Muscle mass is not only essential for physical strength and performance but also plays a crucial role in managing blood glucose levels and reducing the risk of cardiovascular diseases.
In this episode we welcome Dr. Richie Kirwan, a lecturer in nutrition and exercise physiology at Liverpool John Moores University. Dr. Kirwan's research focuses on the critical role of muscle mass in cardiometabolic health, particularly in cardiac rehabilitation.
His work explores how muscle mass influences cardiovascular health, blood glucose control, and lipid profiles, highlighting the importance of exercise and high-protein, Mediterranean-style diets in maintaining muscle health and preventing disease.
During the discussion, Dr. Kirwan explains how muscle mass is not only essential for physical strength and performance but also plays a crucial role in managing blood glucose levels and reducing the risk of cardiovascular diseases.
He elaborates on the metabolic functions of muscle tissue, its impact on blood lipid levels, and the protective effects it offers against diabetes and related cardiovascular conditions. The conversation also touches on the significance of muscle strength in older adults, addressing issues like sarcopenia and its implications for balance, bone health, and overall longevity.
Join us for an insightful dialogue that bridges the gap between muscle physiology and cardiometabolic health, offering practical insights for researchers, clinicians, and anyone interested in the intersection of exercise, nutrition, and chronic disease prevention.
________________________________________________________________________________
This podcast episode is sponsored by Fibion Inc. | Better Sleep, Sedentary Behaviour and Physical Activity Research with Less Hassle
---
Collect, store and manage SB and PA data easily and remotely -
Discover ground-breaking Fibion SENS
---
SB and PA measurements, analysis, and feedback made easy.
Learn more about Fibion Research
---
Learn more about Fibion Sleep and Fibion Circadian Rhythm Solutions.
---
Fibion Kids - Activity tracking designed for children.
---
Collect self-report physical activity data easily and cost-effectively with Mimove.
---
Explore our Wearables, Experience sampling method (ESM), Sleep, Heart rate variability (HRV), Sedentary Behavior and Physical Activity article collections for insights on related articles.
---
Refer to our article "Physical Activity and Sedentary Behavior Measurements" for an exploration of active and sedentary lifestyle assessment methods.
---
Learn about actigraphy in our guide: Exploring Actigraphy in Scientific Research: A Comprehensive Guide.
---
Gain foundational ESM insights with "Introduction to Experience Sampling Method (ESM)" for a comprehensive overview.
---
Explore accelerometer use in health research with our article "Measuring Physical Activity and Sedentary Behavior with Accelerometers ".
---
For an introduction to the fundamental aspects of HRV, consider revisiting our Ultimate Guide to Heart Rate Variability.
---
Follow the podcast on Twitter https://twitter.com/PA_Researcher
Follow host Dr Olli Tikkanen on Twitter https://twitter.com/ollitikkanen
Follow Fibion on Twitter https://twitter.com/fibion
https://www.youtube.com/@PA_Researcher
This is the Physical Activity Researcher Podcast, a podcast for researchers of sedentary behavior, physical activity, and sports. Join for a relaxed dialogue about research design, practicalities, and well, anything related to research. Learn from your fellow researchers useful and relevant information that does not fit into formal content and limited space of scientific publications. And here is your host, researcher and entrepreneur Ollie Tickenham. Welcome everyone. So in this episode we have a great guest. We are going to discuss about muscle mass and aging, and our guest is working in Liverpool, John Morris as a lecturer of nutrition. Ladies and gentlemen, please welcome our guest, Dr. Richie Curvin. Welcome. Ollie, thank you very much for having me today. Yeah, nice to have you. So could you maybe start, could you introduce a little bit of yourself and what kind of research you are doing? Yeah, sure. So like you said, I'm a lecturer in nutrition and exercise physiology here at John Morris. And my main area of research is looking at the link between muscle mass and strength and how that relates to cardio metabolic health, in general, but more specifically, cardiovascular health. And then if we get even more specific, how that affects our risk of, let's say, blood, fat, blood lipid related disorder, so things like cholesterol, triglycerides. And yeah, basically how muscle mass can protect us from that. And then a lot of my research has in the past as being with cardiac rehab. So people who've had some form of cardiovascular disease in the past. Yeah, so I think it's interesting, we talk about muscle mass. Usually we link it more to muscle performance in a way, strength, speed, but you are looking more like cardiovascular health. So could you tell us a little bit? How does those two to link together? Why muscle mass is important for cardiovascular health? Yeah, absolutely. I like, like you said, a lot of people don't kind of make the connections straight away. So muscle is obviously a very metabolically active tissue. And we know that there's a lot of, let's say, population cross-sectional research that shows that those with a higher level of muscle mass and usually a lower level of body fat are at a lower risk of developing cardiovascular disease in the first place. And even in populations that have cardiovascular disease, we see that those with the highest levels of muscle mass seem to have the lowest risk of death. So there seems to be some sort of a protective effect there. And that has put a lot of people questioning why, why does muscle mass seem to be protective? And one of the things that we can talk about quite definitively is the effect that muscle mass has on, let's say, blood glucose control. So we know that muscle mass is, let's say, one of the primary sinks for dietary carbohydrate. So whenever we eat anything that contains carbohydrate, we digest it, it gets converted into glucose, it goes into our bloodstream, and that raises our blood sugar very, very slightly. And when our blood sugar goes up, it's an automatic response, our body's like, okay, we need to maintain this in a very, very tight homeostatic range. So it tries to bring that little blood glucose down. And it does that by directing our blood glucose to a few different metabolic fates. So it can burn it, but we can only burn so much at any given time. So the natural thing for our body to do is to try and store it. And if we have lots of nice, active, healthy muscle, we're able to store quite a lot of carbohydrate in that muscle in the form of glycogen, so we can store it there. And if we kind of max out those muscle glycogen stores, then we can also store it in body fat as well. But yeah, having healthy muscle is a really great way to help with blood glucose management. And we know that individuals who are able to maintain healthier blood glucose levels have a lower risk of diabetes and a lower risk of cardiovascular disease, which is actually one of the main causes of death in individuals with diabetes. It's not just dying from diabetes. You usually die of some sort of a secondary condition related to the diabetes and cardiovascular disease is a big one. So that's one. But then my main area of research is the effect that our muscle mass might have on our blood lipids. So when I say blood lipids, I'm talking about things like cholesterol specifically, and then also triglycerides as well. And there's not a huge amount of evidence in this area. And that's what the research group that I work with here at John Moore's, that's what we're trying to figure out. We're trying to figure out how does our muscle mass affect that? Those blood lipids, how does it affect HDL cholesterol, our LDL cholesterol? And you know, maybe we can talk a little bit about those as we as we speak today. Yeah, so maybe let's go in the lip. It's a little bit later. So you said that the muscles are good, carbs sink basically. So if you haven't exercised for a few days, so basically, or you haven't depleted your carb stores in the muscle, how much there is kind of space to store more like the chain or carbs? Do we know that? So we don't, it's hard to put a very solid number on that because there are so many factors involved. Like you've just mentioned there, if somebody hasn't exercised in a few days, there's a good chance that their muscles are quite replete with carbohydrates. But I think within the context of somebody who's quite physically active, let's say somebody who's relatively physically active every day, we do know that their muscles are more susceptible to taking on extra glucose. And that's basically through, well, in the short run, through the activation of certain pathways, such as the glute for pathway, which primes muscles to uptake more glucose into them on a, as soon as we eat something and around the time of exercise. But it's very, very difficult to kind of say, okay, this person who hasn't been exercising for the past few days, and let's say they have been eating quite a full diet already, high in carbohydrates, there's a good chance that those carbohydrates are already replete. So it's not going to have a major effect then. But we still know that those individuals with those higher levels of muscle mass seem to process that glucose a little bit better than sedentary individuals, for example, who have lower levels of muscle mass and who aren't exercising at all. Yeah, I'm not the expert, but for marathon and ultra events, you can do the carb loading. So you can basically go over the base level. So I was maybe thinking of this kind of how much you can go over. Does it happen like in a normal situation when you eat carbs that you kind of get a little bit over and then then you can start depleting it with exercise. I was maybe thinking that loading phase that does it does it play into in normal situations also. So I think one thing to think about is that we're not always, let's say, at 100% glycogen saturation within our muscles. And very, very few people will. We will be close to that. And then those who train will be at a higher level. So we do know that training status has a major effect on how much glycogen we have and how much we can store. So if somebody is well trained and has healthy muscles, they can store more. And then if they do consume a few more carbs, they can bring that level up a little bit higher than the average person, or about considerably higher than the average person. Yeah. Yeah, no, that's very interesting. So what are the kind of implications everybody should have higher muscle mass. So then their carb control works better is that basically what would be their solution. So if you look at if you look at cross sectional data, you'll see that there is actually a nice trend between what we would say skeletal muscle mass index and just to give people a bit of context. So a skeletal muscle mass index is the amount of skeletal muscle we have in relation to our height. Okay, so it's not just the absolute number of the amount of muscle mass back. But we see that there's a nice correlation between that and our risk or sorry, our chance of not getting diabetes or pre diabetes. So basically, the more muscle you have the better, but I would be, I would say that that is within the general population. And I would say if we start looking within athletic populations, it's not a case of you really need to try and put on the most muscle you possibly can. And what I would say is that it's more likely the healthier your muscle is, and by healthy, I mean, muscle that is is active, that is relatively lean, that doesn't have a huge amount of what we call intramuscular triglycerides, right? So fats that build up in muscle, and basically if somebody is healthy and exercising regularly, they're going to have healthy muscles. So if you have healthy muscles, you know, you have a relatively decent amount of muscle mass, I'm not saying anybody needs to be Arnold Schwarzenegger by any means whatsoever. But if you're physically active, you maintain a good level of muscle mass, that is going to put you in the best position to help control blood sugar, at least, to the best of your ability. For most sedentary behavior and physical activity researchers, collecting the research data is one of the most frustrating steps of a project, especially as inefficient data collection steals too much of your precious time, causes unnecessary stress and hassle, and can easily derail progress of your project. This is why we devised a revolutionary new way to collect data, introducing Phibian Sense Motion, the beginning of a new era. Phibian Sense Motion is a cutting edge next-generation system that allows you to easily and remotely collect, store, and manage data. Our solution features a tiny waterproof device that captures the sedentary behavior and physical activity data, a mobile app for automatic uploading of the data from the device, and a cloud service for managing the data. Even better, all collected data is GDPR compliant, and you have access to automatically analyzed variables of activity types and raw three-axis accelerometer data. Don't compromise on the quality of your research or the project timeframes. Discover the convenience and power behind our solution at sense.phibian.com. That is S-E-N-S.phibian.com. Phibian created by researchers for researchers. Yeah, makes sense. And you said about the link between muscle mass and cardiovascular health. Are these studies done usually with the older people, or do you have studies, basically the whole lifespan, also younger, younger adults? So the studies related to blood glucose control, as far as I know, are done from people in their 40s onwards. But then if we look at studies with younger populations, we also see a similar correlation between those who have slightly higher levels of muscle mass and better glucose control. Yeah, yeah. And how do you see this playing the role? I did my PhD. We had a task that older people need to climb stairs. I think it was five flights of stairs. And basically, the muscle strength was the limiting factor. So basically, the ones who were the strongest were able to do this. So it was not the cardiovascular health. The cardiovascular fitness that was limiting the stair climbing ability, but it was the muscle strength. So basically, I'm thinking that if you have a lower muscle mass, maybe you don't have enough strength or kind of muscle entrance to do aerobic exercise. So basically, I think it's been shown with the older people that if your strength levels are low, then they are not capable of doing cardiovascular exercise. So do you see this playing maybe a sub confounding factor here? It is a possibility. So let's say if we look at all a lot of the research that's done on exercise and cardiovascular health, a lot of it in the past has focused exclusively on aerobic fitness. And there's a very good reason for that. We know that VO2 max, for example, is one of the best independent predictors of risk of cardiovascular disease in the future. So it is a fantastic measure. And we do know that individuals who have very, very low levels of muscle mass, so sarcopenia. And just for anyone who's not familiar, sarcopenia is just the title for the condition where we lose muscle mass gradually as we get older. So basically, from our 30s or 40s, most people are gradually losing muscle mass when we get into our mid 50s, 60s, that starts to speed up considerably. But one thing to take into consideration with that is sarcopenia is not just loss of muscle. It's also it contains an aspect of something called dyneopenia, which is the loss of strength as we get older. And I would probably argue that that loss of strength is actually much more important than the loss of muscle size itself. And the reason I would say that is, is you can actually have a muscle that is relatively large, let's say, if you measure it with DEXA. But DEXA is quite a gross measure of muscle size. You just get a this is your muscle here. It looks rather large. But if you let's say do an MRI with that muscle, which gives you much more detail, you might see that there is a lot of fat infiltration into the muscle, which is an indicator of poor metabolic health. Okay. And usually when you see a large amount of that fat infiltration, that will also have an effect on muscle strength, because those muscles aren't able to contract as as strongly as they should be able to. So what we see is that dyneopenia, the the the the the muscle strength seems to be a much better predictor of long-term health and cardiovascular health than muscle size. And you know, there are a number of studies that that have done and they've looked at. The one that's quite commonly used is grip strength. And we'll see quite an association between grip strength as a proxy for overall muscle strength, a nice association between that and longevity, and also a risk of heart disease. But we've also seen some studies where they've done even more, let's say specific muscle tests or things like chest press strength or leg press strength. And again, an association between level of strength and long-term health. So yeah, I would say that I think muscle strength is actually much more important than muscle mass. But you can actually work on both when we think about how to how to develop those and how to maintain those as we as we get older. And when you say in dyneopenia, you said that it's often related to kind of quality of the muscle. If there's a lot of fat inside the muscle, how much do you see that it's kind of the quality of the muscle and how much do you see it's the motor control, how how well you are capable of activating it. Because if you're not using if you're not doing leg press ever with the big weights, you're not very good, good with your legs, exerting force in a certain test way, at least. What would you say? What's the kind of the ratio there? I see. And that's a really, really good question that I can't give you an answer to because we just don't know. We do know that like, and it's an excellent point about the actual loss of motor control as people age. One of the reasons why we see people losing muscle mass and lose muscle strength is because of inactivity. And because people are not actually putting in the work to maintain muscle over time, they're not doing anything that requires a large amount of muscle control and use of those motor units. And what we see is that we actually see a decrease in those motor units over time and the control of those motor units in order in older adults. And that also contributes to the problem because we know that sarcopenia is multi factorial. It's not just, you know, it's not just people just lose strength for one reason or another. There's a number of reasons involved in that loss of strength over time. And one of those is the loss of the motor unit and particularly particular types of fiber. So for example, we see in older adults a particular loss of preferentially type two muscle fibers, which are, let's say, what grows in what we would call the fast switch muscle fibers for one of a better term. And one of the particularly interesting outcomes of that is if you think about those fast switch muscle fibers are things that we use for doing, let's say, powerful quick movements. But in older adults, if you think about when do they use powerful quick movements, a lot of them don't. But if you think about when a situation might arise when we do do it is for something like balance. And if you think in older adults, so older adults are, if an older adults slips, for example, if you and I slip, there's a very, very good chance that when we slip, our type two muscle fibers will kick in sufficiently and we'll be able to quickly recatch our balance and we'll be able to stop ourselves from falling. With older adults, because they've got this preferential decline in motor units and in these type two muscle fibers specifically, they're not able to catch themselves as quickly and react as quickly. And what happens is we see these older adults falling, hitting the ground. And then another associated condition of sarcopenia is also low bone mineral density or osteoporosis. And that means if you've got somebody who's hitting the ground with osteoporosis, they've got a greater chance of breaking a hip or breaking a bone. And we also we then know that people who break a hip in later life are at an elevated risk of death within one year of that happening. So it's it's a very, very there's a lot of cumulative conditions that come along with sarcopenia. And that can kind of really contribute to a lower quality of life for these individuals for a long period of time. Thanks for joining us this week on physical activity research through podcast. If you like the show, make sure you never miss an episode by subscribing or following the show on Twitter. This podcast is made possible by listeners like you. Thank you for your support. If you found value in the show, we would really appreciate rating on Apple podcast or whichever app you're using. Or if you would, in a real old-school way, simply tell a friend about the show. It would be a great help for us. We have a fantastic lineup of guests for forthcoming episodes. So be sure to tune in. Thank you all for your support and have a great day.
