CEU: Rehab Concepts: The Intrinsic Foot Muscles - 203

Hey, this is Sandy. And Randy? And we're here on AT Corner. Being an Ath Eye trainer comes with ups and downs and we're here to showcase it all. Join us as we share our world in sports medicine. Welcome back to another episode of AT Corner. For this week's episode, our Education episode will be focused on the core, but not the core that you would normally think of. We're talking about the core in the foot, the intrinsic foot musculature.

And like Randy said, this is an education episode and it is ACU episode. So if you're listening to it as it comes out in your athletic trainer, you can actually claim this as category AC US. Thank you to athletic training chat and clinically pressed. So if you're interested in those, make sure you head down to the show notes episode description wherever you're listening. Go ahead and the link is down at the bottom to do the quiz and

course evaluation. So as with any education episode that refers to any muscle or joint or anything, we're going to describe the anatomy specific to the intrinsic foot musculature. And then we're going to describe how the intrinsic foot muscles kind of what their role is in stabilizing the foot. And we'll just discuss some of the rehab techniques to improve our intrinsic foot muscle activation and strength. Awesome, So why don't we get started with the anatomy? Yes, let's do it.

Who doesn't love a little anatomy in the morning? So I feel like it's been such like a big like buzzword lately, the intrinsic foot muscles, right? I feel like maybe maybe not as popular as it was maybe a couple like a few years ago, but I still feel like some people are kind of already starting to be in tune with it. But essentially the intrinsic foot muscles are just the small muscles that originate and insert on the foot, right? They're very local. They they're basically chilling

there. And there are both dorsal and planter intrinsic muscles, but most of the research does focus on more of the planter aspect. I don't know if anyone really talks about the dorsal intrinsic foot muscles. Yeah, it's not really talked about a lot. And plus like the planter aspect, I feel like there's more going on to look at. So there's you could say there's probably more, they're more involved. And there's like deeper layers, where's the top of the foot?

Really, there's just a lot of bone. Exactly. There's there's a lot there. Right, right. And like you said, right, So there are deeper layers and there's actually 4 layers that actually lie deep to the plantar fascia. How it's kind of broken down are those first two layers. Those first two kind of superficial layers are really parallel with the longitudinal arches. So this is like your abductor halicus, abductor digiti minimi,

flexor digitorum brevis. And then the next layer you have the quadratus plantae, which almost kind of follows the plantar fascia. It kind of comes off the calcaneus and starts to go towards the toes, but not all the way to the toes. And that one actually inserts into the flexor digitorum longus tendon. So it actually helps kind of stabilize that tendon and help make that tendon perform more efficiently.

I mean that this, this is super helpful to know obviously for whatever population you're working with, but especially if you're working with performing artists, like a lot of times they are going to have you'll, you'll commonly see either like tendonitis in the feet, like a flexorhalicus longus tendonitis

or, or some sort of musculature. Or if you're dancing barefoot, or if you're doing a lot of plantar flexion, you know there's a lot of things that can happen to the surrounding musculature that also then bleeds into the intrinsics. For sure. And I feel like like the performing arts kind of realm is probably a little bit more familiar with this concept than probably like team sport athletes who think this is probably witchcraft. We start having them do the exercises.

Right, right, right. As you go deeper are kind of those last two layers really kind of align a little bit more with the transverse arches, not necessarily completely. This is like your abductor Halicus oblique, which I'm sure everyone had that on their bingo card of muscles they remember, and then the actual inner OCI muscles. All right, So as I started the episode, right, these muscles are kind of viewed as like a core, right?

And when you really kind of break it down, if you start thinking of like, oh, well, what do the Multifidi do? And like transverse abdominis and stuff like that, right? These muscles act in the same way. They're very local. They're very small and you know, the, the, the idea is, oh, they should be kind of similar with the multifid I do in the spine. They should be stabilizing,

right? And what this is kind of referred to in the research is like the foot core system and they kind of broke it down similar to the spine, right? So it's made-up of three elements. So your passive elements are like your, your Bony structures, your ligaments that support the arch. The active is obviously the musculature. And then kind of that the nervous system or the neural subsystem, which is just the nervous system and how it interacts with the, the nerves or with the muscles.

And really the planar intrinsics kind of play 2 roles. Obviously the active because they're muscle, but also because they're smaller muscles within the foot themselves, they also have a big kind of neural subsystem component because there are a lot of muscle spindles within them within those muscles that help kind of feed information to the central nervous system about the type of stretch that's going on at the

foot. So it kind of gives your body a good idea of what what's happening at my foot. I mean the foot really gives you so much information just in basic gait. Yes. And another thing that kind of gets forgotten are the plantar cutaneous nerves within the planter aspect of your skin of

your foot are highly innervated. So you get a lot of sensory information from just the skin of your foot, let alone the actual muscles within the arch that help kind of, again, guide your foot on, letting you know where you are in space, what kind of surface you're stepping on, what is it uneven? How to react to that surface? Yeah, exactly right.

So the overall goal of these muscles is just to provide stability to the longitudinal arch and it actually does assist in transferring energy during propulsion. Most people kind of view this like idea from like the plantar fascia, like that whole windless mechanism, like kind of acting as a spring. But actually a lot of it does come from tension from the foot intrinsic muscles. And without them, the plantar fascia really wouldn't be able to do the job that it would be able to do.

So you can already kind of start to hint if we have dysfunction there, it might piss off the plantar fascia. So what you're also saying is the if these help with propulsion, then intrinsic muscles can also therefore help with Sprint speed. It could help with performance as well. Absolutely. That's how you get by in with your athletes. Yeah. And it it makes things more economical. So if you're a distance runner, right, your whole idea of is you want to be moving as efficient

as possible. These muscles help with that. So how these muscles kind of function during gait? Again, the goal is, hey, let's keep the foot stable, right? If the foot's stable, you're able to propel more force, there's less wasted energy, all that stuff. And where you really kind of see these muscles tend to like have their peak activity is towards the end of the stance phase.

So this is when you're starting your heel's starting to get off the ground, your toes are starting to extend, all right? So the idea is it's placing a stretch, right? You're getting a little eccentric contraction, which is very, very forceful anyways. And this is really kind of what kind of led the idea of like, oh, these muscles might be a little more involved in the propulsion of the foot. You know, it's not just the plantar fascia doing all the

work. If anything, these are probably doing a little bit more to help take pressure off of that passive kind of tissue. Another idea to kind of look at too is some of these muscles do have longer tendons, right? Which means when they add tension, there's a lot bigger of a spring that can happen. So again, add a little attention to that tendon, it stretches and then it recoils. Bam. The only thing is you can't really do eccentric muscle contraction of intrinsics.

I mean, it's, it's just. Yeah, it's just that's hard. You're right, right? If anything, it's more like hopefully you activate them and hopefully it transfers to that type of muscle contraction, right? But again, it does show the idea of man, if these muscles fail, right? It it might lead to the plantar fascia doing too much and then you get those plantar fascia issues right. It was interesting that that was

pretty consistent. Late stance phase tended to be where a lot of high activity was at and a lot of them that's where they peaked at like that was the highest of their activity. There is some stuff that showed a few of them, a few of the intrinsic muscles had some high activities like right at like heel strike or like where the almost early stance where you're actually starting to load the

foot but not quite mid stance. And I think the idea behind that is it's preparing the medial longitudinal arch for the collapse that occurs during mid stance, right? It's help preparing to control instead of your foot just flopping on the ground. Yeah, we can't have. That no, I can't have that. We weren't ready for these sound effects this morning. I was not ready for that sound

effect. Right. So I think that's the kind of idea, but also you have to remember when we look at muscle activities, right, a lot of it is done by surface EMG. Well, a lot of these muscles are really close together and so there could be a lot of crosstalk. So surface EMG studies are really limited and actually like giving you a good sense of what's truly happening. So they do try to do like fine wire EMG where they actually inject like a sensor into the

muscle. But then obviously you have this like fine wire thing in your muscle and you're told to OK, now go ahead and walk with this. That's. Yeah, some people don't feel, but some people can't tolerate that so. So there's a lot of limitations to this research, but the idea is kind of you at least have a general idea and it does make sense of, OK, let's prepare the foot to actually accept weight, right? So that's the gist of just, OK, what are these muscles doing

during gait? And again, the idea support the arch, right? Make sure we can control it. And if we know anything about the foot, right, it kind of sets the table for everything else, because that's our first contact with the Earth. And I think just to almost preface this, I know we're going to talk a little bit more about it later, but the goal of this is obviously to provide a

foundation. But also when you're thinking about this foundation, really start to apply it in your mind of things that like things you see in rehabilitation are like, OK, if we know that these are helping us prepare to accept weight, then think about like your post op athletes or your freshly acute athletes that maybe you're not weight bearing and then you're going to be placing weight on that foot and just like weight shifts and stuff like that.

So kind of it's not necessarily meant to change your rehab, but just kind of have a different approach in your thought process in your rehabilitation. Oh yeah, that's a good idea. Like before you like like someone who was immobilized for a while Or like I said, post op before they start putting an actual weight bearing. Maybe we should wake these bad boys up. I mean, we really should be. They're really not. That's a good question.

That's a good. Thought this is not necessarily something you have to do when you're weight bearing. Yeah, for sure. And we'll talk a little bit more about that too. And there's another video that we're we're going to talk about too.

Yes, my little throwback so those that's the anatomy of it and what's interesting is again, it does really serve that kind of support role to all our extrinsic muscles like our post post tib flexor hackness longus flexor digitorum longus because at a certain point in the gate cycle, right, they're not in a good position anymore to help with that propulsion that comes from like the calf, right. So again, these the unsung

heroes of gate basically. So as we kind of start looking at the rehab of OK, what do, what do we do?

Like, what am I supposed to do with this, right? And there are actually some tests to actually kind of identify, OK, who actually has like weak intrinsics. Now you can actually evaluate this. It's they're not the best, but it gives you an idea. Some of it is just looking at posture, right? If they have a flat foot like PES plainus, right? The assumption is OK, they probably do have weak intrinsic foot muscles. Again, it's an assumption, so it

may not actually be true. Also claw feet, right? If they have like really like curled toes, right, that it can be an indicator of that as well. But there are special tests, which I thought was pretty wild. First one is a is called the paper grip test as basically you put a paper on the ground and the patient flexes their toes and then you pull the paper away. So if they have weak intrinsic muscles, the idea is the paper doesn't tear, just kind of

slides out, whereas. I feel like you really have to. What kind of, I guess, do you have to start the tearing of the paper first? I feel like that's really hard to. No, I don't think so. I think they got to lock in and then you pull in it like, or at least it like crumples like, you know, you see the resistance. OK, so you get some resistance. I feel like tear, like tearing paper, like just. That's what you're looking for, Yeah, so. Maybe we'll have to test this.

Yeah. So if they don't, if there's not really resistance or it doesn't really grip the paper, then OK. I can see that. Intrinsic muscles are trash, right? And then there's also the knuckle test. So the wording on the knuckle test in the article was weird. So it might change a little bit, but essentially the patient flexes the metatarsal phalangeal joints, and you're looking to see if the heads basically pop out, so making knuckles in your foot.

Now, again, here's where the wording was weird. If the metal metatarsal heads showed, like if you saw them, the test was positive. But that indicates that they have strong intrinsic muscles. OK. Which is weird to me because I feel like that would be negative because you're looking for weakness. And then obviously if the heads don't show, like that was a sign of, oh, you have weakness, right? Because it you didn't actually get the curl of that joint.

You mostly just got the joint pushing down. I don't know. So it did, it did show a relationship with the paper grip test. So that's how they kind of were like, OK, yeah, I see it test the same. Thing this is, is this have to be done on the like flat on the floor or is it? Not this one, the knuckle test. You can have them. Just relax. Yeah, again, the problem is they

just don't like the wording. And then also these tests are limited as well because Flexorhalicus longus and flexor digitorm longus also perform these actions. So it. And they're probably going to take over. Take over. So it's almost like how valid are these for the actual intrinsics? It's kind of up in the air, right? It's not like they necessarily looked at like compared it with like EM GS to show if there really were activated or anything like that, right?

I feel like that's a really, I feel like this is just a plug for the Flexorhalicus longus. If you are not as familiar with that muscle, it's there's such a great involvement of the FHL in gait and just support of the arch and great toe and countless things. So like this isn't your plug, your action item in the middle of the episode to go. If you don't know what the flexor holicus longus is or where it runs, go find some anatomy.

Go find where it runs and where it originates and where it inserts and and start to notice like in your foot. Patients start looking at where if that is part of the problem because it's something that's really easy to target. For sure and I I feel like we should do an episode on flex. I would love that. But also too the posterior Tib too. I mean, if you look at the insertion theoretically, it's literally everything on the on the planar side of the foot catches everywhere, right.

And so yeah, like you said, like even though they're not they're technically extrinsic muscles, they do have a really large role in also helping support support that arch are. We ready to go in rehab? Yep. So now that we've identified that, oh, those are those bad

boys aren't doing their job anymore, now we got to do something about it. And in general, there's kind of four exercises that kind of been viewed to be used for intrinsic foot muscle strength, or at least that have actually been researched. I was going to. Say tow yoga. And then there was another one. They referred to it as toga. Toga. Which I thought was funny. I don't know why.

So actually this is our plug. We did an episode on this like way back when, I think one of our first years doing this podcast, episode 72. It must have been like season 2 or something maybe probably actually. So we did bonus content where we actually filmed ourselves doing a whole episode or for that plantar fasciitis episode. But there is a video that you can actually learn Toyoga. It's episode 72 and we will link it down in the show notes below

for sure. And that one's also eligible for CU. So if you go on clinicallypressed.org, you can find it in the courses and it's it's bonus content. So in the actual episode, I can't remember if it was like .5 or .75, it might have been .5. And then whatever the bonus content is, it adds like .25 to your CU. So if you do both, then you get like however many, yeah. So the exercises are toe spread. So it's actually splaying your toes, great toe extension.

And that's great toe extension alone, right? So it's just should be the great toe, not your toe came up and all your little toes came up. Now it's just should be just great toe and then there is just little toe extensions. So again, just the little toes great toe stays down and then I feel like this one, it has become pretty popular, the short foot I. Feel like it is, but it also can be one of the hardest for people to.

Pick I was going to say this one is just just motor learning Hell for for people that that are doing it for the first time they look at the best part is the looks athletes have when they do this. They're literally just like staring daggers at their foot as they're doing this to try and get this done correctly. I think that's some of the fun of it too though, like when you're 'cause I think it helps or helps with that buy, you know, just like man, this is

actually really difficult. Why can't I do this? I can't do this right. Oh yeah. And then they look like when you explain it to them, they're like, huh, What? Yeah, just do this. I can't. I think we did short footer arch doming in the. Well, I think we did. I mean, you are pretty good at toy yoga. Thanks. You're highly skilled at the movements. You guys can test out your

skills. And what was really nice is the literature that actually looked at like, OK, how do these muscles activate during these exercises? Actually showed a lot of them just activate all like pretty much all of them have the same level of activation no matter what exercise you choose. So it's not like you're this one. I'm preferring to activate this one over this one. No, like they tend to kind of activate all together with them, which is kind of cool.

So you don't have to feel like you have to change it up too much. Like you, you give these, Hey, you're, you know, you're hitting what you need to hit, right? I mean, it was really cool how they kind of identified. That one of the studies used functional MRI so you actually could actually identify each individual intrinsic foot muscle that is. Pretty cool on its. Activation, yeah, so like it really kind of took out the guesswork on like oh surface EMG or fine wire EMG.

And again, it takes away that pain that sometimes is that is accompanied. With because also pain. If you have pain then obviously it's going to change your which then it's like how? How true is this? Absolutely. How true. Yeah, no, that's a good point for sure. So the studies that actually kind of looked at the the

effects of, OK, what if we do these strengthening and really kind of looked at like 4 to six weeks, right. So what did it look like at that point? It just seems so long. Yeah. And again, it's not like every day, right? I think they did it like every other day, three days a week, or it was like something like that. And training was shown to improve the motor control there of these movements. So the movements got easier, they got better at them.

They actually showed decreased navicular drop. That's great. Yeah. Improved balance and just overall foot strength improved, right. So that sounds great to me.

Sign me up for that. One interesting thing that some of the studies did look at, which is kind of an interesting concept and actually might help with those like kind of beginning stages of someone learning how to do this, is looking at how neuromuscular electrical stimulation, so like settings like Russian and stuff like that, how does that affect our activation of these muscles during rehab? That's a really good point. I've never thought to do Russian on your. Foot, right.

And really there was no difference at the end of like the trial, right? Like at the end of four weeks, both groups did the same whether they did it on their own or whether they had the neuromuscular electrical stimulation to help. They still were able to increase their strength decrease like all that stuff. But what was interesting was the neuromuscular electrical stimulation group saw the improvements, the initial improvements in their ability to do all that two weeks sooner.

I mean, that's solid. Yeah. That makes all the difference. Yeah, for sure. Especially like in a sports season. Yeah. And I the idea is kind of the same as like when you have post ACL, right, You can't really as much, as much as you really want to, you can't fire that quad. So we do like Russian neuromuscular electrical stimulation to help trying to get the body to remember how to do that. It's same thing, same idea as this. That's really cool.

Also, I think going back to that last point, I think this is also something to stress with the people who you're working with after they're doing this rehab. Like if someone has a flat foot, like they're going to continue to have a flat foot, that's like not our goal of changing that anatomy. But if you do have a flat foot or, and and that's coming from an increased navicular drop, you are going to want to strengthen

that. Whereas if you have a more like if you have a higher arch that's a lot more rigid, you're going to want a lot more flexibility. So I think just also having that education piece also helps within this rehab because then you're making strides and knowing that the attainable goals that these athletes, patients, whoever you're working with are trying to get to. Yeah, because I think that's important to remember, like, 'cause like Pez, plaintiffs are

like, you know, flat feet. Sometimes that's just that's anatomical. Sometimes that's just how their foot developed. And you're not necessarily going to change change that. You know. So yeah, for sure. Also, what I thought was interesting is just with like that neuromuscular electrical

stimulation, right? It also triggers that kind of neurological input from from the foot and help kind of increases that kind of reflexibility of the foot because remember there are a lot of muscle spindles in there, right? So if we can get it to actually be able to react to a sensory kind of stimulus like stem, you should be able to see it's that reflex pathway get better, especially if it's already been

diminished. 1 interesting thing is they compared it one just even one session of neuromuscular electrical stimulation and even just one session of it they saw improvements and just how it activated. That's awesome. But they also compared it to like like a sham group. So they just did 10s, right. So 10s just, oh, just you feel the tingle. That's great, right. So like not trying to get muscle

contraction. And the the group that just had 10s on their on the planar surface of their skin did improve balance. I could, I could see. Why? Yeah, because the cutaneous receptors were firing and, you know, and increased the sensory input to the brain, and the brain was all about it. And it was like, I know I can be efficient now. I mean, ever since you brought up, I think in the I don't remember what episode 'cause it wasn't tens 10s was a long time ago that. Was a long time.

Ago, there was an episode more recently that you talked about putting 10s on with rehab. Yeah. And that's changed, like that's changed my practice. Well, I'm glad, yeah. But yeah, so I thought, I thought that was interesting. And, you know, right now we're taking a neuromechanics class and it just really kind of, I don't know it I, I felt like I, I could see that link and it was like, oh, I know why that happened. Talking about H reflexes and stuff, right?

Oh, the H reflex. So in general, what what could we kind of use this kind of rehab concept for like any pathologies that you could see this being beneficial And really it is a lot of just lower extremity in general. So it really doesn't have to just be foot issues. You could really expand from there. They've looked at chronic ankle instability slash ankle sprain and saw improved balance and improved self reported function. So the patients felt better. It could be used for

patellofemoral pain. That's just pause for saying like that's crazy. I love this connection of how like the foot can help with like a different joint. Yes. And I mean, I know that we talked about like it's all connected, but like just seeing this right here and just taking a moment to recognize like the impact of like the core of the foot can really and like you do gait with everyday activities. Like you're usually walking on your feet. I assume for most people you're

walking on your feet. The fact that it has so much impact up the chain. Yeah, for sure. And like obviously there's the Pez Planus component to it, right? If you're, if you're, if you have an uncontrolled arch, right, it's putting a lot of rotational stress on to the Patel femoral joint.

But also just from thinking like the aspect of like this is where the foot is, where the initial absorption of force is going to be. And if it's not going to be efficient, it's got to go somewhere and it could just go right up to the chain to the knee to absorb that force, right, right. And really when this is applied to patellofemoral pain, they saw a decreased pain. And obviously those that had an avicular drop or a significant navicular drop, they saw a decrease in that.

This, I mean, the knee, you really have to think about like the where is the alignment coming from? It's either coming from the hip or it's coming from the ink. The foot, yeah. Yeah, for sure. The knee's not just doing this on its own. And then, of course, plantar fasciitis, plantar fasciopathy, right, help kind of support that passive tissue.

And again, we've already kind of talked about how this musculature might actually be doing a lot to take load off of the plantar fascia that maybe we're not necessarily accounting for. Sweet. So what's your action item from this? The intrinsic foot muscles are just very important to movement and we should probably be considering them for most of our

lower extremity rehab. And if you have someone who's having a hard time trying to activate them, don't give up on them, just throw them on some rush. Especially that short foot man. Yeah. Yeah, that's short foot. It takes a lot of just dedication to that bad boy. Yeah, action item. Check out our bonus content of plantar fasciitis so you can learn toe yoga yourself if you haven't already or toga is some like to call it also action item. Check out the flexor halicus lungs.

I know it's not a foot intrinsic muscle, but it's important in foot musculature and gait and repetitive plantar flexion. There's so much it's important and so check that muscle out while you're while you're looking at the rest of the intrinsic muscles. Again, if you guys are interested in the CU clinically pressed and athletic training chat. Thank you again so much. We have this LinkedIn the show notes below or in episode description wherever you're listening.

If you're interested in the in the references Randy used for this episode. How many about did you use for this one? I think we. Got to about 20. Nice or got close to it. OK, so those will be on our website again linked below. Everything is in the show notes which also is a great plug for our Med bridge if you are interested in like a more long term subscription of Cusi think we have about 35. I think we have about 35 just for AT corner.

Totally smokes. Yeah. So it so you can't, you can't do all of them through us yet. But we have about 35 right now which are all up on clinicallypressed.org. But if you're interested in like a more long term subscription like a one year which this is a reporting year but also accounts for next reporting cycle since you'll have it through the part of the next reporting cycle, you can use code 80 corner for $101.00 off Med Bridge.

Yeah, and some subscriptions also have like a lot of other cool features that you can use for your practice too. And with that, oh, we also do different types of episodes, not all C us obviously, but we also have story episodes with stories from real athletic trainers. We are soon doing a softball stories episode. So make sure you keep an eye out on our Instagram stories if you want to submit your softball stories. And I think that's it.

Thank you for helping us showcase athletic training behind the tape. Bye.