Anatomie des muscles et tendons en relation à la performance, le risque de blessure et les adaptations à l’entrainement
BIOGRAPHIE :
Le professeur Folland a obtenu une licence en Sciences du Sport à l’Université de Loughborough ainsi qu’un doctorat en Physiologie de l’exercice à l’Université de Birmingham. Après avoir occupé des postes d’enseignement et de recherche en physiologie et en biomécanique dans trois universités (Universités de Brighton, Massey et Salford), il est retourné à Loughborough en tant que membre du corps professoral en 2004, et a été nommé professeur en 2017.
Les activités d’enseignement et de recherche de Jonathan sont axées sur la performance et l’entraînement, en mettant particulièrement l’accent sur la fonction neuromusculaire, principalement la force et la puissance, ainsi que les mécanismes physiologiques et biomécaniques sous-jacentes. Ce sujet à des applications dans la performance sportive, les blessures liées au sport et la santé humaine.
Il est membre de l’American College of Sports Medicine et de la Royal Society of Biology, et est directeur adjoint du Centre de recherche Versus Arthritis pour la recherche sur le sport, l’exercice et l’ostéoarthrite. Jonathan s’intéresse à divers sports, mais particulièrement à l’athlétisme/course et au football d’un point de vue scientifique. Il a également un intérêt de longue date pour le canoë et le kayak, ayant compétitionné et entraîné au niveau international.
jul conf [Music] for par for State love bro welcome Jonathan it’s a great pleasure to have you on board today uh and I’m really keen and I’m looking forward to to listening to to your talks biology Bri for per again thank you for being here jonan and anio the floor is yours thank you g thank you everyone for for being here thanks Jonathan for for coming and for proposing you also to share with us some some of your your work I’m just gonna sorry open the my presentation um there we go so yes as G said the idea um I I just started speaking English so I was just saying I I will continue in English uh the idea here was just to do a little contextualization of the presentation and also take the opportunity to show some of the wide variety of work that is being done in our laboratory so again I won’t go too deep into details it’s just giving very quick some of the questions that are being targeted and uh related to to the career of Jonathan and also your topic it’s a um talking about muscle strength is not only important from a mechanistic point point of you in different areas of research such as biomechanics or physiology but also it remains at the heart of what many of us think when we try to optimize uh performance so very basic questions such as how force is produced how the active tissues and passive tissues can interact each other those remain at different levels of our way to think about how we can translate Research into into appli research and in this context that’s where we thought it it was maybe a good opportunity to show you some of the work obviously is not exhaustive but some of the work that is is being done here uh just some details about a a training intervention that it took place a few years ago now and it was eight weeks of training Nordic hamstring or isokinetic training and some of the main variables that we get to measure here uh were like the the the behavior of the muscle fle along with as you can see here a video I don’t know if if reproduced but you can see here that we are using making use of a Ultras sonography sorry and and more specifically putting together two probes we can overcome some of the challenges methodological challenges that we we face when we try to track faes in low muscles notably and you can see some previous results that were presented in the American college um Congress and uh in which we can see the wide variability but as I said I won’t go too much into it into the results another uh interesting technique that may allows us to go a bit deeper into the mechanical properties of the different issues is elastography here in the same project we used it to track during passive Cycles at the same time the passive torque and also the the elastic properties of the three main muscles of the hamstrings so semitendinous semitendinosus um semimembranosus and bisporus and uh it could it allows us to go a bit more deep into the passive mechanical properties and other interested variables such as joh modulus or historis or at a local level at a mle level um a bit more on the same technique to give you another example of a work that would that it took place in the lab in which we explored the effects of a warming map using either foam roll or cycling active and uh we observed some changes in the elastic properties of the hamstrings as well and uh also a b like a as you can see a wide variety of of topics and and research questions here a work from our colleague es colleague enville who got to see during his PhD the effects of different types of surface and how muscle and tendon was were interact interacting each other and responding when uh when working in different surfaces and little by little we try also to to put together other integrative approaches in which for example you have this work of Adel moras during her PhD who got to see some of the effects of heat exposure and how the the active and passive elements of the muscle tending units May respond during uh some analytic Tas tasks or running as you can see here some of the recent results published in in in in the medicine and and science journal and uh to wrap up like in general as you can see we we can like from this Central topic of a muscle tendon unit mechanical properties we we can have many questions many problem scientific problems that we we we try to to tackle from different perspectives uh but I would say like in parallel technology it’s always at the heart of on one hand the the limitations and also the the difficulties that we have to measure in Vivo these properties uh but at the same time the advances that little by little we try to uh to to keep up with them and uh that allow allows us to go a bit deeper uh into the these characteristics as you can see for example in the pictures we can take the the example of elastography that it’s making progress not only to overcome one of the main limitations which is the 2D Dimension the two Dimension approach that we use to go a bit further in the three-dimension approach and try to better understand how muscle behaves also to be able with some analysis techniques to be able to better Target different isssues tendons AER Neurosis muscles and trying to better understand how they they behave how they respond to different situations the same happens with MRI uh in which up to date it’s really time consuming the fact that we have to segment everything and we have to manually do stuff Ai and a lot of engineering work is going on to make this step quicker and and valid and on the part of mle architecture uh the same things applied uh in which we are trying to to work to develop new algorithms that help to automatize some of the tasks when it come to analyzing the master architecture so I talked mainly about experimental research and this main topic that concerns today Jonathan but uh we are at inp so we are we usually often we have a bigger scope we try to taking into account obviously many other uh particularities that we can find in in Sport and I found this picture pretty representative of what I try to say here is that we try to make X not this way and try to align everything uh to make sure that the transfer and also the good use of technology is being made thank you so Jonathan it’s the floor is yours there you okay okay good afternoon everyone um and thank you to The Institute especially Gail and Antonio for the invitation to come and visit um and thank you for the introduction and a little bit of good context Antonio that’s really helpful for my talk um I first heard about inep uh nearly 35 years ago as a teenager uh I have a personal interest in canoe and kayak racing which I think was mentioned in the introduction and uh I read about some top athletes coming here to study and to train uh so uh it sounded like a really cool place so I’m I’m delighted to finally be able to visit and come and uh and learn a little bit more about what’s going on here at the Institute um I should just uh first briefly introduce my home institution which is lrey University uh lbro is a town here uh placed pretty centrally in the UK um the university is a middle-sized uh UK University uh but we generally rank pretty highly one of the top 10 universities in the UK um we have around 20,000 students on our campus uh which stretches from here back for about 3 km it’s a very Green campus with lots of uh Sports pitches and sports facilities many indoor facilities which you can’t really see on this picture uh and the university has a very strong reputation in actual performance practical doing of sport um but also in the study the teaching and research of sport and we’ve been very fortunate uh to win this Accolade uh in recent years number one in the world for the study of sport related subjects from the Qs World university rankings um so that was my corporate advert done I’m now going to concentrate on uh science so my my topic today is muscle intended anatomy in relation to Performance injury risk and training uh I have three main themes first the importance of mus muscle anatomy particularly muscle size for athletic performance second hamstrings anatomy and implications for sports injury and then finally resistance training effects on muscle and tenderness structures so get us thinking about the importance of muscle anatomy and size for the function and performance of muscles just going to start off with this not very serious question this is in English we would say tongue and cheek uh question who’s got the strongest most powerful muscles in this picture well it’s clearly not me at 75 kilos it’s not even this guy Rob Miller who’s a former PhD student in the lab uh at a little over 100 kilos but it’s obviously this guy his name is is is Eddie Hall and I’ll talk a little bit more about him later in the presentation but of course everybody picks the guy with the big muscles even if you put this picture or this question in front of anybody on the street they will pick the guy with the big muscles because we have this intuitive idea the larger muscles are stronger and more powerful and interestingly there’s a very solid physiological Foundation to that idea um which is captured in this graph here which is the first careful scientific study that I’m aware of which was from Japan in 1968 where they did careful measurements of muscle size cross-sectional area of the elbow flexors actually and looked at its relationship with strength so this is elbow flexor or arm strength and each of these markers is one individual quite a large population in this study and you can see that there’s a broad relationship between muscle size and muscle strength where individuals who are stronger tend to sorry who have larger muscles tend to be stronger and there’s a very clear physiological explanation for that relationship which is captured in this uh simplified cartoon here but comes down to the number of cross Bridges or sarir arranged in parallel across the muscle so we have a simplified muscle here just reduced down to a single sarum here the Myas in uh and AC in here in the cross Bridges uh pulling the ends of the muscle the tendon and white together and it produces a certain amount of force and if we have twice as much or four times as much contract on material sarcomas or cross Bridges aligned in parallel across the muscle essentially larger muscles then we see greater force production so this these ideas have been well understood for decades it’s kind of interesting and surprising therefore that we don’t really know much about the anatomy or the size of the muscles of athletes particularly hyper performing athletes or how important these kind of factors to do in muscle size are in fact for athletic performance so we’ve been doing a series of studies in that space and I’m going to talk a little bit about them now starting with this study which is to do with muscle anatomy and sprint cycling power which was done in collaboration with the English Institute of Sport the aim here was to to determine the relationship between muscle volume and cycling Peak power output in Elite cyclists so we recruited 35 Elite male cyclists competing in different disciplines from track sprinters through BMX track Pursuit Road and mountain biking so a range from Sprint to endurance disciplines and just as evidence for their performance standard collectively they had eight Olympic Games appearances two medals 37 senior World Championships appearances and 10 medals and we had each app attend the lab on two occasions to perform a series of iso velocity Sprints at a range of velocities from 60 up to 180 RPM on this type of iso velocity ergometer and this allowed us to draw the power Cadence relationship for each athlete and actually our Criterion measure of peak power output was the Apex or the Maxima of this power Cadence relationship drawn from these two test sessions the other main measurement in this study was muscle volume with an MRI scan and we had a scan of each thigh in order to determine quadriceps and hamstrings muscle volume and here’s an example MRI image slice through the mid thigh here an axial image through the mid thigh and in the center of the image you can see the bone the femur around the out side we can see the adipose tissue actually a very thin layer in this athletic thigh uh towards the front the anterior you can see the four quadriceps to the posterior the four parts of the hamstrings group and for each muscle you can see here we’ve very carefully segmented or drawn around each muscle in order to measure the anatomical cross-sectional area of that muscle and if we collect images or slices all the way down the thigh or the limb segment and we do this segmentation we can accurately measure the volume of each of these muscles and here’s what we found these are the this is the relationship between Peak power output during cycling and quadriceps muscle volume in cubic cm and you can see each of these marks is a different individual and we can see there’s a pretty good strong relationship here the correlation coefficient is 81 and if we if I show the same data here for the hamstrings is Peak power output again now ploted against hamstrings muscle volume we see a similar relationship not quite as strong not quite so tight this time and a slightly weaker but still fairly strong correlation coefficient of 72 so the conclusion from this study was that the volume of the thigh muscle and especially the quadriceps was the primary determinant of cycling Peak power output and likely a critical factor for sprint cycling performance but there’s a couple of queries to do with this study first of all I’m very conscious that the the outcome variable here was power output on an ergometer which we might expect to be pretty important for sprint cycling performance but is not actual performance the second thing is because we recruited Elite athletes from a range of disciplines the endurance athletes were all clustered down here because we know that endurance athletes don’t have particularly big muscles and aren’t particularly powerful so that wasn’t particularly surprising what would be more informative would be to look purely at Sprint athletes but across a range of performance standards so through sub Elite and ride up to Elite and there are two things that we took on board for this next study uh which where we also change Sports so this is now muscle anatomy and Sprint running performance uh which was done in collaboration with British Athletics of course Elite sprinting is one of the most iconic uh and impressive Feats of human performance moreover the ability to run fast is is largely sought after in many sports not just track and field Athletics but but many others soccer rugby hockey you could go on and on in terms of muscle anatomy well it’s common observation that these athletes are relatively muscular but the specific muscles important for fast running has not been very well defined um previous researchers tended to just look at a a relatively limited small number of muscles and also often not included actual Elite level athletes if we look at the Animal Kingdom these are some of the fastest land mammals when you look at the distribution of their muscle mass what you notice is it’s it’s absolutely not uh distal but the muscle distribution is very much proximal here so our hypothesis was that for very fast running in humans the muscular development would be specific to the proximal part of the leg around essentially around the hip joint point so we did a couple of studies one in males and one in females two completely separate studies but with very similar methods and I’m going to talk through the results together um in the male study we compared Elite sprinters with sub Elite sprinters with untrained controls and here are the 100 meter personal best times for the Sprint groups so for the elite sprinters their personal best time was just ins 10 seconds only five of them which I appreciate is a relatively small group but there really aren’t that many people who can run this fast so by definition it has to be quite a small group if it’s a very elite group um a sub Elite sprinters also had really pretty good times on average 10.6 N9 seconds and we had a pretty good group of those 26 and then we had some untrained unathletic controls in the males study in the female study we only had two groups the elite sprinters and sub Elite sprinters the reason for that is simply because we’d already done this study and we had a pretty good idea that there would be some interesting differences between the two Sprint groups and you can see their performance times were also really good these are really good standard athletes um we had all of the athletes do an MRI scan this time from thoracic verer number 12 here all of the way down the lower body again axial images cross-sectional images down the lower body all the way to uh the anchor in order to take comprehensive measurements of muscle volume of a wide range of muscles actually 23 individual muscles or compartments um that we were also able to combine together to form five functional muscle groups the flexors and extensors of the hip and knee as as well as the planter Flexes in terms of the the data well we can express that both in absolute and relative to body mass terms so cm cubed or cenm cubed per kilo and we can have an interesting can have an interesting discussion about which of these is actually most important um but the findings were actually pretty similar and if you’re interested I would encourage you to have a have a look through the papers which go through both of them in very fine detail but for Simplicity and because it’s a little bit more intuitive and because it doesn’t affect the major findings I’m going to stick with the absolute units uh during this presentation so here’s what we found in terms of the muscle groups this is for males first of all we have our five different functional muscle groups here down the side and this is muscle volume in cubic Center CM uh the most pronounced differences within the male study were actually for the hip extensors here so the white bar is the untrained controls and their hip extensor volume was a little over 2,000 cubic cm whereas for the sub Elite sprinters this gray bar they were about a third bigger and then the elite Sprints the black bar were a third bigger again the percentage here is actually the difference between the elite and the sub Elite sprinters for the hip flexes knee flexes and knee extensors there was a very similar pattern with again significant differences between all three groups but not quite such pronounced large differences as there was for the hip extensus whereas when we go to the planter flexes the more distal muscle group there was actually no difference between the two Sprint groups for the planter flexes moving on to the female study again we have the five muscle groups down here this is muscle volume just two groups now sub Elite sprinters and Elite sprinters in this case the biggest difference was here for the hip flexors which was 28% larger in the elite versus Sub Elite sprinters they’re also differences for the hip extensors and the knee extensors but again no differ for the planter flexes so the findings did broadly support our hypothesis there are bigger differences in these more proximal muscle groups particularly hip extensors in males hip flexors in females and not in the more distal muscle groups moving on to the individual muscles so this is an example MRI image slice actually through the hips and the pelvis basically at this level an axial image and if you look carefully what you can see here this is the ball or the head of the femur on both sides the ball within the socket of the hip joint and you can see we’ve picked out some of the muscles here around the hip uh and if I show also this is a typical subelite Sprinter you can see that the muscles mostly look somewhat bigger and if we go to an elite Sprinter they’re substantially bigger again it’s very Visual and pretty clear the differences just talk a little bit about this muscle this is the gluteus maximus which is the large Superior muscle in the backside the average volume of the gluteus maximus in an untrained control participant was around 900 cubic cm the average volume of the gluteus maximus an elite Sprinter was is nearly twice as big nearly 1,800 cubic cm which is a pretty dramatic difference and just to have a little bit of fun with that the difference between the untrained control and the elite Sprinter is essentially equivalent to two 16 o rump staks within the backside one buttock of an athlete and two more on the other side of course in France I should be using the metric unit so you could say two Stakes of about 450 G um to uh to show some more specific values to do with the individual muscle differences on this plot I’m going to show the differences between Elite and sub Elite 100 meter sprinters for the 23 muscles and compartments that we looked at so this is first of all for the males and this is the percentage difference between Elite and sub Elite so zero would mean the the muscles are the same volume in those two groups and anything this way is greater in Elite and anything that way is would be greater in subite and we’ve ranked the muscles according to the size of the difference biggest difference is here all differen is in favor of subite down here and this is exactly the same for the females ranked according to the size of the difference zero would be the same this would be greater in Elite this is greater in sub Elite there’s awful lot of information here so I’m just going to highlight a couple of things the first one is the the difference or the pattern in the muscularity is is a very pronounced pattern it’s not that sprinters are uniformly got bigger muscles everywhere it isn’t like that there’s a really pronounced pattern here where some muscles are way bigger and other muscles are more or less the same or even a bit smaller which is is really interesting it’s anatomically specific uh pattern that they have to their muscularity in terms of the muscles that showed the biggest differences well if we look at these two completely separate studies in males and females what you notice it’s the same three muscles which show the biggest differences in both studies the tensa fasia lat which is a small muscle at the hip the sorus and the gluteus maximus I’ll just make a few comments on two of these muscles so firstly the Sartorius the unique thing about the Sartorius is that it is a hip and knee flexor it is the only muscle that is a hip and knee flexor and that is a simultaneous action that occurs early in the swing phase of running essentially when an athlete takes their foot off the ground they then Flex the hip and the knee at the start of the Swing phase and that’s actually actually pretty important because until tow off their leg is actually moving backwards relative to their body at high velocity and it has a backward momentum compared to the center of mass and therefore to then change the direction of that limb very quickly in a very powerful way would seem to be useful to have a very welldeveloped sartoria so biomechanically this makes sense then the gluteus Maximus well the gluteus maximus is the largest hip extensor muscle um that likely plays a critical role for high leg momentum in late swing essentially in late swing the leg is out in front of the athlete but they need to bring it down very quickly to hit the ground hard in order to try and Propel themselves forward and then when the leg is on the ground the gluteus maximus and the hip extensors are important for propelling the body over the leg so again biomechanically this makes sense another interesting point about the gluteus maximus is aside from sprinting it’s actually the single biggest muscle in the human body which is really interesting now why would humans have a big gluteus maximus why do they put a lot of energy into doing that well in evolutionary terms perhaps because this muscle has a use which is it enables humans in general to run fast a little bit more on the gluteus maximus so here are the correlations of the glutitis maximum size in terms of absolute volume and relative volume for males and for females with 100 meter times so we can see here all of these correlations were significant uh ranging from -48 up to -66 and here’s an example scatter plot so this is glus Maximus volume in cubic cm for the male amongst male sprinters and the population here is the elite and sub Elite all plotted on the same graph and season’s best 100 meter time and you can see there’s a pretty clear relationship here and uh if we go on and from based on these correlations actually calculate the coefficient of determination what you find is that the volume of the this one muscle the gluteus maximus appears to explain between 23 and 43% of the variability in perform performance between athletes to put that in context 100 meter performance is generally considered to depend on a really wide range of factors technique psychology nutrition all manner of different anatomical physiological and biomechanical factors and yet one muscle seems to explain perhaps 30 or 40% of the variability which seems quite remarkable so it’s just summarize from this these studies on uh Sprint running uh across these two studies Elite sprinters were more muscular than sub Elite sprinters they showed a distinct pattern to their muscularity with the biggest differences in the more proximal muscle groups particularly the hip extensors and hip flexors and these specific hip muscles the gluteus maximus tensor fasul lat and sorus and as we’ve seen the Sprint speed was also consistently correlated with gluteus maximus size where expressed in absolute or relative to body mass terms I think there’s also uh an interesting wider implication to this um and that is that if a sport task or a event requires anatomically specific muscle characteristics for Success then training should be anatomically specific and targeted to develop these characteristics treating a whole person and training the whole body in the same way doesn’t really make sense or even a whole limb it seems to be useful to develop the prerequisite characteristics for success in that event with very targeted anatom ically targeted training so returning to my overview slide we’ve done this first theme now going to move on to hamstring’s Anatomy implications for Sports Injury here’s a few reasons why it might be interesting to study the hamstrings muscle because hamstring strain injury is the most common injury in association football with five injuries per professional Club per season hamstrings are a key constraint stabilizing the knee and preventing severe knee injuries particularly ACL anterior cruciate ligament rupture and in this regard you may be aware that there are large differences in the incidence of some lower limb injuries between males and females for example ACL injury incidence in females is 2 to 10 times higher that of males in agility Sports we were interested in whether there might be sex differences in NE knee flexor predominantly the hamstrings strength and size that might contribute to these differences in injury incidents here’s some data on maximum strength relative to body mass this is isometric maximum strength relative to body mass in untrained females compared to males so looking to see if there are inherent sex differences so this is force isometric maximum Force Newtons per kilo in the knee extensors the quadriceps and you can see very similar scores in males and females but when we look at the knee flexors mainly the hamstrings we see a different pattern where females are at a disadvantage significantly lower by 15% neee flexion strength so if we go on and calculate knee flexor to extensor strength ratio often referred to as the hamstrings the quadriceps ratio and widely thought to be an index of knee joint stability and injury risk what we see is that females have a lower ratio of 50% compared to males at 56% and this could influence stability of the knee joint because the hamstrings is a key constraint holding the Tibi in place preventing anterior tibial translation one of the movements that often contributes to ACL rupture we were interested following this in why what might account for that difference in knee flexion strength and therefore the strength ratio and a an intriguing possibility was that females simply have a disproportionately smaller hamstrings or knee Flex of muscles so we went on to do a an MRI study um to determine knee flexor to knee extensor muscle size ratio now so not the strength ratio but the size ratio of these muscles and this is what we found this is the knee flexor to NE ex densa size ratio where the measure of size was maximum anatomical cross-sectional area measured with magnetic resonance imaging and again this was in untrained males versus females and whilst there’s a wide scatter of points here within each sex group there was a significant difference where females appear to have a disproportionately smaller knee flexor relative to the knee extensors than in males so the conclusion from this work was that females appear to have inherently smaller and weaker knee flexes which may contribute and logically does contribute to their higher incidence of a injuries I’m going to delve more deeply now into the structure of the hamstring’s muscle and particularly the structure of the bicep for moris Long Head this muscle is interesting because the majority of hamstring strain injuries occur within this muscle the bicep foror long head which is shown in context here it’s actually the muscle colored in red here and then if I show on this picture this is in isolation we can see uh the bicep for moris long head and these are the bundles of muscle fibers within the muscle belly and then this is the proximal tendon and this extension of the tendon called the apine eurosis which runs down the side of the muscle in a penate muscle such as this one the muscle fibers actually uh attach and therefore transmit Force predominant actually onto the apine eurosis rather than directly onto the tendon I highlight these structures because the most common injury site within this most common injured muscle is this proximal region adjacent to the apine eurosis so just here just inside the apine eurosis furthermore modeling studies indicate a concentration of mechanical strain adjacent to the proximal apine eurosis so this is a diagrammatic representation of the muscle wall this is the proximal tendon and then the black line is the aine eurosis extending extending down the side of the muscle and then the muscle fiber strain has been colorcoded where the highest strain is shown in red and yellow and we can see that that is concentrated in the same region proximal or next to adjacent to the apur is so we were interested in well if this structure the apine eurosis is important in injury risk could it be a a potential risk factor for hamstring strain injury and we started simply by characterizing this structure in terms of its size so this is a study that looked at the size of the proximal aponeurosis of this bicep moris long head muscle and in particular the contact width or distance or the contact area essentially the interface between the apine eurosis and the muscle uh and we did this in 30 healthy untrained young men again using magnetic resonance imaging and you can see this is the bicep for moris Long Head and the adjacent semitendinosis and actually we have picked out the apine eurosis there it’s not showing that clearly it’s a little better on this zoomed in image so the black region here is the apine eurosis and I’ve drawn on here the contact distance what we kind of simplistically call the width um which is actually the interface between the muscle and the apine Neurosis clearly this is just one slice or image and this aponeurosis runs down the side of the muscle and if we measure measure this contact distance in a sequence of slices along the muscle uh then we can actually measure a contact area between the muscle and the apine eurosis which is to some extent captured here so this is the muscle apine eurosis contact distance measured in centimeters at different points all along the muscle and here’s data are actually from three individuals and what you notice is there’s wide VAR ability in the size of this apine eurosis between these individuals we found really large variability in aine eurosis size such that the contact area between the muscle and the apine eurosis range by more than threefold even in this relatively homogeneous group of healthy untrained young men so this led us to the following hypothesis that a small bicep for moris L head proximal apine eurosis May concentrate mechanical stress in the muscle tissue adjacent to the apine eurosis and predisposed to strain injury essentially the mechanical stress from the muscle is becomes very concentrated because it’s attaching on to a relatively small apine eurosis so we went on to do a retrospective injury study of May athletes we first recruited 23 athletes with a prior hamstring strain injury of the proximal bicep for moris L head muscle the injury definition was two or more clinically verified strain injuries to the proximal region of the bicep for Morris L head but importantly all of these athletes had returned to normal training and competition at least 3 months prior to the measure measurements so these were historical injuries they were not current injuries now some of these athletes in this group of 23 had injuries to both legs so they were B had a history of bilateral injury but 12 of them had a unilateral injury history so they had a history of injury on one leg but the other leg was completely healthy and it always had been healthy and I’m just going to show some analysis from these individuals comparing their previously injured leg to their healthy leg and these are two measures of apine eurosis size so firstly maximum width and then apine eurosis area and comparing the leg that had the prior hamstring strain injury to the leg that had no prior hamstring strain injury or was healthy and what you can see is is that in both cases the previously injured leg had a smaller apine eurosis by both measures the other analysis that we did was we gathered together all of the legs that had clinically verified injuries within this group and there were 28 of those legs and we compared them to healthy legs from a contr Ro group of 23 a athletes who had no prior hamstring strain injury history so they had always had healthy legs but were match for sport age sex and height and we had obviously 46 healthy legs in this group and we compared these injured legs to healthy legs for exactly the same measures of apine eurosis size maximum width apine eurosis area and again we saw that the prior hamstring strength bra injured leg had a smaller apine eurosis compared to healthy legs in both cases so the conclusion from this study was that a small apine eurosis seems to be associated with hamstring strain injury history however from a retrospective study we can’t be sure about cause or consequence it could be that a small apine eurosis leads to injury but it could equally be that injury leads to a small apine eurosis we can’t be sure of that from a retrospective study so certainly more work and prospective studies are required but this looks like a candidate to be a risk factor for hamstring’s strain injury returning to my overview slide so we’ve covered the first two themes and given that muscle size seems to be important for athletic performance um and the size of tenderness tissues seems to be important for athlete resilience and avoidance of injury trying to increase the size of these muscle and tenderness tissues has had a lot of attention um and one obvious way to potentially do that is with resistance training which I’m going to come on to now and in the first study also as a nutritional component because nutrition could amplify potentially the effects of training on the adaptations of these tissues so this is a study that looked at muscle and tenderness tissue adaptations to resistance training as well as collagen peptide supplementation collagen peptides appear to have some bioactive properties and have been suggested to enhance the growth of various tissues including muscle and tendon in response to exercise and training so we recruited 39 young men who completed 15 weeks of resistance training three times per week so 45 training sessions of knee extension leg press and knee flexion with a fairly standard pretty heavy loading regime and each participant uh was supplemented with 15 G per day of either collagen peptides or a placebo in a randomized double blind design I’m going to present the muscular findings first of all uh so this is for isometric strength so knee the change in knee extension maximum voluntary torque measured isometrically from pre- to post in both the collagen peptide group and the sibo group and you can see that the improvements were pretty much identical around 22% Improvement in both groups this next finding was more surprising to me certainly um his quadriceps muscle volume again measured with very careful magnetic resonance imaging so relatively thin slices all of the way down the muscle at least 20 slic is contributing to the volume measurement and this is the change in quadriceps volume from pre-to post training expressed as a percentage and what you can see is that the collagen group improved by more than the placebo group uh around 15% versus 10% which is actually quite a substantial amplification of the training response and when we looked at total muscle volume so this was the summed volume of the quadriceps the hamstrings and the gluteus maximus measured pre and post training we saw the same thing the collagen peptide group around 16 and the placebo group around 11% and a significant advantage of the collagen peptide group moving on to the tenderous tissue adaptations This Is tendon size the cross-sectional area the mean cross-sectional area of the patella tendon pre and post training for the for the placebo and collagen peptide group and you can see there were no significant changes tendon size did not appear to adapt or at least the changes were less than 2% and not significant however the material properties of the tendon in terms of its tendon stiffness which is its elongation under load did adapt to the training as has been well documented in the literature this is Patell tendon stiffness pre and post training and it increased significantly in both groups by 21 and 17% but there was no difference between the two supplementation groups and then lastly this is the Apon Neurosis size now this isn’t the same Apon Neurosis I was talking about earlier on within the hamstrings but it is an apine eurosis nonetheless this time within the vastest laterales and we can see that apine eurosis size does seem to adapt with training but wasn’t sensitive to this type of supplementation so improvements of around 10% in both groups and it’s interesting that the apine Neurosis seems to adapt even though the free tendon doesn’t seem to adapt considering the free tendon response in a little bit more detail one possibility is that the free tendon just needs more time more training time in which to adapt so we’ve also done uh some study looking at how does long-term resistance training affect muscle and tenderness tissue uh in this study there was a comparison of two groups of young men long-term resistance trained individuals 16 of those with an average four years of heavy resistance training so week in we out heavy training for many years compared to untrained controls 39 of those with no history of resistance training first of all the muscular changes or differences this is maximum voluntary torque isometric strength as you would expect the long-term train group were nearly 60% stronger than untrained controls similarly for quadriceps volume muscle size the long-term trained group 56% bigger muscles than the untrained controls nothing that surprising here we were particularly interested in the tenderness tissue differences though and this is apine eurosis size vastus lateralis apine eurosis size which was 177% bigger in the long-term trained group so a modest difference compared to these muscular differences but a difference a clear difference nonetheless suggesting that perhaps again the apine Neurosis is adaptable to training and this is the free tendon patella tendon mean cross-sectional area which was identical between these two groups that that’s despite the fact that this group has been training regularly for many years and because they’re strong and they’re training regularly with heavy weights they’re exposing the tendon to these very high forces on a regular basis yet there’s still no apparent adaptation of the tendon in terms of its size which is maybe quite surprising so the conclusions from this work was that apine eurosis size but not tendon size increases with medium and long-term resistance training collagen peptide supplementation May enhance muscle hypertrophy with with resistance training but doesn’t seem to affect the tenderous tissues and also somewhat curiously that hypertrophic effect didn’t flow through to strength gains which is maybe surprising but might perhaps be because strength gains depends on a lot more than just hypertrophy and perhaps the neural factors also interfere or dilute that hypertrophic difference just going to finish off with a little bit of fun science um if you’re interested in long-term resistance training uh and muscle and tendonous tissue adaptation it might be interesting to take some measurements from this guy I mentioned him earlier on his name is is Hall and in 2017 he was the World’s Strongest Man meaning he won the world’s strongest man competition he’s also a double world champion at the deadlift uh for a number of years he held the world record for a deadlift by deadlifting 500 kilos and uh as you can see we got him to come to the neuromuscular lab um uh about a year after he won the world’s strongest man title um and we did a range of functional test with him but the most interesting thing we did um was we got him in the MRI scanner and we took a uh spent a lot of time with him taking some detailed measurements there and I’m just going to put those measurements next to the data I’ve just shown uh in terms of untrained controls and long-term resistance trained individuals so this is his uh quadriceps muscle volume you can see this is the untrained controls about 2,000 cubic cm the long term trained about 60% higher and then this is the World’s Strongest Man where his quad recepts was two and 1/3 of the size of untrained controls and this is the patella tendon data for our untrain controls long-term trained as I’ve said not really a difference between these groups but the World’s Strongest Man well he did have a somewhat larg attendant 30% bigger than untrained but of course he is a very big man so you might expect him to have big tendons inherently and when you look carefully actually his tendon size was is not really out with the range of values that we’ve seen in these other populations and then one final measurement with him which I haven’t mentioned in the presentation but the patella tendon moment arm which is simply The Leverage of the quadriceps around the knee joint the mechanical leverage and train controls long-term trained individuals pretty similar but the world’s strongest man he had 21% greater moment arm or greater leverage which you might expect would be useful for strength and power performance so in summary the World’s Strongest Man had a number of anatomical advantages for high muscle strength and robust tissues large muscles large tendons and high joint leverage just me remains for me to thank the funders of the work of the neuromuscular lab and these key collaborators who played a huge role in uh the studies I’ve talked about and thank you very much for your [Applause] attention thank you Jonathan is there any question thanks Jonathan for your great presentation just a question about the first part of your uh presentation about muscle morphology how do you explain the tfl uh hypertrophy and the impact that uh uh it’s can have on on running phases as gous Maximus and the Max Muscle on the hip muscles you know yeah yeah yeah I kind of skipped over that that because in a way we don’t I don’t have a very specific explanation for why the tfl is is is is very large in Elite sprinters apart from um anatomically there are only two muscles that attach onto the ilot tibial band one of them is the gluteus maximus which is obviously very large in those sprinters and the other is the tens fasia lat um so it’s just possible that in some way because of the very high development of the gluteus maximus the tensor fasil lat becomes developed perhaps it needs to in order to stabilize the ilot tibial band um that’s my best explanation um because it’s not a very big muscle it’s not particularly powerful or you would think important um but something around the AL to be or bound perhaps good question thank you any other question I’ve got one question Jonathan I was wondering about the hypothesis of the proximal aerosis did you get to measure that uh that measure in the very strong man that you show here um we we we we could we haven’t actually measured it okay reasoning like that I was just thinking about your first study when you compare like a very elite uh sprinters with sub elit and in which you show that there is a significant differences overall in mcle volume yes I was just wondering whether when when we think about this appon neosis size yes yes do we think like in absolute terms or is it relative to the muscle volume of the leg that that’s an really interesting question so we think the app eurosis can adapt it does adapt but it seems to adapt more slowly than the muscle which if you think about the transmission of Force if the problem is a concentration of mechanical stress um then sure making the apois bigger would should help but if the muscle gets bigger and stronger and produces more force and it gets disproportionately bigger compared to the apine Neurosis that would almost seem to create more of a problem if that makes sense so but the rational may not be correct so we don’t really understand how these things into connect um but we do we do now have some data from a training study that that indicates that that specific apine eurosis within the bicep femoris long head does adapt with training um but yes but by less than the muscle which is slightly counterintuitive from a training seems to reduce injury risk point of view thanks thank you very much Jonathan it was very very interesting number of questions but maybe a very basic one uh regarding the role of the glut on performance because you show this relationship between the size and potentially the performance in ecological conditions and we have discussions with some Federation which may relate it to do you think that there is a sailing or do you think that this relationship will continue because we have some example uh where we see some athletes with morphological aspects like bub leg sprinters they develop very strong glutes MH but we are not so sure that they are sprinting faster than rugby players or whatever but we we we are interested in how to use the way they are training to develop this muscle mass but do you think that it’s still interesting above a certain level of muscle mass and strength yes an open question maybe yeah it it it’s hard to know is there a ceiling um we we simply don’t really know um uh I I kind of suspect probably not actually I think when we what what what we did there was look at amongst sprinters which means they have certain fairly common characteristics um for example in likely in the the anatomy of their foot their anchor they probably have some very similar characteristics which means their transmission of force to the ground is much better than the general population or many people um so that might be an issue so if you put a huge glues maximus in somebody who had doesn’t have that ability to transmit Force to the ground maybe it’s not so useful and you lose more of that Force um uh you know I mean I I I me mentioned briefly you know the the the the use of absolute values and relative to body mass values for the muscle volumes which is a really interesting debate um you know based on what we found I would argue that that you know everyone has always assumed that it should be relative values because you have to use your move your body mass when you run a Sprint which which makes sense on one level but based on what we found in the fact that there are are uh clearly differences and relationships for absolute muscle volumes that seems to me to be telling us something the absolute muscle volumes cannot be irrelevant else there just would not be those differences in relationships um so why is that um you know there’s a number of possibilities um certainly amongst the males my uh feeling is or my anecdotal impression is and the is very little data on this although it’s very simple is that Elite sprinters the average is quite big people actually quite tall now it’s not I don’t think it’s selective so you can still get sprinters who are average size but the average I think is bigger um uh so I think there is a and that and that suggests absolute size hasn’t have some kind of value um it’s that’s a little less clear in females but uh sorry if I kind of spun off in different directions there but if I may maybe a last question in relationship with this one I was just wondering in one of the graphs that you show uh there was the relationship between glutose Max and the the performance Sprint performance and I’ve got the impression that on the left so those who run faster it was more dispers the data I think we have some points in which there may be like a huge differences in in volume how do you you interpret that what’s the Reon yeah hard to know hard to know I if that’s genuine or Le a a thing a phenomenal or not um uh I mean so certainly you know the the the male sprinters that we we assessed they were quite big guys no doubt about and they’re not all um and with an end of only five it’s it’s really hard to know if if there’s something system there uh but certainly they they did have very pronounced glus Maximus and hip extensors in general um yeah thanks any other question so maybe we can leave it here thank you very much Jonathan thank you everyone for coming thank you thank you for your [Applause] attendance