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Christos is a practicing physical therapist who published a paper titled 'Running economy: A comprehensive review for passive force generation'. On The Run Smarter Podcast today, we break down the concept on running economy and how you can apply this into your running to become a more efficient runner. We remove the scientific jargon so any runner can understand and finish with some practical take-aways. Some topics we discuss are: What is running economy & why is it so important? Why is lower-limb stiffness a good thing? How can we test our leg stiffness & running economy? What can we implement to help running economy including strike pattern, footwear and strength training If you have any questions for Christos you can e-mail him here If you would like to support the podcast and participate in future Q&As sign up for $5US per month at https://www.patreon.com/therunsmarterpodcast Check out our new website!! https://www.runsmarter.online To follow the podcast joint the facebook group Becoming a smarter runner click on the link: https://www.facebook.com/groups/833137020455347/?ref=group_header To find Brodie on instagram head to: https://www.instagram.com/brodie.sharpe/
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On today's episode, Understanding Running Economy with Christos Ziliaskoudis. Welcome to the Run Smarter podcast. The podcast helping you overcome your current and future running injuries by educating and transforming you into a healthier, stronger, smarter runner. If you're like me, running is life. But more often than not, injuries disrupt this lifestyle. And once you are injured, you're looking for answers. And met with bad advice and- conflicting messages circulating the running community. The world shouldn't be like this. You deserve to run injury free and have access to the right information. That's why I've made it my mission, to bring clarity and control to every runner. My name is Brodie Sharp, I am a physiotherapist, a former chronic injury sufferer and your podcast host. I am excited that you have found this podcast and by default become the Run Smarter Scholar. So let's work together to overcome your injury, restore your confidence and start spreading the right information back into your running community. So let's begin today's lesson. can appreciate me trying to pronounce Christoph's last name. He is Greek and I asked him before we started recording how to pronounce it and that was my attempt on pronouncing his last name so hopefully I got that right. Sorry Christoph if I um yeah blew it but... Without further ado, today is going to be around understanding running economy. We're going to delve into what that means. There is a paper that was published by Christos and colleagues and the title was Running Economy, a Comprehensive Review for Passive Force Generation and we will delve into that. It doesn't get too scientific. I think Christos did a fantastic job of relating it to everyday runners. I chimed in with my own trying to come up with my own metaphors and whatnot just to make it more practically achievable and easier to digest. So I think we did a really good job. I think you'll go away with knowing a lot about running performance and ways that you can help improve your running performance. Before we dive straight into the interview, I had some feedback. from some listeners and it's happened on several occasions so I thought I'd act. A lot of people like they love the content, they love everything that they're learning and they're applying but they don't know much about me and so I thought what would be a really cool idea is if I start sharing my running experiences with you guys and the kind of like what I'm working on, what sort of injuries I might be currently working on, what sort of symptoms I might be getting, how I'm kind of engaging or like being proactive and how I'm changing up my running just to let you guys know that I'm also trying to make these smart decisions and I'm trying to become a smarter runner myself and it also it takes away or it helps you learn that running injuries happen, like running injuries happen to a lot of people. And it happens to everyone happens to the best of us. But what we can do is try to make the smarter decisions to reduce their risk of injury, but then once symptoms arise, trying to make as smart of a decision as we can to return back to pain-free running as soon and efficient as we can. And yeah, just taking these kind of countermeasures. And so if you haven't heard my progress, my episode on me overcoming six years of tendinopathy, podcast episode a couple of months ago. Um, if you haven't got, if you haven't listened to that, please do that because that kind of takes me to where I'm at today. And if you have listened to it, fantastic. Um, me overcoming that to date. everything's gone super well like I think in the last couple of months I have noticed an increase in symptoms, maybe once or twice and It was doing a bit more mileage But it really I could only just notice it for maybe half an hour one morning And then just went away and I remember doing isometrics that day because it was particularly sore But if you remember from the episode that I did I was constantly doing isometrics because that helped that I just don't feel the need to do it. I feel like I'll just go for a run, do a gentle warmup, go for a run, come back. You know, the next day, like later on that day, the next day, I really don't feel the need to address that tendon. It doesn't really, I don't have a reminder to look after it just because it's now like dissipated from my memory, which is a really nice thought to have because I'm not thinking about it. And yeah, so that's where we're at with. the knee issue. Hopefully that's at bay for now. My running itself, in that last podcast that I did, I was building up to 15 Ks. Now in Melbourne, lockdown with whole COVID is quite tricky. We're allowed to exercise once a day for under one hour. And so I have been sticking to around about 10 Ks and just like my 10 K slow run, I'll do for 50 minutes or just over 50 minutes before I scamper into the house and before I get arrested. But it has limited long runs that I can do. So I've been doing about 30k weeks. I have been doing some slow runs, been anywhere between maybe 5k and 10k and just hitting a really nice stride. I'll probably do that three times a week and I'll probably cycle about three times a week. And yeah, in terms of symptoms, I did a couple of weeks ago start noticing some pain at the top of my foot. And as soon as that started happening, I thought, oh, here it is. It's a stress fracture. Um, I think most people go to doom and gloom, uh, straight away. And then upon thinking about it, I was getting it during my run, but afterwards is okay, the next morning was okay. So, um, thought it might've been the way I was tying up my shoelaces, maybe tying up my shoelaces a bit too tight on the top of my foot in a certain section where it was sore and have become more conscious of how I'm tying my shoelaces now. and that's gone away, so really happy with that. However, I think at the start of the week, I think it might have been Monday this week, I was jogging with my brother, and started noticing some slight heel pain at the last K during a 5K run. And that was a bit weird, it probably lasted 300, 400 meters. Afterwards was okay, the next morning was totally fine, so taking on that principle of observing pain over 24 hours, I'd... I went with that and my just trying to get a glimpse of what's happening over that 24 hour period so the next morning was fine. I went for a run that day. I did a really slow 4k so slower and shorter than my usual just to see how it'd go. It was fine. I don't think I really noticed it but the next morning I definitely noticed some sort of symptoms, some like sharpish pain coming from the heel, kind of deep in the heel, and not too sure what the cause was, not too sure what it actually is, but I know that pain the next morning does show some sort of inflammatory thing or some sort of tendon issue, so decided to not completely avoid running or not completely rest because I know that from one of our principles at the start, rest is not always best. So want to still stay active. So I have spent the last three days cycling and now my morning symptoms, I don't have any, which is a good sign means like it's, I guess it's kind of recovered, but still staying active, still cross-training, still doing my strengthening exercises. So I'm still staying active. I just haven't ran the last three days of Spent It Cycling, even though I'm getting swooped by Magpies at the start of Spring. But yeah, I'll keep paying attention to that. I think tomorrow might be my first run back and I'll see how I go. I'll see how I feel over 24 hours after that. And then if I'm fine, I'll slowly build up and build up and build up. And hopefully that's just a... really fleeting kind of symptom that just happened but can't help but notice if someone ignored that or did the wrong things what might happen to them. So that's just what's happened with me. I have made the decision to start strength training with my calves and I do a lot of strength work with my glutes, with my quads, my knees trying to keep everything nice and strong. I don't do a lot with my calves and... I decided to change that. So I haven't started just yet. I made this decision yesterday, but I do have a couple of calf issues like over the past maybe six to 12 months. Every now and then my calves feel really tight and every now and then my calf gets a really mild strain. And so following these principles and knowing the importance of strength training, I've decided to start doing some. I'll start with single leg calf raises, probably weighted, something I can just do at home and- see how we go and that's it. That's it for my update. So Let's learn together. Let me share my experiences as we go through. Maybe I'll do it once a week or so. Um, especially if there's something new to report, I'll let you know how I go with these new car phrases and yeah, we'll take from there. So, um, enough about me without further ado, I'll see if I can give this second name a go again. Here is Christos Zilias Koudis. I think I first heard about you with your, um, publication and the, the paper around running economy. and thought I'd just reach out on Facebook and see if you're interested in the interview. So let's start with just thanks for coming on. Thanks for having me, Vibrodi. It's been a pleasure. Yeah, I've written this paper like one year probably ago, and I'm really pleased that someone found it interesting and spent some time reading it. So yeah. anything about running I'll be interested in. Can we maybe start off with just, I guess, introducing yourself or where you're from and what you're doing career wise on a day to day basis? Yeah, sure. So I'm from Greece. I'm 27 years old right now. I finished my physical therapy studies back in 2011, I think. So It's important to say that in Greece, physical therapy studies is on the bachelor's level, so it's not a PhD degree or something like that. So I did that, then I worked for about one year as a clinical physical therapist. At that time I was more oriented towards the neurological patients, but then running came into my life. So, That changed a lot. I decided to do a master's degree. So I moved for the next two years in the US. I did biomechanics and exercise physiology studies there for two years. Then one year ago, I came back to Greece. I started again my clinical career as a physical therapist. But right now, I'm more on the musculoskeletal, let's say, area of things. And at the same time, I'm very interested in working with runners and helping them improve their running mechanics and all this stuff. So in terms of running, I'm more on the mechanic side of things, not on the physiological side. So I cannot say that I'm a running coach, but I'm a running mechanics, let's say guy. So that's more or less what I do. Yeah. Cool. I've had plenty of running coaches on the podcast already. So we probably, um, would like to diversify a little bit when you said that you developed like an interest in running and then got into the, um, I guess, developed that, that interest. Was that when you became a runner yourself? Yeah, exactly. Exactly. I started running myself. So it's like, wow. Yeah. And are you still running these days? Are you, um, What, what sort of races have you done? Uh, so my race events, I'm more focused on, uh, trail running. Uh, and my distances are like between 20 and 30 kilometers. I don't know what's the equivalent in miles, but yeah, that's my range of distance and yeah, I'm doing, I'm doing like a trail running competitions. Fantastic. Yeah. Pretty similar to me as well. I didn't really have a specialist in. I didn't really have an interest in running until I became a runner myself. And especially when I became an injured runner and then I had to learn kind of myself, how to treat myself. And then as soon as I started seeing runners in my clinic, that's when I had that kind of heightened passion to learn more about it. So it's cool. It's very similar to the way I went about things as well. Let's dive into running economy. The title of this podcast is understanding running economy. So I guess what would be a really nice start was like, how can you best define what is running economy for like the everyday runner? Oh, yeah. So when I'm trying to describe running economy, I use the example of a car gas consumption type of thing. So let's say that we have two different cars running at the exact same speed, let's say 50 miles per hour. The more economical car will cover a greater distance before running out of gas. I think that's normal. It doesn't matter which car has the greatest maximum speed or engine power. The more economical car will cover a greater distance before running out of gas. So more or less the same goes for running. At a certain running speed, its runner has his or share individual energy consumption rate. So if we have two runners of similar fitness level and when we say fitness level, we talk usually about the conventional measure of fitness which is VO2 max. So let's say that we have two runners of similar VO2 max ability and both of them are running at the same pace. The more economical runner will be able to keep moving for a longer time. at this particular pace and she or she will cover a greater distance. So in the same fashion, if the same two runners will be asked to cover, let's say, a distance, a marathon for example, as fast as possible so they are in a race, the more economical one will be able to sustain a faster running speed and thus cross the line first. She will be the winner. distance running, because that's what we are talking about. Since one of the major performance barriers is fuel depletion in our sport. So that's more or less how I could define if we can say that running economy. Yeah, sure. And you've touched on a couple of things there, which I really liked that car analogy. It's, I think most people can get around that and kind of find that quite relative. And when it comes to runners themselves, I think it matters. Like if you're doing say ultras and you've got a vast distance that you have to cover, it makes a whole lot of sense that you need to be as economical as you can in order to create, um, or in order to, uh, I guess run that distance or run further than your competitors, but then you're also saying in the shorter distances, if we're getting to like maybe a 10 K or a half marathon where you're depleting everything, you're saying that someone who is more economical can actually travel at a faster speed when they're using the same amount of energy as their competitors. The more economical, let's say, middle distance runner, she will be able to sustain a faster running speed compared with cheese or sheep competitor. which is not that economical as she is. Yeah, yeah, absolutely. It makes a lot of sense. And it's really good to know that it applies to the ultra distances, but also kind of the, the shorter distances around that 10K mark as well. It still matters entirely. And it ties in really well with my discussion with Izzy Moore that I had last week. And she introduced this optimal cadence, or like the theory of optimal cadence for uh, increasing economy and she kind of based it on heart rate and the method of someone, uh, changing their cadence by like, uh, 5% like increasing or decreasing by 5%, seven and a half percent. And then in those different variations, trying to see what your heart rate is doing and in any of those variations, like your lowest heart rate is starting to explore your more ideal cadence. And. I guess this kind of ties in really well because if you're manipulating your cadence to try and get your heart rate as low as you can traveling at the same speed, that's kind of getting as close as you can to a more economical run. So I think it ties in really well with this, but with your paper, it introduces the concept of what we call lower limb stiffness and doesn't really talk much about economy. So maybe just... As an addition to Izzy Moore's interview, maybe we can explore this lower limb stiffness and maybe we can start by answering the question like why is it so important to running economy to have this lower leg stiffness? Yes. So, before starting talking about lower limb stiffness, we should mention that, yeah, running economy is really multifactorial. So it's not only lower limb stiffness that can affect. running economy, there are so many different variables that actually affect this measure, let's say, this ability of the human body. So yeah, cadence is one of that. One of these. Another one can be the environment and all the environmental conditions, like temperature and humidity and all these things. So yeah, in my paper, I've just talked about one of these variables. that was lower limb stiffness. So yeah. Okay. Fantastic. What, like if someone is just a recreational runner and doesn't have much of a science background, can you maybe just explain what we mean when it comes to lower limb stiffness? Yeah, sure. So I will use another example here to just make things easier for the recreational runners. So when we see the leg, the lower limb, that's a goal. we could describe it as a bouncing spring, especially during running. That's the model that most receptors have used in the past and they continue using it. So when the running leg strikes the ground right after the swing phase, we can say that it behaves like a compressing spring. And as we know, when a spring is being oppressed, it stores energy which will return when it will be released and a load to regain its prior condition, its prior shape, let's say. So for the leg spring, this release phase during running happens approximately at the moment of push-off, when the ankle, the knee, and the hip joints explode, let's say, to achieve forward propulsion of the body. So we have the leg spring being compressed at heel strike. And then, that's the time point when energy is being stored. And then we have the leg spring being decompressed, approximately at the push-off. And that's the point when energy is being returned. So this extra amount of returned energy, let's say, is being added to the work of the contractive muscles. So we have. two sources of energy when we run. We have one energy source coming from the contractive muscles. And this is how I call it active force generation. And I call it active because it consumes energy, because the muscles are contracting. So we have fuel consumption. And the other source is passive force generation. And it comes actually from the spring like a behavior of the leg. So that's more or less how I could describe the concept of lower lip stiffness. I don't know if that's okay. Yeah, no, it's absolutely fine. I think the, um, as long as people can understand that the lower leg is behaving as a spring, I was trying to think of a few analogies before the podcast as well. And I was thinking of something like a spring or like a trampoline. Like if you see athletes that, um, like a gymnast, like an Olympic gymnast, when they're on that type of trampoline, that's like really bound up, really tight. And as they impact that trampoline and they get maximum height that like, it absorbs the load and then releases that load really, really quickly. And I guess if you compare that to a non-optimal trampoline, that's like a bit more flimsy, a little bit more weak. And you sink down really hard. That return of energy isn't going to be as invested where, if you have that really wound up trampoline with the really tight cords, then you're going to, um, the amount of energy that you put in, you're also going to get out. It's like the, that return is a lot better. So if you apply that to a runner, like you were saying, as soon as you, your heel contacts the ground, we don't want to, we don't, we need to absorb that load. Otherwise, you know, your bones would shatter. So what we want to do is have a energy absorption phase where You slowly, you try and make that impact quite soft and you try and absorb that load. And we do that through things like pronation or making sure the knee is bent and the hip is where we bent and we try and absorb that load carefully. But then what you're saying is as we rock into that mid stance and almost get into that more propulsion phase, we want that energy to start being released. So we absorb the load through one phase and then we want to. release it through the next phase and it's how efficient we are at returning that absorbed energy. And that's when it comes to becoming really efficient. And then you did mention the active versus passive and it took me a while to kind of get a grasp of this. But when we talk about a spring, if you load it up and then you let it go, you're not pushing it, you're not doing anything. All you're doing is like... storing that energy in the spring and then you don't do any other any other work but just release it and then it flies off into the air so you're not Lifting it you're not throwing it. You're just letting that That stored energy just let it go and I guess that's what could be If we're using this spring analogy, that's what could be the passive Energy system whereas the active would be the muscles Like if you can feel your calf actually pushing off the ground and your calf muscles talking. That's more of the active Exactly. Unfortunately, we do not behave, we human beings, we do not behave like perfect spring. So we have these two mechanisms. If we were a perfect spring, yeah, we could run forever without running out of energy. That would be the case. Yeah, there's a bit of a mismatch between what we absorb and what we return. And interestingly, in your paper did say that about 40 to 50% of the total energy is recovered by that passive or elastic energy. I thought was great. And I guess the more like if your leg is quite stiff, then you'll have that return more efficient. You'll have a better return than someone who absorbs a lot of load and then is less efficient with returning that into a propulsion phase. So how might you compare the two? Like if you have two runners running side by side, one has a really high leg stiffness. and one is really poor with like with that return, how might they look? What might characteristics might they have? So yeah, it's for this comparison it's like comparing a new spring that just came out of the box with you know with the new used one. The new one will be able to present greater resistance to a force that it's trying to compress it so it will have greater stiffness. And this means that it will recoil and bounce back harder and it will return more energy. So in the same fashion, a stiffer skeletal system will return more energy at the decompression phase. So this type of energy, as we said, is more or less free. since it has a relatively low metabolic impact. So for the same amount of work, a stiffer musculoskeletal system will consume less energy compared to a less stiffer one. So the one with the low stiffness will have to recruit more muscles for the same amount of work that is being required. And the more the muscles work, the more energy they consume. So that's like. That's how it goes for the comparison between a more stiff and a less stiff runner. But at this point, I think we should mention that it's not like the more the best. There is an optimal level of fitness and that's specific and personal for every human body. So yeah, we need to keep the balance. It's not like trying to be the stiffer. It's like trying to find your personal balance between stiffness and flexibility because there are studies proposing that a stiffer an athlete is the more prone to injuries here she can be. So that's, and if you are injured, you can't run, you can't train. So your running ability and running performance will be negatively affected. So yeah, we'll need to keep that balance. That's, that's a good, a form take away message I think. Yeah and so it almost sounds like you're saying that they will get to a certain point where you become so stiff that your functional range of movement or your biomechanics just doesn't take advantage of the situation. Exactly, exactly and you will go the opposite way, you will become less economical than expected. I guess that's the same with cadence. most people will need to increase their cadence because I guess most people's preferred, like just if they just go out for a run without any training, their preferred method of moving is at a slightly lower cadence. Whereas if we bump it up even just by 5%, then they can see some benefits. But then if you increase it by say 15% or 20%, it almost like the. Benefits start to plateau and then almost reverse where you're turning your legs over so quickly that you're actually using more energy than if Preferred cadence so if we're talking about stiffness we can go in the same way like most people when they run Could benefit from lower leg stiffness like increasing their level of stiffness But if you go too much the other way then it's when it becomes detrimental Yeah, exactly and there are actual studies regarding the cadence variable there are actual studies that actually verify these studies. If you increase or decrease your preferred stride rate over a certain percentage then yeah it becomes such mental for your performance. Yeah cool, ties in really well and I love what you said about like having a new spring versus an old spring and that's kind of what I think about if I was to see one runner versus the other and I You know, usually when I run in a more populated area, I like to just have a look at how different people run and see if their cadence and see their technique and just wonder at all the different sort of techniques that are out there. But I do see the ones with very poor stiffness and you can see them like almost bouncing up and down quite a lot and you can almost see like when they impact the ground, their knees, like the joints and the angles of their hips and their knees and their ankles, that it kind of like moves. greater amplitude almost looks sloppy, you know, if you have a really sloppy runner and that's what I like to call them anyway. They probably wouldn't appreciate that. But like you're saying, like if you have a new spring, if you get a new spring out of a box, it's kind of, it's kind of rigid. It's kind of harder to bend and it's kind of harder to move. But as soon as you like let go of that new spring, it like releases so much energy. It's just like the ability for it's like we said, the passive. force generation is enormous. And so those runners with a very high stiffness, you can see that they kind of just recoil very, very quickly. And it's almost like a really efficient kind of just spring that they have. And if anyone's listening and they do run around like a park or a lake or something, have a look at people and just see the, notice the differences, whether people do feel like they're absorbing and recoiling that. that load and whether they're acting like a really efficient spring or whether they're acting a little bit sloppy. Could be a nice little something you can observe. Is there any testing that we can do if someone is a runner and doesn't see a physio or anything like that? Is there any tests that they could do at home or anything that they could look at themselves like on a treadmill or if they're, I guess, maybe recording themselves on the treadmill, anything they can look out for to see if they do? need to increase their lower limb stiffness? Yeah, so if we talk about direct, let's say quantification of lower limb stiffness, this can only be conducted in a clinical setting for research purposes. And this is because special equipment is required and it's not really. practical because it needs a lot of mathematical modeling and a lot of calculations. So it's not really applicable to for an everyday recreational runner to do that. But the good news is that we can actually indirectly determine our stiffness level and quite accurately, let's say. One of the ways is by measuring our jumping performance. That's a very common way of doing it. There are lots of jumping performance tests, especially the ones that include repetitive jumping and jumping on the spot or different types of drop jumps. And if we can go another step forward, we can also use the EMG device. by which we can determine the rate of force development for the major lower limb muscle groups and the higher this rate is the greater the stiffness but as you mentioned earlier we can just record ourselves and take a look at our technique and compare it with like very economical and very well known and well established runners like or more far and because these are one of two of the best examples of these lower limb stiffness mechanism. So yeah, we can just record ourselves and see how our body moves, how we strike, how we recoil and all these things. But yeah, I think that's the easiest way to do it. Yeah, for sure. And I guess what I do in my clinic is I often get someone to jump up and down. So I'm really glad that you mentioned that and you'll see differences. Like if you compare them to a whole bunch of different runners or a whole bunch of different athletes, you'll see people develop like different strategies and you'll see people having just like their quality of jumping or hopping is extremely different compared to other individuals and someone can be really strong and slowly lift or squat something, but if you tell them to hop, and hop quite quickly, we're not aiming for height, we're aiming for how fast you can recoil and absorb energy and you're looking at fast kind of hops. Some people really struggle with that and they can lift slow heavy amounts and sometimes it doesn't necessarily translate to something that can recoil quite quickly and they probably need to do a little bit of like power exercise or something quick short burst. But yeah, I think that I think that's great double leg jumping like on the spot. I think some people call them pogo jumps, you're really trying to yeah, you're trying to jump on the spot, but trying to be like quite stiff through the legs and trying to see how many you can do like really, really quickly. Rather than going for height. It can be a really nice test and then you can compare hopping and you can do one side hopping and the other side hopping. I love hopping as a test, especially when people had prior injuries and a history of say like Achilles or calf or knee or something. And you find that their quality of hopping on one side compared to the other is completely different. It's like, Hey, we need to iron that out before we can improve your running or start to increase your running or get back to running because, um, the hopping test really just identifies a lot of, or highlights a lot of problems that some people might have, uh, yeah. So I reckon if someone's listening to this, have a, have a go at just hopping on the spot. start with double leg and see if you can generate a lot of force with keeping your hips, knees, ankles, quite stiff, and then try a single leg stuff. But I guess what you're saying is another, another tip would just be record yourself running and compare yourselves to the best that are out there. Yeah, yeah, it's that's more on the running technique side of things, but running technique can be representative of your stiffness level. So yeah, it's even more indirect, but It's still a way to do it. Yeah, it's something to do. And it wouldn't be much of a podcast if we just talked about this and someone, a listener was to go away and see that they have really poor levels of stiffness without really talking about what they can do about it. So, um, I think we might highlight some ways that we can improve our stiffness or manipulate our lower limb stiffness. And, uh, I think, uh, is there any, is there any way that you'd like to start with the runner if they're. if you have identified that they have really poor strategies with running, with absorbing and producing force, is there any way you want to start with them? So, yeah, there are a bunch of different ways to manipulate, variables actually to manipulate in order to improve your stiffness. We could start with the way people land. So if they are forefoot strikers or if they are rearfoot strikers. But to tell you the truth regarding the foot striking pattern, the literature is quite divided in this realm. So for the forefoot landing, there are studies saying that it actually increases mid-joint stiffness, decreases ankle joint stiffness. And for the rear foot landing, it's actually the exact opposite. So we have increased ankle joint stiffness and we have decreased knee joint stiffness. And that's quite frustrating for a person who's just trying to improve things. So when we talk about the striking pattern, most studies have actually tried to investigate different joint stiffness values. So they examined the ankle and the mid-joint separately, and that's why this frustration comes. But from the perspective of energy conservation, let's say, in the running economy, we are more interested in the magnitude of global leg stiffness, not just the ankle or not just the mid-joint stiffness. So in this regard, gender literature is quite divided. But if you want my opinion for this aspect, the main issue is how we could significantly reduce breaking forces by manipulating an athlete's striking pattern. So when we investigate striking patterns, our I think we should not actually focus on improving lower limb stiffness because there is not a lot of evidence that can actually guide us through this process. So if we want to do something with our striking pattern, we should actually focus on finding the optimal striking pattern for us, which will reduce the breaking forces during our running, let's say, movement. Ah, yeah, another aspect is footwork. So in this case, the actual dilemma is running barefoot or running with shoes. If we were to consider just the stiffness variable, the answer would have been pretty straightforward. So barefoot running has been repetitively related with increased stiffness and higher due to that. But we need to say that although stiffness is crucial, it's not the only variable that affects running economy. So why stiffness increases when we run barefoot? It is probably a neuromuscular adaptation that favors the shock absorption that we mentioned earlier. But this doesn't happen without the cost. It is related with increased metabolic costs. So when we need to absorb shock, we increase our muscle activation levels. But when we wear our fancy running shoes, this adaptation is not really necessary. We have the shoe midsole material to do this job for us. So yes. When we run with shoes, the stiffness decreases. And there are numerous biomechanical scenarios trying to explain this. But it is worth mentioning that muscle activation also goes down. And this is rather beneficial in terms of running economy. So just take a look at the recent marathon racing shoes. It's not a coincidence that they have huge layers of cushioning underneath them. Of course, plus some carbon plates and all this hype. And the material development process and all the technology that comes behind it allowed us to provide maximal cushioning while keeping the shoe weight lower than ever. And Dr. Crum from the University of Boulder, Colorado has beautifully talked about that. And in the world of running mechanics, she's a cost of cushioning hypothesis. That's how she calls it, cost of cushioning hypothesis, is very well known. So in terms of training, getting the neuromuscular stimulus from barefoot running, yeah. It has an interesting potential and the good rationale behind it. But when it comes to race day, yeah, please lace up your shoes. So no discussion on that. Okay. There's a lot to unpack there. Writing down on my page furiously as you're delivering. Great. It's awesome information and a lot to unpack there. So what you're talking about with strike pattern. is we're almost shifting away, like shift our attention away from low links, stiffness and just focus on economy to start with. And what you suggest is when we're talking about global running economy and trying to return as much energy as we absorb, what we don't want to do is waste a lot of energy during a breaking force. And so what you're doing is if you're creating a breaking force. Um, or a high breaking force, what we're doing is wasting all that energy that could have been used for performance or propulsion. And so what you're proposing is, uh, if a runner, if you witness a runner or assess a runner who has a high breaking force, one of your first go-tos is to try and minimize that breaking force in order to approve, improve running economy. And I think what most people have. what most people go to when they think of breaking forces is more of like an overreaching initial contact. So they're contacting the ground in front of their body further than another runner. Is that right? Yeah. Like a huge, huge striking pattern can create a massive amount of breaking force. So that's the first thing we should look about finding ways to reduce these breaking forces. So yeah. So we're impacting the, um, what we call, um, closer to our center of gravity. So almost closer to underneath your body when you first make that contact. And it doesn't necessarily mean you're contacting with your toes or your heels or your flat foot. What does matter is how far in front or how far underneath you were aiming for. Okay. That makes a lot more sense. And then when we're talking about footwear and the whole debate around, do we want something that's cushioning? or do we want something that's more barefoot qualities? You did mention that the aim, I know there's a fair bit of studies looking at how light a shoe is, and the lighter the shoe, the more economical a runner seems to be able to perform. But what you're saying is, there's also more muscle activation with the barefoot? Yeah, exactly. So when we run barefoot, we have nothing underneath our feet to absorb all the searching from striking the ground. So this happens by recruiting our muscles and when we recruit muscles we consume energy. Right, it's more of that active energy phase rather than that passive which is what we're talking about before. Exactly, exactly. So but yeah, when we activate our muscles our leg becomes more stiff. which is good because we've said that stiffness is a variable that positively affects running economy. But when the muscle activations are too high, then the cost for this is rather big. So running economy as a global measure is being negatively affected in this case. So we need to stay. Yeah, exactly. Yeah, so we're trying to find the balance. Like we want a lighter shoe. because we know if you're running with something heavier, you're literally like picking something up and placing it down that's more cost effective or it's more cost, like it's a, what am I saying? It's costing more energy. But if we can try and find a balance between something that does apply a cushion, so it minimizes the shock attenuation and the muscles don't need to contract as hard. but still remains quite light. That's a really nice balance. And I think there are more shoes out there that do offer that. They do have support, but the properties that they do have, the actual shoe itself is quite light. And I think that's what we're seeing with the increase in running performances and all these shoes that are coming out, they are quite light. We're not getting those bulky kind of traditional shoes like we used to see. Yeah, yeah, exactly, exactly. And I think that in the future, the technology will help us even more because materials will become even lighter and their cushioning abilities and properties will become even better. So we don't know what we can expect in the future. Yeah. If you're seeing like a runner who is one of those sloppy runners or they're jumping on the spot and they're really, they're really struggling to recoil and have these powerful kind of movements. Do you work with them with any exercises or any kind of training, strengthening exercises? Yeah, yeah. So in this case of a runner who is really sloppy and he cannot recoil and he cannot perform these type of activities, I think I probably would start working with him to improve his coordination skills. .. plyometric training is a really good... choice, in this case... because it seems to promote mechanical characteristics of... muscle tissue... .. which... which are related with... the stretch shortening activities and that stiffness... and also plyometrics and promote... optimal muscle fire... firing coordination. which in turn promotes stiffness again. So let's say that we have a leg that it cannot coordinate when the quadriceps are firing and when the calf is firing. So we need to make this thing work as a whole. So plyometrics can be really beneficial in this scenario. Another aspect is heavy resistance training or explosive training like explosive squats and explosive deadlifts which more or less provide the same benefits. And if you want my opinion I think that neuromuscular training like plyometrics and explosive training and all this stuff. It's the most effective, I think, intervention for improving stiffness and driving economy. So if we actually want to improve one variable and isolate it and focus on that, and this variable is stiffness, so the best way to do it is by neuromuscular training. And what I mean by that is by improving coordination, by improving the rate of force generation. how fast you can jump on spot to link it with all the things we talked about previously. So yeah, that's a couple of alternatives that I would use in this case. Beautiful. I think it ties in really well. At the very start of this podcast, I did a whole season on strength training and educating the viewers or the audience about the benefits of strength training, how can it improve running performance. there is a lot of evidence to say that if you are strength training, it does all the things that you were suggesting. It increases coordination. It increases like the, the muscle fire patterns, and then just increases low limb stiffness in general. So like if, if someone is quite, um, quite a sloppy runner and they're not doing strength training, maybe one of the first things they can do is just start strength training. It doesn't need to be so honed in or so specific. Um, but someone is like, quite a, a gym go on, they're already familiar with squats, lunges, dead lifts, calf raises, all that sort of stuff. And they're still seeing some deficits in stiffness. Perhaps maybe they might need to add in some plyometric exercises in order to start to promote more of that quick fire pattern and start to become a little bit more detailed if we're doing, if we're implementing plyometric exercises. for someone who isn't familiar, can you maybe just give one or two examples of what that might look like, or maybe one or two of your favorites that you'd recommend for most runners? Yeah, yeah. So when we talk about plyometrics, we don't only talk about like jumps and all this stuff. Strikes can also be a type of plyometric training, stripes, you know, 100 meter repeats or. 200 meter repeats or even shorter distances. So after finishing your easy day run, don't just go back home, spend a couple of more minutes and do some strides. They can make a huge difference in your stiffness and in your running economy in general. The same goes with all the running drills like kickbacks and high knees and all this stuff. Again, when you finish your easy day run, don't just go home, do your drills, then do some strides, and then you can go home and relax. But don't miss and don't skip all these things. They are small, but they can make a huge difference in your... overall performance and in your health too because they can actually help prevent a lot of injuries. Yeah if it's worked within the right I guess adaptation zone they're not doing too much too soon absolutely and it's a good point that you made I didn't actually think of that doing some strides or maybe even just some short like hill repeats or yeah anything that involves some sort of sprint work that You know, you're not overdoing things. Make sure if you do start that you're well within your adaptation zone. But yeah, they've got like a recreational runner who just say is, um, they stick to the same pace every time. Like I know there's a certain population of runners that just, they do five to 10 Ks a couple of times a week and they stick to the same slow, easy pace the entire time, and then they expect to be like an efficient runner, but in order to get the strength benefits. And. have that low limb stiffness and that running economy, you kind of need to challenge your body a little bit. You kind of need to start triggering some sort of strength. And so that's a really good point. If someone doesn't, isn't a gym goer, doesn't want to lift weights or do plyometric exercises, implementing some sort of fast work into or some short heel sprints into your routine can be really effective. Yeah, yeah, sure. And that's another point. I mean, you don't need to go to the gym. You can start from easier things. You can start from things that you can actually do right after your run. So you don't spend time, you don't spend money, which is rather important, I think. If you are a rather, let's say, recreational runner, so you don't want to invest a lot, you can do these simple things and still see some benefits. And as you progress and as you become better and as you want to improve even more, then you can go to more specific type of training interventions. But I think these are good start. It can be a good starting point. For sure. And a skipping rope is very inexpensive as well. And that can be some really nice short, quick kind of rapid exercise you can do just doing skipping drills. Yeah. Yeah, of course. Yeah, perfect. Is there any other take-home messages as we wrap up now? Anything that we hadn't covered that you want some runners to think about or some runners to know that we haven't discussed? Regarding our topics, I think we did quite a good job discussing lower limb stiffness, what is it, how it can affect running economy. Yeah, I don't think there is something I could add. Yeah, I totally agree. I think we've covered enough and almost everything that I wanted to cover. So that's been fantastic. Usually in this part of the podcast episode, I ask the guests if they have any social media platforms that people want to be directed to. But because I just found you on Facebook, I'm not too sure if you have anything that you want the audience to be drawn towards if they want to learn more about you or is there anything that you encourage runners to go to? to learn more about this topic? So I mean the reference list from my paper, I think it's a good start. There are quite a few interesting papers that they can go and reach out and read and gain more information if they want, if they are interested, go more in depth. The thing is that I'm publishing not science based papers, more like easy to digest type of writing stuff, but it's in Greek. So I don't know if that's a good choice for Joe. I have to check how many Greek downloads I get. Yeah, that's a point. But if they have any questions, they can use my email address and send me their questions. I have... no problem. I can get back to them and answer and solve all the questions. Brilliant. Yep. They can just send me an email or they can find me on Instagram and DM me there. Yeah. Cool. What I might do is I might link to your paper. I might put that link in the show notes and then I might just provide your email in the show notes as well. And people can reach out to have any questions. Yeah, sure. Sure. Christos, this has been amazing. I think we covered so much. I think we compliment each other really well back and forth with some really nice ideas. So I want to thank you. Thanks for taking the time for coming on and sharing your knowledge. Thank you so much for having me. It's been a pleasure and yeah, it's always a good experience to talk about our passion, running is our passion. So yeah, I always enjoy talking about it. Absolutely well said. All right, you take care. 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