E34: Running Injuries | Karen Troy | Biomedical Engineering

{sound of running sneakers hitting the ground}

Jon Cain: Running is a great way to get exercise, you know, clear the mind, strengthen the heart, but a lot of runners have to deal with injuries. On this episode, we're exploring running injuries and the high-tech engineering research aimed at preventing them. Whew. Lemme catch my breath. Hi, I'm Jon Cain. This is The WPI Podcast. Your home for news and expertise from the classrooms and labs of Worcester Polytechnic Institute. Today's guest studies how mechanical loads from physical activity like running influence bone health. Karen Troy is the John Woodman Higgins professor of biomedical engineering and head of the Department of Biomedical Engineering at Worcester Polytechnic Institute. Her work seeks to prevent stress fractures, and fight bone loss. Karen, thanks for being on the WPI Podcast. 

Karen Troy: Thanks. I'm excited to be here. 

Cain: A lot of people love running and the way it makes them feel. But running can also result in injuries. So I'm wondering if you could talk a little bit about what are some of the common injuries among runners?

Troy: So I'd say the most common injuries are gonna be overuse type injuries, either overuse of, uh, bones or overuse of like tendons. So imagine bone stress injuries are very common. Tendonitis, plantar fasciitis. Uh, sometimes people call like runner's knee. Those are all musculoskeletal tissue injuries. 50% of runners, uh, report a running related injury in any given year, so running injuries are quite common. The injuries that I study are bone stress injuries. So those are a type of overuse injury, uh, sometimes called a stress fracture or like a stress reaction, but it's specific to the bone. 

Cain: Can I ask you a little bit about the stress fracture? How is that different than a broken bone? I've always heard of the stress fracture, and I'm wondering is it like bad, but not as bad?

Troy: Yeah, it is bad. It can be as bad. Um, but the mechanism is a little different. So when you fall and you have a fracture, basically the force that your bone experiences is greater than the bone strength. And so you the bone breaks In a stress fracture, it's uh, what we call fatigue damage. So, uh, basically you don't have that much force, but you have a lot of repetition of that force. And so you can get micro damage that is in the bone and it accumulates normally your body's actually really good at repairing damage, and so we have all of these cells that come in and they fix the damage and nothing bad ever happens. But in the case of a stress fracture, um, we're doing so much of an activity that we're accumulating the damage faster than you can repair it. And when you do that, eventually it will start to become painful. Um, that's usually when we detect a stress fracture or a bone stress injury, but sometimes people will continue to run on through it. And even though it hurts, right? I'm sure lots of runners we know have run through painful things. And if you continue to run on it, eventually those micro cracks can all come together into a macro crack and then you really do have a, a true stress fracture. 

Cain: Wow. Um, are there any differences between women and men and the number or prevalence or the types of injuries in running.

Troy: Yeah, we know that in bone stress injuries, women tend to get injured with this type of injury two to three times more frequently than men do. We don't know exactly why. Some of it has to do with physiology and our ability to repair damage. Some of it may have to do with the types of physical activities that we did when we were growing up. Men often will start running a little bit earlier than women, but not always. Uh, but we know that it's, there is this difference in the sexes and, and it's a really important difference. Um, in terms of locations of the injuries, uh, most common sites for bone stress injuries are sites like your distal tibia. So basically right above your ankle is very common site. Um, your metatarsals, which are the long bones in your feet, is very common. That's one that we've been currently studying. Uh, and then there's some other sites up further up your skeleton, uh, around your hip and your pelvis that tend to be more common in women than in men.

Cain: So, Karen, your research really looks at what can be done to prevent these injuries, and part of that is really understanding why the injuries happen in the first place. Uh, you've talked a little bit about this, but I'm wondering if you could talk a little bit more about what are the factors that you're investigating in particular in your research?

Troy: So as an engineer, I think about bone stress injuries as a mechanical process mixed in with some physiology. And so we do a lot of focus on the mechanics, and that means that we need to understand how the bones are loaded when people are doing an activity so that we can understand how we could maybe change those loads. But we also know that bone is super smart. It doesn't just sit there in your body like a brick. It can adapt. And so if you give your bone a mechanical stimulus, you load it and it puts stresses on the bone, most times your bone will adapt to become stronger. We hear about this in popular literature, when you think about astronauts who go into space and we know they lose a lot of bone.

Cain: Right? 

Troy: Right. They lose it because they don't have those mechanical forces anymore. So on the flip side, if you do a thing, your bone will get bigger and stronger. 

Cain: I hadn't thought about that. Right. Yeah, that makes, that makes a ton of sense. 

Troy: Yeah, so, so we wanna be able to understand how and why bones are getting stronger so that we can have stronger bones to prevent the injury. And then we also wanna understand when are bones getting loaded too much and maybe getting damaged. In order to do that, uh, we've been focusing, as I said, mostly on the, the foot right now. Um, so we study a lot of different things. We measure the biomechanics of how people are moving. We try to understand how feet are behaving. Feet are very complicated. There's a lot of little bones, there's lots of ligaments and connective tissue. Uh, so we, we don't understand exactly how different people's feet move. We also know people's feet are different. So some people have very high arches, some people have flat feet. We all have muscles in our feet, so those muscles might be strong, they might be weak, and all of those things can affect how the bones in our feet are being loaded when we take a step during running, we also have factors like the physical activity that you did when you were growing up that can affect the structure of your bone now. And so if you did a lot of impact loading as a kid, like gymnastics or cutting sports such as soccer, that can lead you having stronger bones now because of this adaptation process. So, when we are growing up, especially in our teenage years, we're growing very quickly and at that point in our life, there's about a three or four year period where we gain 40% of our lifetime bone mass in that three or four year period. So a huge amount of bone is acquired during that time, and what we do during those teenage years roughly age 11 to 15, really matters in terms of how we've set ourselves up for adulthood. So if you were a very physically active person during those teenage years, chances are your bone adapted while you were doing those physical activities and while you're growing to be pretty big, strong bones. If you were a sedentary person during those years, then your bone didn't receive the same types of stimulus and you probably just don't have the same adult skeleton that you would have otherwise. Mix into that then some physiology, right? So now imagine you have, uh, you're struggling with an eating disorder during your teenage years. Even if you're doing a lot of physical activity, now you don't have all the right building blocks to build those big, strong bones. And so you may have set yourself up for, uh, adulthood where you're just always gonna have to be careful about bone injuries because you missed the window. The good news is that young adults really up until about age 40 have the capacity to continue to adapt and build bone. So even if you look back on your teenage years and say, oh gosh, you know, I wish I had done x, y, z, I might have been in a better situation now, it's never too late. You can always add bone and, and we know even older adults, uh, can continue to add bone with physical activity. So we need to understand what are the factors that might put you at risk for an injury. And what are the factors that might be protecting you from an injury, and then how does it interact? There's a whole other set of things having to do with physiology, so we need to understand things like your diet, uh, how your training habits, all of those things can affect your ability of your bone to actually repair and adapt.

Cain: It sounds like there's so many variables that you can look at. 

Troy: There's a lot of pieces to this puzzle. We are certainly not an expert on every piece of the puzzle, but we try to really understand the pieces that we are interested in having to do with the biomechanics and the bone structure. 

Cain: I'm wondering how you do your research. How do you look into some of these, uh, factors? 

Troy: Yeah, so we collect a, a few different types of data. The first type of data that we collect is imaging of the feed. So we use a high resolution ct. It's basically a very fancy CAT scan to get information about the structure of the bones and the feet, and we can analyze that data quantitatively to actually get estimates of bone strength from the images. The second type of data we get is biomechanical data, so that happens in a motion capture lab. We get information about people’s footwear, how their feet are actually moving in the shoes that they're wearing while they run. Uh, and we also have these very cool pressure sensing insoles that we can put into their shoes so that we can understand where under their foot the forces are getting transmitted. The third type of data that we get has to do with physical activity history, and some of those metabolic risk factors, and we get that information through surveys. Uh, for example, we have a number of validated surveys where people can report all the different sports that they did when they were growing up and the ages that they did them and the frequencies. And then we also get information about some of these metabolic risk factors. This is called Relative Energy Deficiency in Sport or REDS. And, uh, it, it really is the intersection of not eating enough food or having, having insufficient energy availability for the amount of activities that you're doing, which can disrupt some of your hormonal profiles. And those hormones interact with the bone metabolism. And so when you have this disruption, which is particularly common in women, but can also happen in men, um, it can result in increased risk of bone stress injury really through the ability to not repair your bone as well. Especially if you are a young woman who maybe had a history of disordered eating during adolescence, that can also have affected the ability of your bone to be strong as an adult. We've been measuring bone density using a tool called DEXA, so that's your clinical bone density scan that your grandmother might be getting every year or two. And so we measure DEXA measurements of bone density and then the entire body, but then we also get some specific regions. 

Cain: Gotcha. So how many runners, uh, are involved in your study and do they come into the lab and, and regularly run on a treadmill to help you with, uh, getting some of that, uh, motion uh, imaging?

Troy: Over the years, we've had 70 to 80 runners come through the lab. We've collected different types of data on them as a group. Everything ranging from the biomechanical data to the imaging data to other, uh, questions that we've been answering on runners. So when they come in, uh, a motion capture area has some force plates actually embedded in the floor. So those are very fancy scales that can measure forces in vertical direction, but also horizontal forces. We pair that with a camera system that is mounted around the walls, depending on what question we're asking we have people walk across the force plates, run across the force plates, and then we also have a treadmill that we can move into that lab space so that they can run on the treadmill at various speeds.

Cain: You've captured a lot of data. What do you do with it once? Uh, you have all of it compiled? 

Troy: So one simple question we can answer with the imaging data is that we can use it to do a virtual mechanical test on people's bone. We can look at your specific bone and simulate a load, for example, a twisting load or a bending load, and predict how strong that bone would be when it breaks.

Cain: For the individual?

Troy: For an individual person. Yeah, so that's a really great, because now we have a very objective physics-based way to compare your bone strength to my bone strength, and that allows us to compare different groups of runners and understand why is this person's bone stronger than another person's bone. The goal at the end of that is for us to develop interventions so that I can make your bone stronger if it needs to be. Another goal is that I wanna be able to develop predictive tools. Imagine that you are a runner and you wanna train for a marathon, but you also don't wanna get an injury. Right? And so I would like to be able to make a tool that says, here's your physiologic profile. You know, you are X number of years old male runner, and your risk of bone stress injury is low if you run, let's say 30 miles a week or less, but it becomes substantially higher if you start to run 50 miles a week or more. So, we know that people have training goals and performance goals, and then we also have injury risk tolerances. We wanna be able to make tools so that we can make better choices about our training relative to our individual injury risk. So that's one of the ongoing projects is to continue to collect the data, but we need to understand what are the risk factors that are important so that we can start to develop these tools.

Cain: Karen, how do you hope the research that you're doing will benefit athletes, whether they're the professional or the weekend warrior?

Troy: So, I'm a runner, and this is a personal interest of mine, and I know a lot of runners suffer from overuse injuries. It's incredibly common. Lots of athletes have their identities really tied to their performance and when you're injured, it can be incredibly frustrating and really make you question whether this is the person that you've, you were cut out to be. So anything that we can do to help prevent these injuries would really be a great outcome, and I hope that we're getting data that can help people find that sweet spot between overuse and training too much and then not training enough so that you can really balance the performance goals that you have, but also manage injury risk. So ultimately we're hoping to empower people so that they can run smarter, not necessarily run less. 

Cain: So as a, as a casual runner myself, I really don't know what the best type of running sneaker is for me. I just will pick something that sort of feels comfortable in the store, do a quick lap around. Um, does your research look at all into the optimal footwear for running? 

Troy: Yeah, it's a great question. There was actually a study a few years ago that tried to answer this exact question and they paired runners with what they thought their optimal footwear would be. So for example, if you had really flat feet intended to over pronate, they would give you a stability shoe. They found that putting people in that type of footwear did not prevent injury at all. In fact, it seems that the best advice is to do exactly what you're doing, which is try on several different types of shoes, pick what's comfortable for you, and then go with it. Our current research is looking at how minimal footwear, sometimes people call it barefoot footwear, um, that's shoes that have no arch support and a really flexible sole. We try to understand right now how that wearing that type of footwear is associated with changes to foot, muscle, and bone strength. We know that walking in more barefoot style shoes can increase the strength of your muscles in your feet, and we know that usually strong muscles cause strong bones, so they work together. Um, so we're trying to understand whether we actually see differences in people who usually wear barefoot styles of shoes compared to people who wear typical cushion shoes during running. So there's certainly trade-offs with this type of footwear. And I wouldn't necessarily recommend that everybody goes out and buys a pair of minimal shoes to run in every day. But if we find that people have stronger bones who typically wear these shoes, then there may be some ways to incorporate them into training that could prevent injury by enhancing the bone strength through that adaptation process. 

Cain: So stay tuned. It'll be really interesting to see what, what, what comes out of that.

Troy: Yeah. I think it'll be really exciting and it may, and I, I think what we may find is that you don't have to run in them every day or all the time to get a benefit. If we see one, probably there are other things that we can do to get that same benefit. 

Cain: And in the meantime, I will continue to do my goofy looking laps around the, uh, the sneaker store.

Troy: For sure. For sure. 

Cain: So you've been looking at some of these questions for, uh, quite some time. I'm wondering what are some of the, the findings that stand out to you from, uh, your years of doing this work? 

Troy: When we start to compare injured runners to those who have not had any history of injury, we see some things that are pretty obvious at the start. Our injured runners tend to be a little higher performing. They tend to be running longer miles at a faster pace. That's not really surprising because we know that training habits are associated with injury. We found that the runners with injury in our group tended to be a little taller or have bigger feet, which is kind of interesting. I think there's some mechanical reasons behind that. If you have bigger feet, then every time you're pushing off, you actually have a little bit of a, a larger lever arm. And if you're running at a faster pace, then you are also pushing off with more force. So those bones are just physically experiencing more force in your feet than you would if you had smaller feet. We also see a connection with REDS, this Relative Energy Deficiency in Sport, and that's consistent with what others have observed. It's not surprising that individuals who are injured have more risk factors related to energy availability and bone metabolism. And one of the things that's been interesting is when we look at the bone density data, we found that many runners have just fine looking bone density in their hips, which is a typical site that we'd look for, but then they have quite low bone density in their spines or even in their forearms. 

Cain: So, it's not uniform. 

Troy: So it's not uniform. And when you look at your whole body, it looks okay. 

Cain: Hmm. 

Troy: What we think is going on is that when you are a runner who maybe has some of these energy deficiency issues, your body is trying to adapt to its mechanical demands, and so it prioritizes putting bone in your lower extremities where it's most needed because you're running, but it's at the expense of the bone in your upper extremities or in your spine. Other studies, not my own work, uh, have shown that there are some specific training habits that are also linked to injury risk. So, for example, if you have a very long, long run in your week compared to your weekly mileage, that can increase your injury risk. And the other thing that can increase it is training spikes. So if you're increasing the distance of that long run very quickly from week to week and you're not also increasing that base volume that goes with it, those types of changes in training habits are seem to be what's associated with injury risk more than running speed or weekly mileage. 

Cain: Really fascinating information and that, that kind of leads me to my next question. I wanted to sort of dive in a little bit on that, uh, because chances are, we've got some runners listening who probably wanna know, okay, right now what can I do? Um, you know, what can I do to try to prevent these types of injuries? Are there, you know, additional practical steps that you might recommend for them based on, uh, your research and the research in the field? 

Troy: Yeah, I think my research is early enough stage that I don't have very specific results directly from my findings to help. However good training habits is absolutely one of the key steps. In terms of foot injuries in particular, there seems to be some evidence that having strong feet may help, and so doing some foot core exercises can help. These are things like towel scrunches, so you know, take your barefoot and try and pick up a towel. There's other types of foot strengthening exercises we think those may reduce the risk of injury in the feet. In particular, there's other habits that you can have to reduce running injury. Good stride mechanics is another one. So we actually have evidence that overriding, so stepping too far, you know, stepping too long, that can increase your risk of running related injury. Uh, it increases the forces on the knee. Uh, it also increases forces on your bone. And in fact, there was some earlier work done by my colleague, Brent Edwards, that showed that if you shorten your stride but don't change your overall pace, that could potentially also reduce your risk of bone stress injury.

Cain: Karen, you mentioned stride mechanics, and I know people run differently. They sort of land on their feet differently. Everybody's a little bit different. Is that a factor in injuries based on the research that we know of? 

Troy: One of the questions that I frequently get when I talk about my research is, should I try and change the way my foot hits the ground? I have heard that a rear strike foot pattern is dangerous, for example, or might cause injury or a fore foot strike pattern is a better way to strike. The answer is it's complicated. Oftentimes, rear foot strike patterns are associated with injury because somebody is overstriding, so then you're really sticking your foot out and striking on your heel. But many people have a rear foot strike pattern that is not overstriding and it's not associated with injury. So I would say key things to keep in mind is shorter stride length as I mentioned before. Staying light on your feet so you know, you can listen to the sound that your feet make on the ground and if you're really pounding, see what you can do to adjust it so that you sound quieter. And then, um, just run in a natural way. 

Cain: And Karen, I'd love to widen out the view a little bit further. What about a person's overall training regimen? Do you have any tips for how runners can go after their goals while navigating any potential injury risk?

Troy: Yeah, I think the most important thing, and this I'm, I guess I'm mostly speaking about longer races here, you know, half marathon, marathon, um, but I think following a structured training plan is always a good plan, but don't be afraid to modify that plan. You don't have to be super rigid about it. So for example, if you sense that an injury is coming on, or if you always have an ache in a certain spot, it's okay to take a couple of days off or slow things down, do some cross training instead. That can really help with preventing injury. Additionally, if you're a person who's prone to injury, maybe you've had previous running related injuries, uh, or you're recovering from an injury you could even splice in some run-walk in some of the longer runs. That's been always helpful for people. One of the other most important things is just to listen to your body, so if you do feel like an injury is coming on, and I think there's a lot of sunk cost that goes into, especially training for something like a marathon, you get to your week, 18 out of 20, you've done all your long runs, you've put in the effort and something hurts, but you say, my gosh, you know, I have worked for the last four months to train for this race and I'm gonna finish this darn thing. And I think a little perspective of realizing that this is not the only race in your life. And there will be others, especially if you enjoyed the process. Some days are gonna be your day on race day and other days are not. So I think just having that little perspective of realizing that not every race is going to be the perfect race, but there will be others, especially if you can keep yourself injury free. I think that mindset can help you to keep your injuries minimized and maximize your performance goals and, and realize that there will always be more. Racing can really, and running can be a lifelong sport. I can give you an example from my own personal experience. When I was training for my first and only marathon, I had developed some tendonitis and I had gone in and out of cross training to try and resolve it as I got to very long runs. But by the time I got to my race day, I felt very committed to finishing it. I was running with my mom and my sister, and I really should have stopped running that marathon about halfway or two thirds of the way through because it started to hurt quite badly. But at that point, I felt so committed to finishing the race that I completed it. And as a consequence, I have been dealing with chronic recurring tendonitis for the subsequent 15 years. It could have been a minor injury that resolved, but by persisting, I, I'm sure that I damaged something in my foot that has made it worse. 

Cain: Wow. Yeah. It kind of speaks to the, that battle that you, you face. You know, you put so much work into it, you wanna, when you wanna reach the goal and kind of see how that plays into that equation. 

Troy: Yeah. If I could go back and message my past self, I would've done things slightly differently. But, you know, as it is, I continue to enjoy running just not quite at that distance, so.

Cain: Gotcha. And if someone's looking to come up with a training plan for a long run, where is a good place to start? 

Troy: So the internet is full of training plans. Some of them are really intelligently and thoughtfully designed and others not so much. One thing I would recommend against is just typing into Chat GPT, give me a running training plan mostly because it will give you a conglomerate of all kinds of distances mixed together. And so, it often ends up giving you unrealistic goals for times and distances and speeds. Um, but there are many marathon specific training plans if you're looking for that. I personally really like the Some Work, All Play group that, uh, this is a couple of coaches that have really nice flexible training plans, but there are other websites out there and certainly Runner's World has, you know, some very basic formulas. There's many of them out there. There's also a lot of books from, uh, coaches with marathon training plans. 

Cain: I wanna go back into the lab for a, for a moment and ask you how are WPI students involved in the research that you do? 

Troy: So students are a really critical part of our research, and they participate both on the data collection and analysis side of things. And then they also often participate as volunteers because they are often also runners. So certainly a, a large number of student athletes have come into our lab. As engineers to help with data collection, to help with data analysis. They are in the motion capture lab. They're helping to work with research participants. Uh, they're in front of computers doing image analysis on the CT images we get. And then sometimes they are also helping us by being participants in the research themselves. So they might be in the motion capture lab being a participant. And sometimes they span that gap. It's great when we have student athletes who also have those great technical skills because they can help us think about new ways to collect data to get the information we want to get.

Cain: Mm-hmm. Are you actively recruiting participants for your studies? 

Troy: We are actively recruiting individuals who run medium miles. So I would say 10 to 20 miles per week. A typical recreation type of a mileage. If you're a really serious athlete, we're not looking for you at the moment. Um, and we're looking for people who both wear minimal footwear and traditional cushioned shoes. I'll share the website with you and, and anybody who's interested in learning more about the study and potentially participating can click right on the URL. 

Cain: Great. And we'll add a link to that in the show notes. You know, Karen, we've talked a lot about injuries today, but at its core what you do is trying to empower runners so that we can enjoy this activity. Um, is there any sort of message that you have for the, for the runners out there or the prospective runners who've, who've heard this, and, um, what do you want them to take away from this conversation? 

Troy: Yeah, I think running can be so fun, and especially if you're thinking about participating in a road race. For me, that was always a way that it, it reaffirmed my view that humanity is a great group of people. You show up at a road race and there's just so many people from all walks of life that are out there enjoying being outside, like running together. And I think being able to experience that or even if you're a solo runner, like being able to just be out in the, in nature, um, it can be so fun. While everything we've been talking about is injury related and while running injuries are incredibly common. Running is still one of the greatest lifelong accessible sports that there are. It's common for a reason. It's joyful, it's fun. And I certainly wouldn't let the risk of injury be off-putting to anybody who's interested in getting started.

Cain: Well, Karen, this has been fascinating. There's a ton of great information here for, for runners to think about and, uh, I really appreciate you taking the time to share it with us. Thanks so much for being on The WPI Podcast. 

Troy: Hey, thanks so much. This was really fun. 

Cain: Karen Troy is the John Woodman Higgins professor of biomedical engineering and head of the Department of Biomedical Engineering at Worcester Polytechnic Institute. Alright, time for us to lace up the sneakers and head out for a run. And as I do, I wanna thank you for listening and invite you to follow the WPI Podcast on your favorite audio platform. We're now on Pandora and several others. Feel free to leave us a review. You can find all our episodes and other podcasts from across campus at wpi.edu/listen. On there, you can also hear audio versions of stories about our students, faculty, and staff. You can get the latest WPI news anytime by asking Alexa to “Open WPI”. My thanks to the Global Lab in the Innovation Studio on campus turned running track for today. That's where the show is produced. We couldn't do it without the audio engineering help from PhD candidate, Varun Bhat. He's running with me. You just can't see him. Tune in next time for another episode of The WPI podcast. I'm Jon Cain. Talk to you soon. {sound of running sneakers hitting the ground}