 Good afternoon everyone. Good morning to those that are in different time zones. Thank you Stuart for the introduction. I'd like to thank the International Society of Biomechanics in Sports for the opportunity to do this invite lecture. A bit of housekeeping before I begin. I've seen my home, I've got a young child so if you hear any screaming I apologise. Stuart has asked me to keep the camera on however I believe it's probably going to get in the way of some of the slides so if I turn it off I forget to turn it back on again again. I apologise before we begin. Today's lecture is going to be on cricket, bowling and biomechanics and I've tried to put a spin on it where we look at what's important for bowling both pace bowling and spin bowling. A little bit of biomechanics and look into some of the technique and the research that's out there in particular what we've got, the research that I've been involved in. Before we begin I thought it'll be good to have a quick run for who I am for those that don't know me. My name is Paul Felton. I'm an lecturer in biomechanics at 9 and 20 university and I have been since September. I was previously a research associate at Loughborough University where I did my PhD undergrad masters and then I stayed for four years as an RA. Once I finished my PhD on cricket I'm working alongside the England Wales Cricket Board to try and develop some of the ideas within it. I'm currently there biomechanics module lead for the England Wales Cricket Programme's coaching or coaching qualifications and in particular I lecture on the specialist coaching programme which is the programme that the all elite coaches have to have to become head coaches in the professional game. Finally I'm also accredited as an ICC human movement specialist so if a player gets called for an illegal action and gets sent to the UK I'm often involved with conducting these experiments or conducting these tests even. Before I continue I should probably apologise I am recording on my laptop so if you see my double chin I apologise and if I keep looking down it's because I'm looking at my screen. So that's me. Those that want to have more information there's my Twitter handle for if I'm happy for you to try and contact me via that to answer any questions and I follow this. So the menu for today I'm trying to provide something for everybody. I know there's a few coaches that are logging in to see what I've got to say around cricket. So my aim is to try and discuss different bowling techniques as I said at the start using some biomechanical theory. I'm going to focus in particular on momentum and then discuss this with some of the recent relevant research that I've been involved in. So the courses in this menu is going to be some biomechanics. I don't want to get too heavily involved in that from a theory point of view but there needs to be some. There'll be some cricket but hopefully the two combined will make either or of an interest for everyone that's viewing and if you're a bit unlucky like me and biomechanics and cricket is what you enjoy getting out of bed for in the morning then. There'll be both and you'll be happy and hopefully you haven't forgotten what them two things are, what baths being contained. There's some research so I'm going to try and put everything I say from a theory or an opinion point of view. I'm going to try and back it up with the research. Bid some requests online for some children's entertainment so whilst I've been putting this lecture together I've happened to look after my young daughter so every so often I've had to throw in a a few videos, pictures to keep her entertained and keep her quiet when I'm trying to produce this and those that know my research will either be disappointed or happy to know that there's no simulation models in this today. It's got cricket biomechanics focus away from simulation models which is a bit more bespoke and not available to everybody to use. So to begin with I just want to recap going back to basics. I'm just going to consider what the human body is and what it's capable of doing. So we consider the human body to be a multi-segment and system and we have a large amount of segments if we count each individual bone but we often split this up and break it down into larger parts so 10 to 20 segments typically in biomechanics research to consider. Each of these segments still obeys the Newton's laws of motion and they apply to each segment individually but also to the whole system as a whole so on the center of mass of the body. To move these segments to move our skeleton and we have muscles and ligaments and these muscles are able to apply forces using our neuromuscular system and our brain to send signals to each of these muscles in turn when we ask them to move. When we get motor patterns or motor control coordination correct which we learn or start to learn from a young age we can understand or remember how to balance and also how to undertake different tasks with varying complexity. So we start by trying to sit up, roll over, walk, crawl and some unfortunate people in the craze a few or a year or so ago decided to start doing this dance move which some people are better at than others and I just want you at this moment to have a look at this video and just consider the speed of the different segments. So we're going to look at momentum in today's talk but I just want you to consider how the different segments have different velocities and how that relates to their different masses and we'll discuss this later on as to why this happens. So considering that video how and in what order should we move our segments to generate speed so sport often has an intended outcome of trying to do something as fast as possible whether that be kicking a ball or throwing an object or hitting an object we're trying to make the endpoint that impacts either the object we're trying to hit or what we're trying to release as quickly as possible. So going back to hopefully some first year maybe even school physics we know Newton's second law and Newton's second law can be rearranged and to say the following that the amount of momentum an object has before an impact is equal to the amount of momentum after the impact and if we consider this practically we can consider or we can use demonstrate this using a Newton's cradle. So in this video we've got five ball Newton's cradle each ball is of the same mass and if we apply some momentum to each of these balls we can see how after the impact the momentum stays the same and this will continue until the Newton's cradle is interfered with again. So you can see if we take one bead comes off the other side after impact and it carries on backwards and forwards then if we double the mass and increase the momentum we can see that the momentum on the other side matches the input and we can continue doing this so we can do it with three bead or three balls but every time the momentum before is equal to the momentum afterwards so give me a second to remove myself and so we can see that the momentum is conserved before and post impact and the same happens in humans as we move or transfer momentum across our joints by the muscles that are acting on both segments that so if we have a joint we have muscles that connect across a joint and briefly ignoring biotically muscles for a second but if a muscle applies a force to one segment Newton's third law suggests or provides evidence to say that it will apply an equal and opposite force to the segment connecting the other end of the muscle so we know that before and post these forces are applied the momentum has to stay the same across these joints so how do we generate momentum in the human body so we know that momentum's conserved but actually what is momentum so momentum is inertia times velocity and it's and value which defines how much motion an object has it's difficult to visualize other than with a Newton's cradle and also the second word in this equation which might be unfamiliar to some people is inertia so what's inertia or inertia is just the reluctance of a body to change its state of motion intuitively we know inertia is mass so in a linear direction we know that things that are heavier are harder to move and things that are lighter are easier to move what's less intuitive however is how inertia is used in a rotational sense so rotationally or angularly the inertia is known as the moment of inertia and objects with large moments of inertia are more difficult to rotate than objects with smaller moments of inertia so what does a moment of inertia mean what a moment of inertia is just how spread out the masses away from the axis which you're trying to rotate about so many of you will know ice skating and will have seen this example so you can see that when the ice skater tucks their arms and legs in they rotate faster because you reduce the moment of inertia by pulling the mass closer to the axis of rotation when they spread out their arms and legs they then slow down another example of this is if you try and turn around on the spot it's very easy but as soon as you try and pick up a wardrobe or something that's quite wide it becomes much more difficult it's because when in the process of picking up the wardrobe you're increasing your moment of inertia and and we know that objects with smaller inertia move faster so both linearly and angularly if your inertia is smaller you will move faster with the same momentum and this provides the basic underlying theory to how the human body should move for speed we should move the heavier segments so the legs and the torso to generate momentum and then transfer it across to the lightest segment such as your arms and your hands or maybe you off up one leg and down the other leg in the case of kicking so if we provide another demonstration or an experiment where we change the mass of the beads now and we start by generating momentum in the heavy bead we can see what happens as the momentum transfers the beads with reducing mass to the endpoint so just watch the smallest bead and what happens so if we provide an initial amount of momentum we can see that it's transferred across the beads and the velocity has to increase as the mass decreases due to momentum being conserved and momentum being defined as mass times velocity reduce the mass we have to have an increase in velocity this process is referred to as multiple different things either sequencing and kinetic chain transfer momentum or there's a summation sequence which explains how some sporting actions should set a base and then produce the movement for throwing or hitting so how does this all fit into cricket I know some of you have probably sat there thinking well about time so I've gone and met Pepperpig and George to try and define what cricket bowling is for those that are not be familiar to it it's a sport which is only played in a handful of countries so the aim of the game is for one team to bowl and field and one team to bat similar to baseball except for it's played on a field which is quite large and you bowl a ball on a wicket which is in the middle and you can hit the ball on both sides and run and there's no home runs so to speak but this example shows that the aim of the bowler so Pepper in this example runs up let's go the ball and it travels towards George who attempts to hit it I mean I'm sure it's going to talk more this afternoon about the batting element of it but Pepper is aiming to dismiss George and there's a number of ways you can do this but as a bowler you're trying to do it by deceiving the batsman so that they're either miss the ball and get bold which is demonstrated in this picture they hit the ball in the air and they're caught or they miss the ball and they it hits their body in front of the wicket and that can be given out as well but we're not to get too much into the rules of cricket today but ultimately Pepper is trying to deceive George there's also another rule that we must consider which changes technique quite significantly compared to other thrown sports in the fact that you have to keep your elbow straight so to explain this rule cricket was developed as a sport where the elbow or the arm was meant to stay straight over various years in the past it was shown by research that this wasn't the case that the elbow did bend a little bit due to the large amount of forces that go through the arm and now the limit is that you're not allowed to extend or straighten your arm more than 15 degrees between up arm horizontal and ball release as demonstrated by these two or between these two pictures this role as I've just discussed has had an impact on technique during it due to it reducing the degrees of freedom which we can use during the kinetic chain to develop speed at this point I'm going to define what I'm going to talk about is my bowling phases so lots of different people split up the bowling action into different parts for today's talk or for the rest of today's talk I'm going to discuss the pre-delivery phase which is the run-up and everything pre-front foot contacts that includes back foot contact and I'm going to talk about the delivery phase being from front foot contact through to ball release now we can generate momentum during cricket bowling in two ways we can generate linear momentum in the run-up or we can develop angular momentum during front foot contact when the front leg hits the floor and this is similar to javelin I'm going to show you a video of spongebob converting linear momentum into angular momentum to clear a high bar in a second but also during this front foot contact to ball release we're able to produce additional momentum using our muscular forces so the deep-prize polvo if we want to do a run-up spongebob develop the linear momentum in the front foot contact and convert the angular momentum now if we want to start he does a similar thing and now I can kind of get an idea of what happens in bowling when he lands and the whole thing flies over and releases the liquid which weighs much less at a fast velocity towards the crowd looking this down simply into a model of two segments up or lower body and please forgive me for this initial run-up angles of the legs and the body I know it's not realistic but due to PowerPoint in-built animation functions I couldn't get my rotations to work because they decided to let me do 90 degree rotation so we develop linear momentum in the run-up and we try and maintain it through back foot contact we swing the leg in front leg into a position out in front of us to provide a breaking force which when ups done optimally converts as much linear momentum to angular momentum as possible we then use our muscular forces to produce a kinetic chain where we develop momentum using our muscles and then this plus the angular momentum that we gain from front foot contact allows the trunk and the arm to move forward and the ball to be released and the momentum transferred to a ball with small mass of high velocity so this is similar to what we've just seen in the video with SpongeBob where they run up developing a linear momentum they plant the pole into the ground which converts the linear momentum into angular momentum and then when he lands when he lands on the fat handle and it flips over it's a similar process to him applying a force which converts the linear downward velocity into a rotational velocity to throw the fat towards the crowd we're going to talk a bit more about this now going forward in different methods but ultimately usually to display this and I'm going to refer back to this graph a few times we developed some linear momentum in a pre-delivery phase up to back foot contact try and maintain it through to front foot contact and then our linear momentum decreases as we convert it to angular momentum and due to the conservation of momentum these two should equal each other so the amount of linear momentum you convert should equal the amount of angular momentum you gain but also during this delivery phase we can generate some additional momentum from our muscles so we can build total momentum through the delivery phase and then we need to convert this momentum using a technique which sequences the body to provide as much of that momentum to the ball as possible to increase what we're trying to do the pace bowling or spin bowling so velocity is generated as the momentum transfers from the heavier segments of the torso up to the arm and the hand and the ball and you can consider this again if you think back to the slide earlier it's exactly the same as how these beads work where we've got a heavier bead which you could consider the torso and then you've got the lighter beads which in the middle which could be upper arm or forearm and then you've got the lighter beads which are the hand and the ball so in pace bowling how does this work so the ultimate game of pace bowling is just to maximize the velocity in the sagittal plane so it makes sense then to try and maximize linear momentum within our run up in the sagittal plane so we try and generate as much linear momentum as possible in the run up now you may wonder why I haven't built a line like this well um what goes on after the run up through back foot contact and front foot contact is a consequence of how much linear momentum we've got there's likely an optimum for each individual where if you run up too fast you lose um you're unable to maintain the momentum through back foot contact and you end up in a much worse place at front foot contact then if you run up slightly slower and are able to maintain it so it's worth considering that when I say that you need to run up as quickly as possible you do but you need to be able to do it in a way which you can maintain it into front foot contact at front foot contact we have this conversion from linear momentum into angular momentum and then we can generate some additional momentum using our muscles free to bore release so we end up with a total load of momentum for fast bowling which is similar to the diagram I've already shown so what's the best technique to be able to sum this momentum towards the ball so theory suggests that we want to generate as much as linear momentum in a sagittal plane as possible convert it to angular momentum at front foot contact use as much as use the muscles where possible and then transform it from the ground up so I would expect the technique to look from the ground up to transfer the momentum through the sequence so what does the research suggest so Worthington et al at Loughborough between 2006 and 2010 completed a PhD where he looked at 20 elite fast bowlers which bowl between 75 miles an hour and 90 miles an hour or in other parts of the world 120 to 145 kilometers an hour and did a regression analysis based on some key parameters which explain the variance in ball speed so their outcome was that there's four parameters which explain 74 percent of the variation in ball speed and the fastest bowlers had faster run-ups so generated more linear momentum than the slow bowlers they had straighter front legs at ball release which implies that they convert that linear momentum more efficiently into angular momentum they're more trunk flexion which suggests that this momentum and muscle forces is produced to pull the body forward and they had a delayed bowling arm so ultimately this technique is quite simple that you try to generate as much linear momentum as possible and transfer it to angular momentum and then the top half of the body holds onto the ball as long as possible to give you the most time to apply this momentum in up the chain towards the ball and increase ball speed and we can see this technique occurs in most of the modern day great fast bowlers and yes the advanced bowlers i notice i'm going to just come back to this point that actually it looks quite similar to what we had from the sponge bob square pants example so we've got this position at front for contact and it simply with a two segment model can show what we think is going to happen so i often get shouted at all about the other bowlers the rotators how do they work so um i've called them rotators and this will come clear up for the reason why on the next slide but the theory for why these do it slightly differently is there's likely to be either an individual limitation which is a constraint which means they can't develop as much linear momentum as the bowlers that bowl with the technique previously seen um they can't convert it to angular momentum so in this picture of shunt 80 bends his front knee so this is an example where he may run up too quickly and the therefore can't efficiently convert that linear momentum to angular momentum or he may not be able to um run up as fast develop as much linear momentum so his techniques changed to um maximize what he can do and there's various different things which make limit this it could be strength flexibility technique running speed um but ultimately they've got less momentum at front for contact um and this allows them to then use more of their muscular forces through the delivery stage phase because they've got more time between front for contact and ball release so if we look at that from this diagram we can see what the best technique is um if we remove them for the time being uh and propose what these rotator bowlers do well they don't they generate less linear momentum um so have less linear lentiment front for contact but because they're moving slower at front for contact they have more time between front for contact and ball release um they then convert some of this linear momentum the same as the other technique but they have longer to therefore generate momentum using their muscles so if we sum these together we can see that momentum or rotate for the rotator bowlers has a similar path um where they lose momentum in the first part of the pre-delivery phase but can gain some of it back in the delivery phase what we don't know at the moment is how close can these get together can the rotator bowlers match the ball speed of the best technique um and history would suggest that some of them can get up to those sorts of ball speeds um that the other the optimal technique can why do i think this theory for the rotator as well we look at some research that i conducted at luffbro where we use 20 elite man and 20 elite female bowlers um the females have significantly slower run-ups um and they lose more of their linear momentum through back foot contact than the males they also weigh significantly less so they have less all of this weighs up to them having less linear momentum at front for contact um so this results in the females when we looked at the data adopting a completely different technique to what we see the elite males uh or the fastest elite males adopt so they develop momentum during the front foot contact phase using the large pelvis and shoulder rotator muscles similar to how you would develop momentum in a throne so is this similar to what the males do well it's unlikely that technique is uh gender specific it's more likely it's linked to strength or uh individual constraints which prevent um the optimal the best of the optimal technique being achieved so i'm a male rotator probably do the same thing but it needs to be a lot more research on this um but what's clear is that one side doesn't fit all in terms of fast bowling coaches and in particular it doesn't seem right to coach females the same as the elite males and there might be a relationship here between using momentum and using strength to develop or generate balls and finally on fast bowling how what happens to the ones that don't look like they're trying so the boomers and the juffer archers of this world where people just say well they don't look like they're really trying well they probably are trying but they get an added bonus from a physiological advantage such as elbow extension so elbow extension is where the arm goes past straight and there's a couple of pictures that show you this example um and you're allowed to extend as much as you want past straight without accounting in this part of the elbow room uh a piece of equity for my masters showed that the effect of elbow hyperextension on ball release speeds so i would hope that an elbow hyperextension of 20 degrees can provide an increase in ball speed of in excess of 5 compared to a bowler so if you have a bowler bowler at 90 miles an hour and he can't hyperextend versus a bowler that can bowl at 90 miles an hour with 20 degrees of hyperextension the bowler bowler with 90 degrees of hyperextension is going to bowl at 94 and a half miles an hour so you can see how big an increase this can provide when you get to an elite level um and 20 degrees is probably about what juffer archers in this picture however boomer has a significantly greater elbow hyperextension so potentially great so great even greater benefit from it so the reason for this is you've got an extra joint to transfer momentum and increase velocity so we're adding in that degrees of freedom again um another question often asked is shouldn't taller heavier bowlers bowl faster well the theory is that momentum is equal to inertia times velocity so heavier objects have more inertia so if they have the same velocity they'll have more momentum but it's harder to move heavier objects they generally don't have as much velocity and we also know that longer objects have more inertia because the mass is spread further away from the center of mass so they're harder to move so ultimately taller bowlers need to be stronger to generate the same amount of momentum and we know that strength doesn't scale linearly with height or mass so there's likely to be a height and weight limit on potential momentum based on the individual strength so fast bowlers need to be strong and well conditioned um which the s and c's are like but ultimately the taller you get this doesn't necessarily you're going to bowl quicker in fact you might there'll be a tipping point where you start to get slower um i'm just going to finish off for a couple of minutes and now i'm sort of getting over time but cricket bowling also exists for spin bowling and we need to develop velocity in two different directions which are outside the saddle plane for spin bowling so if we start with offspin um what's the best technique for offspin well the theory suggests that we're not going to need as much linear momentum in the run up because we're not trying to develop pace purely towards the batsman anymore um and we're going to look to use them large hip and shoulder muscles similar to the female bowlers to generate uh velocity through the bowling action and we need to find the technique again which best allows us to transfer this momentum from the ground up into spin or into the ball so if we compare spin bowling momentum to fast bowling it's quite different so the linear momentum is no longer important um and it's quite easy to maintain this amount of linear momentum through back for contact however we have a much um and again with the conversion doesn't matter as much but we have a much greater time to generate momentum using our muscles and this is where the majority of our momentum in spin bowling is generated so we can see that it's quite different um and it's an exaggerated example of those rotator bowlers that we saw so what's the best technique for offspin some work that I was co-supervisor on by Liam Sanders investigated 23 elite finger spin bowlers and they found that 43 percent of the variation in spin rate could be attributed to the pelvis position at front foot contact so those bowlers that had a pelvis position which was more front on at front foot contact had higher spin rates now this doesn't mean that you want to be completely front on it means you want to be in front of front on what we found was they actually led to an optimal front foot contact position the some of the other parameters linked to spin rate were the shoulder position at front foot contact and the maximum x factor at this point so you want to maximize x factor and your pelvis position is a byproduct of this but you don't want to allow your shoulders to go side on so this front foot contact position is highly individual based on the amount of flexibility you've got and the x factor you can generate but you want to be able to keep this upper arm behind or in front of side the further follow-up piece of work show this position was highly individual and that flexibility of both the shoulders and the pelvis were linked to spin rate in this cohort but if we compare these results to the five leading test match wicket takers for finger spin bowlers of all time we can all see that they're in a similar position at front foot contact in their own way where the shoulders are about side on but the pelvis is rotated forward to maximize the x factor the body should then rotate sequentially so the pelvis should move forward then the torso then the shoulders and finally the forearm should pronate why does the forearm pronate well this keeps the finger in contact with the balls for longer and it's similar to other sports such as american football so if we watch this video we can see that the last finger to leave the ball is the fore thing is the index finger and this is exactly the same with exactly the same technique in off-spin bowlers and this is why off-spin bowlers can get in so much trouble with trying to keep their arms straight is that the natural method to spin a ball is to throw it with this technique finally leg spin and I'll be quick we know that the underlying momentum theory is the same but what's the best technique for leg spin well this research is quite new or in its infancy so as part of Liam Sanders' PhD we collected some data but it is ongoing still but we believe that the pelvis and shoulders are important and there's likely to be a difference of how the shoulders and the forearm work based on the need for the spin to be in the opposite primary or pilot findings have shown that based on tenally finger spin bowlers the pelvis and shoulder rotations are significantly different our significant leg spin rates but very different to off-spin so you tend to leave your pelvis and shoulders behind and a recent paper published by Spratford shows a similar result shows similar results but they and they also went further and showed have shown that the shoulder and the wrist kinematics and kinetics are also linked to spin rate more research definitely needs to be done in this area but one thing's clear that off-spin and leg spin should not be coached similar so in summary I've given you some biomechanics and hopefully some theory on momentum I've proposed how we build momentum during different cricket bowling stars and why considering them to be the same may not necessarily be appropriate I've looked at some techniques to determine what's the best movement sequence for each of these bowling actions and to transform momentum generated from the run-up and through the front foot contact is and I've discussed why some cricket bowling especially in fast bowling looks different and why individual variations need to be taken into consideration when coaching and applying biomechanics. Finally I'd like to finish by saying sorry for running over time I'd like to thank anyone that's contributed to this work that I haven't mentioned and apologies if I haven't put your name in here I'd like to thank all the people the cricket researcher out there that I haven't mentioned has played a big part in where I am today reading the research that you've done and no offense by leaving some of that out and I'd like to thank all the cricket coaches who I get to impart his knowledge on but whose knowledge also is informed a lot of what the work I do. Finally thanks for listening I'm sorry this has run over time I'll be on after to answer any questions and please don't forget that Stuart's going to teach Pepper and George about batting next thank you and please don't forget that there's these presentations next week I'm really looking forward to your hands and we too so please