 Hello and welcome back again to the sports biomechanics lecture series, as always supported by the International Society of Biomechanics in Sports and sponsored by Vicon. I'm Stuart McCollane Naylor from the University of Suffolk. And with me today, I'm very grateful to be joined by Professor JB Moran, who is at the University of Côte d'Azur in France, and probably slightly cheeky on my behalf, JB was actually due to present a keynote at the ISBS conference this summer. And with that being cancelled, he's agreed to do a very similar talk for all of us to benefit from through this series. So I'm really grateful to that. And if anyone has any questions as it's going on, if you use the live chat function on YouTube, then we'll go through those questions at the end and discuss some more with JB after the talk. Yeah, thank you very much for joining us, JB, and I'll hand over to you and allow you to tell us a little bit more. Thank you. Thank you very much, Stuart, for the introduction. And yes, that's basically partly what I wanted to present at the ISBS conference in Liverpool should times be normal. So yeah, we're going to cover this kind of topic. So we are going to cover the topic of force assessment in sprinting. Just for people who want to have more information about our work, current and projects, you can log in and connect to my website to have some more information. So I'm going to go through past, present and future around that topic. And I'm also going to try and discuss the balance between lab and field assessment because I think one of the missions of biomechanics today is to bring knowledge. And it's also to transfer knowledge to applications. And this is important to discuss both. So the first thing people need to realize is that, and that's something that we covered on the review a few years ago, basically trying to measure any type of force, muscle force, ground force in sprinting is almost impossible currently. So one reason is that, as you can see in this video, people move at more than 10 meters per second. So measuring things in these conditions is almost impossible. So the idea is that we are going to the challenges, we are going to get as close as possible to something that's currently impossible. So by definition, nothing will be perfect in everything I will present after that. So, yeah, what the force, basically today, you have many, many, many different levels, many different scales of force, you can consider isolated muscle fibers or isolated muscles force that's individual measurements. If you go to humans, living people, you can consider muscle groups, single joint forces, like you have in isokinetic testing or single joint testing. If you want to get closer to the actual sports movements, you can get some force measured during isolated exercises, such as jumping or sprinting. And of course, the dream everybody has is to be able to measure force in these different scales during real life movements, such as football movements. And what we need to realize is that basically here on the left, isolated muscle fiber force is very interesting, but it's relatively irrelevant for sports and sprinting, you know, performance analysis. Because it's not fibers that sprint. Okay, so the information is very important, but it's not relevant to the sport context. And the in game outputs are currently impossible to measure. So, you know, we are between two things that are not really appropriate. We rely on some measurements of single joint or single tasks. And basically, these are very different informations. They don't correlate well in trained people. So it clearly means that they are different outputs because of velocity, geometry coordination, many, many different reasons. Because of single versus multi joint movement, and because of non specific or sprint specific context. So basically here. One thing that biomechanics has to cover these limitations is inverse dynamics and modeling. And so I've listed in this slide, some studies that I find very interesting in that in that context, modeling the muscle force so that we can think about what's happening in sprinting. So there's been a lot of very good works by Trumanov, Dorn, Fiorentino, for example, Ken Clark and other people. One of the papers I really liked in the recent times was the paper by Anthony Shashi and coworkers last year in the Journal of Experimental Biology. And so basically here, yes, we have some force estimates during sprinting. All right, but the big problem here is that these models are absolutely insightful. They bring information, but they are simulations that are based on postulates that come with assumptions, simplifications as any model, and that are most often made in steady state running context where sprinting is a changing movement. And so I understand that these models are all very insightful, but my point is we should target more real life experiments and real life measurements. But it's almost impossible. And so maybe the future is direct measurements within the body of players of athletes. In my opinion, a very important step has been published two years ago now in nature by this US team led by Donald Fallon, where they were able to estimate the tension within a tendon, which is indirectly connected to the muscles force by using ultrasound and vibration as quickly this study, they were able to connect the vibration speed wave wave speed to the tension in the tendon. And because there is a proportion between the two that was validated first in Achilles tendon and first in animals tendon but then live during walking and running gates, you can estimate the tendon tension. So the muscle force output indirectly in running and you see here this picture where there's a little sensor that's facing the biceps femoris tendon and that delivers an ID of the tension in that muscle group. Even that's high speed running so maybe that's the future of force measurement in sprinting. But for now, if we go back to the basics, the only thing that we can measure in sprinting is the force output of the system that's applied onto the supporting ground. So basically, the model of sprint performance a few until a few years ago was a model based on kinematics that said running speed is the product of step length by step frequency which is correct. But the problem with this model and this has been very well discussed by Akisalo in his ECSS presentation last year, I advise that you watch this again. The problem is that this model is correct, but it does not relate to the causes of movement. Its step length is not the cause of movement and step frequency is not the cause of movement and as we know in the Newtonian dynamics context, forces are the cause of movement. So I like this sentence that says it's not because we can measure step length and step frequency correctly and accurately that they are what counts. What really counts is the force that sprinters apply to the ground to move and to move fast. So the model that we propose and the model that we follow is this model practical application of sprint acceleration and top speed. To run fast, you need your body to produce force. So yes, that's the muscles, they produce force. This force is then transmitted to the supporting ground. And you move as an effect of the ground reaction force on your mass that is propelling you forward. Okay, so of course, you can then plug a context here, a list of things that's super high velocity, very short contact time. Depending on the sport, you can bring some specifics because sprinting on the track is not sprinting on the football pitch. Okay. And of course, you need to think about the entire spectrum of velocity from acceleration to top speed. In my opinion, the key variable is muscle force that turn into ground reaction force that turns into impulse and acceleration. So that's the kinetics ground reaction force analysis. And for the kinematics, the movement of the segments, you can rely on typical motion analysis here. So, for example, accelerating in sprinting means applying force to the ground and the resultant force will drive the center of mass in a given direction. And what many different research teams have shown is that not only the magnitude of force is important, but also the direction of that force. I think what we call technique in many sports is in fact orientation of the force output. Okay, my shooting technique in basketball, the way I hit the ball in tennis, a lot of that is orienting my force output. If I orient my force output the good way or the wrong way in basketball, I will miss the shot or I will have that shot. In that study in 2011, we showed that basically, yes, the magnitude of force output was important, but to accelerate well, you needed that force to be oriented correctly. So the components of the force that drives your center of mass forward was important. And it's funny because if the law of motion of Newton was tweeted like 400 years ago or 500 years ago, Newton would have done two tweets because it's too short to do it in one single tweet. And so he would have started his tweets like this, the alteration of motion is proportional to the motive force in press. So people say, okay, if you want to accelerate a lot your body, you need a lot of force to drive your body mass, fine. But there was a second tweet. And it's like today's tweets, nobody reads the second tweet, you know. So the second tweet would have been the acceleration is made in the direction of the right line in which the sum of the forces is impressed. And this means, yes, you will accelerate a lot if you push a lot, but in the direction of the push. And the second term is key, because basically as you understand if your push is not oriented towards your goal, then you don't accelerate a lot towards your goal. So now let's go to the methods. This is a quick summary of the model produce and transmits. And the body of a sprinter has the machinery that produces force, but it has also the entire transmission machinery. And you need to understand that performance is having all the pieces working efficiently, not only the producing force pieces. So how can we do. So I'm going to go through history, because the first attempt to quantify the ground reaction force were made by pioneers in our field by mechanics, and one of them was French. And if you check his book, the movement, the movement that summarized all his research on, you know, chrono photography and all that stuff. You see that here, it was measuring pressure, dynamic force with pneumatic systems, so that was only air, paper and ink. And basically here you have an illustration of a jump. That's made. And the first observation of jump force or pressure traces and analysis were made here. It was before the years 1900. And so today we use air and Mac labs, but the principles are exactly the same. So this was the first measurement and if sometime you go to the northeast of France, close to a city named Dijon. There's the Museum of Etienne Jules Marais and you will see some incredible tools that he used for movement analysis. And there's also some very good wine around. So that's two good reasons to visit the name of the city is born. So we are going to skip many things and go to 1971 where Giovanni Cavagna, who is another pioneer in biomechanics, published this paper. So Cavagna is based in Milano in Italy. And they published in 71 this paper that's the mechanics of sprint running and what they did at that time was very novel. They use the track with force plates embedded you see here so the four force plates of point five meters. And they asked the runners to sprint really accelerate and they collected several spring data so they could virtually reconstruct a full sprint analysis. And it's very interesting to see that the way they calculated the force exerted by the foot on the platform in the direction of the run. This is the key was following Newton's equations of motion very important very simple mass times acceleration plus the friction forces. By the way, this was published in the Journal of physiology, and this is very interesting because I don't know what happened since 71. But today we tend to split what's biomechanics and what's physiology, which is in my opinion stupid because we all study how the how the body functions how the body works. And it's very fun to see that sprint mechanics paper published in the Journal of physiology, you know. So, a few years after with my colleagues in Paris at the National Institute of Sports in a study led by Giuseppe Rabita, we did exactly the same. So, at the Insep in Paris, they have seven meters of in series false plates, as you can see here, it looks like gold, you know, boom, boom, boom, boom, each of them is a kiss their first plates, and they were connected into the track. So we could assess ground reaction forces during sprinting from acceleration to maximum speed. And so here, we did exactly what Carania did. We asked the sprinters, because they were elite, they were very reproducible. We asked them to do several springs, because we cannot move the false plates, of course, so we moved the starting blocks, and we could virtually add the data to reconstruct a single sprint. And so this was done by the engineer at the Insep and you can see here, from the starting blocks on the left to maximum speed on the right. You have almost every single step, not of a single sprint, but of the same sprinter and we could here confirm many of the results that we obtained differently. And the most recent update to that false plate technology research was built in Japan in the lab of Ryu Nagahara, who is a sprint researcher. And they published in 2017, the first study of a long series of studies where they use a 50 meter false plate system. And when you read the paper, it's fun because they say it was just 50 false plates installed in series. When you know the connection, the data processing that's behind, you understand it's a huge work. But what you see here is exactly the false trace I showed you before, except that here it's one single acceleration. So you can see here when the sprinter crosses the finish line, they come back to the start line and the data are already processed and ready to analyze with the coach. And this is key. And in my opinion, Ryu Nagahara basically killed the game with his lab because what else can you do? You have false plates under every step, so you can just analyze everything. But nobody has 2.5 or 3 million euros investment or something to build the lab. So instead of having athletes running over a long stretch, biomechanists invented argometers to have them run in place so they could analyze their mechanics. So this is what we call instrumented treadmills. And the first attempt I know of, I mean, serious modern devices was made in UK by Henry Lakomi in 87. And basically the idea was to attach the sprinter for obvious reasons, otherwise they would leave the lab. So you attach people by the waist and you measure both their running speed and the pulling force that they apply at the level of the center of mass. So of course, this was the first attempt. The data were not really sprint-like, but it was the first of a long series of improvements. So that's an historical argumentary, if you want. One improvement was made in France, in Saint-Etienne in my former laboratory. And basically they added a motor to overcome the big friction and the big inertia of the system and to allow people reach some very fast running speeds. And they also added an angle sensor so that we can get the real horizontal component of the push and not only the components in the direction of the attachment. So this gave this kind of traces. This was published in 2001. And funny enough, this is me running on that treadmill because I was one of the subjects during my master thesis almost 20 years ago. So that treadmill was measuring force and velocity, but it was not ground reaction force because there was no sensor on the ground. So that's innovation was made, for example, in the US, in the lab of Peter Wayand. And what you see here is an elite sprinter dropping themselves on the treadmill. The speed here is 11.5 meters per second. So that's crazy fast. And that treadmill records ground reaction force. And the very good thing is that we have ground reaction force and possibly kinematics because we can film what's happened. But as you can see, it doesn't allow you to accelerate. It's only a top speed window of observation and many, many sports require acceleration. So it was a very big step forward, but still some limitations. But I think that's what science is. So in 2010, it's funny because the paper was published exactly 10 years ago tomorrow. We published with the University of St. Etienne, an update of a sprint instrumented treadmill that was allowing people to accelerate from zero. So you saw the beginning of the video was a standing start, still start up to top speed and back. So the key point in this treadmill is that it is mounted on Kistler sensors, very accurate force sensors, and the motor is exactly reacting to the horizontal force output. Just like in real life, when you accelerate horizontally, the speed increases and vice versa. So this is exactly how the motor reacts to the actions. And I'm going to show it one last time. You see that when my colleague is going to decelerate because I say stop is going to put more breaking impulse than there is pushing impulse. And so the motor is going to decelerate exactly like on the field. So this improvement allowed us to plug some EMG to synchronize EMG with the forces to bring some kinematics, 2D kinematics, and so on. So of course, it is treadmill running, but it allowed us to do some laboratory studies that we could never do on the field. And one more information you need to know is that when you compare the force outputs and the behavior there to what happens on the track, you find some very similar outputs. So I think it's a good argument that's close to reality. So in summary, you can measure the ground reaction force. You just have to find a track with force plates. There's only a couple in the word or such an instrumented treadmill. There's only a couple in the word and basically, you know, the treadmill is getting nowhere. It's a classic gym rent. So it's a bit frustrating. So with a PhD student, Pierre Samozino, we asked that question. Okay, can we try and get some data from field conditions with field devices as inputs instead of treadmills or force plates in the track. So we followed an approach that we like. It's a macroscopic approach, trying to get good quality data from simple inputs. This is a challenge, but this is something that my mentor, Pietro de Prampereau and Robert Alexander, a famous biomechanist of animal locomotion, used. Basically, Alexander, when they said in very good paper about modeling and biomechanics, when the model is simple, then it's a very good first step to analyze. You can get things more complicated afterwards, but the first step should be as simple as possible so you can understand better what's going on. So this study was published in 2016 and basically everything is computed from a basic observation. This is a constant sprint, healthy humans giving their all out efforts. The speed increases. No, that's not big news, but the increase in speed follows a pattern that's clearly exponential. And this is a constant observation that you do in track and field people in football rugby. I have thousands of tests where people follow that exponential increase. This is the world record of using balls. It goes from zero to top speed with that pattern. This is my boy. This is an old sprinter 96 years old goes to his top speed like this. And so from that observation, we just used very simple classical Newtonian dynamics to compute the horizontal acceleration or acceleration of the center of mass in the horizontal direction. And then estimate just like Cavani did the associated force output. So the force output in the direction of motion. So let's go back in time. This ID was already out and already published by the works of Archibald Hill. So Archibald Hill is well known for Nobel Prize in physiology and medicine, but he did crazy biomechanics studies. So in 27, they could measure the velocity outputs of sprinters of human sprinters human runners. And they already observed that yes, there's an exponential increase. So it's crazy because it's very complex. And you can summarize that complexity into two variables that define an exponential function. So that's what they observed back in the in the in the 20s. And this was published also a few years later. Elite people also behave the same. The only thing that changes, of course, is the time constant of acceleration and the top speed. Okay, so this is how it was described. And then over the years, it was systematically observed by other biomechanists. So this is from a study from Russia, published in 79 where they attach a wire to the sprinters. And they just check here. This is this graph is very cool. You see the time distance impulses. So they do exactly what Etienne Julmare was doing. They have something, a wire that's, you know, stretched, and they have one impulse every point to second, and they check the time distance relationship, and then they compute the velocity distance relationship from that. So basically, to summarize the method, we take the time velocity relationship, we calculate the horizontal component of the force output over time, or time from that. And we can calculate also the vertical component of the force because because when humans run the vertical component of the force over time is equal to body weight. Okay, because you never fly and you never go down on the ground. So on average, over several steps, the vertical component of the force output is equal to body weight. So from that, we could calculate all the mechanical outputs. And in 2019, we did another validation study this time in Japan with the collaboration of Ryu Nagahara, where we showed that basically, and you can see that here. When you compare the line, that's our simple model to the values of the force plates here, you have what I just said, the horizontal force output for each step is really close to body weight. Okay. Of course you have interstep variability that's normal, but the fitting is pretty cool. And the squares are the horizontal component of the force over the entire acceleration. So, basically, the ground reaction force output can be estimated very correctly from the simple speed or position, velocity or position inputs. The black circles are the equivalent of power associated to the horizontal component of the force. So I'm going to discuss that later. It's not the entire mechanical power output. It's the part of power that's associated with pushing your body forward in the horizontal direction. So in summary, the method requires very simple inputs body mass position or velocity. It has a very good cost accuracy, feasibility ratio. It means the systematic error is pretty low, and the feasibility is very high. And all you need in practice is people to accelerate from zero to maximum speed, which is something very easy to ask to athletes, or it should. So the last part of my talk will be around practical applications in testing or training. So part of our research is done at the lab, because we want to know more but part of our research is done in the clubs. Okay, with directly with players and athletes, and that's where we use these methods. So, very simply, because what you need as an input is positioned as a function of time, you can use high speed cameras to film the movement. And today's iPhones and iPads have very high frame rates, 240 frames per second if you take biomechanics of locomotion papers, and you list the frame rates of what people do. Good frame rate. That's basically what Etienne Jules Marais did very long ago. His frame rate was 24. So we are 10 times more accurate today. And this led to the development, for example, of this iPhone application that's my springs. I have no relationship with the development of this application except that they use our equations. So basically, if you can film the motion, you can then point the position and you can derive the speed time curve and calculate everything. So you can also do that with modern speed sensors, for example, that 1080 machine, you attach the 1080 machine to the sprinter and you get their instantaneous speed that you fit with the exponential model. So we've developed a spreadsheet where you can enter the inputs and calculate the output. So that's very good for students and coaches to get into the biomechanical concepts with, I think, a very good level of accuracy. So for example, that's not even published yet, or that's been accepted recently. Some people in France and Finland adapted that method to Heishoki. So to my knowledge, there's no Heishoki anywhere where you have ground reaction forces in Heishoki acceleration. It's going to be published in sports biomechanics in a few days. These guys said, okay, let's film the movement of the player when they accelerate and let's recalculate the horizontal force component. So of course, there's no validation possible, but it's based on something that's been validated. So this is how they do. So there's no iPhone in the place. So if people don't like iPhone science, they will not be pissed. So that's a GoPro camera. It's a high speed camera. And basically, they film the player that's accelerating on the eyes and they recalculate everything. And I was very happy to see that paper out because the authors also provided a spreadsheet where you can recalculate exactly the placement of the markers to get the center of mass position, well, let's say the hips position, pretty accurately, depending on where you film and how you film. So this is a very interesting practical application. So now, another example, use and bolt. We played with the data of use and bolt speed during the world record to recalculate this force output. So what I want to stress here is that in Berlin, there was a very good speed measurement device, but there was no force plate. Under the feet of use and bolt. But our studies show that basically if you had force plate that day, you would have calculated some mechanical outputs that are pretty close to what's on this slide. So it means we get some information that's good level of validity, and that's very, very insightful. So right now we are doing some studies where we try to see what training inputs develop what part of the force and velocity spectrum. So if you need more force at the beginning of the sprint, what's going to work to improve that, etc, etc. So this is one of the applications towards sports training. So my last point would be limitations, of course, everything I've presented so far has clear limitations, the works of Hill, the works of more in the works of everybody. So I love this sentence that says that all models are wrong, but some of them are useful. So we need to accept the limitations because we want this information. So one of the limitations of the horizontal power, let's say approach is that, yes, we don't quantify all the sources of power outputs that a sprinter generates. And this, this is a great study that's been published last year by Gaspari Pavei. Thanks to 35 video cameras, they were able to quantify all the sources of mechanical power in a sprinter. So that's the external power in the vertical and horizontal direction. And of course the internal power and the intrastep power because between two steps, your mechanical energy changes, and this is associated with power output. So basically they could collect the entire power output where our model only focuses on horizontal force associated power and neglects clearly the, as you can see here, because we fit the row velocity changes with an exponential model. We miss some information because we are analyzing the body as something that smoothly rides to the ground, where in fact printing is a lot of push and breaks. Okay, so it's very interesting because in that study they quantify everything. And they show, for example, here that internal power is pretty high. External power is there. And so the total power output in sprinting is much higher than we analyze when we stick to that horizontal power analysis. So we have to keep in mind that when we analyze power like Newton would do from the horizontal force output, we are not exactly quantifying everything. So here, very simply, this blue bar is the horizontal power only, whereas the total power output is much higher. But one thing I need to stress here is that even if we don't quantify everything, we don't know if what we don't quantify is important or not to sports performance. You see what I mean? And I love this sentence again. Not everything that we count actually counts for performance. You see what I mean? So of course, horizontal power is only one part of the entire power output. But in my opinion, that's a very important part to performance. I made a funny video here just to express what I think. In this video, I have a lot of internal power because I do a lot of very intense movement with my segments. So the internal power is high. I also punch the ground a lot vertically. So my power associated to the vertical force is pretty high. And what's going on? My movement goes backwards. So it means I am counterproductive. So I generate a lot of power, but that power is not used to move my body forward. So what I want to summarize here is that, yes, even if you don't quantify everything, what's important is that you quantify what's associated to your body moving forward. And that's the horizontal component of the ground reaction force. So key points. As you understand, force printing is a long journey. And there's been, I don't know, maybe 50 or 100 people involved in building that knowledge step by step. There's still a long way to go because we are very far from getting to the actual real experimentally measured force output. So we use indirect estimations and we can do some things on the field, but we have to be cautious because there are some methodological non negotiables. Okay, so the source of error comes from the methodology and we need to be careful. It's not because you have an iPhone and the app that you will do some accurate measurements. But we need to keep assumptions, limitations and their consequences in mind. So I think it's okay if biomechanists and coaches do some force measurements, but it's important that they keep in mind what they are missing and their limitations. So that's my conclusion point. Thank you for listening. Brilliant. Thanks, JV. That was awesome. Yeah, I didn't expect to see Obama, Homer Simpson and tweets from Isaac Newton all in a biomechanics presentation, but I really enjoyed that. You need that otherwise students leave the room. Well, I really enjoyed it and I think I really liked the quotes as well. There's at least three quotes that I've written down there that I'll definitely be using in future. Thanks for that. Yeah, just while I give everyone a chance to catch up with the live stream and leave any questions in the live chat if you want for JB, just take a look at what's currently on screen for the schedule for the next four weeks. And you can obviously go back and look at previous weeks as well. Stay on YouTube. So if you enjoyed that, please share with whether it's colleagues, students or anyone else you think would benefit. And as well, if you subscribe and click on the bell button, then you should get notifications when more lectures are being scheduled as well. Yeah, just first kind of question for me, JB, was just what advice really you could give to anybody wanting to start applying some of these ideas. So if I work in a sport, but I've never done the kind of force velocity profiling before, what you'd recommend as a good starting point to read or watch or even just, yeah, how to go about getting started really. That's a very good question. Honestly, my opinion is that if you really start and you're not from the field, I'm not convinced that reading something will be very helpful as a first step. My advice as a first step is to connect with people like, you know, local biomechanics or people and ask them if they agree to give you an hour to teach you the basics and guide you to some reading. You see what I mean? So I know it's not easy to say that, but I think every professor, every lecturer in biomechanics should accept to find one hour or two sometimes, you know, to connect with people to discuss on the phone or anything. Because if you just send people papers, and there's a gap between what they what they can read and what's in the paper, then they're going to say, okay, that's too complicated for me. Where in fact, in fact, maybe it's not. It's just a way you just have to take them there. So that's my advice, connect with people and try and see some courses, try and see some online stuff. There's so much online good stuff that I would start there. And then of course, you can read some papers, simplifying assumptions and so on. Yeah, thanks very much for advice. I think, yeah, it's another question really isn't like I really enjoyed the kind of not tripped down memory lane so much for me but the trip back in time and looking at where we've come from in this area of force assessment and sprinting. What do you think kind of the next big breakthrough might be or, yeah, what do you think in 10 years or 20 years time could be the next step. If you'd ask me that question five years ago I would have said the fully equipped track with false place. Well that's done. Now to me the next step is definitely joining external measurements to internal measurements and so the external measurements today. Basically, you have these tracks, you have these video cameras what else can you do. So the next improvement will be inside the muscle, inside the muscle tendon units, or maybe not, not inside but at least, you know, around the muscles and this first step done by telling is huge. You know, EMG went from surface EMG to intramuscular EMG and there's going to be some more steps. That's where muscle tension and muscle force output is going in my opinion. And there's, you know, technically speaking, there's nothing absolutely not feasible. So but for of course it's not going to be next year I understand that, but it's going to be internal because external is is is pretty good now. Yeah, definitely and I think we're a little opportunity for a club there but speaking to Stephen Lindley from Delsis yesterday who's going to be doing their lecture and he was talking as well about kind of the next steps in electromyography and some of the things he's going to talk about with where that can go in the future and even maybe some of the advanced things that people aren't necessarily aware that we can maybe already do to kind of, yeah, decomposition of the EMG signals. Yes, because on the external side, look, what Archibald Hill was doing one century ago is not very far from what we are doing now. I mean, you know, processors are more powerful but the overall idea is exactly the same. So the big step is in the muscle now. Yeah, I think just probably one more of my own curiosity one last question or opportunity. I guess an opportunity for a bit of myth busting. Are there any misconceptions out there in this area that you think people don't understand or that people do incorrectly that we should maybe try and correct. So there's a misconception that that we ourselves do sometimes for laziness or lack of, you know, rigor is the use of power and mechanical power. Where it's, it's, it's been correctly discussed by people like and Ruby God's key or other people, but this is not much of a misconception. It's more a misuse of the terms, because we all agree it's the change of mechanical energy of a time but we, you know, we call power as something where it should be more carefully called. But I think one very important misconception is the difference between the magnitude of numbers. You know, that's you see a graph when you see 2000 versus 200 it's this is more important. No, it's not more important to movement. It's a higher magnitude of Newton's, but it doesn't mean it's a higher magnitude of resultant in sprinting. You see what I mean that so that's a key misconception, because when you move around, you carry your own body weight. So part of that force output is already so I don't move. Right now, my body is exerting my body weight as a force just to stand in front of the computer. Do I move. No, so it means the number of new turns doesn't mean the degree of importance to sports performance. You see what I mean, but this does not apply only to sprinting. It applies to many other sports. You miss a shot in basketball for just a couple of new turns. You see what I mean. So, yeah, that's that's a great point to for coaches and people who want to apply science but even students to focus on the degree of magnitude doesn't necessarily tell the importance. Have you seen my my I did that video to have an, you know, we call that an absurd argument. You know, I don't move and I just generated hundreds of watts for not moving. You see, so that's that's important. And for me, that links perfectly to finish off on back to your quote that you used twice from, I think it was new Einstein, but not everything that count not everything that can be counted counts and not everything that counts is whatever. Yeah, that quote. Yeah, I think that sums up pretty much exactly what you just said there is choosing the right measures for the right research question and the right purpose really. And it's it's exactly summarizing by mechanics, because there are some things that we really need to measure to know more about human movements. Sometimes we can, great. Sometimes we cannot. And on the other side, there are some things that we can measure. Yes, I can do that. And they are totally useless. So, we need to be aware of that and not make something important just because we have the device that can measure it. I know it's very frustrating, but Yeah, thank you. I think the last, yeah, last quick question for me is just you mentioned earlier on about kind of your advice for people's first steps being to reach out and contact people. If anyone does kind of watch this video tomorrow or the day after if they're not watching live and they've got any questions. Is there a best way of getting in touch with you. Yeah, so, like any academics in the world I have my university email and I respond to every email I receive so that's the first step. And on my website there's a contact form that you can just feel and it falls down to the same email box. So, yes, it's very often that I eventually connect with people to further discuss things so feel free. I don't have time to respond. I respond that I don't have time to respond. But eventually I I'm busy enough to be able to respond to to every every email so feel free. Perfect. Thank you. So, hopefully you're not about to be inundated with fan mail. But yeah, thanks very much for that. And yeah, thanks very much for taking the time to present as well. I know I've really enjoyed that and I think judging from the feedback I got in advance. A lot of people were looking forward to it and hopefully have benefited from that. So yeah, thank you very much. Excellent. Thanks.