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[Physio Explained] Muscle power, not strength, the key to falls prevention with Dr Mariana Wingood

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In this episode with Mariana, we discuss a recent article looking at the difference between muscle power and muscle strength in predicting falls in older adults. This paper found the 5x sit to stand as a measure of power was a better predictor of falls compared to manual muscle testing or strength testing using a dynamometer. We discuss:

  • The implications of this paper for our patients
  • The difference and the relationship between muscle power and muscle strength
  • Best tests to use to assess power output in your patients
  • How you can use strength exercises to improve power in patients of all ages with and without equipment
  • Importance of power and strength for balance training in this population

👉🏻 See Mariana’s full Research Review here - https://physio.network/reviews-wingood

Dr Mariana Wingood is a clinician, a program director of a CEU company that provides courses related to Geriatrics, and has a PhD on physical activity prescription among physical therapists.

Reference to article: Simpkins C, Yang F (2022) Muscle power is more important than strength in preventing falls in community-dwelling older adults. J Biomech, 134, 111018. 

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Our host is @James_Armstrong_Physio

SPEAKER_02:

I don't know a single person that doesn't lose their balance no matter what their age, but most of us have the power and the reaction time to react quickly and generate fast velocity muscle contractions to stop ourselves from falling. But as we get older, you know, power muscles or the fast-acting muscles are the ones that degenerate at a faster rate than the endurance muscle fibers. So it's even more important among those populations.

SPEAKER_01:

In today's episode, we're joined by Dr. Mariana Wingwood to talk about muscle power and its importance in prevention of falls in older adults. This is based on a research review that Mariana produced for the Physio Network from a paper by Simpkins and Yang. And in this episode, we really do explore how important power is in prevention of falls in older adults and how just looking at strength is often not enough. Mariana is a physical therapist and an implementation scientist whose research focuses on increasing healthcare care providers use of physical activity assessments and behaviour change techniques to address inadequate physical activities among older adults. She is an active member of the Vermont Falls Coalition, the Gerontology Society of America, National Council of Falls Risk Assessment Awareness and Prevention and the APTA's Academy of Geriatrics. As always you can click on the link in the show notes to access this research review. So without delay let's get on with the episode. I'm I'm James Armstrong and this is Physio Explained. Marino, it's wonderful to have you on the podcast, the Physio Explained podcast today, talking about a research review that you've done on an interesting paper. But first of all, it's really good to have you on the show.

SPEAKER_02:

Thank you so much. I'm so excited to be here today.

SPEAKER_01:

Wonderful. We're going to be talking about a really, really interesting topic. paper and a concept that I think is really, really important for listeners today in regards to falls and prevention of falls in community-dwelling older adults, and particularly around muscle power and how that's a really important element that we should be focusing on. First of all, Mariela, do you want to just give us a brief overview of the paper that you reviewed before we kind of get stuck in?

SPEAKER_02:

Sure. So the paper looked at the difference between muscle strength and muscle power for predicting falls. And they really found that for when they looked at strength, particularly knee extensor strength and flexor strength, there was no difference in the level of knee extensor flexor strength between fallers and non-fallers. But then when they looked at muscle power output, they identified that there was... A, non-fallers had a significant less time needed to complete the five-time sit-to-stand, a measure of power, and they demonstrated much higher leg muscle power strength compared to fallers. So in conclusion, they found that leg power, as measured by the sit-to-stand and leg power machine, is much more predictive of falls than just regular strength-measured by handheld dynamometers or manual muscle testing. They also provided some classification of fallers and non-fallers using a formula that really looked at 1.3 watts divided by kilograms times meters to measure leg power output during a five-time sit-to-stand or for ease of calculations, they said 12 seconds. is a good cutoff four to five times set to stand, which is one that we've seen in plenty of other articles related to falls.

SPEAKER_01:

Brilliant, which I think is a really interesting paper. And I think if we're honest, an awful lot of clinicians out there would probably take a step back at this and think, actually, that's an unexpected outcome. But we often think strength is so important. But there's this hidden, often, I think, sometimes missed element of what we call strength and conditioning, ultimately, whether it be in the older adults or in the younger athletic population, we're still looking at a dimension that's super, super important. For those who aren't too sure listening, can we get a bit of a definition of what we're talking about when we talk about muscle power as opposed to strength? I think a lot of people will know, but there will be some that aren't so sure.

SPEAKER_02:

Yeah, so the power is really about the high velocity ability to generate force over a short period of time. And for falls, that's really important because I don't know a single person that doesn't lose their balance no matter what their age, but most of us have the power and the reaction time to react quickly and generate fast velocity muscle contractions to stop ourselves from falling. But as we get older, power muscles or the fast-acting muscles are the ones that degenerate at a faster rate than the endurance muscle fibers. So it's even more important among those populations.

SPEAKER_01:

Absolutely. And I've heard it quoted before. You can have all of the strength in the world, but if you can't put that strength into practice quickly, it's not so great when you're falling over a curb or getting out of a chair. So I think it's coming down to those sorts of things, isn't it?

SPEAKER_02:

Yeah, the speed and the force of it.

SPEAKER_01:

We need a bit of both, but power is really, really important. So with this in mind, I think, obviously, I'm hoping lots of people are thinking, well, actually, I need to be looking at this. I need to assess this power output in this population if I've got someone in front of me that is falling. You mentioned in the paper, the five sit to stand. What are the sort of assessments can we use that are relatively accessible in clinic to look at this with this older population?

SPEAKER_02:

So the five time set to stand is probably number one measure. And most of us just use the 12 second cutoff. You can calculate power. And I'm happy to share the formula on that. But it's really the velocity, the force and the power output put together through the five time set to stand. And then the other one is called the four step stair climb power test, which requires four stairs and it You measure the amount of time it takes to climb those four stairs. And there's a similar power calculation. And if we remember a good old physics states, you have the body weight in kilograms. You have the gravity force that's put on you. And then you also need the height of the stairs if you're using the stair climb power test. or the height of the chair if you're using the five-time sit-to-stand to calculate your power output. But both of those have watts that are recommended and known to be associated with falls. And the great thing about using the watts is that you can actually get more detailed and sensitive measures, and they have minimal deductible changes for those as well. So there's good insight on using watts for that purpose, not just a 12-second cutoff.

SPEAKER_01:

No. So we're getting a little bit more of an accurate measure to see, as you've mentioned there, particularly differences and are we making a difference to that patient? And that leads us really nicely onto how do we train this? How can we take this population and help them by supporting an improvement in power output?

SPEAKER_02:

Yeah. You know, it's really exciting. More and more literature is coming out this, the last two years, a couple of systematic reviews have looked at power training or the high velocity resistance training involving really the high velocity contraction during a concentric phase of an exercise followed by controlled eccentric phase, which is really the hallmark of power training. And what is recommended is that, first of all, Prior to starting power training, an individual should be able to perform the full range without any pain. So it's just to keep that in mind. But for the power training, usually the reps are a little higher initially and the 1RMs are a little lower. So starting with 20 reps at a 20% 1RM as people get accustomed to the exercises and then really progressing it to doing four reps at 80% 1RM to really focus on that power is the dosage of the activities. And it should be done at least once a week. But any exercises that you do for strengthening can be turned into power exercises. Obviously, the five times sit to stand and the stair climbs are a great example because they're also used to measure power. But other things that I tend to do I actually do a lot of lunging with my patients, lunging in multiple directions and stepping up in multiple directions. So those are a variety of things you can do with patients with really little equipment.

SPEAKER_00:

Are you struggling to keep up to date with new research? Let our research reviews do the hard work for you. Our team of experts summarize the latest and most clinically relevant research for instant application in the clinic. So you can save time and effort keeping up to date. Click the link in the show notes to try Physio Network's research reviews for free today.

SPEAKER_01:

We're going back to the paper that you brilliantly reviewed for us. And I recommend the listeners have a look at the review you did because you kind of really put into very easy to understand elements of this, including the formulas that you mentioned as well. But if we look at this in terms of some of its limitations, is there anything that you think that we need to be aware of when sort of looking at this research that we can take into account and be aware of?

SPEAKER_02:

Yeah, I think, you know, the overall accuracy of the test was somewhat lower. It was about 65% accuracy of determining fallers versus non-fallers, which is not 100% which we would like to see. But we also have to remember that this is just part of the puzzle. If they don't have the sensation or the balance, particularly anticipatory and reactive balance, then it doesn't matter how much power they have. So a big limitation is this is just one piece of someone's fall risk.

SPEAKER_01:

Absolutely. And we talked about in the paper finding that strength is not correlated, but do we ignore strength? Absolutely.

SPEAKER_02:

We can't ignore strength because you need a certain amount of strength to produce power. So it's definitely something we can't ignore. And it's kind of like a predecessor of the power output. But I think the highlight of it is that we kind of have been ignoring power in a way when we assess and really train our older adults. So instead of eliminating strength, I say adding a component of power to our patient training sessions.

SPEAKER_01:

Definitely, definitely. In terms of, because we know sort of strength and balance put together, would you say that the same thing sort of keeping that, incorporating that balance training as well as reactive training as well?

SPEAKER_02:

Yeah, 100%. You know, especially with reactive balance where individuals lose their balance and they have to have the ability to recover, that's a great time to introduce some power pieces to it. And it's okay to let your patient take a few steps after they lose their balance to try to recover it because that's your goal is for them to be able to recover it and you're not always going to be there. I love harnesses. I just wish every gym could have a harness so the patient and you as a therapist feel comfortable with letting your patient lose their balance, knowing that the worst case scenario and a harness will catch them.

SPEAKER_01:

It is, isn't it? I mean, I think hopefully I'm right in thinking, you know, when we're training balance, we need people to be off balance. We need to challenge that balance to a point whereby they are close to falling, which doesn't sit well in our safety conscious, risk adverse situations. practice. And it's difficult, isn't it, to incorporate that into what we're doing, especially in sort of public funded arenas where we do have accountability to other people as well.

SPEAKER_02:

Yeah, I've seen more and more harnesses, I think, for that reason. In a way, we also are causing harm by not pushing our patients to the point of failure. It's just a different type of harm that we need to consider. Yes.

SPEAKER_01:

Yeah, it's almost that unseen harm whilst we're working with the patient. It's not an immediate harm, but a potentially long term where we're undervalued, under challenging patients a little bit in that sense. So with power, is there sort of scope within the research? Do we need to see more? Do you think there's other elements, gaps in the research that we could see being filled over the next few years, do you think?

SPEAKER_02:

Yeah, it's interesting. A couple of the systematic reviews I was looking at that looked at the impact of power training on strength as well as fall risk. A lot of them actually had really low dosages of their intervention. They were not reaching that 80% of 1RM. I think we need more high quality research that follows exercise prescription standards that are recommended and having more of those at a randomized control trial level. So I definitely think there's more work to be done, but the initial evidence is really promising.

SPEAKER_01:

Absolutely. Yeah. And as you say, systematic reviews are great, but they're only as good as the evidence and the RCTs that go into them. Exactly. So they don't automatically mean they're the best. Marino, thank you so much for your time. This has been a real whistle-stop tour of a massive subject, but I think there's a really big takeaway for clinicians today, and that is that don't be afraid to train and test power in our older populations.

SPEAKER_02:

Yes. Thank you so much for having me on today. And I really appreciate the time.

SPEAKER_01:

Wonderful. And for those listening, Marina has done an awful lot of research reviews for the Physio Network. They're all absolutely vital if you're working with this population to be aware of, if only to introduce you to the research. But the research reviews, as Marina will attest to there, they're a really good breakdown of what that research is, the limitations and how you can use it in your practice. So thank you as well, Marina, for producing some really, really great reviews for us.

SPEAKER_02:

You're very welcome.

SPEAKER_01:

Wonderful. So listeners, do head down into the show notes because we do have a link to go to so you can actually get access to hundreds of these reviews, including ones from Marianne and other world-leading people in their field. Once again, Marianne, thank you so much and have a good rest of your day.

SPEAKER_02:

You're very welcome and you have a great day as well.