 Hello and welcome to lecture six of the Sports Biomechanics lecture series supported by the International Society of Biomechanics in Sports and sponsored by Vicon. In the first of our three lectures today, I'm joined by Pedro Maruso from the Polytechnic Institute of Lyria in Portugal. Pedro was actually winner of the ISPS new investigator award in 2014 and he's got a lot of interesting research involving the biomechanics of swimming. So today he's going to give us a brief overview of some of the literature in the area of swimming biomechanics. So thank you very much and over to you Pedro. Well, thank you very much Stuart. First of all, I really would like to thank the opportunity for making this presentation. Really, thank you for ISPS, but also, and most of all, thank you for Stuart for coming up with this hard work, getting many people talking about their passion and what they love to make research about. So indeed, when I was invited to talk about swimming biomechanics in this type of situation that we are living in, I got a little bit stressed up about what to talk about without taking one day totally or something like that but to make a short presentation about half an hour on swimming biomechanics. So before that, if you saw some of the previous lectures and if you didn't, I really invite you to do so. I would like to start by telling a little bit about myself, because I really think that is very useful for the ones who don't know me. But there's one big thing I would like to tell is that I was born fat. So really, I was born really, really fat and probably because of that my parents put me to play almost all sports that you may know. Apart from sports, they also put me on the ballet. So as you can see on that picture that fatty guy over there. It's me. So for the beginning that I remember human movement was always on my mind. So I was one of those guys who didn't have any type of doubts about what to do in the future, and it would be something related to sports. Indeed, I come from a small city here in the middle of the country you can see over here. And so when I had to study to get my degree, I went up north to a faculty of sports of the University of Porto that many of you already know that is a very big regarding sports sciences and where biomechanics as a role, a fundamental role for the students. And from there I took a very, well, let's say hard decision on 2001 on the exact same day of the World Trade Center came down. So I had to choose an option and I decided to take the option of swimming. And that was something that was by the time something that really was challenging because what we used to say is that when you put water, everything becomes much more difficult. So as you can see, we were a small group of people over here, if you see the picture of the ones who selected, for instance, soccer, you will see that they are much, much more. So we had the challenge to really come up as a group interested in swimming, mostly interested in swimming biomechanics and physiology. And so it came up to be one of the best decisions I took in my life. These gentlemen over here, some of you may know it's Professor João Paulo Vila Boas. If you go to the Web of Science and you search for the topic swimming, you will see that he's the top leader author. And most of all, he was probably responsible for being the father of so many young researchers that's in Portugal and abroad are making very big, very important research on the field of swimming. So it was for me a huge pleasure to be student of him and try to learn with the best. There are some examples like Professor Ricardo Fernandes or Professor Tiago Boas that many people know are top researchers on the field. But apart from that, and I was supposed to be talking also to some of students that are nowadays taking for instance their first degree or even their master degree. And I have to tell you that swimming became my passion. So indeed, when you are studying you should try to find and reach what you get in love with. It will become much easier. And of course it will be much more interesting for you to keep working on that on your free time. So I really got enthusiastic with the idea of the idea of the waters induced biomechanic issues. And I tried to do everything I could to get involved with the ones who could benefit the most with the swimming biomechanics that is the swimmers. Of course the coaches, and even when you find obstacles on your path, don't quit. So there was no funding for me to go to the World Swimming Championships in Manchester, but I was able to get a backpack and sleep in a hostel and by myself become a volunteer of the organization and get to know the best swimming coaches of the world. So just a final remark about who I am, who knows me, tell me that I'm a workaholic, but I do expect that before this situation that we are living a little bit like this and after I suppose that it will keep being the same. So regarding biomechanics, the main question that I really like to talk about is how can it be useful for swimming performance, indeed trying to increase the swimming performance of our athletes. As you can see down here, there's my email so please feel free to use my email or my Twitter account to get in touch. I will be more than happy to keep the contact further this presentation. So about biomechanics, and you can see here, I'm sorry, now starts. You can see, you can see here then the video that this is front crawl on both videos. This is the same swimming technique, the same swimming stroke, but the truth is that they are totally different from the left to the right side. So the main thing that I got interested in the last few years is that when you are talking about the same stroke, you might be talking about different biomechanical constraints that will surely have an impact on swimming performance. And so I made this draw over here, and before we're live getting feedback response in real time, I would like to ask you how do you think it will go with the world record for the 50 meters freestyle to the 1500 meters freestyle. So if you would put here the 100, 200, 300, 400, etc., if it will go like the orange curve, the blue curve, or the green curve. The interesting thing that you might do this homework is that you will come up with an almost perfect correlation between the time and the distance. And indeed, when we start thinking about this, we come up with a very interesting idea is that swimming is a very easy sport regarding the rules, and what you have to do. If you go to the starting walk, you already know the distance that you have to travel. Most of the elite swimmers already know how many strokes they will have to do to finish the event. And so you have to make it the fastest you can. And that's it. The main issue is, indeed, how can you make it faster? And how can you make so that your, the energy that you are using is really, really used for the purpose that you want. So are not to spend energy that it's not efficient. And as I said at the beginning, swimming, swimming biomechanics need to become your passion to really go over this and try to understand clearly, how can we come up with tools that might improve the performance of our swimmers. So this is a small example of some of the things that I got really enthusiastic about. And I think that studying is one of the most important things that you can do for the rest of your life. Because when you study, you have, you must have your open mind. And with that open mind, you'll be able to see what others are coming in conclusion with, and how can you use that for your daily work. But also from studying comes a different thing that really should be questioned about that is your experience. And the experience that you go through will tell you a lot of things about how to work. I have a small experience that I really, really came up to me when I had some time to think over it. That was with the Olympic Games in Beijing 2008, when I was making some biomechanical evaluation, not from the swimmers but from the national Olympic throwers. And by the time I was really, really only looking up to the biomechanics and the bio energetics that was only the only, it was the only thing that was I was thinking about because I really thought that would be the only important things. But I was able to understand that even if you make the most rigorous work on this side, there will always be a mental side that really comes up with the final result. I do not try to elevate something and forget all the other aspects because there is a multidisciplinary issue regarding some performance on sports, and most importantly on swimming performance. With that in mind, well probably most of you know about this issue here on the Beijing Olympics and the finish of this event. And I usually say that when you look about genetics, they give us the tools like everyone tells about how the mechanical issue for Michael Phelps could be improved regarding his anatomy. But indeed, I do think that biomechanics teaches how to use them. So if I have some type of genetic profile, and that will give me some type of stature and arm length, probably biomechanics has the skills to teach me how to use them the most correctly as possible. So with that in mind, I would like to tell you that regarding the forces that the swimmer produces inside the water, that's something that we've been trying to understand for years. And most of the evidence really comes up for what the swimmer does, and then we try to understand why does he does it. Some different type of evaluations come up. Some of them on dry land, some using and pressure systems, some using some mechanical models or some forced reducers on the mad system, and the one that I was working most. I'm working most throughout the last years is indeed using a load cell connected to the swimmer so that the swimmer can make his stroke at the same spot using both arms and legs, while you are recording the forces that he is producing. And that idea, well, Majel in 1970 came up with this proposal, however, here you can see it was in paper. So it was really, really hard for me to understand how can we, without the technology that we have nowadays, make some type of evaluation on paper and trying to understand for instance, average, the difference between the right side and the left side, etc. But he came up with this approach regarding, well, he used the idea of Carpovic in 1939, and then he improved it, and he came up with this situation. And indeed, throughout the years we have so many advances on technology and for sports sciences that was also very, very interesting because it made this available to get much more data and much more information. But the main thing I really would like to come up with is that throughout these years. And as I said at the beginning, my main issue has always been trying to understand how can these approaches, how can these swimming biomechanics, how can these evaluations be useful for the swimmers and coaches. Well, it's my idea and my way of working, but I'm not so much concerned about publications about making the papers on the best impact journals. I really think that it's important to spread that and this disseminate the knowledge, but most important and the first situation is indeed trying to be useful for the athletes and in this case, for the swimmers. So I do know that getting in evaluation system and trying to see how am I able to draw the profile of the swimmer. That will event me find me that will identify me at that precise moment, which are strengths and in week of those weaknesses. And these are just some coaches from Portugal, taking a step further on their course on their skills. And the main issues that they are always questioning is that, indeed, if I do know what parameters should be evaluated, how can they be evaluated. When should they be evaluated and even even more important, how often should they be evaluated, because, at least from the research that we've been witnessing in the last years, we do know that when it comes to swim practice, there is a big doubt about how to increase volume and how to increase intensity. And we cannot go infinitely to increasing volume. So we need to work on the appropriate intensity so that you can get the best outcomes of your training. And indeed, this is something that they they know that I focus a lot is that how can the results be used in the real situation. And many times we are well surrounded by the pressure of publishing or perishing. And so we do a lot of intricate studies, but without the tools that really are useful for the streamers that sometimes are very, very easy to come up with. And so, this is just a small example of something that, well, it comes up with the passion that I talked about. And in 2003, in my city, there was no chance of having a subaquatic camera. And so I went to a shop, and I bought this surveillance camera over here, a very cheap surveillance camera, and with some few adaptations I was able to put it recording underwater. And at the same time, using an above water camera, I was able to get a dual system. And I can tell you that forgetting this camera over here that is a conventional camera, I'm talking about 100 euros over here, and I'll tell, well, 15 or 20 euros, this type of trolley. So it's very easy to get this type of approach. Well, in 2003. Now we have GoPros, now we have other full systems. But the most important thing is really don't quit when you don't have the best equipment that you should like, or you would like to have to make your research. And so, getting a little bit with imagination, I was even able to get the four cameras working at the same time, and so that I could record on the frontal plane and or the surgical plane at the same time and indeed try to be useful making some kind of qualitative analysis. So this for me was very important just to say one thing that when you get some obstacles that you probably will don't give up. Never. So try to talk to everyone you know try to come up with an idea of how can we overcome this difficulty, and now can we really come up with the ones that you were things that you want to study. I'm sorry let me just get this volume down because indeed it was very, very loud for me but just to give you an idea like this is the swimmer swimming, what I will call free swimming so there is no nothing interfering with his swimming technique is swimming comfortably throughout the pool, and I selected back stroke on purpose because you can use well any type of stroke that you want, you can get the instantaneous velocity of the swimmer, but what you can see is that he has attached to him a speedometer. So you get instantaneous velocity of the movement, but many times the kicking will interfere with the results that you are trying to measure. And you are restricted to one swimming pool, as you can imagine if you are working on a 25 meter swimming pool. That's the distance that you can cover. So feather swimming for the ones why not so aware of it. It's using a swimmer so you put the swimmer connected to a load cell over here. There is a small angle so that you can avoid that kicking process on the wire. And so he swims on the same spot, you can change the intensity, as you notice he started slower, and then we got the whistle and he started working it with more intensity, you can use it for the fourth stroke for strokes, you can use it using equipment or not and you can see the differences. So there is a real world that you can use for this show. I just would like to get something that when we read the papers we really don't get with that idea. I think many people think that when I talk about the useful that that would seeming can be they see some kinematical changes. Well, of course they do. And if you go to the gym, you will see that a bench press it's much more different than these two real stroke but they keep doing bench press so the idea is not use these as a tool for training by itself for many for, well, high volumes. The idea is using these to make evaluations and indeed try to understand all the forces produces in water are getting what's the behavior of those forces. So, with that in mind, we come up with some ideas on how could we validate this approach and try to understand if it was very similar or not to free swimming, and it is worldwide people are using tethered swimming and comparing it with free swimming and the differences. Well, there are some kinematical differences but so short that indeed it can be used for swimming evaluation. And for instance, both things stroke rate a biomechanical aspect or in the elected production, more on the physiological side, you see that there are indeed very small differences between the two approaches. But with something like these so as long as he's swimming, you are getting these instantaneous force production. And something that I really would like to make give up the challenge the challenge to you that are hearing me is that this is something that we come up after 30 seconds of stroke, and you can see, there is an average, and there is some variation. But the challenge is indeed we should be looking further to something that came up in 2007 on sports biomechanics that is these movement variability, and how can these be really really important for the athletes performance and on this case for the swimming performance. On that side, you can see that we have the instantaneous force, you can separate the right side to the left side I call the dominant and the non dominant, and you can see some asymmetries regarding the force production. You can even see some type of behavior that all swimmers presented, apart from their level. So I'm talking about elite streamers, but I'm also talking about lower level swimmers. They are asymmetric, and they are symmetric not only on the force production, but also as already stated by research French researchers on upper limb coordination, or even on the end path. So if the swimmers are symmetric. Let's call it like that. How can that be useful for me on the biomechanical side. Indeed, how can we know if those symmetries may alter the optimal function, or they are within the thresholds of normal variation. So I really suggest. Well, I, you might see the link over there but it's easy to find the papers from Ross Sanders on 2011 12 and 13 on the journal swimming research. So we come up with some interesting ideas on a symmetry. And don't forget what I started to say that is swimming the 15 meter freestyle. It's totally different from swimming the 1500 meters freestyle, both using front crawl, but with several differences regarding the biomechanical issues. So apart from that, you may also use that route swimming to put the swimmer using both the upper limbs and the lower limbs, or you can constrain his movement using only the upper limbs and only the lower limbs. So if you can do so, you come up with something also very, very interesting. There is, as expected, when he uses the old body, he makes much more force he's able to produce higher levels of force, of course. And when he uses only upper limbs then he can produces higher forces than using only the leg action. One interesting thing that really come up with my mind was what's happening with these 15% when you make some calculations of a swimmer that okay. I would say that he gets 100% of the force production when using the all body, but only using upper limbs is able to reach the 85.7%, well with the standard deviation around eight. And then when using only the leg kicking is able to reach 35%. So this is the results from one swimmer, but on average, that's something that we've been having. When you make these plus this, you will get over 100%. So what can that tell me, what can these value over here tell me when I've made these deficits of, I will call it a deficit of force production, how can that be useful for me. Once again, this is also a symmetry. This is also regarding the differences that you can achieve from the upper limbs to the lower limbs, and how can we know if they are not are or not in the normal variation. And this idea over here from Kaskin in the late 90s, when he was stating that indeed, when you are talking about propulsive forces and swimming velocity, they should be balanced. And if they are not balanced, if you fit over here, probably you will need to have some improvement on your propulsive forces, and if you are somewhere over here, you need to have an improvement on your swimming technique. Well, this is a theoretical statement, but a very interesting statement regarding the relationship between the forces and the swimming velocities. And we do know that swimmers aim to be, well, applying most of the time forces in the water. And with that, they will come up with an, well, it will certainly occur a variation of velocity in each stroke cycle. And this is a very interesting issue that there are a huge amount of manuscripts working on this inter-cyclic velocity variation and how it can be considered an efficiency parameter. Once again, always having in mind the performance optimization. So for me, the main result comes, as I previously said, looking at the subject, looking at the swimmer at that precise moment. So I come up with this data, these are different swimmers, these pots are different swimmers with their swimming velocity, and the forces exerted. And that tells me something that I really should look at. Each one of these is a different swimmer. I should know who's, who's, who's who, so who's this red one, who's this blue one. Why? Because I really should understand that they are in a stage where they should increase their strength, I need to focus on their coordination. Only with that inappropriate coordination, it will come a speed increase. And with that speed increase, we should also be aware of that coordination. So if you take a look at this situation right here, and if you study the same subject, and you evaluate them again three months left, again later, see what happens. They are over here. And now they change. They change some for the right, some for the left, some for up, some for down. But the, well, if you are only interested in the average, they will keep more or less the same. But indeed, watching this will tell us if the strength increase that we are achieving is, or it's not being useful to increase speeds in the swimming speed, the speed, the swimming speed. And if that is not happening, coordination work needs to be done. Some of the later approaches that we've been working with is that indeed trying to understand if the inter-cyclic variation of velocity can also be used as the inter-cyclic variation of force. I didn't put here, and I would like to ask you to try to guess which one is force and which one is velocity. You see, they are very similar. Right. When I come up with the values of course then you can notice that it's the velocity and lower is the force. I'm talking about the technique for evaluation that comes up with very similar resources to free swimming. And if so, probably using also the inter-cyclic variation of force. That is something that I'm researching with Spanish colleagues right now. It's using it on the swimming full moon as a way to make some quantitative analysis of the swimming technique. But as I said, most of the times I'm really, really interested how can we be useful and how can we translate this to something for coaches that are not available to have a load cell and measure the strength forces that the streamer produces underwater. So just to finish and to tell you something regarding the future and what I'm looking up further is that trying to get interesting results on swimming biomechanics that are user friendly. And that is something that, well, every biomechanist is always thinking about how can we be useful for the coaches. The device that you can see over here is attached to the back of a swimmer. And there's something that I really think is interesting for everyone to understand that is with this device, the swimmer can go and make all the practice and I'm talking about two hours in the water or more than that in the water. And then the coach comes home. It takes the data on his computer. And one of the important things that the system does immediately is that the coach doesn't have to tell the system which stroke he was swimming on training. So immediately we can recognize if it was front crawl backstroke butterfly or breaststroke. I will show you a short video, it will run very fast because I really cannot show this yet, but just give you an idea about the future. As I said, you just need to select which is the length of the pool and upload, and it will run very fast but try to understand that we immediately can get the results on each stroke and get very data on one training and have reference of past trainings for all the swimmers that are using the equipment. And this is something that I really think that we will be looking in the future, because we need to understand that the tools need to be useful for training. And so the coaches cannot be waiting one week or two weeks for the results. With this system they will be able to immediately get results on body rotation, trunk inclination, stroke rate, stroke length, velocity throughout two, three hours of training. Finally, telling you that this statement is very interesting, but nowhere in sport is performance so dependent on the interaction of the athlete with the surrounding medium than in competitive swimming. So if you are studying and you really want to come up with some challenging ideas, putting water on this equation will certainly be a very interesting challenge for you. Finally, thank you once again for ISPS for having me, never forget to learn with the best, because keeping humble and keeping your open mind will certainly have a very good result for yourself. So, as I call myself, be a pain in the ass and try to, well reach the best you can and try to get the most information you can from them. Just don't go to conference and sit quiet if we have questions, please ask them get in touch with the speakers, etc, etc. Thank you very much all the swimmers that I had the chance of meeting throughout my life because indeed this would not be possible without their cooperation. Thank you very much for listening. Okay, brilliant. Thanks Pedro that was really really interesting I know I said at the start when we were chatting before we went on air that swimming biomechanics is an area. I find really interesting, mainly because I'm terrible at swimming. But also just because of all the problems in data collection that Pedro touched on. So I know for most sports biomechanists could rock up at the venue set up their equipment and start collecting data. But if a swimming coach said to me, can you come along and collect some data in our training next week. So I'd have to go away and do a lot of reading and research into how can I actually collect that data, because a lot of the techniques we normally use wouldn't work for obvious reasons with the water involved so that was really interesting. I'll quickly go on to a few questions, just to shout out that all of the other lectures scheduled are on the screen now. So if you haven't already go back and look at the five lectures from previous weeks. This is the first of three today. So we've also got a couple of talks relating to football or soccer, and then there's another couple coming up next week as well as some more after that. But my first question for Pedro, I'm really interested in movement variability and functional variability, which you touched upon a little bit. So I just wondered if you could go into any more detail on either the asymmetry or just variability between strokes and, for example, do elite swimmers have more or less variability than lower level swimmers, or are certain aspects of the stroke more variable than other aspects. I don't know if that's something you're able to touch on, but it's something I'm quite interested in. Well, well, yeah, to be honest, that's something that I'm really, really interested also. And well, when I was making, for instance, my PhD, I was not even looking at that, but I have all the data. So I'm looking at that in the last few years. And indeed, it is quite interesting that you find similar variability both for the elite swimmers and for the lower level swimmers. And that really came up with me with with my mind, regarding, for instance, the idea that I had about the asymmetries. As I, well, theoretically, I was thinking about being symmetric would be better for the swimmers. But the truth is that for very high level swimmers, swimming the 50 meter front crawl, they want to be the most propulsive as possible. On the strokes, most of them really use one end to make much more impulse than the other. So they are swimming asymmetrically in purpose. And indeed we were able to many to measure the mechanical impulse and understand that they can reach higher impulse than a symmetric guy. There are so very big differences in the same swimming stroke because if you then go to butterfly or for breaststroke. Well, it comes up to be some other different challenges because as you can imagine in the simultaneous techniques, you will have for sure long periods when you are not able to make propulsive actions. So I really think that in the future, much more research needs to be done regarding this variability because to be honest, on my PhD, we use the average and the standard deviation and the coefficient of variation to understand how was the variability. And we are far from understanding how can these variable variability be one of the most important issues for increasing the swim performance. Yeah, really interesting. Thank you. And my other question that I was quite interested in was this idea that the arms of the upper body in isolation, and it was around 85% of the force produced or applied by the whole body, and then the lower body in isolation, thinking about 35%, but the idea that both of those numbers together is considerably more than 100%. And kind of, I wonder if you could go into a bit more detail on why that might be. That's something that I do think that they have the link of some of the manuscripts that I made a reference. And so there is one paper regarding this relative contribution of the upper limbs and the lower limbs. Because what I noticed is that when the first studies were done, they were really stating that, well, it's about 85% to 90% dependent on the upper limbs. So in your mind, you start thinking that the leg kicking is only important by 10%. But if you start reading some manuscripts and you start making some testing, you will see that the importance of leg kicking is probably much higher than 10%. Because indeed, we are not talking about just taking the less of the 100% minus the 90. What we came up with was values for all swimmers above the 100%. And what we were able to understand is that the last coordinated swimmers were the ones who were able to achieve higher values of the upper limbs and higher values of the lower limbs, and were not available to reach such higher levels when using the all body. So that value over there that I presented, we call it force deficit, was higher for that swimmers. And this is interesting not only when you are using feathered swimming, but to put a swimmer making a trial, making a free swimming on your swimming pool, using the all body or using only upper limbs or using only lower limbs. You will certainly see that you have swimmers who are not able to translate when using the all body. And for me, it is mostly due to the coordination of the swimmer and his ability to make the perfect synchronization between the right and the left side. And with that, with the upper limbs and the lower limbs. Okay. Yeah, really interesting. Again, so just as a follow on to that, because I was wondering whether it was in any way due to certain musculature being involved in both the upper limb and lower limb aspects, but based on what you said about coordination. Do you think that the actual figure, as in how far over 100% it is, would maybe vary for different levels of swimmer and that might be some kind of indication of coordination within the stroke. Yes, yes, that that's my mind idea. So, as you as you can imagine, like, well, all all the high level swimmers they make strength training on the gym, for instance, and if you notice that your first thing if you notice that your swimmer is increasing the strength on the gym. You should be expecting that he's being able to increase the force production in the water so his speed will increase. So that's the first question that we need to understand is really having a transfer a bit one between what's being done in the gym and then using it in the water, and if it is. Is it making equitative improvement regarding the upper limbs and the lower links and the coordination between them. And indeed, what I came up with is that that idea of having each swimmer understanding what's the behavior of himself is that if you have a swimmer that comes down and right on that evaluation. It's probably a swimmer that needs to improve his swimming technique and the swimming coordination so it's not the most useful thing to keep increasing the strength on the gym, or in different tests that you do in the water, without working the coordination of that swimmer. Okay, well, while you're answering that we've now got a couple of questions from viewers on YouTube. So I'll try and kind of will try and get through those quite quickly. And but the first one from the fit owl, who says, since swimming is a whole body movement is any kind of kinetic testing of any use or application to that. I'm sorry, Stuart. I think that the question was, if we are using the whole body. Can we do some type of measurements. Yes, so with isokinetic dynamometry so strength testing and say the knee extensors or knee flexors. For example, would that transfer to swimming do you think or is it a bit too abstract. Yes. Let me just tell that. Many years ago, there is a book by Wilkie and medicine. Many years ago, and it is quite interesting to understand the tools that they propose to increase the swimming speed by the time they really got some my interesting ideas regarding the velocity of the movement. So isokinetic systems are being used mostly to understand something that all swimmers are worried about that is lesions. So injuries, let's say injuries are one of the issues that we really need to be aware of. The using isokinetic systems is one of the ways of measuring the real the ratio between, for instance, the shoulder, the shoulder anterior and posterior length of the of the muscles and power of the muscles. So, indeed, not so much on the swing performance because when you are talking about the stroke cycle, you do understand that the velocity of the end is increasing throughout all the movement, and that is probably one of the things that most motivated me to use the isokinetic system because you are indeed not changing the pattern of the and and the velocity of that and while if you are using isokinetic system, for instance, in dry land, we're using the swimming bench, probably you are changing a lot of the also the swing velocity of the end. And so, as I said, if you have the swing bench and if you can use it to make the isokinetic evaluation, try to use it try to see if there is some imbalance between right and left arm, but try to understand further on the approach in the water and, indeed, those, well, weaknesses that should detect are or not transferred to the water. Thank you. And the second question is from DeGal Bronsky. Apologies if I've pronounced that incorrectly. And but DeGal says thank you for the talk. I was doing a PhD about the fluid mechanics of underwater fly kick. And I was wondering if you've ever had to estimate the efficiency of this technique. And how would you do it, or I guess, if you haven't, how would you estimate efficiency of any swimming technique. Thank you very much for the question because, indeed, that's something that I really never got into it. We had, as I said, I made most of my research on the first degree and on the master degree in the Port University. They have their biomechanics lab and they have a very strong research group on swimming biomechanics. But most of the issues that we were studying at that time was indeed trying to understand how the kinematic and the kinetic analysis could be performed or could be enhanced in the water. And so studying the fluid mechanics is something that they come up with very brilliant ideas, mostly regarding the approach that they had with the engineering faculty that is just on the other side of the street. And I would be more than interested in giving some manuscripts and some papers that I have. I just, well, we edited a book on a sports science performance that I would be more than able to share with him. If he just sends me an email where there are some ideas on how you can measure that efficiency. I have some Japanese researchers that are making a very interesting work. They presented it in the last biomechanics and medicine conference. And so I really wish you the best on that PhD because indeed a very interesting idea. And if I can give you my ideas that don't quit with the difficulties that you will have because when I was in Manchester in the World Swimming Championships, I saw the most interesting underwater click kicking and indeed that's something that in the future it will make an even bigger difference between the gold and the silver medal because the underwater phase is something that we really need to look. And I'm always telling the coaches over here that they spend, well, I will say 90% of their time on the swimming and 10% of starting interns and that needs to be thought about and probably give much more interest, much more detail on the start interns technique. Thank you. It's really great to offer your advice and insight and kind of help current students out as well through that. So I think if anybody else does have any questions for Pedro, then either use the comments on YouTube and we'll keep an eye on those. If you get in touch over Twitter and we'll try and get any answers to you. Yeah, all that really remains for me is just a huge thank you Pedro that was really really interesting and something I know myself and hopefully a lot of other people will have benefited from and kind of been exposed to a whole new area of biomechanics and research. So thank you very much for that and the people watching please don't forget the other lectures on the screen as well. Thank you very much.