 Hello, and welcome back to the Sports Biomechanics lecture series supported by the International Society of Biomechanics in Sports and sponsored by Viacom. For the second part of today's hat trick of lectures, we're joined by a special guest. We've got Architz Navander, who is a lecturer in biomechanics at the European University of Madrid. Architz is going to take us through a brief overview of hamstring injuries in soccer and some of the research relating to that, and hopefully focus a little more on some of the applied research and implications of that literature. Thank you very much for joining us Architz and over to you. Thank you Stuart. It's a pleasure to be part of this great initiative, organized by yourself and supported by the ISPS and Viacom in particular. And before I start, I hope those of you watching at home are safe, are doing fine in these difficult times and sorry your family members and your close ones. The situation isn't the best, but hopefully we'll come through this stronger and better. So, today what I'm going to be talking about is simple biomechanics behind hamstring injury in football, in soccer or football, whatever you may call that. My talk is going to be very basic. It's focused on, I'm trying to be as simple as possible, trying to explain simple biomechanical concepts to somebody who may not perhaps have a background in biomechanics. Again, feel free to get in touch with me. You have my contact details there. And I'd be more than happy to help and talk about other research that we've been doing. So I'm, you look at this, you say, this is a guy, he's got a weird name. What's he doing in Madrid? So I'm not a Spanish citizen. I'm from India. And that's where, like I said, the journey begins. I've not heard of biomechanics about 12 years ago. What I heard was some, I remember watching a documentary done by researchers in Western Australia about cricket bowling. And when I was back in university in India, and I got an opportunity to come to Spain for an internship. And I said, let me go try it. And obviously I love football. And that convinced me that once I finished my engineering degree to come and study my masters, my PhD, my postdoc in Spain from 2011 onwards. And right now, I'm working as a lecturer, enjoying the broth life. And I've been working in this area of hamstring injuries in soccer, been trying to research in this area since 2012. And I want to make it very, very clear that I'm not an expert in this, because I'm still learning, and every day I learn something new and or learn something which might be contradictory to what you've learned earlier. So if one would just search for hamstring injury, the word hamstring injury on PubMed, you'd come up with about 3000 for 3000 records. It's very difficult to read about 300 studies every, every year. That's the number that those are showing in the graphs. Specifically in soccer or football. It's a hot topic. You talk about 482 articles which have already been published on PubMed. There are a lot of articles which aren't on PubMed. But again, there are, which have gone through peer review. There are 32 reviews, specifically, again, looking at PubMed data on hamstring injury in football or soccer, when you search for these things. So, one more to ask, where do we start with so much information, you might be, what do I do, where do I, where can I start I'm interested in this is a hot topic. I'm, I want to know what can I do to understand hamstring injuries, or I have an athlete that has hamstring injury where do I start how do I go about looking for for rehabilitation program. So, a good source probably would be to look at the cause of integral model of the cause of injury. So, because this is a model developed by researchers in my few couple of Nordic researchers who are this and this paper is really well explained So, just to simple things down. You have an athlete who's participating regularly due to his certain internal characteristics his age his anthropometry his history is exposed becomes predisposed to injury with some internal risk factors. And predisposed athlete is exposed to some external risk factors, which are not in his control equipment location. And makes that makes it susceptible. The sum of internal risk factors and external risk factors, make an athlete susceptible to injury. And then finally, you have the injury mechanism, and you have the athlete who's getting injured. This is what we call on the cause of an injury, we can identify risk factors, external risk factors energy mechanisms. These are three things that we need to tackle in order to prevent injury from occurring or reducing the incidence of an injury from occurring Because there's a lot of people who say that you know you cannot prevent an injury completely but you can what you can do is try to reduce the risk of it. So, talking about injuries and football. It's football and soccer is basically a very injury prone sport. On an average, in Spain this data from Spain. You talk about 81 injuries per team per season. A single injury on an average can vary from a couple of days off single day off to about six months or eight months off. But an average would say about 11 to 12 days. So it causes a loss of playing time and a loss of money as well. Apart from the loss of resources, we can especially look at non contact injuries, of which almost 50% of non contact injuries are muscle injuries. Among these, in soccer, almost 85% affect the lower extremity. There's the thigh, the shank, the foot, and the majority of the thigh injuries affect the hamstring muscles, specifically the bicep femoris. So what are these hamstring muscles that one refers to? These are muscles located in the posterior part of your thigh, consist basically of three muscles, the bicep femoris, the semitendinosis and the semi-embranosis. The bicep femoris is the biggest of these two muscles and is biarticular because it goes over the hip joint and the knee joint. The main functions of these muscles are to flex the knee, help in the extension of the hip along with the gluteus maximus, and this biarticular mechanism, biarticular characteristic of the muscles, and a unique characteristic of this muscle of, especially the bicep femoris, is its dual innervation. It's not a single nerve that activates the muscle, but there are two nerves. So you see over here that the bicep femoris has got two heads, the long head and the short head. These are innervated by two different nerves and that many believe could be a cause of an injury. So if you're looking at where to start about to understand the hamstring muscle complex, this reference from Beltran is really, really good. So what makes one susceptible to hamstring injury? Obviously, the most common risk factor is having sustained the previous injury. The athletes are more susceptible of getting injured, that is, the younger you are, lower probability of getting injured. Males are more likely to be injured and have a higher injury rate as well. And there might be a deficit of force, especially in the lower muscle strength in the hamstring muscle complex. But how do hamstring injuries occur? They have various injury mechanisms, but the majority can almost 50 or 60% of these injuries occur during sprints. During the final part of the sprint, as you can see over here, just when the hamstring muscles change from eccentric to concentric action, if they change, they move to decelerate the knee in order to flex the knee more just before heel strike. And this movement causes a large biomechanical loads on the muscles. This increases the stress on the muscles. So imagine this happening continuously, constant elongation of these muscles, greater stress, and over a long time, this constant stress going over and over and over and over again, lonely cause the muscle fibers to be susceptible to injuries. So why is it that these, why is it so common in sprinting? I'm not here trying to say that hamstring muscle injuries only occur during sprinting. No, no, no. There are other injury mechanisms as well. Kicking, extending the intervallor through phase, or doing a back heel, jumping, there are different type of mechanisms. A person who is running a 10 kick could also get a hamstring injury. I'm not saying that doesn't happen, but why is it most commonly in sprinting? To understand that, we got to understand a couple of things specifically about force production. In running or sprinting, we can talk about two types of forces. We mainly talk about vertical ground reaction forces, which are, which are used to define the body weight, and to generate movement, generate flight, or horizontal reaction forces. Now these reaction forces are very important because these are forces which cause movement in the anterior posterior direction, that is in the movement direction. There's a breaking force and there's a propulsive force. So at lower velocities, these forces are mainly accounted for by activities of the lower limb. Basically, muscles, such as the tibialis anterioris and the calf muscles, the gastrocnemius and the soleus. This is fine when I have sufficient ground contact time because I have the achilles tendon working, some sort of, to put things very, very simply, working like a spring, absorbing and compressing and expanding, giving away the forces. But at higher velocities, when I sprint, the ground contact times reduce. I spend more time in air than contacting on the ground. So what happens? To do that, I need to be able to generate a lot of forces. I need to increase, I need to be able to generate a lot of forces as my speed increases. So as the speed increases, not only do my breaking forces increase but also my propulsive forces. So if I were to look at an evolution of how stride length and stride frequency change when it comes to running, walking, jogging, running and sprinting, we see that initially, we see large increases in the stride length. If you were to look at stride frequency, it's not so much. However, at higher velocities, when you go above seven meters per second, that's about 23 kilometers per hour to about almost 30 kilometers per hour or 30 kilometers per hour, you see a huge increase in stride frequency. So at these velocities, that's when the hamstring muscles become very active. You have some great work coming out of researchers in France and New Zealand, if I may remember correctly, explaining why this horizontal ground reaction force, especially from Jean-Bennon Maureen, talking about how the hamstring muscles work very, very work a lot to generate these forces at these velocities to produce horizontal force. So if you want to look at EMG activation of the hamstring muscles, basically the bicep hemorrhage and the semitendonosis, as the speed increases, so does the activation. Here the activation of each muscle is given as a percentage of the maximum voluntary contraction. So this is through electromyography where I measured the signal amplitude. So as you can see, the higher the number, the more the activation. So at higher speeds, if I were to divide the sprinting movement in different phases, the stance phase when I'm on the ground, the early swing phase when I just about leave the ground, the mid swing phase and the late swing phase. So as I increase velocities, the hamstring muscle activation, both for the bicep hemorrhage and the semitendonosis increases, especially in the mid swing and the late swing. So what happens with such a great activation and such a high load? There's a greater chance of suffering an injury. What happens to the hamstring muscle complex when there is a previous injury? Recently, there was an interesting paper coming out of some Japanese researchers who analyzed 10 university sprinters and found that in the last part of the swing phase, just before landing for his strike, there's a reduction in activation of the bicep hemorrhage muscle, comparing the uninjured limb with an uninjured limb. Uninjured contralateral limb with the same 10 sprinters, but university level. But however, and this was something that I found just yesterday, studies with Aussie rules football found something totally different where they compared seven injured athletes with eight uninjured athletes. And what they found was that what you see athletes with the previous hamstring injury were recovered from previous hamstring injury in orange. And those without a previous hamstring injury in black had similar muscle activation patterns. So what comes to be what comes to question over here is what is happening? And what happens when muscle is injured? When a muscle is injured, can it does the activation change or does recovery if it activates the same if it activates in the same way as it does without an injury. As in the case we see with professional athletes. Is there a greater chance? Why is there a very high chance of a re-injury? Moreover, can I strengthen these muscles and target them individually? So this was study which we did recently where we looked at three simple hamstring strengthening exercises. And looked at the co-activation between the hamstrings and the quadriceps and compared them for three phases. The downward phase, eccentric phase, isometric phase, the upward concentric phase. Just to put a long story short, what we found was that muscle activation differed between muscles of the same group. So you see the quadriceps consisting of the rectus femoris, vastus medialis and vastus lateralis. Each having different activation patterns in different moments. And the hamstrings, in this case the superficial muscles of the bicep femoris and the semi tendonosis, having different activation patterns as well. So can we really target a single muscle when we try to strengthen it? So far it's not possible. So what do we need to do right now when you look at solving a problem of hamstring, previous hamstring injury. So what we need to do right now is we need to try to eliminate internal risk factors through rehab program, prevent an athlete just getting onto the predisposed state. Is that possible? So a lot of testing has been done, a lot of research has been done all across the world. And many researchers have used, over time have used isokinetic machines to test for the strength. So an isokinetic machine is a machine that works at a constant velocity. As a name suggests isokinetic. And you apply a force, you apply a force against a resistance of the machine, which moves at a constant velocity. And you measure the force that's being applied in these cases. So what they found was that a force deficit in these tests done with this machine could help identify a previous hamstring injury. So identify a force deficit, again, work on the strength and possibly reduce the cost of injury. Do some exercises work better than the others? There's a famous Nordic hamstring exercise which has proven to work in some athletic populations. So well, that if you were to look up some great studies from the Queensland University of Technology, especially headed by Dr. Tony Shield, you'd see some great work coming out of there by the views actually being able to find use the Nordic hamstring and created a Nordboard to evaluate the hamstring strength and determine when an athlete is more susceptible to sustained injury. You also see some other studies such as the Askling L protocol where you try to lengthen the muscle fibers. And again, this has proved to work in the athletes where they have tested with such a converse with the lengthening protocol of these muscles because there's one of the risk factors is having short hamstring muscle fibers. So lengthening them probably could reduce the risk of injury. So these are some exercises which are done off field. Now what about what can I do to work with external risk factors or the injury mechanism itself? So looking at these two factors, what I can do as external risk factors is I can test the athlete in his or her context. If an athlete is a soccer player, I would do the testing on a soccer pitch. Basically, I have wonderful motion capture systems which I can use to analyze movement. So what have some studies found when comparing the differences of a previous injury in the running technique or sprinting technique or sport specific movement. So we're looking at sprinting technique. They found differences basically in the coordination and this coordination was linked to having a higher injury risk. A coordination with a greater trunk lean in the case of having sustained a previous hamstring injury compared to athletes who do not have a previous hamstring injury. It's a very good study by Shermans in Gaten posture, which I really suggest that you should read. For my PhD thesis, I studied the kicking and found something similar and the coordination was what was the most effective when identifying when comparing a previously injured muscle, previously injured subject to an injured subject. So keeping this in mind, can we create a model to prevent not just to reduce the risk of injuries, but actually just eliminate having an athlete predisposed or being susceptible to the problem. And one more thing to keep in mind over here is that an athlete, especially a high performing athlete needs to come back. And continue to perform at a high level. Let me give you an example. If a player is performing, scoring, let's say in soccer, scoring a game, a goal every two games. I need that player to continue to come back and score a goal every two games because that's what's going to define success for me. So my rehab program now becomes a rehab and reconditioning program. So keeping this in mind and keeping the previous studies that we have found some brilliant studies and you have, like I said, you have a lot of studies to look into and some great evidence, scientific evidence, which tell you what works and what could work rather. So the question is, can we prepare a rehab and reconditioning programs specific to professional soccer players, which makes sure that the athlete comes back for sure, stronger, comes back and performs at a very high level, and has a reduced risk of re-injury. So this was a problem planted by a colleague of mine for his BSD thesis. And he's a colleague who works in a professional soccer team. And what he did was he prepared an on-field rehabilitation program, on-field rehab and reconditioning program. The program, just to put it in brief, and this paper is down in the links and you have an open access. It's open access so you can check the exercises or whatever. And it starts with an indoor movement where you have a lot of controlled movements and moves on to a non-field reconditioning program. So indoor is used mainly for strengthening control movements, get the confidence of the player back, move on to on-field reconditioning so that he's not only gaining strength but also performing at a high level. How do we know this player is performing at a very high level? Because all these training methods are being controlled with GPS data. We have technology in professional soccer today. There is technology which one can use to control and monitor progress. So this model was sent out to experts around the world who were working with professional athletes, professional soccer players, and basically they said, yeah, the plan sounds good and let's see if it works. So they validated it, was validated by experts, because it focused on not just strengthening the athlete but also helping him or her make decisions and prepare the athlete for possible injury mechanisms. Making him or her strong to be prepared for the event of the eventuality when such an injury mechanism could affront itself and the athlete can go through unscathed. So did the model work? It's validated, but it worked. So over three seasons, he followed 19 professional players who had suffered an injury, specifically a grade two hamstring injury, which the layoff is about 23, 24 days, about three weeks. And what we did was we looked at their performance before injury, the day that they got back, the return to play, and we did a follow up six to 10 weeks after the return to play. So we considered a game a player to have returned to play completely when he performed, played more than 45 minutes in a match. And the second game was played within 10 weeks. Now we've got to understand in soccer. A lot of times the schedule is not in your hands. You don't decide when the players return to play because a person might be ready to play and it's in preseason. There are no matches. Or the player might be ready to play and he's not selected by coach or does an international break. So the return to play data is not really in the hands of the staff because it's determined by a lot of other factors. So what do we find when we apply this program? The return to play took more or less the same time in three weeks, about 22 days. But what you did find over here was their performance, especially at higher velocities improved. So if I were to look at, I know that here there are a lot of speeds and a lot of graphs over here. So let me try to explain that. So these are velocity distances run at high intensities, very high intensities. And these are any sprints above 25 kilometers per hour. The point represents the distance run per minute in the game before an injury at return to play and at the second competition. So we have at lower or at high intensities, not so bad, the distance they ran stayed more or less the same, improved a little bit. But what we did, where we did see it was this one we're able to run, cover more distances at higher intensities. One good way of seeing that is looking at the work, work to rest ratio. Work to rest ratio is basically a ratio of the distance run to the distance what is it the distance run about 6.4 kilometers per hour to the distance run in those 6.4 kilometers per hour. So regardless, it has stayed the same. But what has increased is their intensity performance. And the players are performing as good as they are, as they were earlier, if not better. And there was no cause of injury. And this model what you've seen is over three seasons. Obviously, this hasn't, this wasn't done overnight, you don't have 19 injuries in one season. And these are data from two clubs, not just one club. So that is something that has to be kept in mind. We have been able to prepare the athlete to come back to play. One thing that I forgot to mention was that the athlete didn't suffer a re-injury in the eight months for in the follow up that we, that we did eight months after having sustained injury. So an athlete is more prone to having a re-injury within one or two months in the case of hamstring injury. So we did a follow up for eight months. And in eight months, there was no injury. But now the question comes in is, can we shorten these timelines? Instead of three weeks, can we reduce it to two weeks? So this is something that was just accepted like yesterday or two days back is a case study with two players. And where the return to play was done within, where the player returned to play within two weeks. And missed only a single competitive game. Not just that we reduce the time loss, but the performance of the player was sustained. Now, all this sounds beautiful, sounds great when it is done in practice. And these are results that we have got. But there's one thing that one has to keep in mind. I'm just going to show you a video so that you can understand this concept a little better. So this video, I'm sure some of you have seen this, is a mother trying to explain how to jump head straight into the pool towards your kids. So basically what I wanted to say over here is that I may have the same rehab technique as a professional. But I got to know my audience, I got to know who I'm treating over here. I can't treat the same person. I can't apply the same program to everybody and that's not going to work. I need to understand the characteristics of the person that I'm treating. So if you are a biomechanist, how could one help in the rehab and reconditioning of a professional athlete? What is your role as one could go to? You could identify risk factors. That's the first thing that you're going to do, specific to the sport. Identify the demands of the sport. Look up research because I'm sure that how innovative your idea that other people simultaneously equally talented is not better already working on it. What of that research can you adapt? What can you accept? What can't you accept? For example, there's research which shows that the Nordic hamstring injuries, Nordic hamstring protocol worked brilliantly. But for some reason or the other, coaches and players are reluctant to implement that program. So you need to do something that they accept to do. It's very difficult to convince people when you're working the professional athlete and you're just a biomechanist. Make sure you monitor programs and always, always look to improve. So these six points I think are very important that one can keep in mind when you're looking at improving the rehab and reconditioning for not just for a hamstring injury, but for any other injury that you're looking at. And for those of you who are just about starting off or in the middle of your research program, doing your PhDs, doing your masters, or thinking about doing a masters, thinking about doing a PhD, think about learning more in this field. I would say just dare to dream. And you never know when the opportunity would come knocking on the door. Be prepared for that. I've had the chance to work with professional athletes at the elite level. But like I said, I've also had a lot of times when I didn't have that opportunity. But at the same time, make sure that you make the most of the time that you have at your hands. Don't be taken aback by rejections. You get a lot of rejections. My first article was published after being rejected. I think eight or nine times. And my first project as a lead investigator was accepted after, again, 12 project applications. So you need to persevere. But at the same time, one of the most important things that I've learned in these ages these times is don't forget to have fun. Make sure you make the most of it, especially given the times that you are that we are in. Enjoy your time with your family with your friends. And with your colleagues as well. So I just want to say a big thank you to all my fellow researchers to the athletes who have participated in particular. My colleagues at the university out of pay and my previous university, the technical University of Madrid, and stay safe. I'm here I'll be more than willing to get in touch with you so feel free to send me a question. Or write me by email or by Twitter and Instagram and I'll be more than happy to answer your questions as to the best of my knowledge. Okay, so that's my job. Thank you very much. And over to George. Thanks, that was great. I really enjoyed it. I've told you this before, but I really like your slides. I think they're brilliant. I love the stay home messages at the end. Thanks for that. Personally, I really like the fact you displayed individual data points as well from individual athletes rather than just masking them with group means. So we can really look into it and say, are there responders and non responders or how did what's the individual variation between the athletes and I thought that was really cool. The other reason which I mentioned to you beforehand why I really like this is a few people are where I previously torn both of my hamstrings. So this was relevant to me, what not quite so many people know is actually tall the first one while putting my sock on. So that's my kind of embarrassing story out of the way when you said hamstring injuries don't only occur during sprinting. That's definitely true for me. The kind of first question I just wondered if you could touch upon a little bit was the role of other muscle groups in hamstring injuries. So both in injury risk factors or injury prevention, things like the quadriceps and how that interacts with the hamstrings. So that's a very good question that you that you raise over here so I can talk about a couple of things over here and not just research that we've done and but also research other other groups have done. And especially we see a lot of work from from different researchers who said that you know hamstring muscles can't be targeted individually or as a group as a whole, and one must look at the complimentary muscles. And what we found in kicking, at least what I found my thesis was that there are phases if I were to divide the kicking in different phases that probably you'll see that in needs lecture a little later on. There is first the backswing phase for the hip extends and the knee flexes. Then there's the leg cocking phase where I have the hip. Beginning to flex while the knee continues to flex. The leg acceleration as the hip flexes then the knee accelerates, extends sorry, and the follow through phase is after the kick where the hip continues to flex the knee extends for something sometime and then begins to flex again. So the first phase of the backswing where the hip extends and the knees flex is very important. Because that's where the hamstrings are really, really active that's, that's their role extension of the hip and flexion of the knee. Now, the second phase, you have the knee flexing and the hip flexing at the same time the leg cocking phase that phase is very, very important so we found a lot of coordination differences there in that phase. So what would pay an important role would be the role, not just of the hip flexors, but also of the hip extensors, especially the gluteus maximus in its role as the extent, the primary extensor of the hip. And, and they also ask muscle and the quadriceps muscles for the flexion of the hip. These muscle groups were something that we tried to target in, it's in Sergio's thesis what he tried to target in his, in his rehab work. So, that's what's helped the rehab program in, in our opinion is that we looked not just at targeting hamstring muscles but also looking at the surrounding muscles, especially what we found to be very crucial was to be the hip extension work that we did the first movements that a player starts to do is control movements in the larger in control lateral movements. And when the player is able is pain free and is able to move in the societal plane. Then we look at hip extension, mainly, but avoid simultaneously it's initially avoid something is hip and the flexion. And then you slowly as you progress, you bring that into the equation. I hope that answers your question. Yeah, that's brilliant. Thank you. And that speaking about different muscle groups and their interaction leads me on quite nicely to a question we've got on YouTube from surprise char and apologies if I pronounced that wrongly again. But they've asked specifically to do with isokinetic testing I'm not sure how familiar you are with kind of dynamometry and isokinetic testing. Whether you prefer the traditional HQ ratio, so concentric hamstring concentric or the functional ratio. Concentric quads and eccentric hamstrings to see a symmetry. And then a follow on question or an alternative question is for sprinters. Is it better to test them at a high velocity, because they're sprinters, and because that's a greater power output, or to test them at a low velocity to get maximum strength. Good luck. Yeah. It's a good question from from superior. I'm talking about isokinetic testing and what sort of ratio would would work. Obviously, if you were to read literature, it would would say to the functional ratio that's better. And here this is a big, I would say a big problem, if I may say so, or a big question that might come up is the athletes willingness to participate in the test. Because when a person participates nice kind of testing. He has his quads and his hamstrings quite loaded, especially when you test at lower velocities and lower velocities require a lot of strength and that takes out a lot of strength, a lot of movement because you have restricted movement for an athlete. And that would make it very difficult for the player to participate. So from personal experience, I did do isokinetic testing once. Sorry twice. Once when I was working for my master's thesis with semi professional club in Madrid, and they actually what happened was they lost. They, they couldn't train for one day after doing the testing, but didn't have so I wanted to do a follow up testing of regular testing with them. And the coach said, no way, my players are very tired after doing this testing we're not doing this testing again. And when I was working with a professional club, this testing was done only preseason with injured athletes. So, the problem with low velocity testing is that you would see a lot of forces, a lot of strength. You could see the maximum power develop the maximum torque that can be developed by these in these movements. But then again, and what's what's your trade off. What's your trade off. What we found is, again, and there's some research coming out from from Qatar from the aspire group, which says that, you know, I said, can you take testing may not be the best way to break hamstring injuries in soccer players. And they've tested like about 200 or 300 players that's some very good research from Nick, Nick Van der Horst, and the aspire group in Qatar, which has some interesting data. So, what we have done is we are lucky over here in Madrid, or this is where I've worked is we've looked at the strength in using using EMG. And it's not invasive. It doesn't hurt the player such these are regular strength exercise that a player does. So, that could work as an alternative, but is it going to predict injuries. I think injury prediction is very, very something that's very, very difficult to to determine to just certain in my opinion, because you never know because you might say, we do this, this works brilliantly. I got the solution for for for that's a XYZ in this XYZ thing and then the next very next day. You have three country muscle tears. That's happened. I've seen that face to face and that's how it is. Unfortunately, hope that answers your question. Yeah, thank you. I think on that. It's really important for us to remember that EMG doesn't measure muscle force, but I think getting a holistic view and adding everything in, adding in the muscle activation patterns as well as isokinetic testing and HQ ratios obviously gives a component that could be an extra little layer to the picture. And that line, I think if you're looking at those studies, I mean this again from the QUT group from from Australia from from Queensland, Steven do pick if you see his paper D you HIG do he's got some great work on on isokinetic testing and any energy. Thank you. And, and yeah, just if, if they're not already down there the all of the papers that archit mentions during his lecture will be in the description below the YouTube video as soon as possible. So check back for those and follow the links and hopefully I believe they're all open access as well. Just a last huge thank you for that archit that was brilliant. And please do go back and view the previous lectures or look out for the ones still to come, including nails later today, which on soccer kicking biomechanics will hopefully tie in quite nicely to some of the things we've already looked at. So hopefully see you soon.