Biomechanics of Running on Varied Terrain

Dr. Megan Peach // #FitnessAthleteFriday // www.ptonice.com

In today's episode of the PT on ICE Daily Show, Endurance Athlete division leader Megan Peach discusses utilizing hill running as a gait drill for injured runners, explaining the changes in running mechanics between running flat, uphill, and downhill. Megan also explains when and why to recommend uphill or downhill running

Take a listen to the episode or check out the full show notes on our blog at www.ptonice.com/blog

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EPISODE TRANSCRIPTION

INTRODUCTION Hey everybody, Alan here, Chief Operating Officer at ICE. Thanks for listening to the P-10 ICE Daily Show. Before we jump into today's episode, let's give a big shout out to our show sponsor, Jane. in online clinic management software and EMR. The Jane team understands that getting started with new software can be overwhelming, but they want you to know that you're not alone. To ensure the onboarding process goes smoothly, Jane offers free data imports, personalized calls to set up your account, and unlimited phone, email, and chat support. With a transparent monthly subscription, you'll never be locked into a contract with Jane. If you're interested in learning more about Jane or you want to book a personalized demo, head on over to jane.app.switch. And if you do decide to make the switch, don't forget to use our code ICEPT1MO at sign up to receive a one month free grace period on your new Jane account.

MEGAN PEACH I think both YouTube and Instagram are both live. Miracles. Good morning. Happy Friday. This is your PT on ICE Daily Show, and I'll be your host today. My name is Megan Peach, along with the Institute of Clinical Excellence, bring you this topic today of incorporating hills into your gait retraining toolbox. I am one of the lead faculty for our endurance division here at Institute of Clinical Excellence. and I teach both the live and the online versions of Rehab of the Injured Runner. So I'm super excited about this topic today. Let's get into it. So we have a lot of different tools in our gait retraining toolbox that we might use to keep injured runners running or return injured runners to a running program if they've had to take some time off.

CHANGES IN RUNNING MECHANICS WITH UPHILL RUNNINGOne of the tools that we don't often use or that maybe we don't often think about as much of the others like cadence training or forward trunk flexion or maybe quiet running is incorporating hills into their current running program as a gait training tool to keep that injured runner running. And before we talk about specific injuries, I want to talk a little bit about the differences between running mechanics when we're running either uphill or downhill as compared to running over a level surface or a level ground. So when we're running uphill, a couple of things happen in terms of the sagittal plane gait mechanics that are different from running over ground on a level surface. One of those things is that our stride length So the distance from where the foot strikes the ground to a vertical line straight down from the center of mass, that's our stride length, that often will decrease when we are running uphill. And what goes along with that is also an increase in knee flexion at initial contact. So when we're running uphill, our knee flexion tends to be more than when we are running over a level surface. and it tends to be a little bit less in comparison. Also, another change that we typically see is a decrease in the angle of inclination from the foot to the ground when we're running uphill. And so what that means is that, or what that looks like, is that a runner running on a level surface who has a rear foot or a heel strike might look like they have less of a rear foot or a heel strike when they're running uphill. So maybe they look like they have a midfoot strike or they may even have a forefoot strike. It's going to be very, very dependent on the runner and that certainly doesn't happen in every single runner. We don't necessarily see a strike pattern change in every runner when they start to run uphill, but certainly that can happen and it does in many, many runners when we go from running on a level surface to uphill. So that's the third change. And then the other change that we commonly see in that sagittal plane is an increase in forward trunk flexion. So from going from a level surface to running uphill, we will often see that runner shift their trunk forward. And what that does is take a little bit of work off of the knee and transfer it to the hip. And so the glutes end up doing a little bit more work. The quads end up doing a little bit less work when we're running uphill. That has some advantages. but potentially some disadvantages as well, depending on the runner. So then when we talk about running downhill, all of those biomechanics changes that we saw, or that I talked about running uphill, are the opposite when we're running downhill.

CHANGES IN RUNNING MECHANICS WITH DOWNHILL RUNNING So going from a level surface to running downhill, we often see that stride length increase. And so a runner will go from maybe landing with a little bit of knee flexion to nearly a straight knee at contact when they go from running on a level surface to running downhill. So we also see the knee flexion decrease or the knee extension increase depending on how you want to describe and look at that. What we'll also see is an increase in angle of initial angle of inclination at initial contact at the foot and ankle in relation to the ground. And so somebody who was a midfoot or a heel striker or a rear foot striker running on level surface is just going to shift that impact a little bit more posteriorly toward the heel. And it's going to be relative to how they hit the ground when they are on a level surface. So a midfoot striker may look more like a heel striker, or a rear foot striker may look more like a heel striker, depending on how they started out. Again, not in every single runner, but certainly there is that trend. The other thing we see with running downhill is a change in trunk position. And what we see when they're running downhill is more of an upright trunk posture. And even occasionally, we can see that runner almost lean backwards. And this happens for a couple of reasons. One, they're just trying to maintain their balance. It's a different body position running downhill versus running either uphill or over level ground, and so they're just trying to maintain their balance. And another, they're trying to control their speed. So often when a runner leans forward when they're running downhill, that can almost feel like they're gaining speed and it's a little bit uncontrolled, especially if that runner is more of a novice runner or just not used to running downhill. And so they'll lean back in an effort to just control their position and control their speed when running downhill. that has some obvious disadvantages, as it will increase the load on the knee and the lower extremity and decrease the load on the hip musculature.

UTILIZING UPHILL OR DOWNHILL RUNNING FOR THE INJURED RUNNER So, in talking about specific injuries and running mechanics in an uphill or downhill, we want to take into consideration where those specific injuries are and what types of tissue we want to offload. So starting with patellofemoral pain, super common running related injury. It's one that a runner can typically continue running through, at least in some capacity, as long as there are some shifts and adjustments in their training program. They may not be able to do the same amount of mileage, but they certainly can, in most cases, continue running. So when we consider offloading the patellofemoral joint, We typically use gait retraining drills like cadence retraining or increasing the step frequency. So we reduce the stride length, increase the knee flexion angle at initial contact. We might also use something like a forward trunk flexion drill to shift that load from the knee more approximately to more of the hip. And those tend to work very, very well for people with patella femoral pain. I personally treat a lot of trail runners and so they're generally not running on a level surface and they're generally running uphill or downhill and that's just the terrain that they're running on. And so often when we're using other drills like cadence or like trunk control, then we're expecting that they're going to run on a level surface. And so if we have a drill like running uphill, they're very, very much appreciative of being able to incorporate their normal terrain into their current running training program while they rehab that injury. And so with runners with patella femoral pain, we will often incorporate running uphill. Now I know it sounds a little bit crazy and runners always give me a little bit of a weird look, but because of the biomechanics that go into running uphill, namely the reduction in stride length, the increase in knee flexion angle at initial contact, and the forward trunk flexion, all take a little bit of that load off of the patellofemoral joint and shift it up the chain, so it shifts to the hip, and they're often able to tolerate running uphill quite well, even in comparison to running over a level surface. It is important that you remind them that they need to walk downhill, and that's really important so that we don't actually increase the load on that patellofemoral joint. Now, when I talk about incorporating uphill running to an injured runners training program, I am not talking about incorporating this giant steep slope that I expect them to run up. I'm talking about a very low grade, like a three percent grade, which is generally what's cited in the literature as something that the authors or the researchers are looking into as does this create biomechanical changes. And even a low grade like 3% is enough to create some of those favorable biomechanic changes that are going to make a difference in that runner's ability to tolerate that running load. And a 3% grade is enough to reduce that patellofemoral joint stress by about 25%, and that's per step. And so when we think about that cumulatively over many, many, potentially thousands of steps, that's a lot of load reduction on a single joint that is going to allow that runner to continue running as they rehab that injured tissue. So moving down the chain and thinking about Achilles tendinopathy, very different injury, obviously, different types of structures, different types of tissue injured. And we think about the biomechanics of hill training. And when we think about biomechanics of running uphill, like I mentioned, we have that reduction in angle of inclination as one hits the ground or as one impacts going uphill. that reduction of angle of inclination or the shift toward landing on a midfoot or a forefoot is going to also result in an increase in load or stress on that posterior lower leg musculature. So the gastroc soleus complex, as well as the Achilles tendon and some of the forefoot structures. And so with an injured runner, with Achilles tendinopathy, they're actually going to accumulate more stress while running uphill than they would running on a level surface or downhill. So much so, in fact, it's about a 25% increase in stress on the Achilles tendon while running uphill as compared to that level ground. And so with a runner with Achilles tendinopathy, we actually want to discourage them from running uphill. We do not want them running uphill. obviously while they're still symptomatic later on in the program. That might be something that we incorporate as they're able to tolerate more and more load, but certainly not while they're still symptomatic. And so when an injured runner with Achilles tendinopathy, we actually want to encourage running downhill because of some of those biomechanical changes, those runners are going to tolerate downhill running much, much better than maybe even overground running. And often in those, Runners with Achilles tendinopathy, they've stopped running for a period of time in an effort to rest the injured tissue and resolve the symptoms, they're not always sure how to get back to running. And so downhill running can be a good start with less load on that injured tissue than overground or level running or uphill running. Certainly we want to incorporate those later on as they tolerate more and more load. Okay, so the last one I want to talk about and It's been 12 minutes already and I haven't talked about bone stress injuries, so it's probably, it's a little unusual, probably a record. I do want to talk about tibial bone stress injuries. And so with bone stress, it's a little different than other types of soft tissue stress because with bone stress, we get stress from a couple of different inputs. One is an external input, meaning the ground reaction forces. Two are the internal inputs, which comes from the muscles that are attached to that specific bone. So in this case of the tibia, the gastroxilia is complex. And both of those external and internal inputs are going to have an effect on the amount of stress that that bone is accumulating. The internal load or the internal stress being much, much more of a contributing factor to bone stress than the external ground reaction forces. Although it does contribute a little, so it still needs to be considered. Okay, so when we run uphill, we know that there is going to be an increased load on that gastrocnemius complex. And so therefore, there's going to be a significantly increased load as well on the tibia because of that internal load from the gastrocnemius complex. When we run downhill, then we see an increase in ground reaction forces, which is also going to increase the load on the tibia. So we can talk about uphill or downhill, but they're both essentially going to increase the load on the tibia specifically. And so while somebody, although they will likely have some time off of running after they've had a diagnosis of a bone stress injury, while they are returning to running, we want them to run on level ground. We do not want them to incorporate any hills up or down early on in their program until we are absolutely sure they are tolerating level ground running without any symptoms or exacerbation of symptoms. And then we can start to incorporate the downhills, which are going to be less problematic and less provocative than the uphills because that internal load with the uphills and the gastroc soleus is going to contribute much more stress and load to that tibial bone than the downhills with the increased ground reaction forces. Okay, so a couple of other things to add. One is that if you are working with novice runners, hills often have to be trained. So they're not intuitive in terms of how we can most efficiently run downhills, uphills a little bit more so, but certainly not downhills. And because of some of those maladaptive mechanics that I talked about with running downhill, specifically like the upright trunk posture and the increase in the stride length or the over striding, those we tend to just do when running downhill if we're not trained how to run downhill. So if it's in your toolbox and you know how to kind of instruct or coach a runner to have better mechanics running downhill, meaning lean into the hill just a little bit. You don't have to have so much forward trunk flexion that it's making you uncomfortable, but lean into it just a little bit, or to maybe just be conscious of not extending the trunk posture or having a very rigid upright trunk posture. And then maintaining the stride length. So trying not to reach out as one goes down can really help to reduce some of that stress on the patella femoral joint, and the lower extremity as well. And so training or coaching a runner to be able to run downhill can also have really positive benefits in their ability to tolerate some of those hills, especially if they either currently are injured or have that running related history, especially if it's something like a patella femoral pain. And then the other thing to mention with using uphill and downhill as gait retraining tools is that The biomechanical changes are not independent of changes in stride frequency or our cadence or changes in speed. And so just like any other gateway training drill that we might use, so cadence for example, it's really, really important that we maintain some of the other variables that go into running. So speed for example if somebody's running on a treadmill and we manipulate their cadence we're really really sure to maintain that speed otherwise we may be changing too much at one time or we may not be getting the desired effect that we want from that gait retraining tool if we are changing more than one variable. So if you are recommending like an uphill run for example try to maintain some of those other variables specifically like stride frequency or cadence and speed. So obviously easier said than done, much easier on a treadmill than it is outdoors like on a trail, but just something to be aware of. Okay, so to recap, running uphill or downhill can be a really effective tool for runners with specific injuries, such as patella femoral pain or Achilles tendinopathy, that we can definitely put into our running gait retraining toolbox. As long as we keep some of those biomechanics in mind, and as long as we understand how uphill or downhill running can shift some of that load from one structure to another, And then also taking into consideration that there are instances when we do want runners to run on a flat surface, for example, in tibial bone stress injuries, when they are returning to run, it's really important to keep them on that flat surface so that they are not inducing excessive stress on that injured or healing tissue.

SUMMARY All right. So before I let you go today, I do want to mention a couple of upcoming courses. We have, let's see, Rehab of the Injured Runner Online. We are just about to start a new cohort. It is in May, the very beginning of May, so you've got a couple of weeks to sign up, but it's filling up. Sign up now. We have just revamped Rehab of the Injured Runner Online for 2024 and so far it's been really, really fun. We've had a lot of great engagement from current participants and previous participants. in our courses this year. Great questions. It's been really fun so far. So make sure you get into that if that's something you've been meaning to do. We also have Rehab of the Injured Runner live. We have June in Wisconsin and then we have September in Maryland and then Certainly the bike fit course is part of our endurance division and so we have a course this weekend in North Carolina. We've got one in May, mid-May in Minnesota and then up with our friends in Bellingham, Washington in June. All right, so that's it for me today. Hopefully you can add in hill training, uphills and downhills into your toolbox for rehabbing injured runners and just hit the ground running with that and use it right away. That's my goal for you for today. Feel free to ask any questions and hope you have a great Friday. All right, have a great weekend as well.

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