be contralateral rotation. So we got external obliques contralateral rotation, what else might they do? Okay so we got we got the obliquity thing, I told you guys muscles with a diagonal usually do rotation, we got rotation out. There's got to be a couple other things this muscle will do though. It's going to help with flexion right, because the obliques do lie in front of the lumbar spine right, this is the joint that they cross there in front of it. So external obliques flexors of the spine. I'm gonna say yeah. What else might they do? Lateral flexion. How many of you guys think lateral flexion? Yeah I mean how do people try to work their external obliques a.k.a their love handles, because they're trying to spot reduce the fat over their external obliques which absolutely doesn't work, and then they do an exercise which is kind of ridiculous we already talked about this yesterday. They do this one right we talked about this. Well your external obliques actually are not your primary lateral flexor of the spine, but do they lie lateral to the spine? Sure so they'll definitely help a little bit, it will definitely help. Now the other thing you have up on that chart there and this is more just some extra information for you guys, we were talking about connective tissue this morning right, when you open up a cadaver you don't see all these pretty red muscles, you see a lot of white connective tissue that is especially true in this area. The most superficial thing here on your six-pack is not your rectus abdominis, but this abdominal connective tissue. And you guys see a little evidence of that because what actually makes the 6-pack? You have the Linea Alba which is the connective tissue in the middle and then all of this these transverse little separations, which are also made of connective tissue. They're probably there because connective tissue with its rigidity and strength, probably improve the overall strength and ability for the rectus abdominus to prevent what? What don't we want to do with the lumbar spine? Forceful hyperextension right. So we have a nice nice bit of connective tissue here to help help the rectus abdominus to its job. Just reinforce it a bit. I think that's one of the next muscles up here, yeah rectus abdominus. This one should be pretty easy for you guys right. Rectus abdominus runs, which way does its fibers run? Up and down. So it runs up and down in front of the spine. What plane do you think it's probably going to work best in? It's a sagittal plane muscle, being that it's a sagittal plane muscle and it's in front of the spine, what do we think it's going to do as far as joint actions? Flexion. I always love every once in a while I get these calls from like a writer for like one of the magazines or whatever, and of course what do they always ask what's the best exercise for the abs. And of course what are they talking about when they say abs rectus abdominus, and my answer is always the same. What's the best exercise for the rectus abdominus? Flexion. Do you have anything other than flexion? No that's what the rectus abdominus does well. What else could the rectus abdominus do a little bit of? Does anybody know? Like think about your tilts, you remember your pelvic tilts right, it'll do this. Isn't this still spinal flexion though? Yeah you have to do spinal flexion to posteriorly tilt. So they'll be like so so the the rectus abdominus just is flexing? Yeah and it'll posterior tilt your pelvis. But what do you mean? Oh you can do a crunch, or you can do a reverse crunch. I guess isometrically you could do a plank. Would anything else really affect the rectus abdominus all that much? No. No the truth is when we look at EMG studies guess what has the highest activity for the rectus abdominus? Crunches, reverse crunches, like those things that actually do the action of really not that complicated right. What keeps most people from having a 6-pack, is it the exercise they chose? It's diet. How do you get a six-pack? Shut your face, move your glutes right. You want to get that tattooed, that was actually the original title of my first book, and the agents were like you can't have shut your face and move your ass as the title of your book, that's not going to work, and I was like why not. Internal obliques, internal obliques. So we talked about external obliques being this way right, those are the muscles you can see, it's fiber direction as if you put your hands in your front pockets. Guess which way the internal obliques go? This way all right. So it's like the direction your fingers would be if you put your hands in your back pockets. You guys cool with that. Internal obliques, so which way, what what joint actions are we looking at? Rotation. We got the obliquity, we know it's on a diagonal. We know it's probably going to contribute to rotation. You got to tell me ipsilateral or contralateral though. If it's this way and it's going to shorten, and you guys see how that would shorten. Exactly exactly ipsilateral, all right. What else might it do? Lateral, lateral flexion. Yeah it's on the side of the, it's on the side of the lumbar spine. I'll say lateral flexion. You guys think this can contribute to a sagittal plane motion, like you can contribute to flexion or extension. Flexion, why flexion? It's still in front of the lumbar spine right. Now remember your lumbar spine is way back here, so all these anterior core muscles that we spend so much, that we give so much attention right in the popular media, they're pretty much all flexors. Everybody's got this. So yeah so this does get a little confusing, the contralateral versus ipsi- lateral thing. So if you guys, let's pick two points right. These both, both these muscles have pretty broad origins, pretty broad insertions, but let's take the external obliques first, since we covered those first. Put one finger on your ASIS okay, and then put one finger back on your ribs all right. Now try to bring those two fingers closer. Which which direction did I rotate? I ended up rotating a little bit to the left right, so that's rotation to the opposite side. the muscle is on. Contra means against, right against our away, so that's contralateral rotation. Now let's do the same thing with the internal obliques. Let's pick a point, let's let's pick this little angle of your ribs here right, and all the sudden changes let's do that one. Point on your posterior ilium and now try to bring your fingers closer together. Yeah you guys see how that works. So now we have a muscle on the right is rotating me which direction? To the right. So that's the same side that would be ipsilateral. You want to totally freak yourselves out? When I rotate to the left, which oblique am i working? Oh yeah right external oblique right, but my left internal oblique. Muscles work best in the direction of their fibers. Isn't it kind of true that if I rotate this way, that this external oblique and this internal oblique kind of have the same fiber direction, and then if I go the other way its. Transverse abdominus, how many of you guys have heard of this muscle? Definitely a muscle a lot of people talk about. Definitely a muscle of a lot of controversy. But the transverse abdominus is an interesting one, because what joint action based on its fiber direction do you guys think this muscle does? Which is the fiber direction is is what? It's transverse right, that's why it's called the transverse abdominus because its fibers are orientated transversely. Its origin and insertion is basically the thoracolumbar fascia. It's a little different than that in textbooks but you guys get what I'm saying. The attachment goes from here, it wraps all the way around and goes right back into here. So when it contracts what actually happens? It's basically your weight belt right. You guys remember like, you guys seen the big guys with like the, and they do, they have the big weight belts and they it's like pull them as tight as they can before they get underneath something like a squat, that's what this muscle is supposed to do. it's supposed to cinch everything up ,which what that ends up doing is increasing intra-abdominal pressure. It also tightens this piece of fascia back here right, this thoracolumbar fascia, it pulls it like this really tight. Is that gonna help stabilize my lumbar spine? A little bit - yeah. It's like having guy wires on each side just getting pulled really really tight So it'll increase stiffness in the thoracolumbar fascia. TLF not to be confused with the TFL right, we think that these two things together increase the stabilization of the lumbar spine so that make sense. Now there's some varying opinions on how effective that is, but if you guys want to write down a couple researchers there's, I know some of you guys are way into the core you got Richardson Hodges and Heinz, so I'm gonna put Richardson et al. Then there's another guy named McGill who has a little different theory, and then another guy named Liebenson who has more research and a different approach. A lot of stuff out there. You guys heard of your multifidi. Yeah so your multifidi are interesting little muscles, they're fairly deep and they go from spinous process to transverse process. Spinous process-transverse process, spinous process-transverse process. Very segmentally. They're on the back of the lumbar spine so what joint actions do you think they do? Extension, sure they have an obliquity so what else might they can contribute to? Rotation. So we got extension, rotation, and what we believe that's really important about these muscles, these aren't the big extensors of the lumbar spine right. These little tiny muscles that you see in those pictures, but they have something different than the other extensors we're about to talk about, which is they're segmentalIy innervated. They cross only a couple segments at a time, so we think they're important for what we call segmental stabilization. Which is basically, if you thought of your lumbar spine like Jenga, you guys know the game Jenga, right you got to keep all your bricks stacked up, So if these were the bodies of my lumbar vertebrae right, I got my five little blocks there, what we think these muscles do is when movement or pathology or dysfunction cause our blocks to be this way, it might be these muscles that aren't doing their job. When movement causes us to do something like that, one of our blocks to move out of place, we think that these muscles doing their job will cause these blocks to do what? Straighten back out again, does that make sense .So your multifidus basically keep your blocks aligned. You guys ever heard the term segmental stabilization? No. You would. That's segmental stabilization. All we're talking about is keeping our block stacked on. It's a pretty bad thing right, if one block slides over the other starts moving out of place, instinctively guys do you think that's a good thing? No probably not. So we think the multifidi have a big role in this. This is the joint actions they'll help with, but this might be their more important function. Just like when we talked about the rotator cuff, we talked about the rotator cuff doing external rotation, internal rotation, abduction. But what was their important function? Dynamic stabilization of the shoulder right. Same thing with the multifidi and the TVA, they have an action, but their function-stabilize the lumbar spine. Alright let's look at another big mover. No no so the multifidi are very deep and lie right against the the facet joints of the lumbar spine. Your TVA actually more or less stops at the thoracolumbar fascia. Your multifidi there's layers to the thoracolumbar fascia it lies with, sandwiched between a couple of those layers. Does that kind of make sense? I got a bunch of pictures online, if you guys go to those muscular Anatomy articles, you look up multifdi, you look up transverse abdominus; I have tons and tons of pictures showing like cross-sections and stuff, so you get a good idea of where all of this stuff exists relative to something else. The erector spinae. Alright I'm going to ask a question knowing that I'm probably going to get twelve-year-old laughs out of it, what does it mean to erect something? To stand it up right. So if my erector spinae will erect me or stand me back up and I started down here, what joint action is that for the spine? It's extension. I like the erector spinae. I like the little muscles of the back the erector spinae, even the multifidi, I just like the way they're shaped, I think they're shaped cool, you know what I'm talking about? Looks like an upside down Christmas tree. Alright so if only this side of the erector spinae contracted, what would happen to my spine? Yeah contribute just a little bit to lateral flexion. You guys realize how long your erector spinae are? Yeah exactly, so just keep in mind all the way down to your sacrum, all the way up to your mastoid process, depending on which of the erector spinae muscles we're talking about. Another thing to keep in mind, something once you guys start digging a little deeper into your Anatomy is, is there one erector spinae muscle? Yeah, is there only one erector spinae muscle? Yeah there's actually three, and they all do a slightly different thing. So you have your spinalis, your iliocostalis and your longissimus. You know at this level your okay calling it the erector spinae. Like I said your next level once you guys get into graduate school, you start tearing things apart, maybe do some cadaver work, you're gonna start needing to know all of the different erector spinae muscles. How many pushups per ring? I'm going to make you start dancing if it happens again. You have to dance until you get your ringer to stop. Alright so what do I mean by bilaterally and unilaterally, great question. So bilaterally means what? Both sides. If both sides of my erector spinae fire at the same time, what are they going to do? They're going to pull down on my spine, pull down on my ribcage and I'm going to do this. But if only one side unilaterally right, like unicorn one horn right, unilaterally pull down, what's going to happen to my spine? This. Well we could see, this is where the layers come in right, if we start dividing out these erector spinae muscles we'll see that at least one of them will contribute a little bit to rotation, and that's one of the larger erector spinae muscles being your iliocostalis. Usually when you see that word cost, C O S T, costa, costol right it has to do with the ribs. Iliocostalis is the big erector spinae muscle which goes into the ribcage, and it probably can cause a little bit of that rotation. Yes yeah it kind of looks like a Christmas tree depending on which one we're talking about, but it'll be like the iliocostalis does this right. The spinalis just goes from spinous process to spinous process like this. The function of this class guys is to is to get down the joint actions. I'm excited though because you guys are starting to ask deeper and deeper questions. But as I kind of mentioned earlier when we were just warming up and going through our Q&A today, this doesn't ever stop. It's one of the exciting things about getting into this field is, like there are, we keep calling rabbit holes right. There are rabbit holes to jump down forever, you find something you're into you can just keep going, as I mentioned those those functional Anatomy articles that I have up on my site, talking like six seven pages of text on one muscle, and then pictures, and videos and illustrations and diagrams, and research. Depending on what muscle you talk about you may have hundreds of research studies to look at. Fun stuff. Quadratus lumborum, how many of you guys have heard of this muscle before? Cool, so this muscle goes from my 12th rib to my posterior ilium. The thing I want you guys to keep in mind though, this isn't a superficial muscle like out here, it's a twelfth rib to posterior ilium with some connections into these transverse process; it's actually a very deep muscle, comparatively. Your erector spinae are on top of them, your latissimus dorsi, transverse abdominus, internal and external oblique, on top of them. So it's fairly deep it's like just like this. What joint action do you think it's going to cause? Lateral flexion. Anything else? Where would it have to be to cause extension? They'd have to be here right, they'd have to be somewhere behind the lumbar, at least on the spinous process, be behind the bodies of the vertebra, this is right here. No rotation, what would it have to have to do rotation? Some sort of obliquity, come forward a little bit, this is this is lateral flexion. In fact your quadratus lumborum is your primary lateral flexor. This exercise -quadratus lumborum exercise, a little bit of oblique but quadratus lumborum. Sure quadratus lumborum is very important for stability. It is one of those muscles we've kind of talked about though like the iliacus, that has a propensity to get tight. If the quadratus lumborum got tight, what is that going to do? It could pull you this way if it's one side, if it pulls on both sides what's it going to do? Yeah it could, it could start to compress and give you a little soreness, eventually contribute to maybe some pain and dysfunction, you guys see how that would work. I'm not, I totally agree that the quadratus lumborum is important to stabilization. Is this a muscle that I'm going to write down and exercise for in a routine? Probably not. I don't think this is something we have to individually strengthen, and I think targeting it too hard might help contribute to that cycle of this muscle getting a little overactive, a little tight, and contributing to some of that low back pain that we see in so many individuals. This exercise we'd never give anybody, and not just because it makes people look silly, like they're trying to impersonate a wheel wobble, I think it contributes to low back pain. Oh you guys didn't think you'd go a whole hour without doing a graph did you? You know what that means though, we just did, you guys just finished all the muscles for functional anatomy one. So the one thing I think I mentioned there guys is the TVA, although it will play a role in all joint actions, it doesn't have a joint action so it's not going to end up on this graph. Don't forget about it though, that's what that little box at the top says. Action, plane, muscles, exercise that includes that joint action. So this one's a little bit more like the scapular graph we did. Whats that? TVA what about it? TV, TV-transverse abdominus. I'm sorry did I not define that? TVA, yeah TVA is transverse abdominus. Occasionally you'll see it as TA, what's the problem with that one? Tibialis anterior. Your transverse abdominus right, does that make sense? It just wraps around like this. he hasn't, he yes exactly. 

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