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[Physio Discussed] ACL injuries: prevention, recovery & the road ahead with Dr Matthew Bourne and Dr Tyler Collings

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In this episode, we discuss everything about ACL injuries. We explore: 

  • Role of biomechanics of ACL injury
  • Are current ACL injury prevention programs effective? 
  • Use of Functional MRI in ACL rehabilitation
  • What are the long-term consequences of ACL reconstruction? 
  • Injury risk post ACL reconstruction

Want to learn more about ACL Injury incidence and prevention? Matthew Bourne and Tyler Collings recently did a brilliant Masterclass with us called “Mastering ACL Injury: From Incidence to Injury Prevention” where they go into further depth on this topic. 

👉🏻 You can watch their class now with our 7-day free trial: https://physio.network/masterclass-bournecollings

Dr Tyler Collings is an early career researcher at Griffith University, Gold Coast and a member of the Australian Centre for Precision Health and Technology (PRECISE). His research focuses on lower limb injury prevention and rehabilitation using neuromusculoskeletal biomechanics and field-based human movement technology. 

Dr Matthew Bourne is an Associate Professor and research leader in the Australian Centre for Precision Health and Technology at Griffith University. As recipient of research fellowships from Advance Queensland and MTPConnect, A/Prof Bourne and his team partner with industry to develop and apply next-generation, clinic-friendly technologies to identify athletes at risk of injury and inform the design of personalised, evidence-based prevention strategies.

If you like the podcast, it would mean the world if you're happy to leave us a rating or a review. It really helps!

Our host is @Sarahyule from Physio Network

SPEAKER_02:

What is the role of biomechanics in understanding and preventing ACL injury? And are current injury prevention programs effective? Today we explore all of this and more in our Physio Discussed episode with Matthew Bourne and Tyler Collings. Matthew is an Associate Professor in the School of Health Sciences and Social Work and a Research Leader at Griffith University. As a sport and exercise scientist, Matthew partners with industries to develop and apply innovative, clinic-friendly technologies to prevent injury and to optimise human performance. Tyler is a researcher and lecturer at Griffith University. His primary research interests are in ACL injury prevention and rehabilitation and field and clinic-based technology for assessing biomechanics. He has published several high-impact articles on topics such as risk factors for lower limb injuries in female athletes and the impact of prior injury on strength and biomechanics, muscle forces during exercises, and assessing landing biomechanics. Be sure to click the link in the show notes to watch Matthew and Tyler's masterclass for free with our seven-day trial. I think you're going to love today's podcast. I'm Sarah Ewell, and this is Physio Discussed. Welcome to the podcast, Matt and Tyler. Thank you so much for coming today.

SPEAKER_01:

Thanks for having us.

SPEAKER_02:

Well, you've done a fantastic masterclass, which I'd encourage all the listeners to dive into after this, but we might as well dive straight into it with my first question of what is the role of biomechanics in understanding and preventing ACL injury? In

SPEAKER_00:

my opinion, and maybe it's a little bit biased as a background as a biomechanist, but ACL injury is really an injury that biomechanics are really central to. If we boil down injury down to being an issue where there's too much load on a tissue for the amount of tolerance that tissue has for the load, then in simple terms, it breaks. And so we can think of ACL injuries in the most simplest sense as being an issue where too much load has been placed on a tissue and the tissue breaks because it doesn't have the tolerance. So in that sense, we can then think about if you want to prevent injury, you have to somehow either reduce the amount of load or increase the tolerance of the tissue. And the majority of research and approaches to preventing ACL injury is typically about trying to find ways to reduce the likelihood that someone's going to load their ACL excessively. And so in that sense, it's an issue where the control of movement, the coordination of muscles is really the decisive factor to whether someone is going to generate a non-contact ACL injury. So in that sense, for me, biomechanics is really the central focus of injury prevention and trying to reduce the chance of injury.

SPEAKER_02:

Thank you. And Matt, before I get your thoughts as well, can you tease out a little bit what you mean by biomechanics is central to that?

SPEAKER_00:

Yeah. So the kinematics of movement, the body positions, the joint positions, and the interaction with the ground. which is going to generate loads about the knee. The reason why the ACL is so susceptible is because the knee joint is inherently very unstable and it sits in between the interaction between the trunk, which has the torso, the upper body, which has a lot of mass and the high impact forces with the ground. So it's really that weak breaking point between those two masses and the It's when the alignment of the upper body and the foot placement creates really high joint torques around the knee. There's really high muscle forces because of the explosive movements that are performed in sport. The combination of those two will create the loads that are required to drop to the ACL. So the movement of forces is basically in a simple sense what I mean by biomechanics.

SPEAKER_02:

Fantastic. And I think we'll tease that out a little bit later with regards to what that actually means for our rehab programs. Matt, what are your thoughts on the role of biomechanics in the understanding and prevention of ACL injury as well?

SPEAKER_01:

Yeah, look, I mean, I'd really echo what Tyler said. There's no doubt that ACL injuries, like all injuries, are complex and multifactorial, but often that's used as an excuse for, well, we can't measure all these things and so we can't change them. There's undoubtedly a whole host of things that might go into a training intervention or a strategy to reduce the risk of ACL injury. But I think ultimately, if we think about injury as its truest mechanical sense, as Tyler said, things break when there's too much force for the tissue to withstand. And so I think that's a useful framework to approach ACL injury prevention, but probably all injuries as well. And it gives us some guiding principles to understand, well, what are the actual things, what are the mechanisms that we need to change? I think to Tyler's point, almost everything that we do now in the published literature, at least, is around trying to reduce the amount of force or load on the ACL. We see a lot of strategies around changing movement strategies, postures, things like that, changing coordination patterns, for example. There's been little to no published work that I'm aware of that's looked at the other side of the equation, which is whether we can actually change the strength of the ligament. And I think that's an interesting field of inquiry moving forward. I'm not going to sit here and speculate about what we should or shouldn't do, but I think it's an interesting area that hasn't been very well explored yet.

SPEAKER_02:

For sure. And on your comment about injury prevention programs, what's currently out there that's commonly used and are current injury prevention programs effective?

SPEAKER_01:

I mean, I'll let Tyler jump in on this shortly as well, because he's actually leading a exercise and sports science Australia position stand on this at the moment. So very across a lot of this literature. But I think what we do know is that, you know, these multimodal generally warm-up style interventions, things like K-11, footy first, there's lots of different examples of these depending on where you are in the world. We do know that these sorts of programs are generally effective in reducing the risk of an ACL injury occurring. And I think they're a very good starting point. I'm a sport and exercise scientist by trade, not a physio, but I think I probably look at it through a slightly different lens. And when I prescribe training, I think about, you know, what are the adaptations that we're stimulating, promoting from this sort of an intervention? And then what's the effect of those adaptations on patients risk of injury potentially. And so I think if we have a deep dive into a lot of the interventions, they do work. But if we look at the underlying populations, they generally work in fairly young, adolescent, mostly recreational level athletes. Most of the evidence is in girls and women. There's actually surprisingly sort of little supporting evidence in males. And there's also a really limited evidence base in higher levels of competition. I guess one of the challenges with the implementation of these programs is that in elite levels of competition, these interventions are rarely performed or rarely performed as kind of prescribed. And I think a lot of researchers think, well, if only we could just get athletes doing interventions, we'd solve the problem. But I'm skeptical and I'm not sure it's that simple because I just don't think that a very highly trained athlete is going to respond to a warm-up style intervention, which is mostly bodyweight exercises and doesn't have a lot of high intensity tasks, doesn't have a great deal of progressive overload. I'm just not sure that they would respond in the same way that a relatively untrained individual might. So I think there's potentially scope to improve these interventions by tailoring them a little more to the individual. So I would say these sorts of programs are a great starting point. But then when you've got more sort of elite levels of competition or populations that haven't been studied all that well in these studies, then perhaps we need to individualize and personalize the interventions a bit more. This is where we're starting to do a little bit of work. It's in its infancy, but we look at it through this framework of injury mechanisms and biomechanics and can we reduce the load on the ACL or can we increase its tolerance? And one of the things that we're starting to play around with is can we start to target specific muscles that might actually unload the ACL in some of these high-risk tasks? And so we've got a master's student on that topic at the moment, but that's kind of the direction that we're going. I don't have a great deal of sort of evidence to say that it's more effective or more feasible and it may not be. But yeah, I do think that there's potentially some room for improvement.

SPEAKER_02:

Yeah, fantastic. And just on the programs that you mentioned, what sorts of exercises for someone that's not seen them before, what sorts of exercises might they consist of?

SPEAKER_00:

Yeah, neuromuscular programs typically made up of a combination of, say, agility exercises and probably initially included in there because they're a warm-up type exercise. So they can be running drills, side shuffling drills, anything that's really a running-based agility drill. They typically have a bodyweight strength exercise component, if you call it that, which involves things like lunges, calf raises, Nordic curls, bodyweight squats, single-league squats. They may usually have a component which is, you call it plyometric, which involves any combination of double-league and single-league jump landings. Quite often those are used to not only train the explosive side of the movement, but also the movement technique, which is performing them with good alignment between the ankle, knee, and the hip, avoiding postures like dynamic knee valgus, keeping the trunk in a neutral position. Potentially those exercises double up, and them is usually a sort of, if you will, a core strength abdominal part to the programs, which might involve side planks, normal planks, abdominal Crunch exercises, yeah, you might consider that as well to be a form of strengthening component. And so, that really is the four or five components that make up the majority of neuromuscular programs, which is the basis of things like the FIFA 11 and footy first and crypto play and these kind of programs. They're all maybe some slight adjustments to the sports. So, they're slightly more sport specific in what they do, but at the heart of them, they're usually the same body of exercises that are used.

SPEAKER_01:

On that point, Sarah, Tyler did a great job of summarizing what the components of the intervention are. But often we assume that just because they call it a strength training element or something, it's not necessarily like a good strength training intervention. And I think there's some really great work from Kay Crosley and the crew at La Trobe a couple of years ago where they synthesized a lot of the evidence in female intervention. like the effect of these injury prevention programs on low limb injury rates and ACL injury rates in female football. From memory, when they looked at all of the evidence that we had from these studies, it's something like only a third or maybe a little less than a third of the interventions actually met the minimum guidelines for what you might call a strength training intervention. according to, say, like American College of Sports Medicine guidelines. And we've done some work recently. One of our PhD students, Yuri Lima, has just done some work looking at the effects of these injury prevention programs on kinematics and kinetics, specifically in female athletes. And again, we assume that they might work when they do work by changing things like how athletes move. But there was little to no change in a lot of these measures of external biomechanics. So it's worth considering that Just because a researcher might call it a strength training intervention, for example, that's not always the active ingredient. So we've got a little more to do to understand that.

SPEAKER_02:

Great point. I suppose not all strength programs are created equal. So where is it, do you think, that the programs are falling down? Is it underloading or is it they're not including those sort of the plyometrics and that variability component of the rehab?

SPEAKER_00:

I guess they're disconnected at the moment because when these programs are used in the cohorts that Matt mentioned earlier, there is usually a reduction in ACL injury risk. So there is our best evidence available at the moment does suggest that they work. But then as we're saying, there's a number of different exercises in there. We don't really know why those exercises lead to injury reduction benefit. It might not actually be the adaptations from the exercise. It might be purely just a warm-up effect that comes from these programs. So in that sense, most of research doesn't really understand where those programs are being effective. So in terms of trying to come up with injury prevention that is better, well, it really requires boiling this problem back down to something that is more direct and more targeted. And at the moment, that would probably be my biggest critique of the current programs is that they just involve a range of exercises that are not necessarily targeting anything in particular, not necessarily effective, So they could potentially be achieved in a lot smaller number of exercises if they were to be more directly targeted. It might then be more time efficient. It might be more easier to implement in the setting because in most sports settings, the amount of time it takes to do injury prevention is one of the biggest barriers. And the adherence to those programs is usually bad because of just how long they take, the number of exercises and probably the education as well around the importance of those exercises. So, I think if you had more targeted programs, then it would solve not only the improvement thickness, but it might solve some of those implementation problems that we'd have as well.

SPEAKER_02:

Thank you for that. In terms of the volume of exercises, have you found there's a consistent set of exercises that you absolutely think are a crucial component of those programs? Or in short, what would you throw? What would you keep? Knowing that there isn't very much that necessity, but

SPEAKER_00:

Yeah, look, I think there's a very difficult question for anyone to answer. I don't think anyone has a very certain answer to that one. But if anything, I would say the plyometric component, there are, say, meta-regressions that show that the programs that include plyometrics are more effective than programs that don't. So it's something about those plyometrics, whether it is just the preparation of the neuromuscular system before playing, it gives a benefit. Or it is the opportunity to retrain movement. Not sure exactly what it is about biometrics, but if I had to put something as being the top thing that's required, that'd be my best guess.

SPEAKER_02:

And your thoughts, Matt?

SPEAKER_01:

I mean, I'd certainly echo that. I sort of come from a bit of a strength training background, and so I'm always biased. And I'd just love it if it just came down to doing a couple of strength training exercises. It's more than likely not that simple, but I think what we do know from some of the modeling work that's been done, Nero Mania down at ACU in Melbourne's done a lot of great stuff looking at knee spanning and non-knee spanning muscle contributions to not directly ACL loading, but things like the varus valgus anterior translation and these sort of mechanisms that would load the ACL. And we discussed some of that in the masterclass, but I think one of the really interesting things from that is that one of the primary muscle groups that presumably loads the ACL is the quads. And I look around at a lot of organized football clubs, a lot of field and court sports. There seems to be a really heavy bias of kind of quad-focused exercises that we might do in the gym. I walk around footy clubs and you see these athletes front squatting the house down. And that's obviously really good and really important for performance. But if you look at the muscles that are on the other side of the joint, things like the hamstrings are really critical for theoretically unloading the ACL and then a lot of our hip spanning muscles. So things like the glutes and lateral glutes in particular seem to be important for resisting that knee valgus moment. Soleus seems to be another really important muscle to contributing to those knee joint loads. So I wonder if we can potentially be a bit more more targeted with our strength training. We're not going to say don't strengthen the quads, but perhaps there's a role for some selective strengthening of things like the hammies, lateral glutes, soleus, and whether that translates to reduced loading on the ACL. I don't know. It's very much unproven, but it's my bias at the moment. So, you know, I think that's an interesting area going forward.

SPEAKER_00:

Can I present the bias in the opposite direction? This goes for a lot of different areas of the body and that strength is always a big focus of prevention and rehab. But then a lot of the time when you break down the injury mechanism like the ACL, it doesn't take huge amounts of force to stabilize the knee. It just takes a very precise amount of activation of the right muscles like Matt's talking about to balance the forces across the knee and not have it transferred to the ACL. It happens so fast as well, right? When you plant the foot, is 40 milliseconds until the ACL ruptures. So you're never going to reach peak forces in that amount of time. That's not even enough time to respond with voluntary muscle activation after planting a foot. So that side of things sort of points towards it being mainly about the neuromuscular system and the control of muscles rather than how big and how strong those muscles are. And it probably points to the pre-planned activation of muscles in anticipation of loading the joint is going to be much more important than being able to respond really forcefully after the fact. So this is when we start to get into the neurocognitive side of the ACL injury. And I think that is probably where the shift in focus I think is going. It's going from it being a purely mechanical type injury, even though I've sort of pushed the boat for biomechanics, I'd also probably push the boat for the motor control and the neurocognitive aspect of the injury.

SPEAKER_02:

Fantastic points. If only things could be simple, hey? Moving on to the sort of consequences of an ACL reconstruction, what are the longer-term consequences of your ACL reconstructions that involve hamstring grafts and what are the implications for injury and performance?

SPEAKER_01:

Yeah, really good question. And so our group's been doing a bit of work in this space for a while, largely motivated by the fact that my PhD was in hamstrings. And so it was sort of a logical evolution from there. I think when we talk about consequences of ACL injury, if we look at the broader kind of population level stats, the majority, probably close to two in three athletes don't return to their pre-injury levels of training and competition. Those rates are a bit higher in higher levels of competition, but across the board, return to performance isn't fantastic. And then close to a third go on to sustain an ACL re-injury. And often that happens within a relatively short period within the next year or so. And then there's probably a majority, depending on the stats that you look at, maybe close to one in two, there's some data to suggest it might be close to the 60, 70% of athletes go on to develop things like early onset knee osteoarthritis in the next sort of 10 or 15 years. So The longer term outcomes are not fantastic. And we know that ACL injury rates and reconstruction rates are on the rise. And Australia is almost leading the world at the moment in terms of those rates, about 5% or 10% per year. So yeah, we really need to do a better job of obviously preventing them, but then also preventing some of the negative structural functional kind of maladaptations that might happen. In Australia, probably close to 80% or 90% of ACL recos involve reconstruction. hamstring grafts, semitendinosus grafts. It does depend on the individual, of course, but in other parts of the world, you see different graft types or different sort of proportion of graft types being used. We seem to be heavily hamstring focused. And as I said, I think it's a bit of an issue because the hamstrings, one of the primary forms of muscular support for the ACL. And so what we see, you know, when we kind of graft that semitendinosus tendon is for the We get retraction of that tendon. I think it, to some extent, depends on the surgeon and what they do in theater. Like I've heard of some reattaching, others letting it float in the wind. And I think that probably impacts things to some extent. But a lot of the cross-sectional data that we've seen, when we take athletes months to years, sometimes many years post-surgery, there's almost never recovery of that semitendinosus. So we see retraction. We see a lot of atrophy. We see shape changes in the muscle. And that combination of a change in tendon kind of insertion will impact the moment arm, the size of the muscle and voluntary activation and things will impact its force generating capacity. And so then that translates to reduced ability to produce torque around the knee, particularly in some of those higher risk maneuvers. I mean, that's like in a nutshell what we've seen. Some of the work we did early on in healthy athletes showed that exercises like Nordics, which are actually often used in these injury prevention programs, seem to really preferentially recruit semitenosis. And so we had a kind of a theory early on, perhaps this might be a good exercise to use or a variation, a regression of it might be useful to target semiten. We did a study, this was led by Dan Messer a few years ago. We used a technique called functional MRI. And so you can use it to measure fluid shifts within the muscle that correspond to glycolysis. It represents metabolic activity. But we can measure someone at rest and then get them to do a fatiguing session of Nordics. In this case, it was like five sets of 10. That's pretty awful. And then we scan them again. And all of these athletes, I should have said, had a unilateral history of ACL reconstruction using a semiterninosis graft. And so what we're interested in is how well do they actually switch on this muscle in an exercise that preferentially hits it? And what we saw is that that previously injured muscle was significantly less active as something like half as active as the uninjured side. And we also saw atrophy and retraction and all of those things. But it also suggested to us that, well, actually, we might be doing all the right things in rehab. We might be trying to get this muscle going. But as a consequence of surgery and the recovery from surgery, there's just persistent neuromuscular inhibition of that muscle. And perhaps we just can't target it all that well. In a sense, it might sabotage our best efforts in rehab. That's just some of the stuff that we've been sort of working on. But, you know, I do think that it's certainly an area that is worthy of a bit more attention and in particular, whether we can try to improve outcomes in terms of the regeneration of that muscle post-surgery.

SPEAKER_02:

Thank you. That's fascinating research and five sets of 10 Nordics. That's absolutely brutal.

SPEAKER_01:

With one minute rest.

SPEAKER_02:

Oh my gosh. It sounds like that is really the leaning towards the complementary nature of the nervous system and why so many of the programs are trying to incorporate not just the strength component, I'm guessing. I

SPEAKER_00:

think so. And particularly when it comes to re-injury risks, which we know are so high, these kind of deficits, right, they need to be resolved. The central nervous system is a complex system. The control and movement is really complex. But in terms of re-injury risk, it's pretty clear that the impact of that surgery that it has on the coordination of muscles and movement is really severe or else we wouldn't be seeing the rates that we see. And so that's probably a key area is trying to determine the best ways to retrain after surgery or even if it's a first-time injury is to try and coordinate the neuromuscular system in a way where it does protect the ligament from load. And once again, that's an area where I don't think anyone has all the answers in terms of how that training should be done. It comes back as well to the idea of doing these neuromuscular programs where it might just be by chance by doing plyometrics, landing on a single leg a lot, making it sport specific, having multiple demands to deal with in terms of making decisions as well as distractions in the environment while concentrating on coordinating the movement. those might all, by chance, get the system to organize itself in a way that helps. But if performance is the ultimate goal for most athletes, well, there's that conflict between the way that the central nervous system maybe organizes itself for optimal performance, which usually involves high forces, versus trying to protect tissues from high forces. There's also that issue to deal with, which is how do you best train individual athletes So you're not sacrificing performance to reduce injury risk. And this comes from pinpointing these areas which you can change, which aren't going to have a detrimental effect on performance. So that's where if you can activate muscles in a certain way without having to necessarily change the way an athlete moves, which might be ideal for performance, well, then that would be an area that is going to tick both boxes in terms of performance and injury. And I also think as well, making tissues more robust to loading is important. probably the best tool that we generally have to try not affect performance while reducing injury risk. And Matt touched on this earlier. It's not nearly what we understand much about at the moment when it comes to the ACL. We don't know if it's feasible to, say, load the ACL and control the exercises and actually get it to grow in size and strength. But every other tissue in the body seems to adapt to varying degrees. It seems like it's a plausible option.

SPEAKER_02:

And in terms of that element of robustness, it's sounding like we're postulating that that obviously comes from the multimodal forms of rehab, the neuromuscular components, the biomechanical interventions and that pure strength training. So varying the load, is that an accurate summary?

SPEAKER_00:

Not sure on the mechanisms by which it works, but if we were to look at the evidence we have available at the moment, yeah, something about those combination of exercises seems to have a benefit for in particular footballers, adolescents, and that's compared to usually not doing any form of dedicated injury prevention, right? So it's much better than nothing. And it has seen good results in the population. So it's definitely, you know, the recommended minimum standard that athletes should be doing if they're involved in a high risk sport is involved with that sort of neuromuscular training.

SPEAKER_02:

Fantastic. And you mentioned before appropriately exposing an athlete to load. In the context of assessment of progression through rehab, where do you think we could be doing better?

SPEAKER_00:

Good question. In terms of rehab, yeah, it's one of those things where after something as severe as an ACL injury, we have reconstruction. We notice that there's a lot of psychological barriers that come about because of that procedure. And that often comes with not wanting to load the limb and probably into the training as well. So I guess first of all, getting athletes to have acceptance for loading the joint is a must and then probably progressing the loading and probably not being afraid to eventually, you've got to get to a point where you know you're at least exposing the body to the loads that you'd experience in a game. It's not beyond that. I'm sure there's a lot of people out there that are doing a lot of great rehab, but there might also be ones that are really not actually ever getting up to that level of loading that is beyond what you'd see in a game and heavy resistance exercise to overcome that psychological barrier. The very dynamic plyometric exercises, we've got really high rates of loading, really short ground contact times. All of those aspects are key and when you go out on the playing field, so they should really be mimicking that if not trying to surpass that level of demand in rehab.

SPEAKER_01:

Just to add to that, I think, yeah, you've touched on all the important things there. I think moving towards employing objective measures to monitor rehab is really useful for the practitioner, of course, and also for the patient or the athlete to understand progress, to understand the level that they're at. It's worth noting that If we're talking about re-injury, like a lot of re-injuries happen on the contralateral leg. It's not necessarily, you know, like a failure of the reconstructed knee. It's on the other side. And, you know, and I'm not sure that we fully understand the mechanisms for it. There's probably lots of theories. I guess the prevailing theory is that you're attempting to unload that bad leg to some extent, and that's putting more force through the other leg. But, you know, I think we can start to, you know, with the widespread sort of use of like field-based techniques, technologies to measure motion and strength and all these sorts of things. We can start to leverage those tools to maybe get better insights into the level that the individual's at. And hopefully that translates to strategies to minimize the risk of re-injury.

SPEAKER_02:

Absolutely. Those are fantastic points as well. My last question as well, I know in your masterclass, you speak a fair bit about the data around injury risks in female athletes. Can you speak a

SPEAKER_00:

Yes, so one of our research interests is in trying to identify injury risk, and particularly in female athletes. So we've previously done some work looking at pre-season injury screening with biomechanics and strength-based, field-based batteries. And so looking at the vertical ground reaction force, counter-movement jumps, the control of the knee and the trunk during single-league hopping, and looking as well as hip strength as well, isometric strength. So these are all variables that we think are somehow related to ACL injury mechanism. And yeah, by assessing those in pre-season, we've found in our initial work that they are predictive if you use them in combination as a predictive model for identifying around 79, 80% of the non-contact ACL injuries in women's AFLW and soccer. So I think there's a, It's one of these things, and your prediction has maybe a bit of a stigma around it, and fair enough, because there just really isn't strong evidence out there that there's any form of test and model that can predict injury. But quite often, the measurements that are going into these predictions are, first of all, they're only a tiny slice of the multivariable injury mechanism, and they are really not built on strong databases. So, It's not really any surprise that any current tools or anyone that claims to predict any form of injury is probably not accurate and probably doesn't have any evidence. But I think from that simple study we've done, we've shown that if you expand the number of variables that you're considering and you have a strength-based, a biomechanics-based, and you're capturing a little bit more information about an individual's likelihood to experience injury mechanism, then you start to get better estimates of injury risk. And it means that we can build on that and we can do better and better until there is this possibility we were able to never perfectly, but at least be able to assist injury risk to a much higher level of accuracy. And that would then be an avenue to personalize injury prevention by stratifying individuals. And it might not just be ACL injury. It might be all types of lower limb injuries and upper body injuries that you're dealing with and be able to assign those high-risk individuals to dedicated training programs to try and mitigate that risk before the injury happens. And we know there's a much better pathway to reducing the burden of all injuries, right, is to get on top of it before it even happens. But you can't do that if you don't have the information about injury risk. And probably more importantly, what is it about that individual that puts them at high risk? So once again, I think if biomechanics are so central to the injury, we have to be able to somehow assist biomechanics to be able to make that assessment of what needs to change in the athlete to reduce risk. And it needs to be done in a convenient way, right? So field-based technology to measure biomechanics. probably going to be the biggest frontier in injury prevention and ACL injury over the next five, 10 years. And that alongside the injury risk assessment work will probably, it might then make the biggest difference to really targeting and personalizing the way we tackle ACL injuries.

SPEAKER_02:

Thanks, Tyler. And Matt, what are your thoughts?

SPEAKER_01:

Yeah, Tyler's really modest, but he led that work as a part of his PhD. And that was sort of the first study in female Australian footballers. And it was an enormous undertaking. I think we had 330 or 350 odd footballers who were then subsequently followed for ACL injuries. So it's, in my view, like a really nice study. And I think sometimes the conversation... around screening tests and prediction gets a little hijacked in people thinking that it's all about predicting injury. And of course, historically, we haven't been able to do that well. And if we're using isolated tests and measures, we're probably not going to do that well moving forward either. But I think philosophically, it's not about predicting injury because, well, what's the point? You know, predicting injury, the athlete still gets hurt. That's the only way to prove that you're right. So it might satisfy your ego, but it doesn't help anyone else. So it's more about being able to stratify, being able to understand who's at risk and then why, and then informing the design of interventions that might minimize that risk. So yeah, I think we probably need to get away from prediction and more about risk mitigation and using that to drive training.

SPEAKER_02:

Those are fantastic points. That really sounds like it, with no surprise, comes down to understanding the athlete and being specific and using our clinical reasoning and not just zooming in on any one thing, but zooming out to look at the whole picture. I feel like those are actually great key takeaway points, but did either of you have any other key takeaway points that you think our listeners should really look out for?

SPEAKER_00:

Yeah, I guess we probably talked a lot about where we see limitations and what's being currently done alongside hopefully some of the things to take out of it. But yeah, I think this is for the researcher in me, but question all practices and think about what are you trying to achieve with, say, the prevention exercises you use or the rehab exercises you use? What specific adaptation would that cause that might help reduce injury risk? And if you can't connect those dots, well, then there's a good chance that whatever you're prescribing is maybe not going to work. Or if it is working, it's just working by chance. So that would be maybe my little takeaway.

SPEAKER_01:

You stole my point, Tyler. No, I think that's a really good one. Have your bullcrap detector on, but really question what you're doing and why. You need to think about what are the things that you try, what are the adaptations that you're trying to promote from a given intervention. That enables you to cut back on all of the potentially irrelevant things and streamline the process as well. But I think the other point I'd make is that in my career so far, like a lot of the most interesting project studies have come about from speaking to practitioners and clinicians that are working at the coalface. You guys often have insights that we don't have as researchers. And so I think there's room for greater collaboration, certainly when it comes to things like building risk factor databases and things like that. But even just in understanding what are the important questions that we need to be asking and then how can we co-design research studies that are actually feasible? I mean, we might come up with all these great ideas to test an athlete in the lab, but it's just not going to work in the real world. So I think there's a lot of value to be gained from leveraging that clinical What sage

SPEAKER_02:

pearls of wisdom you've both offered. So thank you for such a fantastic exploration of the ACL injuries today from incidents to injury mitigation. And I'd really encourage everyone to click the link in the show notes to watch both of your masterclass to deep dive even more than what we were able to today. So Matt and Tyler, thank you both so much for your time today. I'm sure we've got plenty we can apply to our clinical practice. practice tomorrow.

SPEAKER_01:

Thanks Sarah thanks for having

SPEAKER_02:

us. Thank you.