Physio Network

Top mistakes to avoid when using hand held dynamometry with Dr Claire Minshull

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In this episode with Dr Claire Minshull we discuss important factors for using a hand held dynamometer and errors that clinicians commonly do. We go through how to ensure the readings you are getting are correct and how to generally get the most out of using hand held dynamometry in your clinical practice.

Want to learn more about hand held dynamometry? Claire recently did a brilliant Masterclass with us called, “The Practice changing principles of strength and conditioning for Physios” where she goes into further depth on various principles of strength and conditioning.

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

Claire is one of the most highly respected and research active rehabilitation and conditioning specialists in the UK. She has worked in the field of sports medicine and health for 20 years as a Senior Lecturer, Researcher, Consultant and as a Practitioner and has published over 30 research papers in leading peer-reviewed sports medicine journals.

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 @James_Armstrong_Physio


SPEAKER_03:

if you don't have precision of measurement then what you have in terms of a an index or a number it's meaningless you don't if you don't understand what it represents then you can't use that

SPEAKER_01:

In today's episode, I'm excited to bring on to the podcast Dr. Claire Minshaw to talk about handheld dynamometry. We cover some of the critical and key things that you must know when using handheld dynamometry and if you're thinking about buying one. We talk about how to get the most out of it, how to use it correctly, and also how to make sure that the readings you're getting are the correct readings. So it's a really important podcast for anyone using and thinking about using handheld dynamometry. And Dr. Claire Minshaw is one of the most highly respected rehabilitation and conditioning specialists in the UK and has worked in sports medicine for over 25 years as a senior lecturer, researcher, consultant and practitioner. She's also the founder and director of Get Back to Sport, an international education company that provides evidence-based training for healthcare practitioners. This podcast really does have so many takeaways that I know you're going to find it invaluable. I'm James Armstrong and this is Physio Explained. Claire, welcome back to the podcast. It's great to have you back on.

SPEAKER_03:

Well, thanks so much for the invite. I'm delighted to be here.

SPEAKER_01:

So as listeners who regularly listen to the Physioexplained podcast will know, it's not long ago that you were on the podcast talking about your masterclass. And we've got you back on quite soon after that because recently there's been an awful lot of talk on use of handheld dynamometry. of which you've been putting out on social media, some fantastic content in blogs and tweets or on X, whatever we're calling it now. And it's really interesting. And I've also noticed you've got a course out, which is specifically looking at the use of dynamometry in clinical practice. So my question is, Claire, and we're going to go through the use of handheld dynamometry today, is what kickstarted you starting to put out this content?

SPEAKER_03:

So it's a project or a topic I'm super passionate about. So dynamometry, assessing things, measurement science, all this kind of stuff. And my background is, I suppose it started out in that. So in terms of my PhD, so many years ago, the first studies in the PhD were all about measurement science, assessing performance, assessing strength, rate of force development, electromechanical delay, but understanding the attributes to those measures and understanding the accuracy and precision. Because if you don't have precision of measurement, then what you have in terms of an index or a number, it's meaningless. If you don't understand what it represents, then you can't use that. But I think only recently now is this becoming a topic of interest because we have scores, if not hundreds of now commercially available dynamometers, which is great, on the market that clinicians and practitioners can buy and use. But we don't often get high quality information on how to use them and what that information means.

SPEAKER_01:

And as you mentioned, it is great because they've gone from being something that was very inaccessible to many clinicians, especially sort of your smaller practices and the NHS, to a point now whereby actually most clinicians, most therapists can get their hands on a handheld dynamometry. And I bet, the questions have gone through my mind plenty of times when I've been looking at them is, Which ones should we buy? What should we be looking for? And all those sorts of things.

SPEAKER_03:

Oh, I get that question all the time. Which dynamometer should I buy? Which handheld dynamometer should I buy? Should I buy a compression device? Should I buy a tension device? And the first question that you should be asking yourself is, what do I want one for? So why do you want to obtain... device. Now, is it as a training tool? You know, people love data on themselves, so it can be a motivational aid to your clients and to your patients. So if it's for that, cool. It doesn't really matter. Take a cheap one and you'll get a rough estimate. But if you're intending to use it for data-driven decisions, then it becomes quite important to think about where you're and what types of data you're looking to acquire. So the main one might be isometric force output as a peak, so strength metric. But are you thinking about using it for upper limb, lower limb, both? And are you able to construct protocols that are robust enough and that yield accurate measurements? And some of those are the really important questions to ask yourself and then search for information and aid on that before you go, which one should I buy?

SPEAKER_01:

We've got our handheld dynamometer. We've picked one up. We're really excited about using it. And one of the things we wanted to cover today was some of the key things we should be looking for in terms of using it, how we can get the best out of it, things like that.

SPEAKER_03:

So let's say you've got your dynamometer, you've got your patient there, and you're going to be assessing the strength of, let's say, the extensor group. So you think, okay, they're going to sit on the plinth. And you're going to position yourself in front of them, put the dynamometer somewhere at the front of the ankle, maybe front lower leg, somewhere down there, get them to kick out. And then you push back and hopefully you can resist that movement. And then you get a figure. Now, inherent within that are so many sources of variability. And what that means is that the figure that you get will be representative of that person's true performance plus or minus an amount of error. And the more error you have, or the less precision you have, the less confident you can be that that figure that you see as a digital readout is representative of their true performance versus representative of their true performance plus 10, 20, 30, maybe even 40% error. And if you're using, as I said before, if you're using that data to drive decision-making, it becomes super, super important that we constrain all these, as much as possible, these sources of error and measurement variability to enhance the precision of measurement So for example, some really easy ones to identify, and I don't know if anybody's seen any of the kind of social media posts I've put out recently with video that show one extraneous movement. So what's extraneous movement? Well, that's movement of the individual, the person, maybe even the limb that you're trying to assess. If that is moving, if it's not being constrained, then some of the force output that that musculature is providing is going to be lost into movement of the individual. It might even change the positioning and the direction of force application into the dynamometer. So if it's not completely aligned and it's off center, that will influence the force recorded. Those things are super, super important. And if they look at the other end, that individual themselves especially measuring the larger muscle groups like the quads and the extensors, they're really a lot stronger in absolute terms by comparison to some of the upper limb musculature. Have you got the sufficient restraint strength to be able to restrain that movement and limit movement completely and put yourself into a position that, I suppose, leverages gravity or other things that you can tether yourself to? Because you add muscle a source of variability into that measurement. So therefore, a lot of the advice that I've been giving people is where possible, take yourself out of the equation because immediately that reduces, it takes away one source of error. If you can tether accurately and tightly the dynamometer to something that's immovable, it doesn't matter if you're feeling particularly knackered or tired that day. If you're not really up for it, if, for example, movement happens and it goes from a static test to a test that involves movement, and then if you push against it, again, you've got this interesting scenario of having a make and break test within one test. And what happens during make tests where we're assessing isometric strength, but you could make a strong argument for, well, if you're pushing against that individual and you push into them and it becomes a break test, that's eccentric force. Eccentric force is a greater force output than isometric force. So you're adding another massive amount of variability into the measurement. So the simple thing, take yourself out, not necessarily the room because your instruction is super important as well and the test setup, but that removes one source of variability that can add tremendously to measurement error.

SPEAKER_00:

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SPEAKER_01:

I've been watching a lot of the stuff you've been putting out. It's been really interesting. That's something new, again, that we have to think about in terms of, I was thinking, well, a brake test would be good, but actually, yeah, are you testing what you think you're testing? Another good example was where you said about on one of your blogs, if you're testing knee extensor strengths and there's slack in the cords that are attached in the dynamometer and they get a bit of a kick forwards and that gives you that sudden peak in force, which is then not an accurate measure of...

SPEAKER_03:

If it's in a chord system and it's in line or in series, you know, we set up strain gauges like this, we can set up both compression and tension dynamometers, it's just where it is in that system. If you have a great deal of slack within that system, so let's say the knees flex at 90 degrees and we're intending to assess at 90 degrees, but yet if you look underneath and you see that even though the chord may be inextensible or it's a chain, there's this big loop or big hang down, there's a slack to take up before... you start then to apply force to the load cell. You get the instructions to the participants wanting to kick out and harden as fast as you can. So you do that. The first thing that happens, you take up the slack in the system and then you literally whack into, that's it, whack into the load cell. And if you look on the force traces of unsmoothed, limited filtered data with a decent sampling frequency, what you'll see is this massive artifact, a big peak occurring within the first few hundred milliseconds, couple of hundred milliseconds, that's huge. And then it will come back down to a plateau. And that peak, you might read that as being force. Well, yes, it is force, but it's an artifact. It's not truly isometric force production at 90 degrees. It's something different. So That is another thing that you can dramatically improve precision and measurement error with by making sure that the system is taught.

SPEAKER_01:

You take out that velocity element of that kick forward, don't you? It's just a multitude of things just to be that bit of aware of as well. And the next one I wanted to chat about was something that really does come up and it's something that I'm happy to say I'm currently debating and thinking about in terms of putting this into our service in the NHS. And that's how important and how much should we be standardising. So the position we test our patients in. So, yeah, what are your thoughts around the best position? And I'm sure you get the question a lot. And how do you answer that?

SPEAKER_03:

Yeah, there's a blog on my site, actually. What's the best position for the strength assessment? And this came up at the weekend, actually. I was teaching in Prague. Should we be testing at the optimal position? position for joint force, so muscle force production on that length tension curve. Often I did in many of my papers a position where there's particular vulnerability. So for example, 30 degrees knee extension for ACL injury, for example. The best position is the position that you can most accurately, like you were saying, standardize, repeat and control. So yes, it might be great to get an assessment of muscle force production at 30 degrees knee flexion, But how is that orientation configured? Now, if you're going to set that up with a handheld dynamometer or any strain gauge, you need to make sure that the load cell is perpendicular to the limb shank, the tibia, if you like. Now, there's been one or two posts I've put on social media where actually there is that position, but the tethering of the dynamometer, you certainly don't have a 90 degree angle with a load cell and the tibia. You've got something that approximates more like 30 degrees. If that's very, very stable, you've got quite a lot of mathematical calculations to do, most likely it's not going to be, and it's going to ride up the leg. So the best testing position is the one that you can standardize. That's often why I think, you know, if you look in the literature and we see a lot of knee extension strength measured at 90 degrees knee flexion, how often do we run around and practice sports activities of daily living at 90 degrees knee flexion? It's not all that often, is it? Maybe standing up out of a chair. maybe a rugby scrum, but we've got a huge volume of data at this joint position. So we can start to get some normative values and it's so easy to stabilize by comparison to other positions. So the best position is something that you can replicate.

SPEAKER_01:

Brilliant. We were talking off air as well about if you've got an individual as opposed to a group, how you can get better data from that individual rather than just getting one test, what could we do?

SPEAKER_03:

So testing the individual, again, there's so much that sits behind that number that means it's useful or not useful. So testing an individual requires a much greater level of measurement precision and sensitivity than testing a group. Go to research papers, you will see there are a number of people, participants, subjects within a group or two groups if they're making comparisons. And that's designed or should be, should be designed to achieve a certain level of measurement power to detect a certain level of difference or change. Now you can't, you're not going to be cloning that individual time and time again, are you? You've got that single person, maybe he's taking a single assessment and maybe looking at between limb differences. You've got to be absolutely on it in terms of measurement precision. So what can you do to increase that measurement precision? We've discussed one or two of the methodological factors, and there are more. But another is don't take a single measure and take the best performance. Now, there are arguments in the research and on both counts to take the maximal value or take the mean of two or three. And I published on both. But that's measuring people in a group. And we're looking at mean performance of this group versus that group over time, pre, post-interventions. With an individual, statistically speaking, you can dilute measurement error by taking the average of several measures. So make sure that you're controlling as many controllables as you can. And then I would advise, let's say, take the average of three well-conducted tests, and that will give you statistically a better chance of getting closer to that true biologic value versus taking a single assessment. And hopefully that makes sense now to listeners when we've just discussed several methodological factors that could influence force output.

SPEAKER_01:

Definitely. And again, it's just removing as much as you possibly can, those margins of error and things that can take away from what you're actually looking at, which is brilliant. There's just a long list of things that I want to ask, and we're going to run out of time on this podcast. But I think to finish off, to give listeners something to take away, she's probably going to summarize some of the things we've already talked about. Give us three of your top tips, Claire, on hand dynamometer use.

SPEAKER_03:

So number one, understand why you're purchasing it. Okay, so what do you intend to use that dynamometer and the figures that it produces for? Two, if you are using that dynamometer, and the data that it produces to drive decision-making, like do we focus more on this element of rehab for a bit longer or indeed maybe more financially risky decisions like return to play. So the elite athlete environment, if you're using data for that, then make sure that you optimize that measurement situation, reduce all sources of measurement error to as much as you possibly can. And we've just talked about one or two here. There are lots more and there's lots more covered on my blog. And then three, another, which I've just mentioned, take the average of several measures. Make sure you give enough inter-trial rest. So minimum 30 seconds, maybe a minute, could even be a little bit longer depending on who you're assessing and what conditioning status that they're in. So you're avoiding fatigue, but take the average of several to represent performance rather than a single maximal effort.

SPEAKER_01:

Brilliant, Claire. Fantastic. I've still got about 100 questions in the back of my head already. And knowing you quite well now, anything to do with strength, conditioning and clinically, it's brilliant. It's great to have you on and to chat to you every single time. And so we're going to finish it there. But to the listeners who are interested in getting to know more about the strength and conditioning in sort of clinic and how you can use that and really get some practice changing principles into your everyday practice. Do check out the masterclass that Claire's done for the Physio Network. And also definitely check out Claire's social media. The blogs are brilliant. And I'm sure the course that you've set up on using hand dynamometry in clinical practice is going to be fantastic. I've certainly got my name down on that one. So brilliant. Thanks again, Claire.

SPEAKER_03:

Absolutely a pleasure. Thanks for having me on.

SPEAKER_01:

No problem at all. All right. See you soon. Take care.