Jared Powell:
Welcome to the shoulder physio podcast, a podcast dedicated to exploring meaningful topics in musculoskeletal healthcare. I'm your host Jared Powell. Before we begin, the primary purpose of this podcast is to educate and inform the views expressed in this podcast by myself and any guests are information only do not constitute professional advice and our general in nature. If you act on the basis of any podcast episode, you should obtain specific advice from a qualified health professional before proceeding
Jared Powell:
Today's guests are Franco imp Lazar and Christian Tobo. I invited Franco and Christian onto the podcast to discuss the punitive effectiveness of the Nordic hamstring exercise in preventing hamstring injury. The Nordic hamstring exercise is an established and widely used exercise in sport science and strength and conditioning research and practice. But does the evidence justify its widespread popularity tune in to find out this conversation was originally recorded in December, 2021 for my YouTube show on the shoulders of giants. Before we start the podcast, I'm pleased to announce that the shoulder physio podcast has a brand new sponsor. Clinico Clinico is our practice management software. That's used by 65,000 practitioners worldwide. It's great for busy physios, which is why it's an endorsed partner of the Australian physiotherapy association and the chartered society of physiotherapy in the UK. You'll find everything you need to run a successful physio practice in one place like treatment notes, digital forms, online booking tools, customizable body charts, and much more Clinico meets privately legislation for Australia, the UK, the us and Canada.
Jared Powell:
So wherever you are based, Clinico will help keep you compliant. In addition, charitable donations and giving back are a big part of Clinico. A minimum of 2% of all Clinico subscriptions are donated to charity each month, which means more than 1 million Australian dollars in total has been donated. Since Clinico was founded, shoulder physio listeners can get 60 days free signing up, takes less time than this message. Visit clinico.com slasher hyphen, and you can find a link in the show notes without any further delay. I bring to you the great Nordic debate between Franco and, and Christian and welcome one and all I'm joined today by two esteemed guests professors. We've got two of them here, Franco imp Plaz and Christian. Tobo welcome gentlemen. Thank you very much. Hello everyone. Good? Okay. So before we get to the core of the discussion today, I'm gonna introduce both of you all and there's some very long resumes I've gotta get through here because you are impressive people.
Jared Powell:
So just give me a minute. So Franco first Franco is a professor in sport and exercise science and medicine at the university of technology Sydney, where he teaches research methods and exercise physiology. Interestingly Franco started his career as a coach before moving into research later in his career. And I think this is a really interesting part of your story. Franco Franco has worked in clinical and research settings worldwide, including Italy, Switzerland and Australia. Franco has hundreds of publications to his name and his main research interests are training, testing, training load, and research methods. Franco has also been a strength conditioning coach of several elite athletes who have actually gone on to win gold at the Olympic games. So that's quite the impressive CV Franco. Gotcha. Not, not to be, not to be out done though. Christian, Christian's got an equally impressive CV and also reputation.
Jared Powell:
So Christian is a professor at Copenhagen university Denmark with a special focus on orthopedic and sports physical therapy. Christian's also a professor at London university in Sweden. So one professor ship's not enough for you. Christian gotta go for two that's good. Christian has more than 22 years of clinical experience within sports and orthopedic injury prevention and still works in clinical practice and consults for elite sports clubs and federations at a weekly basis. Christian has provided keynote lectures, literally all over the world. I tried to count Christian, but I couldn't count how many countries you've spoken at. Very impressive again. And Christian's research, which, and this is really cool, has been, has been mentioned in the New York times a couple of times, which is, which is no mean feat. Christian has published more than 200 papers and publishes publishes more than 25 papers. Annually. Christian has expertise in groin injuries in which he's ranked number one on expert scape.com and also hamstring injuries in which he's ranked 12.
Jared Powell:
So you've got some work to do Christian in terms of your ham hamstring injury rating. We'll look, we'll look for that to change. So I'm briefly just gonna give some context about the point of today. So goes without saying based on what, what I've just told you guys that Franco and Christian are highly qualified to talk about today's topic and that is the naughty hamstring exercise and its role in preventing hamstring injury. So before I hand over to Franco and Christian, I just wanna provide some context about today. So if you don't know what a Nordic exercise is, Google it right now. It's very easy. It's simply an eccentric hamstring exercise. And that's probably all that needs to be said about the Nordic exercise. So today's conversation came about cuz there has been some banter between Christian and Franco on Twitter of all places about what the research actually actually tells us about the role of the naughty hamstring exercise in preventing hamstring injuries and the headline of the naughty hamstring exercise is often naughty hamstring exercises, reduce hamstring injuries by 50%. And we're gonna get to Franco in a minute to address this question. But before we get into the questions I'm gonna hand over to, to Christian, cuz he wants to declare some conflicts of interest.
Christian Thorborg:
Oh, thanks for that, Jared. And thanks for, for setting this up really great opportunity to discuss this topic. Yeah. So basically we're gonna discuss the paper which has been publish in SM where I'm also the deputy editor. I've not been involved with the handling of this paper, but still it's important for me to say that this is a journal that I'm affiliated with and then I've also published a lot of the studies. So some of the studies that we're going to talk about today I'm the editor of the book related to hamstring injury prevention as well. That's probably the main thing. So I, I am not affiliated with making money on allic hamstring exercises, but but I do of course have some intellectual buyers related to, to this exercise. I just want that to be recognized before we start. Thank you very much.
Jared Powell:
Thanks Christian. Franco, did you wanna say anything before we get into the chat?
Franco Impellizzeri:
No, maybe that just I also had the conflict meaning with British journal per medicine. That's all, but , you know, there's an old story about our request of retraction predict project with chronic ratio. So my conflict was that one
Jared Powell:
Fair enough. Duly noted. Okay. So Franco question number one, I'm gonna hand over to you first is this 50% reduction in injury rate of hamstrings with the Nordic hamstring exercise definitive? Is it certain you've recently published a paper in the journal of clinical epidemiology, challenging this, can you please summarize how this paper came to be? And also what were the key findings of this review?
Franco Impellizzeri:
Yeah, I, I provide a bit of a ground because initially we wrote a discussion letter to the British journals per medicine, 800 words, just to underline a couple of of methodological issues and proposing the new forest plot just to show how the uncertainties was higher than the one reported for various reasons. The, the, the letter, the discussion was rejected. And therefore we decided to instead just focusing on, on a couple of issues, we reanalyze methodologically the, the, the topic and the review, and we decided to submit to a journal, which is a bit outside for medicine. And that's the reason why we submitted there because it's it's a methodological. So we want you also to be sure to have a, an unbiased radio and by unbiased, I don't mean easy reviewers. We wanted to be sure that our concerns were strong enough and journal clinical epidemiologists journal, specialize methodology, and they are absolutely outside our area.
Franco Impellizzeri:
So I'm quite confident that that the radio was quite open without any bias behind it, just evaluate the methodological quality. And we did that because we found some errors in the, in the, in that meta analysis. And so we analyzed the data and we select the papers based on their research question actually, but selecting using upper meters. So for example, we couldn't include a combined altogether observation randomized trials because this is a bad practice, unless very specific situation. So selecting the papers, just randomized STRs and recalculating, the summary estimates, the and, and also calculating the prediction in Teva, which is very important, especially in practical application, we found out that the uncertainty is, was much higher and, and therefore in general, you cannot say that it's 50% for a simple reason, 50% is the point Testament. So if you focus on the point Testament, you ignore the uncertainty and, and this is quite well known that you shouldn't focus on the point Testament.
Franco Impellizzeri:
In addition, these kind of analysis use a random effect model. So the 50% is not the effect of Nordic enhancing is just the main effect of a series of effect that theoric can have in the whole population. And, and, and this is a conceptual a conceptual methodological issue that is important to remember. So basically our conclusion was that the, the given this uncertainty, the, the estimates are just uncertain. So we can discuss later, which is because that's the main message and this not like someone tweeted that we, we suggested not to use NCA on these kind of things. We also wrote that we also wrote that while the uncertainty is high, we don't have even evidence to say that they shouldn't be used. So acknowledging uncertainty is just acknowledging uncertainty. It's not saying something against the, the, the Nordic ham string, or it's a question of reducing the expectations. So in summary, this is what we have done.
Jared Powell:
Awesome. Christian, did you wanna add anything or ask any questions of Franco or
Christian Thorborg:
Anything? No. No. I, and, and basically I agree with Franco and I, we also agree with their, with their approach. I think the letter provided by francospro is an excellent example of how to actually do a systematic review. And meta-analysis in many ways, I think it would be nice to sort of discuss the research questions that were originally proposed by Fania also by Franco and then by us, because basically we're sort of asking three different questions. So I think this is important to understand first. So that will probably be my, my first comment. So in the, I agree in the fanatic study that they're not looking at the Nordic hamstring exercise or the effect of that, the isolated effect of that. We totally agree on that. And we have acknowledged that previously, and we also acknowledged that in the letter. And I, I definitely understand the confusion around the DY study because it's, it, that's basically, that is what they're trying to investigate.
Christian Thorborg:
According to their research question. When you see it in the abstract, when you then go to their, their conclusion, it becomes a little bit more sort of difficult what they're actually looking at, because what they're saying there is that, that programs that include the exercise reduce, that's probably the most statement of all their statements, but that's basically not what they're out to do with their research question. So, so I think there is a difference if you look at, and again, that's, that's a very broad conclusion as well, because just because the Nordic ham exercise is the, in the intervention there somewhere doesn't mean that that's the effective part. That's also what Franco is suggesting. So we, we completely agree there. I think when you look at the three questions, I think , and, and, and Franco's question is what I would call a meter question.
Christian Thorborg:
So they're BA basically asking whether not the Nordic chemistry exercise is affected whereas, and this is I think that that's why we are trying to provide some context. What does that mean? Does that mean when you've done one repetition that, that you're protected? Does it mean you have to do 10? Do you have to do it for 10 weeks and so forth? And that's why we are providing a more specific question, because this is, has been our research from 15 years ago when we started, we wanted to understand whether an order ham exercise protocol is effective in reducing he. So I think that, that there is a difference there. And then you can say, well, why? I mean, so in some ways I agree with Franco. And, and why do you just ask a different question? I think it's, I think it's important to acknowledge that in soccer players, I think the uncertainty is not big as suggested from Franco's systematic, would my sort of counterargument
Franco Impellizzeri:
Franco. Yeah, I, I think, I mean, I agree with the, with the, with the questions of Kristen and, and these are normal questions, not only for the NAIC M state, but any kind of intervention. So when you have the summary estimate in the whole population, usually also medicine, what you want to do is to understand if there are sub population that can benefit more or less in that case can be even a, a specific sport or, or something like that. The problem is that, eh, we don't have enough data. And I mean, we re analyzed the data based on previous met analysis, we didn't create a new met analysis. So the first point that we should discuss is whether is is work to investigate, or to try to understand, for example, ma doing subgroup analysis or these kind of things, if you want to understand more, just using a bunch of, of studies.
Franco Impellizzeri:
And, and there are in several situations, there are people contacted me for running met analysis. But if you look in the literature, I have actually very few met analysis because I think Ize is a, is a strong instrument is, is very powerful. But if you have few studies, maybe it's not even worth. So you may ask why you, you, you, you made methodology with the six studies because it was done in the, in the literature. So we said, okay as long as you want to do this, you want to approach the problem in this way. You have to follow the rules, the rules of science. So we, we didn't suggest to, to try to, to answer to all these questions, using six studies, the, the, this agreement with the, with the perspective of, of Christian is more logical. It's more methodological because the, the, the questions are absolutely relevant.
Franco Impellizzeri:
So how much I have to do the dose? What are the subpopulation? This is absolutely the problem is that we don't have enough data to understand those questions. And our disagreement in the letter was that the, the selecting those two studies means the selected two studies, according to two different exclusion criteria that usually you don't combine because, or you select the population or you select the protocol. I agree that it's impossible to do with those six studies, honestly. So I think that the conclusion of the letter, so the reanalysis of the reanalysis of Christian ignore the, the study that are excluded, because usually what you do is you have a bunch of studies with some characteristic and other, with another characteristic, you compare the estimates and you say one is higher and lower. The, our disagreement, and in our replies that C basically omitted the others.
Franco Impellizzeri:
He didn't run a subgroup analysis. The other problem is that, and, and I, I, I, how open Christian understand why we were a bit strong in a warning about the risk of the cherry picking, which is not something you do voluntary. Sometimes I did in the past the same in voluntary, but I can also do the same. I can restrict a new research question to select specific studies, so I can say, okay, I want to see if only in north Europe using this kind of protocol. And and I can head other criteria so that I, I develop a research question to select a number of studies. And that's why methodology, usually you, you, you use everything you have and you run the subgroup group analysis. So I, I think that we disagree to the meter, but we agree the, with the, with the, with the goal and the necessity to understand those those questions.
Jared Powell:
Yeah. Yeah. Good. So I'm just gonna provide some clarity here. So, so because we're playing like there's analysis re-analysis and then re-analysis and letters and all this. So, so the first re-analysis from Franco was proposing some methodological issues with the Vandyke 2019 review published in BJ SM, and then Christian, and his co-author Christian, who is your co-author
Christian Thorborg:
Leslie, sorry. And I think it's important to acknowledge him because he's actually the first author. Yeah. He's a PhD student here with us. Yeah.
Jared Powell:
Awesome. Yeah. I just wanted to, wanted to get his
Christian Thorborg:
Thanks. Yeah. Thanks.
Jared Powell:
And then, and so you guys sort of proposed or hypothesized taking out two additional studies and then taking out those two additional, or taking out two studies, not additional taking out two studies, and then that actually made the prediction interval. Well look a little bit better. Is that, is that roughly where we're at here?
Christian Thorborg:
Yes and no, but because I think, I think the most important thing is here is, again, that I agree with Franco that there shouldn't be, there should have been done animat analysis on this. So, yeah, and we didn't, we didn't want to do that either. So it's not, we were in the same boat. You can say ASLE. If I were to look at the evidence today, as it is, I would say in 2008, if we look at football pairs, there was a crazy randomized study suggesting from Norway where they, where they didn't really randomize, but where they looked at two groups, somebody who did Nordic and somebody who didn't nor didn't do Nordic from two different countries. And they saw that if you did Nordic, you had a preventative effect around 65%. And this, because this quite a lot of bias in this kind of approach, we did the RCT in, in 2011.
Christian Thorborg:
And and actually, and I was completely biased against an audit, but we actually showed exactly the same. So there was a 65% reduction in he injuries once again. And then I would say, so this, these are two large studies and our study had 500 each group. And then that study was replicated by FHO in, in Belgium. Oh, in Holland, sorry, Nick. And they saw, again, a very similar result around 60% production in, in hams H. So this is one of the few protocols, and this was the same protocol across the studies that has actually been replicated by different groups in the literature. So, so for me, and that in itself, I think is a pretty strong evidence suggesting that, that this might be effective actually to the level of 60 to percent, but then I agree with you. It's still with, and I agree with Frankel that we still don't probably have enough high quality studies to do a analysis on this.
Christian Thorborg:
And I, I don't want to sort of sound bitter or anything, but if, if we are struggling here with the Nordic now with where we have replication, I think we are struggling with everything in, and this is just something we have to be aware of. And this is not an excuse welcome the robust approach by. So I would, I would say our sort of approach on, on reanalyzing, the reanalysis from Franco is, was more to say that that where we were coming from was actually only looking at teams, full teams and on soccer players. So, sorry, Australia, but we were actually not interested in in AFL or your kinda football with this question. And we've only conducted in male soccer players as well. So I think that's probably gonna be sort of the main counter argument against Franco, but at the same time, I totally agree. Franco, what do you think of that?
Franco Impellizzeri:
I, I think we, at some point we should discuss a bit about the quality of research that is out there, because the problem now I want to, to, to, to approach the problem from a bigger perspective, when we publish full studies, let's say we are adding noise. So even if we have good studies, we just put all the noise around and you may miss important effects. So as a, since we are both researchers as a scientific community, we need, I think we need to make the publication of poor studies much more difficult. And this is the first, in my opinion, the first consideration I would make based on, on, on, on, on the analysis of these studies that I agree, there are other areas in which you have even less studies, the problem of reanalyzing, the data, providing a different a different summary estimate is because I think that if we want to help practitioners, we don't have to create excessive expectations.
Franco Impellizzeri:
So I don't want to say that the, the, no, I mean, I I'm saying that actually, that, that, that made analysis created too much expectations because the, the 60, 70% of decreas in injury risk or whatever is huge. So when you implement something in, in medicine that it has this kind of effect, usually you realize quite often in practical setting. So I'm not saying that the estimates are wrong. I'm just seeing that the estimates may be potentially biased for various reasons, which doesn't mean that the study was bail. It means that this is normal in research because that's, that's what, I mean, we need more studies just to, to understand how all the results distribute around my concern with the, the, the, the second research question of, of Kristen is that for example, they exclude one study because there was a subgroup, but subgroups are very important in met analysis.
Franco Impellizzeri:
Because most of the time we want to know if there is a subgroup that can benefit more. I give you an example, even in the paper of Paterson, the paper of of Christian in the conclusion, they suggest that maybe those at higher risk may benefit even more of the Nordic chemistry. And this is something I agree. It it's possible. So if you look from this perspective, the study of selected a, a high risk group, of course, how to define high risk is a bit arbitrary. And, but this is for, for a lot of issues, but they, they had high risk group. So when you analyzing the methodology status, you can try to see if there is a subgroup, for example, the high risk group that can benefit more or less. For example, in that case Ang Brein is one of the few that run a per protocol analysis in their study and the per protocol analysis, basically comparing those data dear to the protocol compared to those that didn't the effect was even less less evident, and the answer was higher.
Franco Impellizzeri:
So this, just to say, that subgroup analysis and inclusion subgroup is something that we need actually to consider in a met analysis. Eventually we don't combine everything together and we separate and we provide different estimates, but the addition of subgroup is is clinically very relevant. So that's why we didn't agree actually, with the, with the exclusion of subgroup, we may agree with the subgroup analysis, but you cannot ignore that group because if we analyze the data and we, we may say that those that are, are at higher risk have no benefit, which is a bit strange. If you think is a bit, it doesn't sound so good. It may be a, it may be a problem of the study. Absolutely. I'm not saying, but even in the study of, of Christian Day, they, they discuss about these subgroups. That's why I'm saying subgroups are important when you, you analyze this kind of information. I, I know if C agree, Christian
Christian Thorborg:
I, I don't, I don't, this is probably one of the places where we, where we disagree a little bit, and it could be very difficult to sort of that, because some of it is think that if we look at Franco's study, that's also a sub analysis and we've done a sub analysis. And we also call it a post hoc analysis. We call our own a post HOK analysis. And I would say, Francois, if you look at your sorry, or your re-analysis, frankly, you, even though you say, you're looking at Nordic chemistry exercise, you also have interventions where you have stretching in, in the study. Actually, if the, if these players had other previous injuries, they would also have to do other sorts of program than the Nord chemistry exercise. So even there, you could say there's some kind of contamination. So you, you could even argue that you've, you've pulled out studies that are not completely the Nordic hamstring, isolated interventions as well. So I think we can go back and forth and say, are you, you have picked out the wrong ones, or you, you shouldn't pick out in this way, or so I think that's probably not very productive. I'm not saying ours is the, is the right way to do it. I'm providing some arguments for a way to look at it as well.
Franco Impellizzeri:
Yeah. I mean just to clarify, our was not a analysis, the, the reanalysis, because the problem is that when you want to examine the effectiveness, you cannot use the observational, especially observational study, which are poor. So the, the, you can use the observation of where you don't have randomized trials, or when you think that randomized Triess have problems or sub, or, or a very different groups and so on. So you can do that. You cannot combine. So we didn't run a subgroup of only randomized trials. We, we used the studies that are the necessary to answer to the research question of the original orders, not our research question. The research question was to examine the effectiveness, and this is what we have done. And in that case, effectiveness is because there are pragmatic studies, not because is, is because sometimes effectiveness is used in the context of our observational studies, but in that case, it's just because pragmatic.
Franco Impellizzeri:
So we didn't do any subgroup. We just select the studies that are appropriate for answering the research question. And, and the, the, the issue with anger Bradon is, and we, we have done this in the, in our reply, if you exclude and, and Brad, you still have a very wide prediction in tur. The only way to reduce is when you also exclude the, the, the other study that had a different protocol. But the problem is when you exclude, because at a different protocol, you in theory need to have a physiological reason and a strong reason to do that. So why starting very fast can influence the effectiveness of the intervention for the whole season. So in any case, these are two different criteria. So I may agree that the study of Ang breath can be a bit mixed. And so, okay. You say, we may exclude, but I don't see why we have add up the exclusion of the other, because if we always add new criteria, of course I mean, it's, it is not very useful.
Franco Impellizzeri:
So just to clarify, we didn't run a sub. Our was not a sub analysis. Our was the analysis that you should do if you want to answer to that question. And the observational, especially the one in the, in the, in the, in the ity should be excluded. And even if you want to include, because we, we have the table with the, with the few observational in reality that use only the Nordic caming. If you have a look to our table two, you see that there are other kind of problems. The reason one studying, which there were 102 and 12 injuries. And in the Ize, there were only 10 injuries. So 102 were, were missed. I don't think, I I'm sure there was not on purpose. There was just a, a, an honest error, but it was an error. So we didn't, we didn't wanted to, to go on in the direction of the observation about the data there. You can combine the observational, if you want, just to use the observation and you will see that the estimates are even worse. So just to clarify is not a sub analysis, is, is the analogy that, that they, that, that you should do. If you want to answer to that question, Christian,
Jared Powell:
Just before I go to go to,
Christian Thorborg:
Yeah, I would. Can I comment on that?
Jared Powell:
Yes, yes. Go for it.
Christian Thorborg:
Yeah. So again, I would say, cause if we go back to then the quality of the studies, I would completely agree with the Franco one, especially those small studies that are added to the analysis. I, I would totally agree that they, these are actually the studies that add a lot of noise. That would be my counteract and the, the, the quality of those studies are not very good as well. And, and again, I would also just highlight that the reason why we took out the, the Australian study was, was, was mainly because it wasn't on soccer, then we can it's, we can go back to the interventions probably later, because that's, I think that's very interesting as well is whether nor exercise can be defined as just that or whether there's very different approaches to actually doing that. That would be my argument
Jared Powell:
Franco.
Franco Impellizzeri:
No. Yeah. I mean we, we, we, it seems to me that the main problem we have is that there are not enough studies. So we have plenty of research questions and we don't, we cannot give an answer. The only thing I'm saying is that it's I, I think it's more honest to present. If you want to run a met analysis, you have to present the results, how they are without trying to, to, to, to propose in a way that are more positive than, than they are. They really are. So it's a question of transparency. And in my opinion, this is the way I always, when I work with the teams, the coaches, I always try to provide information. Not necessarily. We have to decide what the others have to do. I think to say, I think it's better to say, okay, this is the uncertainty.
Franco Impellizzeri:
It's up to you to decide if this risk is acceptable or not. Because one important point of the grade is that. And I think we, most of the time we, we forget is that one of the, the, the, the way, or one of the criteria to provide recommendation are the values and preferences of the stakeholders, because not all the risks are, are, are, are, are the same. And when I have to implement something, my team, I have to understand if the impact of the, the potential impact of increasing the risk when implement something is acceptable or not. I can decide to implement something which is very risky, because in any case, I'm in a bad situation and it can be, even if it's a bit worse, it doesn't matter, but there are other situations in which same intervention are too risky. So I think that really being honest with people and say, this is the uncertainty that we have, because the, the, the kind of approach that Christian made that in, in our opinion was technically not correct, can be made qualitatively.
Franco Impellizzeri:
So one can have a look and say, okay, these are the studies on soccer. There are these two big studies. They show some positive effects. I trust them and I do it, but it's different than going to the, I tell you, because that that's, that was my experience in working with some soccer teams, that it is different than technician, try to, to convince the managers, the coach, to implement Nordic camps and say, oh, we can reduce 50%, 60% or whatever. After this, this doesn't happen. And they are, they, they are fired. So it's different. If they say, if we implement this, there is a good chance that we have something. There is a small risk that maybe nothing happened and a very small risk that something bad happened, and they, they can make a decision. So, in my opinion, in this way, we, we help practitioners, which are not strong like us also to sometimes support scientifically the recommendations.
Franco Impellizzeri:
They just read something in a British journal for medicine, they say, wow, 50%. They go to the team and they say, we need to do that. And the managers don't give a about journals for medicine or science and medicine or whatever journal they, they say, okay, let's do it. Normally, there are players complaining. So that's always is it to implement and maybe something, something the, the next season, you don't see anything, or you don't see a drop in the, in the injury risk, whatever kind of injury. I think this is a bit dangerous. And I don't think this is what we should do. We should be honest. Say, this is the uncertainty it's tough to you. And you take your responsibility if to implement or not, because N caming are easy to implement in research, not that easy to implement in practice and Christian.
Franco Impellizzeri:
I mean, it's difficult to implement, not because it's difficult, the exercise because the environment, the culture is resistant. If I have to be honest, when I speak with people say, use some Ning, because if someone complain, you can say, oh, I, I, I try to do my best, their studies showing that it's effective. And so you can protect your back, but it's, I mean, we have to be because sometimes people think that when we, we enter in. So so, so in depth in the, in the methodology, we are academic, we are associated from the practical sector, I think is the, the deposit. The reason personally, why I care about the methodologist is because I want to provide to practitioners information or reliable information,
Christian Thorborg:
Christian. Yeah. Again, I, I, I think that, I think one of the, the main thing that you could take out of our sort of re re-analysis is also that the hitters was solo well compared to, to the other studies. And, and that seems to suggest that there are studies that might be more relevant to compare than others. And I, I think that's what I would promote to the strength and conditioning coach who came to me as said, I would, I would rather be based on large high quality studies than based on a summary statistics, including everything where the, the mean is 50%. And I would Franco in relation to, to the study, he he's criticizing there. I would also that Franco did a much better job, the original and a more correct job in trying to do a missile analysis of these papers, but still, we are just providing, trying to understand whether this actually works in soccer. I, again, we, there are some studies in there that shouldn't be there in our, if you want, really, to understand how it works in, I think that's our main argument. And, and again, also just highlighting that probably the mid analysis, neither of them should have been done in the first place.
Franco Impellizzeri:
Yeah. But there were thread before and now there is a for analysis. That's why we re analyze, because as I said, if you want to, to play with the, with science, you have to respect the
Christian Thorborg:
Rules. But I agree with that, but that was not our suggestion to do that major analysis.
Franco Impellizzeri:
Yeah, no, I understand the point. It's not true that examining this, even analyzing and running this kind of studies is very complicated because something that we don't consider OC observational studies is that we have a lot of competing events. So if you focus on MC injuries and you analyze the two groups, only based on the MC injuries, you, you, you never know if there is an effect of the other kind of injuries and this is very difficult to control. So I appreciate, I know it's absolutely difficult to run these kind of studies. The, the, if I can suggest something is that maybe we can try to, instead of combining all the summary estimates, maybe we can follow what the medicine they are doing in the last years with the individual patient data, mid analysis, or trying to combine the individual data. So we can maybe try to control for all these potential confounders that we cannot do when we just have the, the, the, the summary estimates or the summary of the status, because basically the unit of analysis is one study.
Franco Impellizzeri:
So if you have six, you have six points, but if you can combine all the data, this is much much more powerful. So I think that the future, because I think we have to provide something, some suggestion for the future. I think the future is associated to more transparency and data sharing. I can tell you that I, for another topic training load, I try to, to have a previous data set to reanalyze and to show for example, that there were some issues, methodological issues, but I, I, I couldn't find anyone sharing the data just one and is the only study that we we use. And to tell you why I think this is important because I, I don't want to, I may ask the money and run another randomized trial to show that analyzing the data, the results may be different, something like that, but it's a waste of money. I mean, we already have some data why we have to ask this data. So why we don't, we combine the, the data that we already have, and we try to analyze in a better way. That's just a suggestion,
Jared Powell:
Christian.
Christian Thorborg:
No, I, I don't, I don't disagree on that. I think it's, it's, it's easier said than done. I think if you want to understand all the, the other injuries these players have, that that's the much more, that's a big task. It's, it's difficult enough to do a large T I'm not saying it's impossible. I just let's look in Australia. They haven't been near doing an ity of this size that has been done in Europe. So Franco is asking for better quality. And so I think, I mean, we are, we are very far from, from getting there. I think one, I think let's increase the numbers in our studies first. Let's not do underpowered studies. There's, there's too many of those as well, but I, I don't disagree with, with Franco suggesting, but if you have to know exactly what happens to all players different kind of injuries, you need very, very good surveillance for
Jared Powell:
Sure. Yeah. Yeah. Cool. All so just in, just in coming to, to the end here, I wanna, I wanna finish off with some, some closing comments. So Christian, I'll start with you. So based on the research, wh where are you at intellectually philosophically in terms of the implementation of Nordic hamstring exercise, let's, let's limit it to, to male soccer players. Is it something that you recommend that, that most elite or recreational sport teams should do to physiotherapists who, who treat for those teams or do, do you sort of leave it up to them based on the players, the culture, the wants and the needs, etcetera. Etcetera. So just, just where are you at? What's your opinion based on the state of play of the evidence.
Christian Thorborg:
If I, this is not gonna be a short answer. Cause I, I would really like to elaborate a little bit on this. Sure. Instead of me trying to tell everyone what they should do, I mean that that would not work. So what I would, and, and we have data to show that as well as Franco says, it's not the compliance and adherence to Nordic is not very good. And it's probably even worse in Australia. Maybe it's getting better in, in soccer actually because they they're using it as part of the performance. The, I know there's some work, but they actually use in. But if, if we go back to the history of how this all started, it was actually sort of, I come from Scandinavia where in the early two thousands this intervention sort of developed, and at the same time in Australia, there was also these hams develop.
Christian Thorborg:
So they were developing sort of in two different areas of the world. The one that that came out of Scandinavia is, is the one we, we are looking at in our studies. So that was came in beginning from flywheel. And then it was used as an auto ham exercise. And it actually came from the field as well. So these were athletic trainers, track and field who used this for performance, but also it came from Iceland football where they saw that they, it seemed to help them. So it was not something in, in invented by researchers. It came from the field and then it was actually tested quite rigorously in, in course, randomized and then randomized, the protocols were very much these eight to 10 to 12 week interventions where you start off very, very slowly, two times five. And, and so you only do 10 repetitions in the beginning.
Christian Thorborg:
And then you build up towards doing 30 repetitions in a, in a, in a set. And then you build towards doing that three times a week. So you're building volume, but very, very progressively. And you can control delayed onset muscle saunas by doing that. I would argue that that is how you have to do it. Whether you have to go all the way up to 90 a week, that's a different discussion, but you need to be very careful and you need to progress very carefully and you need to make sure that you don't get delayed. Now, here is my main point. This is what happened in Australia, in Australia at the same time, hemps lows were introduced in some studies from Camilla Brockett. The intervention they used here was, and this is also what we are alluding to was actually probably more to show how there was a shift in the, in the curve and the descending limb of the, of the curve in relation to the peak ankle.
Christian Thorborg:
So basically that you were getting stronger at longer length when you were doing a lot of Hampton lowers. And basically what they did is what they did. Six repetitions, 12 and 12 sets of that. So imagine doing 72, NDIC in your, on your first training day. So this is what they did. And this was what was implemented in Australia in the study by GA. So this was the first time this was actually introduced to, to the AFL. And then what happened was that they were not very keen to begin with. So 70% went to the first session and after the first session, they had thumbs like crazy up around six on a soon to 10 scale. And what happened on the next session. And they were only supposed to do this five times during a period of, of of every second week. I think then on the second session, only 30% of all the players actually turned on and I, and this naughty hamstring got a very old Hampton laws or whatever, got a very, very bad rep.
Christian Thorborg:
And I don't think the exercise ever recovered from that in industry. So I think you can apply this intervention. And this is our also our point in a very, very pro way. And it might be even be detrimental to your players. I think I'm quite positive, just like you can over sprint your players and make them sore and have injuries the next weeks, if you wanna. And so that's why I don't want to provide a simple answer, but I think that we have data that if you apply this in a sensible way, it looks very, very promising and it has been written. So yes, we use it in soccer here in Europe. I think it's been implemented in soccer in Australia, and I think it should be in there somewhere in the FIFA 11 plus it's only 15 repetitions they have to do so it's, it's much less and I'm, I'm, I'm prepared to die on that hill unless somebody do does an equally good study, high quality, high number numbers target to show that it's actually half, then, then, then I'm, I'm prepared to, to to say that's okay. So I think if, if that's probably, that would be my answer. I, I can't tell you what you should do. I think you need to have the background of the history of this to try and understand a little bit how you could probably use it as a, as a strength in auditioning coach or physio.
Jared Powell:
That's very elegantly articulated. Thank you, Christian. Frank, what do you think?
Franco Impellizzeri:
Yeah, I think that once a team or coach want to implement an exercise, they know usually they know how to implement. There's no one that start with a very high load. So usually they normally progress whatever they do, they always follow progression. So I think that the way I interpret this kind of studies is to extract the principle. So if the principle is that training, the hesing is beneficial. How I reach the goal the, the target the target repetitions. I think this can be individualized by any team, any coach regarding the buy in of the team. I dunno, this is depends on the experience. My experience in professional soccer in a couple of countries is that that is not that high, the buyin and the, but I, I think the idea that they don't implement maybe a bit misleading because maybe they don't implement the NDIC hesing, but I know I have friends using other kind of exercise that lift breeds or fly wheels.
Franco Impellizzeri:
And so they train the, the hamstrings. So the, the, the, the idea that if they don't do NDIC hesing, this means that they don't train NDIC hesing is not actually always the case, at least. So they train. And one of the main discussion I had when maybe I suggest, why don't you add the couple of sets? So you're, you are safe. You can protect your bed, but already train the, the Nordic hesing. So usually here, there is a, a common question. Do I have to include the NDIC cancer because is an century training. This is the reason why you are saying, or suggesting to use the NDIC ING. And this is a question that, in my opinion, we cannot answer because the reason why the NDIC cams in any case is one of the most implemented in studies, because I don't think there are a lot of other exercises implemented so much in terms of injury prevention in, in studies, as, as Kristen said, actually is because it's easy.
Franco Impellizzeri:
You don't tell you don't need any equipment. So there's no the, if you want to implement the flywheel and you want to run a randomized study on flywheel, it's much more complicated. You need the, the device you need, the, the half of the teams have this kind of device. You don't need one, but more. So it's PO it's very difficult to implement. Now, can, it's easy. It's like implementing in theory, sprinting, it' something you can do easily. And that's why in my opinion is very investigated. And that's why it is interesting, for example, for amateur teams, because the professional, they have a lot of equipments. They can train Yas in tons of other ways. Since I started my career in amateur team, I didn't have anything even, I didn't have a gym. So in that case exercise like Nordic Stein or, or other kind of reverse exercises are very good.
Franco Impellizzeri:
But in terms of whether it is, for example, it, the century training that makes the Nordic Stein potentially. So a good, I dunno, actually, because we, what we would need is a study, which we compare a concentric and, and Contra group, and we know that it's much more difficult to do. So I think that I, I agree you, you should progress if we think to the same study in terms of research, I agree a bit less. I mean, first of all, we, we, the way you have to, the way you can progress, there are different ways you can, and that you can use to progress because you can just hold less the, the, the Nordic, and this is a way that normally you, you use to, to progress. So the, when you become stronger, you hold for a longer time. And this is one of the good things, also, in my opinion, one of the confounding factor, because you train, you change the, the, the length of the fibers at the same time. So it's difficult to understand when you test, for example, the strength. So I think there are different ways to progress with the load, not only with the, with the repetitions, but also with the, with the holding less. So, so I don't know if I don't have a direct experience or what happened 10 years ago for that study or that kind of implementation, but I, I think that there are different ways to implement an exercise
Jared Powell:
Christianity, last thoughts then.
Christian Thorborg:
Yeah. Yeah. If I could have anything to that as well. I think consistency for me is the, the biggest thing is, so I think, and when I go to clubs also professional clubs, I think that's what I see all the time is that yes, they have all these machines, they have all these exercises, but there's no consistent approach in place. And what, and I think actually when you look at the two large studies, the one from Peterson and the one from F the interesting thing is that when you look outside of the intervention period, so then you actually have very, very few injuries. So it seems to suggest also biologically that there is an adaptation going on and that you are, it takes time to protect these players. So we have six injuries in, in 450 players in the Peterson study, and we have six injuries in 250 ish players in the fend horse study after the 10 to 13 weeks intervention.
Christian Thorborg:
So it's just to say that, I think it's just like, and these are vaccine days and times I think it's important that this has to, to work first, we need the adaptation. So I think that is one of the main points I usually make. So I, I would probably agree with, frankly, I think you can get your adaptation from many different exercises in many different ways. I'm not so sure that you can just shuffle around between different exercises and it doesn't matter what kind of program you install. I think it's very, very important. And I think that's, if I were to guess on something, and this is why I think I still have a role when, whenever I come out somewhere, this is the first thing I always ask them. What is your sort of approach and what is your program in place? And I get often surprised at the highest level about how little overall approach they, they actually have. So I think that would be my sort of experience from this. So I think there's room for improvement, not in relation to necessarily just what exercise, but also what is the consistent approach you're, you're trying to, to implement, to address this issue.
Jared Powell:
Yeah. I agree with you there, it's all a little bit ad hoc and random in a lot of these, these environments, which is quite surprising from the outside, looking in when it all looks very SM and professional and, and well run. So that's the point? Well made Franco any, any thoughts?
Franco Impellizzeri:
No. I mean, the, the, the implementation is always complicated in professional setting, whatever the, the strategy and I, I, I, I have an idea that there are a lot of stuff that work well anyway, so I'm quite, I think they're doing their best to prevent injuries. So I'm not very, I'm not negative about the implementation. Maybe they don't implement that exercise or other exercise, but they do a lot of things. So I, I, I, I, I think that, I mean, non camps thing is interesting is absolutely. And I'm saying is not, I just have the feeling that is a bit overestimated. And if we talk about practical experience, I think that if you have something that has a 60, 70% of efficacy, as, as long as one implement and they see a drop, they would always keep that kind of exercise. Normally, when I discuss about these things, people say, yeah, but you know, it's multifactorial.
Franco Impellizzeri:
Yes. It's also multifactorial in the study. So if you seen a study, you have to see your in real life. I, I, I want to add something else regarding the methodology. I said that the observation of studies are not am good enough. The one in, in, in the analysis to answer to a causal question, but observational studies are a good kind of design if properly done. So randomized trial is the goal standard, but there is a lot that can be done with observational studies. But the problem is that they necessitate a very, very accurate methodology. Otherwise it's easy to, to, to, to arrive to wrong conclusions. So since I, I focus on randomized trial in the, in the methodized and everything, but I want to say that observation are absolutely something that probably we use very bad. I mean, a case control has a very bad reputation in general, but the case control is very powerful.
Franco Impellizzeri:
It's using medicine for rare diseases and these kind of things, and they are done very well sampling the control in the proper way. So I think that even in terms of injury prevention, we can rely on observational studies to have information that are estimation of causal effects of course, but is better than nothing, but we need to improve the methodology. Not only because the problem is that is that also there are randomized trial. And Kristen, I know I agree is that I randomized trial, but I would never try that randomized trial. I trust more an observation well done because having the label randomized Australia doesn't mean that is, is good as is well done. Randomized Australia are prone to a lot of confounding. Anyway, when you lose someone, when you have dropouts, you have, you are basically losing the randomization. So you are risky to introduce bias and you have to compensate in some ways. So I, I think that to answers to some of the question that's also Chris generalized observation study can be not the best solution, but can be a solution. That's my final consideration,
Jared Powell:
Christian.
Christian Thorborg:
Yeah, yeah, no, I would add to that. I, I, I completely agree. And if I could, if we could switch some of all the risk factor studies to observational studies with intervention, I would, I would prefer that I think we have way too many risk factor studies because they're easy to do and they, they just confuse us. So I would definitely go much more towards interventions at R C T level sometimes, but also back to observational studies where you actually also, and also to implement implementation studies to try and see how does it actually look in the real world when you then try to implement, do you have a similar effect? So I, I completely agree with Franco and I think we are not doing that well enough. And we could, we could really help a lot there. I think, so. Totally agree. Good point.
Jared Powell:
Good to end on agreement. Gentlemen. So I was gonna, I'm gonna finish with a couple of frivolous questions if you don't mind. So do you do either of you do the Nordic hamstring exercise in your own routine, and if so, how low can you go?
Franco Impellizzeri:
I mean, I can, so I, I have my, my rack, so I, I, I use dead lift squatting and, and bench press. These are my three, the three bigs that I use. So for, I don't do Nordic, but I have some athletes that use Nordic canvassing.
Jared Powell:
Yeah, cool. Christian.
Christian Thorborg:
And for me, it's, I don't do it systematically. And I don't get, I, my running is so slow now that I can't get a empty injury anyway. So but I, I do it especially so that I'm able to show it to the athletes. So I keep it up a little bit. So I'm actually able to show how, how it should look. That's probably the, the, the minimal dose I get.
Jared Powell:
Hello. Can you go, Christian? Is that you? That I see it all the viral videos on Instagram.
Christian Thorborg:
No, but that's actually, I, I disagree with how low can you go? You have to hit the ground. So that's the main point is that you actually, you fall down and you resist for as long as you can, and you have to activate as for as long as you can. It doesn't matter how low you go go or whether you can come up again. It's, it's it's a sober max exercise, and you need to sort of resist the fall all the way. So I think that's actually a misconception of the exercise as well. Also those who show what they can hold and what they can come back up from, I think is, is is the wrong way to do it again.
Jared Powell:
Mm-Hmm so whilst it looks impressive, it's, it's no more effective for injury prevention.
Christian Thorborg:
I think it could actually maybe be counter effect.
Jared Powell:
Ah, that's a really interesting point. Franco, do you add anything to that?
Franco Impellizzeri:
Nope. I mean, okay. It makes sense.
Franco Impellizzeri:
As put any exercise, actually.
Jared Powell:
Yeah, very true. And just, just lastly guys I always ask this question dorm, I guess I didn't tell you about this, cuz I, this is fun to see what you're, what you actually can come up with on the spot. So what, what book are you reading right now? It can be any book or what TV show are you watching? And I'm gonna ask both of you this. So, so Christian, I'll put you on the spot first and foremost. Are you reading a book or are you watching a TV show?
Christian Thorborg:
Oh, I'm I'm watching downtown happy with my wife.
Jared Powell:
nice. One nice one good show. yeah.
Christian Thorborg:
So yeah, I think it's, it's a lovely show. Yeah.
Jared Powell:
There's plenty of seasons to get through as well. So it can be apart for months.
Christian Thorborg:
I, I, I do fall asleep as well, so I have to go back from time to time. So it takes quite a long way to go through it all.
Jared Powell:
Yeah. You're you're that guy falling asleep on the couch. That's good. Frank Guy. What about you?
Franco Impellizzeri:
I dunno. He's to answer because you think I'm a nerd, but the book I'm reading now is statistically thinking. So that's, and, but if you ask sense
Christian Thorborg:
Me,
Franco Impellizzeri:
But if you ask me about what I'm watching, I'm absolutely a nerd. So I'm watching now. Okay. Dexter blood the, the, okay. I have the passion, this kind of so the, the
Jared Powell:
That's good
Franco Impellizzeri:
Cartoon, Marvel DC Titans, which then it's not bad.
Jared Powell:
Cool. I've just finished watching the UUs documentary on Amazon prime which was a, which was a pretty cool, pretty cool watch to see all the guys at work and there's, they, I didn't see any Nordics taking place. But Ronaldo's got some interesting thoughts.
Christian Thorborg:
That's my son's favorite club. So we, I watched that with him as well.
Jared Powell:
Yeah. His what'd you think about, about the behind the scenes, it's a with the physios and the sports medicine set up, is it typical from your experience Christian?
Christian Thorborg:
You don't get a real insight from that? I think, but I, but so I wouldn't judge on that I think, but I, I, I love to see those kind of, of serious as well. And
Jared Powell:
Yeah, I think they're really, really cool.
Franco Impellizzeri:
I never watched that because most of the time they're. yeah, I know that what document, but I know some documentaries on things that I Inish, so I really don't trust in, we have a PhD student by the way, so we know what they're doing, but I mean, the documentaries are, are shows though. U usually
Jared Powell:
I, I don't even watch them. It's entertaining. Plus you get to see Christiano walking around with his shirt off and he's in pretty good condition for his, for his mid thirties. So respect to him. All right. All Jen, I'm gonna, I'm gonna wrap this up. So again, thank you so much for your, for your also your commitment to, you know, open science in opening up these conversations for everybody to listen to. I think it's really respectable so well done. You can follow Franco on Twitter, no problems at, at Franco IPEL and Christian here is at K to Borg, and I'm gonna reference all of these below in the show notes. So thanks very much guys. And I'll, I'll see you next time. Thank you. Thank you for listening to this episode of the shoulder physio podcast with Franco Impala and Christian to ball. If you want more information about today's episode, check out our show notes at www dot shoulder, physio.com. If you liked what you heard today, don't forget to follow and subscribe on your podcast player of choice and leave a rating or review. It really helps the show reach more people. Thanks for listening. I'll chat to you. Soon.
Jared Powell:
The shoulder physio podcast would like to acknowledge that this episode was recorded from the lands of the Yu Gamba people. I also acknowledge the traditional custodians of the lands on which each of you are living, learning and working from every day. I pay my respects to elders past, present and emerging and celebrate the diversity of Aboriginal and Torres Strait Islander peoples and their ongoing cultures and connections to the lands and waters of Australia.
