Professor Mark De Set Croix has published over 100 articles and presented at over 100 conferences across the globe. He works predominantly in football, identifying injury risk via screening and implementing prevention programmes. A key focus of his work is to help coaches develop their understanding of prevention strategies.
After undertaking his teacher training degree he knew he had an interest both in children’s sport and physical activity and a growing interest in science. He completed a PhD exploring how children’s muscle strength changes with growth and maturation and is now using that knowledge to explore how to reduce injury risk in youth sport. This has provided him with opportunities to work with some of the world’s leading football clubs.
Mark has just led an Erasmus+ European-funded project with partners in Spain and the Czech Republic to explore the knowledge and understanding of grass root coaches in terms of youth injury prevention. He has also obtained funding from FIFA, UEFA and the English FA to explore injury risk in female youth football, and works with organisations such as the England and Wales Cricket Board, Athletic Club Bilbao Football Club and Bristol City Football Club.
In this episode Mark discusses:
- The many factors that should be considered in an injury risk reduction program.
- The importance of Training Quality as well as Training Age.
- Why Coach Education programs need to be more accessible for grassroots coaches.
- Is asymmetry as detrimental as people suggest?
- What does neuromuscular control really mean?
- Are kids affected by fatigue the same way as adults?
- Is there any truth to the concept of “Windows of Trainability”?
You can listen to the episode in full here.
You can keep up to date with Mark’s research via the University of Gloucestershire Repository, his Research Gate page here, as well as via his Twitter account: @destecroixmark .
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Rob Anderson
Mark, great to have you on the podcast. Thanks so much for joining us today.
Mark De St Croix
No problem, Rob, it’s good to finally get on.
Rob Anderson
So for those who haven’t come across to you as an individual and the extensive research that you’ve done, we’ll delve into that a little bit later on. But give us a bit of an insight into how you first came into contact with sport. How did what are the sports that captured your imagination and how did you get involved in physical activity and how that develop as a youngster?
Mark De St Croix
Yeah, well, I suppose like everybody listening, I’ve always been invested in interested in sport. Firstly, very keen footballer from a young age. Always thought I was going to be a professional footballer, not realising that. There’s very few five foot four, I probably look quite tall here on the podcast, but very few good five foot four footballers. I definitely wasn’t a Gordon Strachan or Diego marathoner, so I was never really going to make it. But back then didn’t really understand any of that. And that sort of context and went for a few trials and things but sort of then moved into sticking with sport at university. I’m going to slightly show my age here and that when I went to university, there were no sport science degrees, you went and basically did a P degree. But the P dreams back then were essentially a sport science degree, a sports coaching degree, and an education degree. So we used to have 30 plus hours, a weak contact, doing sort of all of this stuff, which was great. So always had that sort of investment in sort of kids teaching kids, I’ve done a little bit of coaching, outside of the formal curriculum stuff, so qualify as a rugby coach, a hockey coach or football coach, all of those things. So so always had a had an interest sort of in kids and teaching kids, but didn’t enjoy teaching overly. A couple of teaching practices can maybe quite quickly put you off teaching. But no to sort of felt I wasn’t ready for teaching when I finished just so I’ll tell you what I’ve really enjoyed, in particular, the sort of physiology that I’ve done. So I decided to stay on to do a Masters down next to uni. And it was just by chance that, you know, Professor Neil Armstrong was down there, he was doing all the work out of the children’s house next size Research Centre. So all paediatric focus for search, you know, you’ve had lots of people on your podcast previously, I’m sure that that have come out of that great establishment, probably one of the leading institutions for paediatric research in the world. And stayed on to your master’s sort of went to Neil and said, I want to do a masters. Can I do one? And he said, Yeah, find some funding. So I managed to get some funding. And then he said, what you want to do? And I said, Well, I don’t, I don’t really care, really physiology. And, and he said, Well, we got this new bit of kit. It’s called an isokinetic, dynamometer. None of us know how it works, go away and become the world’s leading expert on isokinetic, diamond, nonmonetary. And kids. And I was like, Okay, any guidance? He said, No, none of us know how it works. It was almost still in the bubble wrap. So yeah, very steep learning curve. But really enjoyed it got a year in and went out to watch this one stay on do PhD. So convert the MPhil never, never wrote up a master’s stayed on to do the PhD. And two and a half years later, there’s me having written a thesis on the development of strength in children with some nice longitudinal data growth and maturation focus, some MRIs in there, which was quite novel back then. Some allometric scaling, which again, was quite novel back then a little bit bland, and Altman, which back then was quite novel. So So yeah, two and a half years later, here, I’ve got a thesis and an interest in sort of children’s strength, and how it changes through just normal growth and maturation. So yeah, and then just from there, stayed on stayed on there for a while, did a postdoc at Exeter, obviously continued working in that sphere, and supporting other projects into kids physiology. So you know, also things on physical activity and power and, you know, all the stuff that was going on in the centre, which was great. So learn, arrived a wide range of skills, but always had that sort of main interest, sort of, I suppose, in strength and strength development in particular, and then we might come on to where that’s sort of morphed into more of a sort of injury risk injury prevention, how that sort of grown into that, that over time. So yeah, a bit of a potted history there.
Rob Anderson
Yeah, that’s, it’s great. I mean, as you mentioned, like that point in time imagining doing MRIs doing isokinetic dynamometry on children would have raised a few eyebrows. I imagine you came across your fair share of stigma in terms of Oh, no, you shouldn’t be doing that with kids, etc, all that kind of stuff that we still hear today, but I imagine at that point, there was a whole lot of it. Occasionally I had that happen.
Mark De St Croix
I mean, there was just the usual class that that we come up against when we’re doing any kid’s work is that none of the kit was set up for, for use with kids. So we designed I mean, the paediatric attachment that’s you now combined, filled by decks were designed. It won’t say it’s designed by us. But they were designed by us in Exeter, because they weren’t any. And so we had Biodex over and said, Look, we need shorter, shorter lever arms for the kids made, we need this, this back doesn’t come, this back seat doesn’t come forward far enough, because the kids have got really small thighs. So we got nine year olds on air, we need to move the seat forward. So we had to have extra pads made to move the seats. So all of that is always a steep learning curve. And as you say, you know, a lot of these things aren’t set up for kids. And then it’s always it was all where you can’t do any centric testing with the kids. Because that’s, you know, that’s, that’s quite, it’s quite hard. So what do you what do you mean? Of course we can they work essentially all the time when they’re running and jumping. So why can’t we? Why can’t we test them? You? centrically? So yeah, it’s sort of interesting. Still, I mean, I think, you know, the fields developed in a little bit, not not, not that much, but the field is developed in understanding that children are dynamic and can do, I mean, they’re more robust and resilient than adults are anyway, so probably safer to do, I’m probably safe to do eccentric testing with a 12 year old than I am with half the people that work down my corridor to be fair.
Rob Anderson
And since then, you’ve, you know, got accumulated a massive breadth and depth of research across a load of different topics, obviously, you know, regularly within that youth population, whether it’s Injury Prevention, or strength testing, or looking at maturation differences, etc. So there’s loads that we could go into. So let’s have a look initially talking with some around the kind of injury theme within you sport. One of the things you’ve been regularly involved in is looking at injury prevention programmes, etc. So how should a coach or those listening, go about the process of constructing or even looking at some some of the stuff that’s already existing around a valid and effective injury prevention programme, watch what should be the key kind of thought process and stop stops along the way?
Mark De St Croix
If I had that magic wand here, I would probably be loaded and wouldn’t, in the kindness sense be talking to you. Because, you know, we know there isn’t a magic wand, we know we’re working with a very complex system. In terms of growth, maturation, the individualised timing and tempo of how that informs, you know, for working in teams, the whole differences there for in what might be in front of you in terms of training age, not just training age, but training quality, which is something I’m quite strong on at the moment, it’s, you know, people are talking quite a little bit training age. Well, I’ve seen kids with high training age, who still can’t move, because the training quality has been very poor. So it’s not just training age, you know, chronological age, gender. So So that concept of fitting programmes together, it’s that usual classic thing of individualization, but also, I think, mainly for anyone working with kids, it’s around flexibility, isn’t it, it’s about being able to see what’s in front of you how that system might change quite quickly, if we’re going through rapid period of growth, and how I can be responsive to seeing that in front of me and making the correct adaptations for that individual to maximise the potential that we that we might get out of it. I suppose the other key thing, so I’m going to be a little bit pedantic here, I would say, I don’t really like the term injury prevention. Because I think if you, if you stick a group of young adults in a room, you do sport and you say who’s had an injury, they’ll all put their hand up. So we don’t really prevent injuries, what we’re doing is injury risk management. And the risks, obviously, for kids are very different to the risk for adults. So it’s how we put all of those pieces of the puzzle together. And, you know, we know in our sort of cycle of being able to put a programme together, we need to understand what the risks are first to make sure that we are putting things in that might be able to compensate against some of those risks. And the difficulty with all all paediatric work is we know that still, we’ve got relatively limited data that we’re working off. In particular, those really good solid, robust longitudinal datasets, where we’ve got loads of kids who are at different chronological ages, different maturation stages, all those things. We talked about different training ages, different training qualities. to map them over a number of years, to be able to really see what’s happening, we still work off a relatively small limited knowledge base. really insane that that doesn’t mean that we can’t sort of try and make some recommendation from where we’re at at the moment. And those might change as our knowledge base develops. Well, I hope I hope it would develop as our knowledge base develops. So that hasn’t really answered your question in any way, shape, or form that’s probably set out the problem of the puzzle. Yeah, well, I suppose it’s, it’s taking all of those things into consideration. I mean, I suppose our key thing is similar to stuff that you would have heard before from Rodri. And John Oliver is around, you know, that athletic competency model, looking very much at movement competency in the early ages through a bit more unstructured, fun, play, movement, type activities, all the stuff John Robbins done recently, as well, well, we, you know, lots of us have been doing it maybe for years as well on sort of animals and animal shapes. And, you know, those things that we know, do all of those more complex things underneath, like anti rotation and core work and bracing and acceleration and deceleration. But without ever mentioning any of those terms. It’s, it’s a frog, it’s a crocodile, it’s a giraffe, whatever it might be. And making sure we work through the whole kinetic kinetic chain there as well sort of toes up to heads and back down. I think sometimes we get a bit hung up on what we should be doing in terms of when we try and plan stuff. I’m quite pragmatic in the if you go down the sort of lower end of the sporting pyramid. So down to that grassroots stuff, you know, you’ve got mums and dads who are sort of maybe taking local teams who don’t have a sports science background, or aren’t a strength and conditioning coach, get booked board, let’s say if it’s football by the FAA on their four pillars anyway, you got to do this, that there’s ball roll time, there’s tic tac, there’s site, there’s social, there’s physiology, and they can they’re like, What does any of that mean? That the importance is DJ organising everything, because I think we’d like to overly jargon ice stuff. So keeping it really simple at that, those those lower levels and just making it fun and, and some additional movements that the kids aren’t already doing. Because remember, kids are nuts. I remember back when I was a kid, I wouldn’t do half the stuff and help it kid. You know, they do loads of loading, I used to jump off my back roof shed into the field over you know, I wouldn’t even climb up to this shed roof now. But you know, the load that was extreme box jumping in those days from you know, not not 30 centimetres. So, so I think there’s, there’s, there’s, you know, we always have that concept of concern about doing too much. But if you just look at what kids do, normally, they do a lot, let’s let’s just make them maybe do some movements better and in different ways. Yeah, so in that early phase, where I think kids tend to do a lot of stuff quite quickly. So I quite like to slow stuff down. So can we do that more static hold balanced proprioception thing, because kids like to run around a lot, which is great. And, you know, we see loads of great clips of people doing obstacle courses, and all of that stuff been great fun. But let’s see how well they also work when they have to slow down, stop, decelerate brake, you know, land from a jump, single leg holding balance, proprioception works so good. Just getting the balance in there in the mix. And let’s not be overly obsessing about, do we have to do certain numbers of reps or sets or make sure that we’re definitely working on anti bracing today, or, you know, anti rotation or core work is in the early phase, let’s just let’s just get them moving a little bit better.
Rob Anderson
Fantastic. There’s loads in that that we could we could dive into. But one of the things you mentioned early on that I want to come back to and dig your brain a little bit more on is what do you mean by training quality? And what would would be in beneficial training quality and what maybe not so beneficial in a training quality? So what what do you mean by that? Let’s dig into that a
Mark De St Croix
little bit. Okay, without upsetting anybody. I think I think the problem that we have is, I think it comes back to that, that issue of you know, that the individuals that are working with these kids at the lower levels are sort of mums and dads and things like that they’re not they’re not strength and conditioning coaches, they’re not sports scientists, they have relatively limited knowledge. And I think what what happens is we that over jargon I stuff so they decide not to adopt things not to implement them not to make and they won’t maintain them because we make it too complex for them and Therefore, the quality of the type of movements that we might want the kids to do, in terms of, you know, maybe simple things, getting knees out over toes to reduce valgus on landing or when we’re cutting and sidestepping, you know, or getting getting hips in good positions, when we’re in particular movements is, is, is making sure that we make the coach education accessible to those groups. So they they give the children better instruction that subsequently hopefully should lead to better quality of movement, that then further down the pathway holds them in good stead and also probably holds them in good stead at the time. Because we’ve probably know if we, if we move better, we might sort of be a bit more successful, and we might enjoy it a bit more, and we might stay more engaged. So so at that lower end. You know, in that regard, it’s great. But subsequently, if we want individuals to progress through the development pathway, and if we’re talking now about more of talent development pathway, we want to make sure that when we do want to start progressing that overload, that the fundamental movements are there. And I sort of I say that because a lot of it really rang true to me just talking with Rob arm. And when we started working with England, cricket little bit, and you know, Rob, just saying, he’s got under 16 players who he can’t load, which, which is incredible, really, you know, and he says, because they can’t fundamentally move. But he says they’ve been in clubs, since they were 10. So they clearly haven’t got what we might call quality training, they’ve got a lot of training years behind them, but maybe just through the education of the coaches or what they’ve had access to. I mean, even in those environments, where you might now well, it’s still developing, isn’t it physical performance coaches in these environments, we don’t have them still in, in necessarily all even all professional environments at all age groups. That if we can get some of those fundamental movement patterns better through that pathway early on, so making sure we’ve got the movement that looks right in our patterning, so that then further down the line, we can be overloading them. And it might be that we want to overload them, and can overload them even a little bit sooner than we think we would anyway. So yeah, I, I think unpicking exactly what I mean by quality. And everything is is difficult, but I suppose our fundamental movement patterns in terms of you know, whether it’s squatting, but also whether it’s just, you know, what position should I be in when I’m decelerating and wanting to change direction? Because I know that’s a high risk activity. So do I get the hips in the right position? Is the knee and it’s sort of in a good position is are we creating strong, stable, robust? I don’t want you to never use the term machines, then they’re not they’re not machines, but individuals that can, you know, cope with the demands? Because that’s the bottom line, isn’t it, that the demands are quite high, the demands aren’t going to change. And in fact, the demands properly, you know, we’ll continue to progress as as we progress and evolve as humans demands aren’t going to go down. So are we building up enough resistance, resilience? robustness? I know, we’re just throwing around words here. But you know, they are the key words to make sure that the the individuals can cope with the demand. Fantastic, sort of ask question, what I mean, I’m just trying to reinforce that it’s not just when people think about training age, it’s, we need to think a little bit beyond that. Because individuals with high training age still can’t necessarily move very well, you might have someone with quite a low training age, who’s just had a really, really good coach, or had access to a physical performance coach, and they might only be doing it for a year or two, and they move brilliantly. So, you know, if then we say, Oh, well, we need to factor training age into our equation, and you’ve got really low trainees, therefore, we’re going to start you here. Well, that might not be right.
Rob Anderson
Yeah, I think I always find it useful when you draw comparisons with other domains mean, you know, we all own maps of school, some of us got to the calculus level, and some of us didn’t get past the basics. We all may have had a similar training age for maths if you like, but it doesn’t necessarily mean we all arrived at the same destination after 1012 years. So yeah, it’s very, I think that training quality piece is really important. And you’ve hit the nail on the head for me. Yeah. And it’s recognising at the grassroots level. They’re usually people who stepped into the gap. You know, there’s we needed a coach for the other third teams. Someone said, Okay, right, I’ll stick my hand up and step into the breach. But that doesn’t necessarily mean that person was given the right level of support or given anything beyond the level one in some safeguarding the first day and off you go for four or five years and no one checks in on you. So it’s not the fault of the person delivering it, but as you said, I think making, first of all, making it simple enough to access for people, whether that’s, you know, taking away the terminology, but also the quality of that coach development, I think a lot of times we can try and do too much. And actually, sometimes it’s better off saying, look at these three or four things, do them really well. Don’t worry about the rest of this point in time, I think it’d be really crucial.
Mark De St Croix
Yeah, I agree. And that’s why one of the key drivers and stuff that we have been dealing with with Rob arm and ECB is trying to get this early in the, in the award pathway, the coachee will perfect. And it’s always difficult their demands, you know, there’s a lot to squeeze into a very limited amount of time. And, you know, we’re moving more and more to those sort of level one II type awards being very non face to face all online, you know, the resource needs to be really good. And, you know, to be fair, the ECB and, and others have got some really good resources now for coaches online. To be able to sort of understand some of these key concepts. As I say, a lot of it I see, though, is still overly jargon iced. And one of the massive things that we spent so much time doing is making it as simple as possible. You know, those sort of, you want to call them coaching cues, keeping them just really, really, you know, simple and saying, Well, we’re not trying to make you don’t want to scare off that person that stepped into the breach by going we’re going to make you an S&C Coach alongside a psychologist and, and, you know, someone that thinks about all time, you know, technical coach, and also probably a voice and a role model and all of these other things, we want you to be about 1001 things Oh, and you’ve done a few hours online course. It’s if you think about it, it’s it’s quite crazy and or sick, we we have things the wrong way round, you know, we always get the better coaches or higher up actually, we want to we actually want the coaches, we should have no physical performance coaches, in any elite teams, we should have them all, at the grassroots level. You could argue we could have that discussion, couldn’t we about? Actually, we’ve got them in the wrong place?
Rob Anderson
Yeah, absolutely. That’s definitely my kind of thought process on it. So one of the things you mentioned is obviously, people like to simplify injury prevention, as you pointed out, there’s a number of different factors. And actually, you know, a, we can’t possibly maybe control those factors at once. But be there’s a lot of other things going on. And one of those things of use, as you alluded to, is around maturation. So we know the obvious things like Osgood, Schlatters and severs and the kind of risk of growth related issues to do with aggravain growth plates. But some of the things you looked at are a little bit more interesting around asymmetries in neuromuscular coordination. So what’s kind of going on under the hood of this ever expanding car from a from a asymmetry and coordination perspective, when we’re going through that growth and maturation process?
Mark De St Croix
I’m quite pleased to use the car LAN analogy, because that’s what I use. I always suggest that you know, you don’t take your car to a garage or to a mechanic that doesn’t understand how a car works. Yet, we let our children loose with people that don’t understand how they work. And that that always worries me for a start, which is, again, why that sort of coach education piece for me is important. But in terms of adding further complexity to the puzzle, and it’s actually one of the reasons I I just enjoy working in paediatrics because it’s complicated, I think I’d be bored if it was, you know, we’ve got a system that’s pretty stable, and we can maybe change it a little bit through a lot of training. You know, the challenges we face if we work with kids are immense. And I think you’ve hit the nail on the head that, you know, injury risk is complicated in itself to try and understand all the whole range of risk factors. So is it? Is it the amount of absolute muscular strength that we’ve got a specific joint angle? Is it the neuromuscular capability at that particular point in time and how quickly the car engine can can cope with the acceleration or deceleration? Is it around the mechanics is it around the non modifiable stuff, the growth and maturation type relate the things that we know probably increased risks in the girls in particular with the widening of the hips, potentially, with the increased fat mass as a percentage of body mass rather than muscle mass, you know, all of those things in terms of peak weight, velocity, peak height velocity, and we’re getting a bit of a clearer picture on some of that now there are there there are now at least four or five quite decent studies that have looked at sort of maturation stage and potential risk and probably unsurprisingly, there most of them are coming out around that peak height velocity period of being a high risk time. If we throw girls into their the other things out, you know menstrual cycle oestrogen, even though the data is incredibly limited around those things about how much risk they play, you can see that we’ve got high risk athletes. So if we’re working with kids, we’re working with high risk athletes. And the data is showing that sort of unpicking all of that alongside then our growth and maturation issues, eg individual timing and tempo. You know, we’ve got loads going on over here in terms of risk factors, and then loads going on over here in terms of growth and maturation to try and put it together. And I think it comes back to almost your very first question, or one of the questions about, well, how do we design risk management programmes when we’ve got all of this stuff going on? And, and there’s no, there’s no simple there’s no simple answers, but we can we can stop probably, you know, at the moment hazard our best guess based on some of the data that we’ve got. So we’re particularly I mean, I’m particularly interested in fatigue a bit that the relationship fatigue may play in compromised neuromuscular performance in the kids. Mainly because we again, we have a little bit of a concept if we do a lot of work with kids that they’re, that they are actually quite robust. I mean, so even when I was working at the Children’s Health next life Research Centre, we’d be doing vo two Max testing on kids and they’d be running to exhaustion. And then literally five minutes later, they’re sat on a bike pedalling at 5000 miles an hour with as much load on as they could because they were bought
Rob Anderson
So one of the things that that you’ve kind of produced some research around is some of the different factors that can influence injury around asymmetry in neuromuscular control fatigue. So delve a little bit into that what what some of the bit I know, you know, previously worked with a lot of physios and rehab programmes that kind of obsessive around getting to, you know, a 10% difference as being a kind of threshold of where we think we’re safe with asymmetries. Is there any truth to that what some of the evidence suggests around asymmetries in youth and injury?
Mark De St Croix
I think with asymmetries, it’s pretty much the same as what we find with a lot of the stuff around your muscular function and control. In that, if you actually look at the data, it’s still really limited. You know, there’s been some really good advancements recently, sort of on how we might look at and calculate a cemetery or support read Stan, quite a bit of that work. But even a lot of that is quite limited on kids. We know thresholds are difficult, don’t we? I mean, it’s, you know, licking the finger and sticking up in the wind a little bit about where, where’s 10% come from? Why is it 10%? Because if you look at normal individuals, there probably should be some asymmetry anyway. And we always think about this, you know, we have to be symmetrical, actually, we probably, we probably don’t, and kids are exactly the same. And actually, if you look at that, if you look at the lower limbs, you know, kids are pretty active, they run around, they jump, they don’t, they don’t tend to do lots of single legged work anyway. So you tend to find that the the asymmetry is the limited data out there is that we don’t see massive asymmetries between kids in the lower body, we might, we might in the upper body, if we’ve got a lot of single sports specialisation where we are maybe using one side significantly more than the other. So there’s a bit of limited data on tennis players, for example. But again, we’re working off a incredibly small pool of information. I mean, we might argue that some form of asymmetry is good anyway. So trying to trying to get to a symmetrical situation might potentially be a risk factor. I mean, that’s a that’s an interesting concept that we’re saying that we’ve got to be within a 10% boundary. Obviously, we don’t want large differences between between between limbs. But from what I’ve sort of seen, and we haven’t really got the data to put that asymmetry data into large data sets with other known variables yet with kids. So you know, to say, asymmetries are one of the more important risk factors. I don’t think we’re in a position to say that as yet, because we need to put asymmetries alongside functional hamstring quadriceps ratio at the right joint range of movement, we need to put it alongside you know, proper, real meaningful evaluation of neuromuscular function. So whether that’s neuro electromechanical delay, or short, medium and long latency, reflexes actual real measures of neuromuscular function, once we put them alongside those things, are they are they do they remain risk factors? Are they or are they covariates? They work alongside other factors. So I think there’s just a lot of interesting work, we still got to do there, particularly, I mean, we’ve touched upon it, but particularly around peak height, velocity and those potential rapid growth spurt periods of what do we start to see in asymmetries around that time? And again, we don’t have that longitudinal data yet. So we can’t, we can’t really say how important that that asymmetry is. I think if we’re seeing significant asymmetries, we probably would want to work on minimising those, but you know, minimising them to walk 10% is still just out, it’s a bit like, it’s a bit like unicorns, isn’t it? We’re supposed to really like them, but they, they don’t really exist.
Rob Anderson
Yeah, I’m always very sceptical when there’s a very round number for a test. So anytime you like, yeah, to 10% I’m like, that’s a little too satis, you know, satisfying to our human brains of going, Oh, that’s a nice round number or, you know, any tests that are you going to do this for two minutes. I’m not one minute and 56 seconds. It’s exactly to me, you know, it’s just too well rounded for my liking.
Mark De St Croix
I’m exactly the same. So we call a 9.9, a low risk athlete and a 10.1, a high risk athlete. I mean, it’s a nonsense, which is why cut offs are difficult, which is why we might start to use different variables, you know, may be is someone two standard deviations outside of the mean of a group, and is that actually risk rather than 10%? You know, what’s the mean of the what’s the mean difference in the group? Oh, look, it’s 8% and therefore, are individuals that are two standard deviations outside of that mean, and that Risk athlete, that would be a far more logical way of looking at it. And also then makes it specific to that group to those kids who are participating at that level. All of those things we talked about, you know, training age, it takes into account all of those things rather than going, it’s 10% for everybody.
Rob Anderson
So dig a bit more into neuromuscular control for us. What are we actually when we’re talking about neuromuscular control? Obviously, we’re talking about the brain and muscular system working together, but what are the specific characteristics that we’re interested in, that we think may be playing a role?
Mark De St Croix
So yeah, I, this is one you’ve got me onto my bug. Bear in topic is, is the sort of, I suppose, inappropriate use often of the term, I’ve measured neuromuscular control neuromuscular function, what that actually what that actually means when someone’s done a counter movement, jump with some kids, and we start really talking about their neuro muscular capability. And it’s a bit like, we’re not really are we? So let’s be a bit cautious about how we look at those sorts of things. I think if you look from an injury perspective, and a little bit from performance perspective, it’s it’s how quickly that neuromuscular system can work. So we have I mean, every individual has a neuromuscular capacity that Max did that’s almost impossible to measure, we don’t really know what an individual’s capacity is. But what we know is someone’s neuromuscular capability. And we want the capability to be as close to the capacity as possible. Now that will change through through growth and maturation. But again, we banded around these terms a bit loosely, and I stick my hand up myself to say that probably when I did my PhD, I did this myself, or where I talked about neuro muscular maturation? What is that? What does that what does that mean? What does it look like? How does the neuromuscular system develop and mature, we don’t really know, because no one measures your muscular capability very, very well. And, you know, within the limitations of things that we can do with, I don’t think I get through my ethics committee indwelling EMG, probes into kids into kids muscles directly, you know, at the tendon or at the end unit. So, you know, the data is, the data is still limited. But I think what we’re talking about here, I mean, things that we can measure and things that we have measured predominantly, we might move from something like Lego Lin’s stiffness, that might give us some indication of stretch shortening cycle capability. And there’s quite a bit of work out there on kids now on on on that. But if we can get down to looking at sort of short, medium and long latency reflexes, and one that we’ve been mainly interested in, because it’s sort of been linked and associated with injury risk is electromechanical delay. Now, again, not an easy thing to measure well. But enough studies, as well with kids to show that it can be measured reliably. So if we can look at electromechanical delay during real world movements, which again, is the problem. So lots of those tend to be still lab based maybe on an isokinetic dynamometer. Where we can look up force generation, obviously. So that we can work out that electrical mechanical delay. That’s, that’s the type of they’re the type of things I’d like to see more of, but they’re just so difficult to do, especially when we still go back to factoring in all of the other stuff that we’ve already touched upon, you know, in terms of factoring all of that out in terms of maturation, and training age, and chronological age, and, you know, where we are in relation to maybe peak height, velocity and things like that. So, I think a really important parameter, but something that’s really lacking in the paediatric literature still, probably because it’s really difficult to do, which is, which is, you know, a bit of a common thing is sort of like, you know, we want to do it in real world settings. And it’s hard to do that stuff in real world settings. Probably as Tech Tech advances, we know, we know, you know, text got way better. And I’m sure eventually we’ll get some really nice, funky small wearable texts that we can use more effectively out in real world environments to be have a sounder grounding when we’re talking about neuromuscular capability and kids and how that links to both function performance and injury risk.
Rob Anderson
And you kind of touched a little bit as well on fatigue in terms of kids previously around, you know, your example of doing a big max test and then five minutes later being ready to go again effectively. And we know that you know, enzymes are slightly different in terms of you know, really, really young kids in terms of, you know, being predominantly aerobic dominant versus, you know, anaerobic. So I guess that leads to an interesting question around fatigue, because, you know, is there is does fatigue look different in kids and youth? And therefore, does it, you know, influence injury differently than perhaps in an adult athlete that is going to fatigue? How does that situation play out? What some of the specifics, or do we not know that yet either?
Mark De St Croix
I think so there’s some, there’s some really good work by Kelis on this on this area, sort of around around some of the fatigue related stuff, I think, and some of the work Sebastien Retal has done out France as well. I think we need to be careful of what we mean by the term fatigue again, in the first instance. I think what we tend to see now from sort of the oxygen uptake kinetics work, which is obviously really push this area forward is that kids tend to have those Fox faster oxygen uptake kinetics, so therefore, you know, they can glycogen spare they can they can, they can use those aerobic sources much, much quicker than than adults can. And therefore, you know, which is probably why we see this potential fatigue resistance. So there’s, there’s some work by Sebastian that suggests that through maturation, kids sort of lose that ability to resist fatigue, so and that it’s linked to a maturational effect. I mean, it’s an interesting, it is an interesting concept. Again, I still question how much really good longitudinal data that we’ve got that sort of really does plot that loss of ability to resist fatigue better than in adults. So it links back still to that thing about kids being able to be able to have access or even like Wingate tests, I mean, I don’t know about you, I still vomit if I do a Wingate test, kids, kids, you know, look knackered, and five minutes later, again, jumping back in the bike wanting to do it again. So so that definitely does seem to be something that that probably links to that oxygen uptake kinetics, my link, again, still limited data to some of the other things around lactate and quicker lactate removal or less lactate production. So underpinning exactly what it is that makes the kids a little bit more resilient to fatigue, I think we we still need to find out a little bit more. I think one of the things that we’ve done more recently is that there’s been a bit of a suggestion that kids don’t, this isn’t fatigue directly, but kids don’t damage muscle through exercise. So those few studies that looked at maybe CK responses, after you know damaging exercise suggest that the CK responses quite low in kids a couple of previous studies, ones that we’ve done more recently, where we’ve looked at CK responses like over a week in like professional football academy environments, we do see actually quite significant CK responses in kids. And so if we consider that more not necessarily fatigued, but in like a more readiness to re perform re compete replay perspective, are our kids are the kids ready after say a competitive match to retrain on the 48 hours later and then train again and again, again, given you know, workloads that they we know they now do in those professional environments now is their muscle damage, what’s happened to us to say stiffness over that period of time over say that that microcycle of a week from competitive match to competitive match. You know, we’re seeing in the work that we’re doing still compromised systems in kids as young as the under 10s. From match to the next match where stiffnesses still significantly reduced, they’re still high levels of circulating CK. But we’re asking them to re compete. And so does that put them both at risk and also at risk of reduced performance because of those factors. So there’s some really good stuff starting to emerge on that. And then longer periods because we don’t just isolate in the week, as we know, the kids are gonna perform the following week and the following weekend. They’ll be doing stuff in school as well as within the formal training settings. So the overall load is there. So that’s where we then talk about our hours about robustness, resilience and readiness. So can we factor in those potential fatigue, risks, fatigue and damage risks, to make sure that we’re building a system that’s ready, but also a system that isn’t overloaded? And we’ve already talked a bit about some of those overtraining injuries anyway or groups related injuries that we might that we might get alongside functional overreaching. So, yeah, I think I’ve given you a long Wofully answer there. But I think I think, you know, there’s some, there’s some interesting stuff around kids and fatigue, we might think that they don’t fatigue, but they, they probably do in certain ways, neuro muscular capability as well. We’ve done some stuff looking at EMD, like over a week, and it is reduced in kids. So that ability to you know, utilise that neuromuscular system is affected by, say, a competitive match. So we need to consider that in our practice programming and planning.
Rob Anderson
That’s really interesting. I guess, previously, my kind of thought process had been, perhaps is that reduced level of fatigue, because there’s a reduced ability to produce high forces, and then maybe there’s this trade off, that happens, you know, that as we become capable of producing higher forces, we kind of lose the ability to recover between them. But as he kind of suggests, perhaps there’s something else going on there in terms of electrical, electrical, mechanical kind of delay situation.
Mark De St Croix
No, I think that’s I think that is, is a really good point. I mean, there’s, you know, some people would suggest maybe that that sort of reduce force production capability is actually a sensible mechanism for protecting the immature musculoskeletal system. So we don’t want them to be generating high forces, because the bone density hasn’t been laid down yet. And all of those things, so actually, the goal, the goal, the tendon units, that’s maybe stopping us producing those high forces in kids is a good is a good thing. Although when you look at, you know, the type of forces that kids are still producing, per unit, kilogramme, body mass, they’re the same as adults, you know, they’re not, they’re producing less absolute force, but as a, as a as a per per body mass force production. They’re generating the same forces that adults are generating. So. Yes, yes.
Rob Anderson
Yeah, money. Yeah, it’s good. I mean, there’s obviously a lot of a lot of exciting kind of discoveries, I guess, to still be made in the area. So that’s part of, you know, part of what it’s great having people researching it, one of the things that has kind of popped up from time to time and you know, I guess, originally come out of kind of the propositions of this family, and that kind of crew was around the idea of windows of trainability of you know, this specific periods during our lifetime, particularly in childhood and adolescence, where we kind of have these, you know, almost these periods where we’re really maximising the ability to do this. And then perhaps we then kind of closes and we’ve lost the opportunity. Is there any truth to the concept of Windows or trainability? Or any, anything that perhaps people need to be a bit more critical of that?
Mark De St Croix
I think the answer to your question is no, and potentially,
Rob Anderson
doesn’t really.
Mark De St Croix
I would say, it sounds like I’m a bit of a broken record here. But you know, the problem with any of these sort of assumptions about Windows or trainability, is you need really, really good, robust, longitudinal data to make these inferences. And we just don’t have them, or we probably do have them actually, you know, now, we’ve got loads of data in football academies, where, you know, probably, if we pulled a lot of this data together, we could we could map some of this potential for windows of trainability. But I mean, I think what we what we do have is, we, we know certain things, so we know that we’re going to get increases in testosterone as we go through the maturation process. So we might say that, okay, of the studies that are available, we know that any changes in force production, in pre pubertal kids is more likely to be related to any sort of like neuromuscular maturation, rather than, excuse me dramatic changes in muscle cross sectional area, because we’re just not laying down big, big amounts of cross sectional area of muscle. So might we say that, during those periods where we’re getting changes in the length of the long bones, or excuse me, that actually we’re going to see more improvements in power because we get changes in muscle volume rather than changes in muscle cross sectional area. So we we could potentially infer that there may be times throughout this process, because we we know and we have identified that kids are interesting because they go through this period of change, which we don’t get with other with other athletes. So as you say, if we are getting these periods where we might be able to maximise something, then we should try and try and seek those answers to those to those potential questions. I think that if you look at what we have in terms of the models that are out there, they are quite sensible now, in terms of sorry, bear with me having a an internet problem there, sorry, in terms of the, the progression, and I’m thinking again of John Rodriguez, athletic movement competency models, where we have a suggestion that there might be periods where we might be looking at focusing on particular types of training, based on a whole range of factors, I think. And I think John Ward would probably look at updating that model where there probably still isn’t enough in there around some that training age and training quality. So can’t just say, well, we’ve got somebody that’s I don’t know, minus one year peak height, velocity, and therefore, right now, at this moment in time for that individual, what we’re going to do is, I don’t know loads of sprint training at this point, because sprint training is going to work for this individual one year post, pre peak height velocity, because there’s so many other factors that come into play about must that must inform our decision about whether that’s the right time to introduce sprint training, it might be that it’s not because they’re getting a rapid growth spurt, maybe around that time in the sprint mechanics all over the place, and therefore sprint work isn’t effective during that period of time. So the difficulty we have in saying that there are windows is what are the windows based on? For a start? Are they based on the maturational stage? Are they based on, you know, what do we base them on? And do we base them on multiple things? It comes back down to there for having really complex but in simple ways, individualised methods for deciding what’s best for that individual at that particular moment in time. And then we don’t really know based on the evidence and the data that we’ve got that if we put all those factors together, that they’ll get the get Bennett more benefits during that window than other periods of time. So the reason why I said maybe no, is that I think we just don’t have the data to say, yes, you should otherwise, you know, we’d be we’d all be doing the same thing, because we don’t know what we were doing. And half the time, we don’t know what we’re doing, because we’ve got a complicated puzzle in front of us. So a sensible programme that moves from, you know, that John and Rodri have developed from from unloaded farm, unstructured movement skill, competency type work through to more structured work, where we can start to load at specific periods of time, where we might see added benefits EEG, we got increased circulating testosterone, so we should get some benefit if we do more loading at that period of time. But we need to be able to have those foundational movement skills to be able to load at that period of time. So there’s loads of things that would come into the into play anyway, about whether whether windows would be effective, because if you’re in a window, but you can’t load because the person can’t move, then that window becomes irrelevant in some regards. So
Rob Anderson
injury prevention kind of set of things, and there’s just too many factors to be able to say, this is exactly what you should do. There’s, there’s lots of things going on happening that, you know, need to be individually accounted for, I guess.
Mark De St Croix
Yeah, and again, we want to be working. I mean, you know, we never want to be stopping and focusing anyway, I would say on one particular thing, particular moment in time anyway, because sport is multi complex and multifaceted and and, you know, to enhance performance, as well as reduce injury risk, we need to be enhancing all of the parameters that contribute towards that performance. So by going, Oh, we’re just going to focus on sprint work now for the next three months. What about all the other all the other stuff? That’s also probably equally important.
Rob Anderson
100% So what what have you got coming up mark in the near future? Whether it’s publications or research projects, anything that’s that’s piqued your interest or areas of, I guess, interest or excitement of things that are coming up in the future from from a research perspective?
Mark De St Croix
Yeah, so I mean, suppose most of the stuff we’re doing at the moment is around sort of coach education and coaching grassroots coaches to help with what we actually just described that model of what we want kids to be able to do. So if potentially there are our windows of opportunity that we can maximise those by saying that the kids move well, so yeah, do lots of coach ed ed, sort of work workshop type stuff to get those grasp Which coaches that don’t have knowledge, confidence and experience to be able to implement good movement, competency type training. So really training down at that level so that as those kids do or don’t progress through, you know, a talent pathway that they’re ready for that for that loading, but also that the kids that just want to do it for doing it have more fun because they move better and, and they get more enjoyment out of it. So, so I’m really enjoying doing that stuff at the moment. We’re also doing some work, which is quite exciting, with Southampton football club at the moment as part of their new learning lab that they’ve set up that some of your listeners may have sort of caught sight of, which is a really exciting project with the academy Academy looking at sort of coaching and skill development, skill acquisition, using new technologies. So there’s three PhD students that are sort of linked into this Learning Lab, not so one of them is with us, the others that leave Beth Kitt and one at Bournemouth. And now one is very much focused on sort of constrained Bates coaching, but also thinking about person centred rather than player centred approaches in developing good people, as well as good players and athletes. So that’s a really interesting project that we’ve got going on. And still still keeping my hand in with we’ve got quite a few ongoing longitudinal studies, looking sort of more at that fatigue and risk factors in kids, sort of over whole seasons, because some are poor Reese injury data. And actually, some of the Barcelona Football Club injury data as well seems to show two peaks in injury incidents in use players. So we’re wanting to look at why are we getting a peak, you know, a couple of months into the season, and then a couple of months after Christmas. And that date is quite consistent now. So what is that is that an accumulation of some form of fatigue effect where we’re, we’re getting higher risks athletes during those periods, and then how we can go in and hopefully reduce some of those risks. So as always, plenty going on.
Rob Anderson
You got loads of free time.
Mark De St Croix
I wish. So yeah, I think I think the more anybody listening than, you know, the more longer tuner we can get. And we know that the kids that are in longitudinal settings where we are collecting data is sort of in clubs. So I’d sort of like to see great sharing a little bit. Sometimes Sometimes we get quite protective, particularly in clubs where we think we’re doing something special that no one else is doing. The headline actually is actually no everyone’s probably doing it. And clubs are, are getting better at doing that. And the Premier League’s collecting some of that some of that more data through the Triple P. So you know, I suppose it’s a bit of a watch this space in terms of us, us all, learning and having more information about what happens to kids as they grow, develop and mature in this in this really complex time that makes them interesting to work with.
Rob Anderson
Fantastic. So what’s the best place for people to track you down? Is that ResearchGate? Is that social media? Where can people read about what you’re doing? And kind of, I guess, keep up to date with what’s happening.
Mark De St Croix
So yeah, if they want some really light bedtime reading, if they’re insomniacs, and they want to read any of the papers that we’ve got out there, probably just as easy. Most universities, now all of our papers are sat on our university repository. You can’t get all of the papers from there. So obviously through Research Gate, and if again, they’re embargoed on there, you can there are other ways you can access, you know, the papers. So yeah, I try and keep ResearchGate up to date repository. Definitely everything is on there because we have to post everything on our research repository. I’m reasonably active on Twitter, but I try not to get into Twitter discussions. So you might notice I’m on Twitter but I post and I retweet so I’ve been told I also need to sort out my Instagram and and Tik Tok accounts. So the old dinosaur in me will need to talk to my young children to teach me how to use all of these things. But yeah, at the moment, I’ll direct messages if you want to contact me either through my university email account or messaging me through through Twitter, I can reply to you through that. Oh, we got everything nowadays. And we I’ve also got our LinkedIn account. I look at that occasionally and get notifications from that. So people do contact me through that as well but I don’t use that quite as much. So you Yeah,
Rob Anderson
my fantastic definitely contact with them.
Mark De St Croix
Well, I try not to be I am contactable and you know, people contact me all the time, I’ll try and make time as much as I can, if people have got questions and queries, I’m more than happy to discuss this stuff. Because, you know, the, this is stuff that I enjoy doing and sort of solid stuff about university life that and work that isn’t quite so enjoyable. But you know, this is stuff we enjoy. So you know, you’ll find anyone in this area or want to talk about it, if you if you get in contact with them. Don’t be scared to get in contact with us get in contact with us. We’re happy to share, collaborate, and work with people give them ideas, they give us ideas as well, which is, you know, part of the part of the process. We’re all always learning. So, yeah, if anyone’s got any ideas of how we can measure neuromuscular function in the field with kids, I’d love to hear from you.
Rob Anderson
Well, thanks so much for your time. It’s been fantastic chatting and picking your brain because obviously got such a breadth and depth of research. That’s good to hear it from someone who’s at the front line. But I think you know what you’re doing in terms of the coach education for grassroots coaches, not only fantastic, but it’s vital. And I think there’s probably 1000s of coaches out there, he’ll benefit from it. So thanks for what you’re doing there. But really appreciate your time today. Thanks so much.
Mark De St Croix
Brilliant. Thanks for having me on. Rob.