 Hello, and welcome back to the Sports Biomechanics lecture series, as always supported by the International Society of Biomechanics in Sports and kindly sponsored by Vicon. Somehow we're already on number 10, which seems like a bit of a whirlwind kind of month. Yeah, kind of five weeks in, and we're on lecture 10 already. And it's quite an exciting one today. I'm joined by Alex Atack, who is a senior lecturer in biomechanics at St Mary's University, Twickenham. Alex's research, especially her PhD, which you finished in 2016, has focused on the biomechanics of rugby place kicking. And she's previously spoken on this topic at ISPS and the World Rugby Science Network. So I'm really looking forward to hearing kind of what she's got to say on this topic. So yeah, over to you, Alex, and good luck, enjoy. Hi everyone. I can change the slide on second. There we go. Hi everyone. So first of all, I just like to say thank you to Stuart for the opportunity to talk today. And also to both Vicon and ISPS supporting this lecture series, and obviously to all of you guys as well for tuning in and watching. So as Stuart said, today I'm going to talk about the biomechanics of rugby place kicking. And it's quite surprising to me, but I've been researching this area for almost 10 years now, as he said, primarily through my PhD studies. However, I do still think there are a number of areas that we need to explore within this skill. So hopefully for those of you that are interested in kind of this research area, the presentation might highlight some of these areas that are of interest to you, as well as some practical applications that those of you that work in rugby or play rugby might want to take away as well. Today the presentation is going to be split into three main sections. The first of these is just giving you some background to what place kicking is, and ultimately what determines performance. So I'm aware that some people may be kind of watching this from countries where rugby may not be the most popular sport. So I just thought it was important to give you a bit of background to what place kicking actually is. I'm going to briefly touch on some of the previous literature that's looked at rugby place kicking, and in particular those studies that have investigated the biomechanical characteristics of how you can achieve a fast ball velocity in place kicking. But also those that have looked at what happens to your technique and those biomechanical variables when an accuracy constraint is imposed on a player. And then the majority of the talk will be focused on my research, which has taken a bit of a holistic approach to understanding the biomechanics of the skill. We looked at both the kinematics, so the motion that you can see, the observed motion, and the kinetics, so the underlying causes of that motion, differences between successful kickers and those that are less successful. And they may be less successful for two reasons, so those that may lack distance, and those that may lack accuracy in their kick. So a little bit of background. In rugby, there are two ways that teams can score points. The first of these is through scoring a try where the ball is placed on the ground over the try line. The second is that the ball can be kicked between the goalposts. And the ball could be kicked when the player has the ball originally in their hands, and this is typically termed a drop kick. Or it could be kicked from a position where it's placed on a kicking tee, which is on the ground, and this is a place kick, and this is what we're going to focus on today. So place kicks can be taken for two reasons generally in rugby. The first is if the referee awards a penalty, and the second is after a try is scored, the team then gets the opportunity to take a conversion. I'm just going to play a video of Elliot Daly, who's an England player who typically takes the place kicks awarded from a much greater distance from the goalposts. So he takes the long range ones. And in this video, the ball is already placed on the floor, and he's just stepping back preparing to take the kick. And once he's kicked the ball, it travels towards the goalposts. It goes over the crossbar in between the two posts. So that's termed considered to be a successful kick, and his team is awarded three points because it was a penalty. So obviously place kicks are a good opportunity for players and teams to score points. And between 2002 and 2011 approximately 45% of all the points that were scored in international matches actually came from place kicks. But of all the kicks, place kicks that were awarded in this time, only 73% of them were actually successful. So this means that there was 27% of all the kicks that were taken were actually unsuccessful. And the teams weren't able to benefit from that opportunity to score the points. So this presents us as sports scientists and coaches and players an opportunity to actually improve the success rate and increase our chances of the team actually winning. So a place kick is only successful if the ball actually reaches the tri-line, so it reaches the goalposts that are placed on the tri-line, and if it passes both over that horizontal crossbar and between two upright goalposts. And ultimately, whether it does that is determined on its flight path whilst it's in the air. So those of you with some knowledge of mechanics know that velocity and what is a vector, and it has both a magnitude and a direction. So the ball velocity once it's left the foot will ultimately determine where it travels. And in order to attain a kind of maximum distance, so for it to be successful from a greater distance, we would theoretically say that you want to maximize that speed of the ball, so the actual magnitude of the velocity, as well as obtaining direction, which is kind of the projection angle in this instance of the ball, of around 45 degrees. That would allow us to obtain the maximum distance of our place kick. However, research by Lindthorn and Stokes actually found that as a player tried to increase their projection angle from an angle of around 20 degrees to 45 degrees, the speed of the kick that they could actually achieve reduced. So as projection angle increased speed reduced. And in fact it wasn't an angle of 45 degrees that allowed them to obtain a greater kicking distance. It was an angle of 32 degrees, because this gave the right compromise between ball speed and projection angle. However, that's only one of the factors that actually determine success whether or not it can reach the goalposts. Once it gets there, it also has to be accurate. So we need to consider this if we're considering whether or not a place kick is actually successful. And those of you that understand kind of a no projectile motion, those equations of projectile motion that determine the flight of the ball actually ignore air resistance. And the aerodynamics and aerodynamic forces that act on the ball once it's in flight are quite important for rugby, particularly because it's got a funny shaped ball. So it's not a sphere, it's not like a football where perhaps the flow of the air around it is a little bit more predictable. It's this kind of elongated ovoid shape, which means that the flow of the air around the ball is disrupted. Also, when you kick a rugby ball, it rotates at a high rate around its transverse axis. So kind of the horizontal axis through the middle of the ball, causing end over end spin. And it also rotates sometimes around that longitudinal axis, creating longitudinal spin. And these two kind of rotations of the ball affect the lift and side forces that acts on it. And without considering these, we can't truly know how that ball will travel once it's in the air. I'm just going to play another couple of videos that show the effects of these aerodynamic forces on the flight path of the ball. In this first one, the New Zealand player initially kicks the ball with a straight trajectory and it's heading towards the centre of the goalposts. But you'll see that actually it then curves round and ends up hitting the crossbar. A little bit later in the game, he adjusts this technique and I actually starts by sending the ball to the right hand side of the goalposts, so that when it curves round it can actually pass between them. This is an even more extreme example where he's able to curve the ball around to actually pass between those goalposts. So clearly it's important for us to actually consider these factors when we're understanding how this performance of a place kick, whether or not it's successful and how it travels once it's in the air. It's difficult for us as biomechanists because we don't typically measure, technique and analyse performance on a rugby pitch. We tend to do this in a much more constrained laboratory environment. And we do this for a couple of reasons. The first is that it gives us the opportunity to collect more kinematic and kinetic data. In that picture on the right hand side of our lab you can see that there's some Vicon cameras in the background and they're able to automatically track the markers that are placed on the kicker in allowing us to monitor three dimensional full body kinematics. We also have a ground, well we can also measure ground reaction forces using the force plate that's in the floor. If you look at the orange track next to where the ball is placed, you can see a square, that's where our force plate was so we can measure the ground reaction forces underneath that support foot. This isn't typically possible on a field. This is also a lab environment allows us to control for extrinsic factors that may also affect performance and it allows us to be more confident that any differences we see in the performance are due to technique changes rather than these external factors so things like pitch condition or the wind for example. It does present us with a much bigger problem of how we actually can then determine performance in this environment because we can't see where the ball ends up we don't know if it's actually reached the goalposts if it's gone between the uprights or over the crossbar. So what previous research has typically done is it's considered the two main components of performance separately. First of all, we consider they considered how ball velocity is generally maximized in place kicking. So how do we obtain a faster ball velocity. And the research is focused on the kicking leg for this component, which is unsurprising it's the kicking foot that contacts the ball and will ultimately determine its flight. And so understanding how the joints of the kicking leg allow that to be achieved is sensible. And like in other kicking and jumping skills, an increased hip flexion velocity and an increased knee extension velocity have been associated with a faster ball velocity. Some other studies have then imposed an accuracy constraint on the kicker and look to identify how that affects their technique. And they've actually found the opposite. So, in order to maintain accuracy, they found that a reduced hip flexion velocity and a reduced knee extension velocity allow for a more accurate kick. They've also found that the non kicking side arm is important in order to maintain accuracy. The motion of this segment, particularly in the frontal plane. So coming down from a position away from the body down and across allows the kicker to be more accurate. And the thought around this is that it is able to counteract the kind of opposing motion of the kicking leg, which is coming from a position away from the body on the other side, down and across. And this may either ensure that you obtain a more kind of stable trunk position and more less rotated trunk position and therefore a more accurate kick. However, both kind of all of these studies have only considered the two components separately. They haven't looked at overall performance. And so my first study of my PhD looked to try and determine a single performance measure that would include both the ball velocity and the accuracy requirements of the skill. So obviously the problem is in a lab you can't track the full flight path. You can't see where the ball actually ends up when it reaches the goalposts. But what you can do is you can track the initial flight. So the player does kick the ball and it travels and in our scenario in our lab, we were able to track it for approximately two meters before it was collected by the kicking net. So we knew how fast it was going and in which direction it was traveling at that point. We also knew how quickly it was rotating on its end over end spin and how much longitudinal spin there was of the ball as well. And using equations of projectile motion, we could then predict how that ball flight would continue. Previous studies have also measured the aerodynamic forces that act on a rugby ball in wind tunnels. So they spun in a very kind of controlled environment of rugby ball about all three of its axes and determined the drag lift and side forces that were acting on it. So using all three bits of this kind of data, we could create a mathematical model that would simulate that ball flight. And if you look at the two graphs that are now on your screen, the first one is basically visualizing this ball flight from the side view. So the horizontal axis is representing the ball traveling horizontally from the kicking T towards the goalposts and the vertical axis is how far it's traveling above the ground. And the second figure below it is looking from above. So it's a plan view. So again, you've got the horizontal ball displacement along the horizontal axis. And you've got then this kind of sideways displacement away from the center line of the goalposts along the vertical axis. The blue line that you can see starting to appear is basically the amount of ball flight we could measure. In the mathematical model we could simulate the subsequent flight. So we could project it. And the mathematical model would continue until either the ball drop below the height of the crossbar, which is represented by the horizontal dotted line on the top figure, or it would hit one of the two goalposts. So the two horizontal lines on the bottom figure representing those. So the example that you can see today, this kick would have, what the model was stopped because the ball hit the left hand goalpost in this. So that blue line had hit that horizontal line on the bottom figure. And what this allowed us to pull out was the estimated maximum distance that each kick could be taken from the goalposts and still be successful. So how far away could the kick be taken and still pass between the goalposts and above the crossbar. And it also told us the reason for failure of that individual kick. So was it limited by the fact that it would drop below the height of the crossbar at a greater distance, or because it would have not passed between the goalposts. And this allowed us to group our 33 kickers that we tested into three distinct categories. So the first category was the successful kickers. These were those kickers that we deemed to be the best, and we base that on the fact that they were able to kick successfully from a distance of more than 32 meters. And the reason we use this 32 meters cutoff was because that was the average distance kicks were taken from in those international matches between 2002 and 2011. We then considered the rest of the kickers that couldn't wouldn't be successful from 32 meters to be less successful and separated them out based on their reason for failure. So the short kickers would have were limited by the fact the board have dropped below the height of the crossbar and the inaccurate kickers because it would have passed outside of one of the two goalposts. So having these three groups we could then compare their performance characteristics and also their technique to understand how that might differ and affect performance. So looking first at the initial ball flight kinematics. These colors will be used throughout so the successful kickers will always be represented in black on both figures and in text. The inaccurate kickers are always blue and the short kickers are red. So the first interesting point to note of this is that both the successful and the inaccurate kickers achieved comparable ball velocities or ball speed so they kicked as fast as each other. And this is important because those studies that have previously determined kick success based on maximum ball velocity would consider these two groups of kickers to be equally successful. But when you look at their maximum distances, the successful kickers are actually almost 14 meters better than the inaccurate kickers. So this is quite an important thing to identify to make sure that kind of we do consider performance as a complete package rather than just as individual components. The actual reasons why the inaccurate kickers were less successful is the direction of that ball velocity vector. So the ball was traveling more towards the left hand side of the goalposts, whereas the successful kicks were angled towards the right hand side of the goalposts. And this left hand direction combined with greater longitudinal almost three times greater longitudinal bullspin of the inaccurate kicks meant that the ball curved away from that central line of the goalposts and curved towards that left hand upright. So in golf and in rugby we call that drawing so the ball drew to the left hand side. When looking at the short kicks unsurprisingly the ball velocity so the speed that they kicked out and was slower. But interestingly, the projection angle so if you think back to that Linthorn and Stokes paper I presented at the start, they found that the projection angle as it increased from 32 degrees towards 45 degrees. The velocity that the kickers could achieve was actually slower. And as the short kicks were projected at an angle of more than four degrees greater than the successful kicks. This could well be a factor as to why they are only able to achieve a slower ball velocity. However, to really understand these differences in performance we need to look at the kickers techniques. So the first thing that we did is we looked at their kinematics so we looked at the observed motion of their kicking leg joints. We looked at both the knee in the hip, and we looked at it from the top of the backswing so on the figure on the right hand side you can see the skeleton. That's the position at the top of the backswing, which was turned minus 100% all the way through to ball contact at 0%. And we saw that for the initial 40% of the downswing, the knee was flexing, and then it extended all the way up to ball contact. Looking at the hip, flexion was observed throughout the complete downswing. And this motion is very similar to that seen in other kicking skills so in soccer, in Australian rules football, and in other sports as well. What's interesting kind of in these figures to note is the timing of the peak angular velocities, so for the hip, the peak flexion of velocity occurred earlier than the peak knee extension velocity. And this is generally considered to be a representation of proximal to distal sequencing, where more proximal joints reach faster velocities earlier in the movement before the distal segments and joints then take over. And this is seen again in many sports. The other point to note and is the same as we've seen in soccer and step kicking and Neil spoke about last week is that the initial flexion of the knee. So the knee initially flexes and the reason it does that is because it allows it to or the thigh reduces the moment of inertia in the kind of knee joint. So subsequent rotation so subsequent knee extension can then occur a lot quicker if you reduce your moment of inertia but you maintain your angular momentum. The velocity will increase, and it is termed a whip like motion so by reducing that by flexing to begin with it can then extend a lot quicker through up to ball contact. When we compared between the groups, there was no differences seen so we didn't see any significant differences in the kinematics of the hip and the knee between the three groups. But what you can see if you look at the figures is that the short kickers were slower so on average, the short kickers extended their knee at a slower rate, particularly towards ball contact. In the middle phase of the downswing, there was slower hip flexion observed for these slower kickers. And that makes sense. They achieved a slower kicking foot velocity. And as given both faster hip and knee motion is considered to be better in terms of obtaining a fast foot and ball velocity. It makes sense the slower kickers or shorter kickers were slower. So if we understand how these were obtained, we then need to look at the kinetics. So understanding those underlying causes of the motion. And we looked at two main variables. The first we looked at was the moment about the joints. So, again, those that have done some mechanics before know that a moment is a turning force. And when we're looking at the joints, we look at whether there's a predominant kind of extensor moment. So whether the knee extensors are acting around that joint to cause knee extension. Or whether, for example, the flexors are acting about the joint to cause knee flexion. And then the second variable is power. Again, from mechanics, we know that power is the product of force and velocity. Given we're looking at angular data here, that means that it's the product of the moment. So the turning force and the angular velocity. So it's basically the product of the two graphs on the left hand side. And if we consider this for the knee, we can see that for the initial kind of 85%, almost the complete downswing of the knee, we get an extensor moment. So the knee extensors, the dominant kind of muscles acting around that joint. And because that's initially accompanied by knee flexion, we see a negative power phase, which is K1 on the third graph. That's basically acting to halt the flexion and then initiate the subsequent extension that we see from around kind of 60%. And then we get a positive power phase because the knee extensors are still acting. They're still the dominant kind of moment around that joint. And it's accompanied by knee extension. So that's the rapid extension down towards ball contact. And that's phase K2 on the figure. And then finally we see a flexor moment. So just before ball contact, the knee flexors become dominant. And although we're still seeing and we're still seeing the extension at this time. So they're likely actually acting to try and halt the knee extension that's occurring, potentially preventing hyper extension or allowing a more controllable contact. And that's phase K3 on that power figure. We did exactly the same analysis at the hip, but it's a little bit simpler. Because there was a hip flexor moment dominant pretty much throughout the whole of the downswing. So right up until just before ball contact. And as this was accompanied by observed hip flexion, it meant that there was basically positive power throughout. Just prior to ball contact, we saw some participants actually had a dominant hip extensor moment and potentially like with the knee joint. That's a bit of a kind of protective mechanism, ensuring that the kickers didn't go into, you know, excessive flexion and had a more controlled football contact. The final kinetic variable that we looked at then was the total joint work. And that was obtained through the integration of those joint power time histories. So from our equations, we know that power is the product of force and velocity. If we multiply that by time, which is effectively what integration is. We get that being forced times displacement because velocity is displacement divided by time and force times displacement is work. So that's kind of how we get to joint work from power. We take the knee as the example because it's the slightly more complicated one. You have three phases of total joint work that you can calculate. You can calculate that first negative knee extensor phase of joint work. You can calculate then the positive knee extensor at K2 and then the negative knee flexor at K3. Because of the importance of knee extension in obtaining a fast kicking foot and therefore ball velocity, we're going to focus on K2 for now. So during phase K2, we can see that the long kickers that are successful kickers that are represented by the black bar do substantially more positive knee extensor joint work than both the short. So the red and the inaccurate kickers that are the blue. So they do a lot more knee extensor joint work. But then if we look at the hip, we see something slightly different. Here the short kickers are still doing less positive hip flexor joint work than the successful kickers. But now the inaccurate kickers are actually doing more than the successful kickers. So they're managing to do more positive hip flexor joint work, but they do less knee extensor joint work. And given they're both able to change the same ball velocities, it appears that they're using two different strategies to do this. And the reason for these two different strategies might be explained by analysis of the upper body. So if we look at the upper body and particularly the pelvis and the torso, which are depicted in these skeletons on the right hand side, you can see that at the top of the backswing, the kickers tend to orientate their pelvis and their torso towards the side. So you're looking front on at these skeletons, and you can only see one side of the rib cage of the torso. And you can start to see some of the pelvis, but it's still quite side on. But then when you move to the ball contact, so the skeleton on the right hand side, the both have rotated to be more front on towards ball contact. And this is the case for all three groups of kickers. But when you look at the differences between the groups, a few more differences become apparent. So the skeletons that you can see at the moment are the successful kickers. And then you've got the inaccurate kickers in the middle and the short kickers at the bottom. First of all, I would hope the most obvious difference you can see is that the short kickers are far more front on than the successful kickers. You can see a lot more of their rib cage and of their pelvis, both at the top of the backswing and at ball contact. You can see the chest bone, you can see some of the right right hand side of the rib cage. They are adopting a much more front on position, albeit a little bit tilted as well, but at their front on. A little bit harder to see is the difference between the inaccurate kickers and the successful kickers. They're very more similar. But if you focus in on the torso, the inaccurate kickers do have a more front on torso than the successful kickers at the top of the backswing. In that middle image, the left hand one, so yeah, second down on the left hand side, you can see some more of the chest bone. You can start to see some of the right hand side of the rib cage, which you definitely can't see for the successful kickers at the top. This is likely to have created a stretch across the torso and across the hip. It's previously been identified in soccer and step kicking and thought to be a really positive aspect of soccer and step kicking when the main focus is to obtain a fast kicking foot velocity. And they term it the tension arc. The reason this is a positive thing for fast foot and ball velocities is that by stretching these muscles, the kickers are able to utilize the stretch shortening cycle and therefore contract their muscles through after the stretch when it's released with much more force. And therefore create greater joint moments about their joints and therefore angular velocities. And if these inaccurate kickers are creating that stretch across the hip flexors, that may well explain why they do substantially more hip flexor joint work than the successful kickers who don't create that stretch. The difficulty though is that they, it appears to have a negative effect on accuracy. And this isn't something that's been looked at in the other sports where actually the main focus for them is a fast ball velocity. They're not too concerned about the accuracy of the kick, but in rugby it's far more important. And so actually creating this tension arc may not be a desirable quality of these kickers. And there's a couple of reasons we suggest why it may affect the accuracy. It could be that actually the release of the stretch creates greater rotation of the trunk segment which can potentially affect accuracy. Or it could be that if they're having to use their hip joint to flex and do far more work in the kind of flexion extension axis, they're not then able to potentially abduct or rotate the leg during the downswing and obtain a desirable football contact. So it might actually change the path of the kicking foot. And that's the final study I'm just going to mention today. So in the final study that's been published, we looked at the kicking foot swing plane of accuracy and inaccurate kickers. We looked at it in two different ways. So the first we looked at was the inclination of the kicking leg. So that's kind of how steep the path of the kicking foot was down towards ball contact. And we also looked at it from kind of a bird's eye plan view in terms of its direction. So was it quite a straight path that it was approaching the ball at or was it coming at a greater angle towards ball contact. And what we found was that the inaccurate kickers typically had a steeper inclination to ball contact so they came down at a steeper angle. And that path was directed less to the right hand side of the goalposts than the accurate kickers. And if you think back to the ball flight characteristics that I mentioned at the start, we found that the inaccurate kickers were typically directing their ball to the left hand side of the goalposts. So this might all be starting from actually that kicking foot swing plane initially. And potentially that steeper angle down towards the ball might also affect the longitudinal spin that's placed on the ball. But we haven't yet been able to do a detailed high speed analysis of the football contact. And so to truly understand the effects of these differences, we need to do that. So just to summarize a bit about what I talked about today, I think one of the key take home points from my perspective is the importance of biomechanists to consider the complete performance of a skill. Rather than separate out the different components that can quite often actually being conflict of each other, for example, with the literature looking at maximizing ball velocity and maintaining accuracy they showed that we need to do two totally different things. So we need to actually consider the complete performance. And the mechanics are generally quite similar to other kicking and hitting skills. But the added accuracy constraint within place kicking means that it really does need to be considered separately because some differences are observed. When looking at the short kickers, we found that they tended to approach with a far more front on torso and pelvis orientation. And this likely inhibited the retraction of the kicking leg, and then subsequently the amount of work that the hip flexors and the extensors could do. And this is probably the reason why their foot velocity and therefore ball velocity was limited. The inaccurate kickers, whilst they adopted a similar pelvis position at the top of the backswing, they had a more front on torso, and this created a stretch across their torso, which probably meant that they could do more work with their hip flexors, and therefore achieve comparable kicking foot and ball velocities to the accurate kickers. But this was likely it's a detriment to their accuracy. So what's next. I think there's some potential technical and strength training interventions that could be investigated for both short and inaccurate kickers. So considering the approach of the short kickers towards the ball if they could came from a wider angle, they might be less likely to adopt that front on orientation of their body. If they approached faster they might be able to transfer some of that linear momentum into angular momentum of the kicking leg. The inaccurate kickers if they were just encouraged to adopt a less front on torso that might prevent them from stretching the muscles across their body and therefore using that hip dominant technique, or even just trying to make them think about using their knee extension more could be a factor as well. So in terms of strength training, they both have reduced knee extensor involvement, so potentially it could be a factor to look at strengthening their knee extensors, and the short kickers also their hip flexors. But none of these interventions have been kind of scientifically empirically investigated so take it with a pinch of salt for now. There's still so many different areas that need to be looked at. I've touched on a bit about how the approach to the ball may actually kind of impact on the performance that we're observing during the actual kicking phase so changing that and understanding how that influences it is important, and it's a paper I'm currently writing up so I hope to have published soon. I haven't mentioned or I haven't mentioned the support leg at all today. It hasn't been the focus of investigations in rugby. Despite the fact it's the pivot about which the whole motion is kind of used is rotated around it could be important in terms of balance, or in terms of transferring the momentum to the kicking leg. The coordination of all the joints involved in the motion it's a very fluid skill the place kick, understanding how they coordinate and potential variability in this coordination is important, as is the effect of fatigue. Recent studies have found that actually in phases of the game where fatigue is accumulated place kick successes, a lot less. So how does fatigue impact on the technique, and therefore the success of the kicks is important to understand in order to potentially affect the training of these kickers. And then understanding how this skill is acquired how maturation may affect the development of the place kicking skill is a final area of potential investigation. I want to finish by acknowledging some people that were key in this research so my two supervisors Neil and Grant, who are obviously instrumental in all stages, co author on the swing plane paper sandy. And then John Calard who was the England under 20s kicking coach at the time of my PhD and was very supportive of everything that we did and provided participants throughout. And finally, the biomechanics lab technician Jack from St Mary's who was involved in every single testing session and certainly we wouldn't have been able to have done without. There's three other kind of groups of researchers who are also working within this field that I haven't had a chance to really talk about today. Apologies if I pronounce this wrong but he bear Lewis and colleagues have got a paper published in sports biomechanics ahead of print, looking at place kicking to have a look at that. There's also a group of researchers from the University of Stellenbosch, who have actually started to look at the coordination movement variability within the kicking skill. And finally, they had a abstract accepted for I SPS this summer. So, keep a lookout for that. And then finally my colleague from St Mary's Steph, who's a sports rehabilitator completed a masters research project into the muscular injury in rugby kicking. Initial results of that were published or presented at I SPS in 2018, but hopefully the full study will be available shortly. And I'll pass you back to Stuart. Brilliant. Thanks Alex. Yeah, I think I know I say this to everyone but I really, really enjoyed that thought that was brilliant. I think a lot of my own research focuses on what I call ball striking sports but normally upper body so things like cricket or badminton. And yeah, we compare to similar sports such as baseball or tennis or squash etc. I think I've really considered enough. How many similarities there are to some of the things you presented in rugby, some of the things like pelvis thorax separation. The speed accuracy trade off and the tracking and extrapolation of parabolas, all of that kind of things is things we're wrestling with and looking at exactly the same stuff but for an upper body striking sports I thought that was really useful for me anyway. Don't know about everyone else but I really enjoyed that. Yeah, I think first question I was just going to ask I know, I know you've been asked this before and you've probably got a canned answer ready for whenever anyone brings it up but just the kind of validity or crossover between lab based research and field based research. It's something that we all get asked about and we all have to consider whenever we're designing or presenting experimental research. So I was wondering if you could touch a bit more on how you made sure what you did in the lab actually represented what they do on the field. Yes, of course, so as you say it's something that we all have to consider and try and explain and I guess defend in some ways. But from our perspective we tried to keep as many of the factors that are important to the kicker the same as possible so they were able to wear their own molded boots so not studs but molds. They use their own kicking T they all could use their normal approach though the pacing was exactly the same. We also had a target in the kicking net that they were told to aim for as if it was the center of the goalpost so we're very clear with our instructions. We gave them a long period of familiarization where they could kind of practice and get used to the slightly different environment. I think having certainly for the England players, which were around half of our cohort, they benefited from having their coach there because he was able to talk to them as if he would do in a normal testing session in a normal practice. And then in the kind of, I guess, looking back, we compared all of the bull flight data to that that's been obtained previously on the pitches. And there are no differences in bull velocities that were achieved in estimated maximum distances that were achieved in spin rates in projection angles. And we also asked the kickers so we got them to qualitatively rate their kicks which again they're generally quite used to doing in practice they have to kind of reflect on each kick and consider whether it was a good kick a bad kick and rate it out of 10. And so they did that within the lab setting as well. And all the all the kicks that we used were only a score of eight or above. So they were considered to be a good kick for that kicker as well. Okay, brilliant. I think, yeah, great answer but I think that's a really good guide or example for anyone watching or listening kind of when designing a study just about kind of the steps to go through to try and ensure that ecological validity and yeah I think going to even more detail than I was expecting there so it's a really good example of kind of the steps that you can take. The other thing, more from a selfish perspective that I'm interested in, and purely because we found exactly the same thing in cricket batting is this idea of sort of your theoretical optimum of 45 degrees. But then in reality, people want to say hit, kick their kind of their optimum or their best shot. I think it's at around 32 degrees or 34 somewhere around there. So just wondering if you had any ideas or any more detail on why you think that's the case. It's not something that we looked at, to be honest, but I think comparing the differences between the kicker groups that did actually have the different trajectories so the fact that the short kickers typically did try to kick it up a bit more so that higher projection angle is probably reflective of just the general motion of the kicking foot towards the ball, the angle of that football contact and potentially the amount of extension and flex so flexion of the hip and extension of the knee. In order to for the successful kickers to have achieved that the kicking foot path was likely not anything like a straight it was coming at an angle it was coming curved. And in order to then be able to get a kind of higher projection angle. I think that would be a far harder from a more curved path. And actually it's far easier to do that in that technique that the short kickers adopted that was far more front on far more straight. And so that would be my suggestion but it's not something that we directly investigated. Okay, yeah, good I like again good ideas I think it's something we don't really have an answer for even cricket but it's just looking like one of the things we'd considered was kind of the risk of a negative outcome I in cricket being caught out. Whereas, when you've got the same pattern in rugby where there isn't, in effect, you haven't got that risk if it goes too high, people can reposition and catch it but it's still getting the same result. I thought that was interesting, but it's definitely kind of something I'll probably go away and have a bit more of a read around but we were considering like simulate simulation models or more theoretical approaches to try and change one thing at a time and say, what is it. Yeah, I think some simulation modeling to test a lot of these kind of hypotheses and potential underlying mechanisms is important, and it's probably one of the next steps for sure. Yeah, brilliant. And just, yeah, while it's on the screen, just wanted to kind of point out to everyone but the kind of next three weeks of talks on this saying now the first 10 that were originally scheduled to done, so moving into what was going to be a practical phase two, but I'm kind of dropping it down to one talk a week and then we're going to try and keep this going for as long as we can really. But trying to alternate between a more theoretical approach, something applied, and then a bit of a kind of technical or practical demonstration, especially for people and students that aren't getting that lab based experience at the moment, trying to alternate those kind of three things. So at the moment we've got Bill next week with a description of kind of inverse dynamics and some principles and maybe difficulties or problems with the current approach and some solutions to that. Then got a really interesting talk the week after with Bruce and Jacqueline on tennis biomechanics and then Vicon are going to do a bit of a practical demonstration for us the week after. So that's kind of something to look forward to. And the last thing for me as always, but just a really big thank you to Alex as I said that was brilliant and I personally got a lot out of it so that's kind of the main thing for me is I enjoyed it so hopefully everyone enjoyed it. Thanks a lot Alex. Thank you.