[Physio Explained] Using muscle functional MRI to inform rehabilitation with Dr Kate Dooley

0:05SPEAKER_02:They found that the Nordic exercise it actually preferentially loaded up the semitendinosus more than the other hamstring muscle bellies. Whereas the unilateral 45-degree hip extension, it loaded up semi-tendinosis more than bicep formoris short head, but it was able to load up biceps formoris long head greater than biceps formoris short head and semimembranosis more than biceps formoris short head. So it can guide a clinician then to, depending on which muscle belly they want to target, given the injury that a patient had, this is going to be an exercise that will preferentially load that muscle belly over other hamstring muscle bellies.

0:51SPEAKER_01:What does muscle functional MRI actually tell us that traditional imaging can't? And how does it compare to EMG when we're trying to understand muscle activation? And what does this mean for how we assess and rehab athletes with groin pain or hamstring injuries? On today's episode of Physio Explained, I'm joined by Kate Dooley. Kate is a physiotherapist and researcher with a strong focus on sports injury prevention and athlete-centred rehabilitation.

1:17SPEAKER_01:After completing her Bachelor of Physiotherapy, she spent over a decade working across private practice and elite sporting environments, shaping a clinical approach that integrates evidence, experience, and athlete beliefs. Kate is now a lecturer in physiotherapy and school honours advisor at Charles Sturt University and completed her PhD in 2022, exploring movement strategies and perceptions in sub-elite male athletes with growing pain. Kate has built an impressive academic profile with multiple publications across sports and rehab science, and is actively involved in clinician-driven research through the Musculoskeletal Research in Practice Network.

1:56SPEAKER_01:You're going to love today's episode. It's packed with some clinical insights and practical takeaways. I'm Sarah Yule and this is Physio Explained. Well, welcome Kate. Thanks so much for joining us. Not a problem. We'll launch into the first question today. For clinicians who are unfamiliar with muscle functional MRI, how does it differ from traditional imaging? And what unique information does it give us about athletes with groin pain or with hamstring injuries?

2:27SPEAKER_02:Yeah, so this is not something that you would typically order as a clinician because there are numerous sort of factors that are involved in being able to obtain a muscle functional MRI image. So essentially, muscle functional MRI imaging, it's a way for us to be able to essentially measure the muscle cell metabolism. So what you're looking for is the amount of fluid that is shifted into the hydrogen, amount of fluid shift related to hydrogen into muscle tissue.

3:01SPEAKER_02:So you are going to have someone who has had a 15, 20 minute rest lying down, usually in the magnetic bore, and then you will turn around and scan them doing a T2 weighted scan. Then you get them up, you do an exercise, a running protocol, whatever it is that you want to explore. And then you will get them back into the MRI scanner immediately afterwards and scan them again using the same imaging parameters. And then you measure the difference in terms of brightness, essentially, on the image.

3:39SPEAKER_02:So there's systems and software in place that allow you to measure the brightness. So because you need to have that measurement, the post-exercise measurement needs to occur less than seven minutes after they finish exercising to have a reliable and accurate measurement of the muscle cell metabolism. You need to have a space or an MRI facility that is close to an exercise space or a room where someone could do exercises. So logistically, it's quite hard to organize and achieve.

4:11SPEAKER_02:And to be able to do testing of this, I've found for a single person, you need to book out an MRI imaging session of roughly three hours to be able to achieve it. So it's realistically, as a clinician, to be able to do this and order it, you wouldn't order this as a clinician. It's really beneficial as clinicians for people who are treating people with groin pain or hamstring injuries. Is there's a good amount of research that's come out around which muscles have actually been targeted or loaded specifically in certain exercises, rehabilitation exercises, in particular for the hamstring.

4:51SPEAKER_02:This is where we had Matt Bourne. So Matt Bourne and his colleagues were investigating it was the Nordic curls and comparing that to it was the 45-degree hip extension. So it's what they found was that it was comparing those two exercises. Whereas the unilateral 45-degree hip extension, it loaded up semi-teninosis more than bicep formoris short head, but it was able to load up bicep bicep formoris long head greater than biceps formoris short head and semimembranosis more than biceps formoris short head.

5:42SPEAKER_02:So it can guide a clinician then to, depending on which muscle belly they want to target, given the injury that a patient had, this is going to be an exercise that will preferentially load that muscle belly over other hamstring muscle bellies.

5:59SPEAKER_01:Right. So it's obviously exceptionally useful in trying to understand muscle activation. How does muscle functional MRI differ from EMG studies when we're trying to understand the muscle activity component of these exercises? Yeah.

6:14SPEAKER_02:So the key difference between EMG and muscle functional activity is that EMG gives you information in regards to the contraction at the time of the contraction. So it gives you temporal information, we regard it as, whereas your muscle functional MRI is actually going to give you the cumulative exercise effect. So it's giving you what we call spatial muscle activation information. So in terms of things, it does have its limitations then because we're not getting real-time information of what the muscle's doing at the time of the exercise.

6:53SPEAKER_02:However, the benefit is that compared to doing surface EMG studies where we've got the electrodes on the skin, those studies are limited to only being able to measure muscles that are superficial. So we're looking, yeah, obviously recfem, but we're not able to get information on, say, vastus intermedius ever, unless we do it's fine needle EMG studies where we're going to be inserting a needle into the muscle, which not a lot of people find comfortable.

7:23SPEAKER_02:It can be quite uncomfortable. You also run the risk of having excessive bleeding, or worst case scenario, if there's a large muscle contraction, the needle can actually break. Muscle functional MRI allows us to be able to measure those deep muscles that are otherwise able to be measured when you're doing an EMG study. Plus, there's also the limitation of in EMG studies, muscles within close proximity of each other, you can get what we call crosstalk, which is where the electrical signal that they're picking up may actually be from a different muscle or more than one muscle because they lie close together.

8:00SPEAKER_02:But with the muscle functional MRI, because we're using MRI images, we're able to delineate clearly between the muscle bellies. So it gives us that additional information, really. So there's pros and cons to both. Ideally, it would be great if you could do studies where you would compare exercise doing it with muscle functional MRI and EMG to then be able to fill in those gaps of each other in terms of their research methods.

8:28SPEAKER_01:Yeah, definitely you'd imagine for at least the surface level muscles, they would complement each other quite nicely. Yeah, exactly. Exactly. So it sounds like hopefully a more accurate depiction of the activity of the deep muscles for that functional MRI. What are the practical implications of the fMRI for rehab and how might it change the way we approach exercise selection or progression?

8:53SPEAKER_02:The main way that we can utilize it for rehabilitation is around determining what is going to be the most appropriate exercise for our patients. So, yeah, it's around being able to explore different exercises and determine how you can preferentially load certain muscles. So there's even it was research that came from Norrbrand back in 2011 and they compared it was quadricept, quadricept muscle activation, comparing it was a 10 RM barbell squat and also 2.2 kilo gravity independent flywheel squat.

9:32SPEAKER_02:And they found that your rectus femoris actually had higher activation with the flywheel over the barbell squat. So it was good information, but unfortunately, that's something that we would have still been able to achieve with surface AMG.

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10:11SPEAKER_01:Interesting. And so moving into the studies that have been done, your PhD explored movement strategies and muscle activation in male athletes with groin pain. What clinically relevant factors should physios be considering when assessing and treating these athletes?

10:28SPEAKER_02:So it comes back to we need to be tailoring our interventions to the actual athlete that we have in front of us. What I found in my PhD was there is actually a lot of novel or, so to speak, individualized movement patterns or movement strategies amongst athletes who experience groin pain. And this isn't overly surprising because an athlete who experiences groin pain, there can be multiple factors that have actually resulted in them experiencing pain in that groin region.

11:02SPEAKER_02:And there are multiple pathologies that can coexist. So you can have your adductor-related groin pain and your psoas-related groin pain coexisting in someone, or you can have someone who just has pubic related groin pain. So we need to actually be tailoring our interventions to these athletes that are in front of us. We can't just have blanket sort of protocol ideas of here's the protocol that we're going to apply each time we have an athlete who has groin pain.

11:32SPEAKER_02:We need to tailor it very specifically to the individual because they're, yeah, the kinematics and kinetics and muscle activation patterns will vary person to person.

11:42SPEAKER_01:Right. So were there consistent movement patterns that you saw, or was variability more the key finding?

11:48SPEAKER_02:It was we didn't oh well, we saw a bit of more trunk involvement in reactive change of direction. So it was there was more sort of a more whipping of the trunk using momentum a little bit more in those who had growing pain, a history of growing pain, but it wasn't significant. It wasn't actually statistically significant. So yeah, it wasn't consistent enough. It wasn't in terms of the two groups, but it was around in terms of variability. It was around, yeah, you saw a a lot more of your maximums and minimums in terms of your more extremes in either direction for those who had a history of growing pain, or they were just in terms of timing when they were trying to change direction, the movements of the joints occurring at different times, different event times in the change of direction.

12:44SPEAKER_01:Interesting. Just going all the way back, I know you mentioned that the measurement of the fMRI is less than has to occur less than seven minutes post-exercise. If we're seeing the changes in signal intensity, in terms of from a sort of physiological level, are we interpreting that as more of an activation or a fatigue or or is there some other physiological process that we're tying to that?

13:09SPEAKER_02:So the reason why we have to have the measurement occur within the seven minutes is because the fluid shift, what we're measuring is a T2 relaxation value, it's called. And so that T2 relaxation value actually has a half-life of seven minutes. So that's why it has to occur within that seven minutes because we're not going to actually be able to measure the maximum if it exceeds seven minutes. So it just affects the reliability of what you're measuring if you're exceeding those seven minutes, because you're not going to get that maximum value of what's happened in terms of the cumulative muscle activation.

13:48SPEAKER_01:Interesting. Okay, yeah, it was more a curiosity question than that. Fantastic. And so, in terms of the, I suppose, the difference between the fMRI and EMG, it's sounding like these tools are probably more complementary than competing. Are there any studies that you'd like to see us really zoom in on, or are there any any areas you'd like to see us focus on?

14:09SPEAKER_02:I think it would be really good to have a study where we could be looking at, it was for in particular your adductors, where it would be comparing the measurements that we receive for, say, a strengthening exercise, comparing muscle functional MRI and surface EMG, because you would get that real-time information in terms of say your adductor longus when you've got them, or really more the adductor group more than anything else with surface EMG, but would then be able to differentiate our different adductor muscle bellies with muscle functional MRI.

14:50SPEAKER_02:But then we also have a problem with doing muscle functional MRI for the hip adductors because of MRI parameters. We need to use certain types of MRI scanners. We can't have the magnets be too strong because then it affects the image quality and yeah, there's a lot of constraints.

15:09SPEAKER_01:So we wait and see. Well, it sounds like your research is really helping us raise the bar with our ability to target muscle groups and really provide effective rehab with far greater efficacy. That would be the goal, that would be the aim. Marvellous. Well, Kate, thank you so much for joining us today. I think there were lots of clinical gems in there, and I am very curious to see where the next bit of research goes.