Resistance Training Biomechanics and Physiology PDF

[00:00:00] >> [MUSIC] [00:00:14] This session will essentially review the basic biomechanics and physiology of resistance training, but we're moving forward from the basics and translating it into how do you really apply this in the clinic? So we'll be looking at energy systems, the mechanics, this...

[00:00:00] >> [MUSIC] [00:00:14] This session will essentially review the basic biomechanics and physiology of resistance training, but we're moving forward from the basics and translating it into how do you really apply this in the clinic? So we'll be looking at energy systems, the mechanics, this is really getting into torque, so if you don't love torque yet, you better start loving torque. [00:00:36] And then look at how this relates to different systems in the body and really talk about the biomechanical principles that are applying stress to the tissues. So we're starting with a basic review of the energy systems used for movement. And while we're not going to go into details about the Krebs cycle and all that, which I'm sure you're glad about that, what's really important to recognize when you're prescribing exercise is what energy system is primarily being used in the exercise and dosage you're doing. [00:01:10] For example, if you're having a patient do something that is very, very high intensity, like maximum height box jumps, that is using your phosphagen system. And what this tells us is that you can really only sustain that for up to five or six seconds. So if you want maximum intensity box jumps, you can't give somebody 10 jumps in a set. [00:01:35] And then what we know about the phosphagen system, and we'll talk about this in our dosing, is you need significant rest to resupply it. So now, when we move into things that are in this kind of very high, like high to very high, so more than six seconds, up to 30 seconds, or even up to two minutes, we're really getting into this fast glycolysis, right? [00:02:02] So that's your glycogen system, and that's what makes that lactic acid component when it's not processed through in the oxidative system. So again, what this is telling us is either resistance training or interval training when you are functioning at a level that you can only maintain for 30 seconds to two minutes, your body's going to then need to replenish its glycolysis. [00:02:28] So you're going to need that glycogen available. This also translates to rest intervals. So if you're going in that level of intensity, you have to build rest in to resupply your system. And then finally, as we move into the two to three minutes, and longer than three minutes, that's when we start to see the oxidative system kick in. [00:02:51] Remember, your oxidative system is fairly limitless, because you can process both carbohydrate and fat, and you're working then at a lower intensity, so the systems can keep up. So as we talk about the goals for resistance training and the different type of dosing, the reason we give the dosing based on the goal, it really all comes back to your energy systems. [00:03:22] So you can't escape from torque, right? We all took physics, we hopefully didn't want to have to think about it again, but guess what? Everything about the human body and movement and exercise is about torque. We're going to simplify this for today, and we're really looking at two torques. There is an external torque. [00:03:41] So in this case, we're using the example of a bicep curl, because it's a very simple system. The external torque is essentially your resistance torque, or what the muscle is working against. And in this case, it's created by gravity acting on the weight and the lever arm of the distance of the weight away from the joint. [00:04:04] So for example, you can change an external torque by increasing the weight, or you could move it a further distance. Or if you wanted to reduce the torque, you could take a cuff weight and put it halfway down the arm. So for example, if this was a three pound weight and I moved it here, I'm actually cutting the torque in half. [00:04:26] So that's your external torque. That's what's creating the load that you work against, and it's always about torque. Yes, there's a load, a weight, a cable creating force, but our joints always work based on torque. Your internal torque is the torque created by the muscle itself. And so in this case, the internal torque is the force exerted by the biceps and the lever arm of the distance of the biceps insertion away from the joint line. [00:05:00] So again, we don't really have a lot of control over the lever arm on our internal torques, because that's based on our individual anatomy. But what we're doing here is by the by exercising, we are working to increase the force capacity of the muscle, which therefore increases the internal torque. [00:05:22] So manipulating external torques is a big thing that we do in prescribing exercise. Now, we have to think about all the factors that go into creating an external torque. If we are working with a free weight or with body weight, the force is created by gravity. It's going to be the mass of the body segment or the mass of the added weight and the body segment. [00:05:47] Now we can also use different types of equipment to create that force. So cable machines will also create a force and they're going to have different angles of pull depending on how you manage them. Resistance bands can also provide a force, and now, right, because you don't want to run away from physics, this is now like spring potential. [00:06:10] With a resistance band, the force that a band is exerting increases as you stretch the band. So what does that mean? Well, if you're using a resistance band for exercise, you don't have an even external force. We'll talk more as we talk about reasons to prescribe specific resistance tools. [00:06:35] We can also use manual resistance, and again, that means we can vary the load. And then the most typical that we talk about is things like free weight. So those are all different ways that you modify the force. You can also modify the length of the lever arm. [00:06:52] So as we talked about with the bicep curl, if I move the weight closer to the joint center, I've reduced the lever arm. And so therefore, with the same mass, the same weight, the same force, I've changed the external torque. A really fun project to play with this is to play with things like planks. [00:07:13] If you do a knee plank versus a standard plank, or you do a plank where your hands are on the table or a plank against the wall, I recommend playing with that and thinking about what's happening. Because here's what I will guarantee with a plank, the resistance force is always coming from gravity acting on your body, but you're going to notice it feels a lot easier in different positions. [00:07:38] It's because you're messing with the lever arm. So fun to think about much more when we do more lab-based stuff. So just as there's multiple factors that influence the external torque, there's factors that influence the internal torque. So in other words, the torque that your muscle can produce. [00:07:56] A couple of them that we don't have a huge amount of control over is the point of insertion. Different people may have longer bones or a further distance from the joint center to their muscle insertion, that will allow them to create more torque with the same muscle force. [00:08:19] The angle at insertion also impacts, so what I want you to think about with this, and bicep curls are a really great example of applying your physics. A bicep curl does not feel equally hard through the range, and there's two factors actually going on because your resistance lever arm is changing, but so is essentially the lever arm of the muscle based on its angle. [00:08:47] So these are factors that you've got to really think about when you're looking at an exercise. What range do you want it to be in? What angles are you looking for? Why are you doing it that way? But then there's a lot of things that will also impact force production of muscle. [00:09:03] So length, tension relationships. So you should remember from your basic physiology and biomechanics that when a muscle is overshortened, it's not able to exert as much force. So when you're exercising at end range shortening, you're going to have less muscle force to produce. Your muscle cross-sectional area and pennation also impacted. [00:09:30] Pennation is part of the nature of the muscle structure, but the cross-sectional area is something we can change through exercise, because hypertrophy will increase that. The contraction, velocity, are you going fast? Are you going slow? And depending on how you're using that, it's harder for a muscle to contract quickly. [00:09:53] However, if you do a quick contraction, momentum sometimes takes over. So you again, always want to think about what's your functional application when you're training. And then finally, your joint angular velocity. And what we mean by that is, is your contraction concentric, is it eccentric, or is it isometric? [00:10:14] And that's coming up on the next slide. So when we do exercises in PT, we usually use all of these different joint angular velocities. Concentric is usually our most common that we focus on, right? On a bicep curl, that means focusing on the lifting of the weight. The muscle is shortening while it exerts its force. [00:10:39] However, in PT, especially in early stage rehab, we often use isometrics. For example, if the joint is injured, and you don't want it to move, you can do things like muscle setting, where you do an isometric. You can track the muscle with nothing moving. There's also, which is usually used in sort of the next stage in rehab, the multi- angle, which means the muscle, anytime you contract, nothing's moving. [00:11:09] However, you do that in multiple positions. So with the biceps, for example, you might do an isometric contraction with the elbow fully flexed. Then you might do an isometric contraction with the elbow at 90. And then you might do an isometric contraction with the joint almost fully extended. [00:11:28] Those are considered multi-angle, and those can also help with stabilization. So we use isometrics in PT a lot. The other factor is isometric contractions can actually contribute to pain reduction. So stay tuned, you'll see this more as we get into specific prescription. And then finally, there are eccentric contractions. [00:11:52] Here's the thing, functionally, especially in our lower extremity, we do a lot of eccentric. When you go to sit down in a chair, that is an eccentric contraction of your quads and glutes because you're controlling, right? Those muscles are lengthening while you go down, but you're controlling them. [00:12:12] You're resisting gravity, but the muscle is lengthening while it's exerting force. One of the things that we do see, especially at high loads, is that you will see more micro damage on a muscle with an eccentric contraction than an isometric or concentric, that can be both a positive and a negative. [00:12:32] So again, this is going to play into your stages in rehab. The other thing is, this is very common in tendon rehab. What the research tends to show us, is the action, and the movement of the muscle during an eccentric contraction really helps to stimulate tendon growth more. So as a PT, we use all these different types of joint angular velocity, and when you are prescribing an exercise, you need to know why are you picking to use what you're using? [00:13:05] That's going to be a big part as we move forward in exercise prescription. [00:00:05] >> So the focus of this session is going to be about taking all those physiological processes and the biomechanical principles that we've learned and really start to look at how does this inform how we make decisions and how we prescribe exercise. The image on this slide comes from a handout that we'll be working with next week, and as we continue through this course. [00:00:29] It's going to help you as you make decisions about what you do and how you prescribe your exercise. But just to get started, we think about, we always have to start from what is the major problem that we are noticing? This will primarily come from your movement observation. So after you've talked with your patient, you're going to be observing them do some key movements. [00:00:53] And then you need to start thinking about, why can they not move the way that they want to? Is it because of pain? Is it swelling? Is it injured tissues, right, like a muscle strain or a broken bone? Is it that they don't have enough range of motion? [00:01:11] Do they have too much range of motion and they can't control it? Do they not have appropriate muscle function, so do they not have strength? Is their coordination or their motor control not working right? Or is it just that they're somehow not putting all the pieces together? So as we move through talking about exercise prescription, if we're trying to load an injured tissue, it's usually going to be a pretty low load. [00:01:38] You want to start low, and then gradually progress. If you're trying to manage pain and swelling, a lot of times we'll start with just like an active range of motion or some passive range of motion. If you want to improve the muscle function or muscle performance, so usually we're talking about strength, power, endurance, you need to progressively load the muscle. [00:02:01] If you're trying to improve range of motion or flexibility, then you're going to be choosing things like joint mobilizations and stretching. If you want to improve kind of your motor control, so your balance, your coordination, your agility, then you're going to need to do very specific training for that. So balance is very specific to the condition, and what type of balance, so much more on that to come. [00:02:25] And then, if you're trying to improve a functional movement, you may need to improve some of those underlying factors, like strength and range of motion, but ultimately, you have to work on ways to increasingly make those movement patterns complex. So to start with something doable and continue to increase the challenge. [00:02:46] We will be looking at all of these many, many more times throughout this course. So really, the bottom line from that previous slide is whenever you're going to give a patient an exercise, you need to be clear on your why. Why are you giving it to them? What are you trying to address? [00:03:03] Because that is going to influence what exercise you give, how you set it up, and also how you load it. So what's your dosing of the exercise? So this week we're mostly focusing on muscle performance. And when we look at muscle function or performance, there's typically four different ways that we look at this. [00:03:28] We can look at muscle strength, which is purely how much force or how much torque can a muscle produce. And so what we're going to see is that usually relates to things like heavy lifting, high load. But there's also power, which, remember, power now adds a time component. So it's not just how much force, but it's how quickly. [00:03:49] So athletes that need to jump sprint, any of that, they need to have adequate muscle power. So that is something we need to assess. Often times we have to deal with hypertrophy, which is essentially just helping the muscle physiologically improve the number of myofibrils that it has, or to increase the size of those myofibrils that can often happen after atrophy. [00:04:17] So a lot of times a major injury or a surgery will cause a muscle to atrophy because it hasn't been used. And then finally, we also deal with muscular endurance, which is essentially the ability of the the muscle to exert force over time. So these are things, right? [00:04:35] When you do something like a plank fo a minute or a wall sit or you do 20 squats in a row, that is working on muscular endurance. And as you can imagine, this is an important component in daily function, because to be able to walk out to the garage to take the trash out, or to walk to the garbage can, or to walk the grocery store, that in and of itself, takes a certain level of muscular endurance. [00:05:01] So we will look in the next slides about how do we dose our exercises and set our exercises up depending on which of these is our goal. So this is a diagram from the NSCA book on strength and conditioning. And I really like it because it just makes it really visual. [00:05:21] How your number of reps relates to the exercise goal. And when we look at number of reps in this setting, what we're talking about is reps to fatigue. So if you are trying to train for strength, you're going to be training in this like 2 to 6 range, 2 to 6 rep range. [00:05:44] So in other words, you're picking a weight that you cannot do more than 6 reps with, that's when you're really hitting strength. Now, the hypertrophy, we tend to look more in this 7 to 12 rep range. So if you've worked in a clinic where everyone gets three sets of 10, that's working within the hypertrophy range, assuming they were loaded enough, which doesn't always happen in PT clinics. [00:06:09] And then finally, when you're working on that high rep range, in other words, 12 reps and more, you're working on muscular endurance. So when we talk about dosing exercise in the strength and conditioning literature, they really look at a lot of things based on a 1 rep max. [00:06:32] So some of you may have done this, especially if you were in competitive sports, right? Where you are kind of loading up, if you're doing a bench press, you're loading up the bar until you can only do 1 rep, and that is it. Now, it's helpful because it then translates directly. [00:06:51] You'll see it in our tables to dosing exercises. However, for most of our clinical clients and even most of our wellness or fitness clients, that's not realistic. So things that can be really helpful is, for example, if you set a patient up with an exercise, and you, at the beginning, and I'm just going to tell you, this is pretty much how we all do it, you ballpark the weight. [00:07:13] You're like, I think you can handle 20 pounds on this. And then you have them do as many reps as they can, for example, if they get 10 reps out of it, that's going to tell you that those 20 pounds is 75% of their 1 rep max. So it can help you translate it into the prescriptions. [00:07:35] The next slide is going to take some even more practical ways to do this in the clinic. All right, so number one is what I have used the most often in the clinic for estimating the weight for a certain exercise. So first of all, I need to know what was my goal? [00:07:53] Was I trying to do muscular endurance, strength, power? So let's say that I am trying to train a client for strength on a leg press machine. So I want them to be able to do 5 or 6 reps and no more. So what am I going to do when I start this client? [00:08:12] I'm just going to set I'm literally going to look at them, and based on my experience, I'm going to just set the weight somewhere. And then I'm going to ask them to start. If they can only get to 3 reps and they're not able to do more, that told me my load was too heavy. [00:08:29] And so I need to reduce the load. If they get through those 5 or 6 and they could just keep going to 7,8,9, 10, 11, 12, that load was Is not enough for the goal that I have, so I need to increase the load. So then it just becomes a refining process from there until you really target it in at that load where the client can do the 5 to 6 reps you want them to do. [00:08:54] Maybe they could squeak out 7, but they're getting really tired. Another way that you can estimate load is just using RPE. And it depends, some people are better in touch with their bodies than others, but you essentially are just asking them right when you're using this exercise, does it feel easy? [00:09:15] Does it feel moderate? Does it feel hard? Does it feel very hard? And again, you can just keep playing around, but I find that one of the best things is using these prescription guidelines to identify how many reps they should do, and then you set the weight based on what they're able to do. [00:09:33] We're going to take a look at the prescription on the next slide. So this is the classic dosing of reps, sets, and load based on different training goals out of the NSCA, the National Strength and Conditioning Association. ACSM also has guidelines, and to be honest, they are very, very close, so if you already know the ACSM guidelines, don't try to memorize something else. [00:09:58] These are all. Remember, these all are like, have a little bit of a ballpark element. So this comes back to what we were talking about. If you are training for strength, you're trying to increase the amount of torque or force a muscle can produce. So you need to load it very heavy. [00:10:15] How do we translate this into practice? Well, you're going to be assigning them to do maybe 4, maybe 5, maybe 6 reps before they fatigue. So then you can just set the weight at a level that they can do 4, 5, or 6 reps. The rest intervals, these come back to our physiology. [00:10:35] So if you remember when you're training pure strength, which means you're not doing many reps, you are really training the phosphagy system and the fast glycolysis. Both of those are systems that need to be replenished through aerobic metabolism, which is why you have to rest. You cannot, and I know you have all seen it. [00:10:56] There's plenty of fitness places where they'll make you do super Max stuff and then give you five seconds rest. That's actually not efficient for training for the goal. You need the appropriate loading, but you also need the appropriate rest. So again, for strength, the number of sets can really vary, and we'll talk about this. [00:11:17] But most dosing when somebody is new, we will take it in the much lower number of sets. Power, you can either have single event or multiple event, right? A single event is like a single one or two power cleans, snatch, any of those kind of names, or a maximum effort jump, a multiple effort, once again, might be multiple, right? [00:11:42] Can you do 3 to 5 cleans or can you do 3 to 5 box jumps at a certain height? Once again with power, we see these high rest intervals. That's because of the systems you're using. As we move move in to hypertrophy, you're using more fast glycolysis and even starting to get a little aerobic metabolism, which means you can have a shorter rest interval if you're training for hypertrophy. [00:12:13] So this is especially if someone's had major muscle atrophy after an injury. You're working in this, 6 to 12 rep range. And then finally, muscular endurance. This is the one, if you have someone that's like, I can do I can walk the first little bit fine and then it's just, everything gets tired. [00:12:33] Well, that's an endurance issue, so muscular endurance is going to help out. And that's your higher number of reps, and you do less rest because you're working at a lower load, and so therefore there's more of the aerobic metabolism that's helping out. So this table has a little less standardized dosing, but this is to help you determine how do you set up your exercises for someone who's really in these earlier stages of rehab. [00:13:06] What do we see in those earlier stages? This is where we're going to see more isometric exercise or that muscle setting when you're first trying to get a muscle going after it may have been inhibited. Or maybe you're working active range of motion, so the goal of the exercise is not the muscle function, it's getting the joint moving. [00:13:28] And then maybe you're just trying to get that muscle kind of firing again in a more functional way. Or the final one, and this will come up more when we talk about balance and some other coordination exercises. If you're training for something like motor control, you need high reps, because motor control, really what you're doing is, you're changing those synapses in the brain. [00:13:52] But just sort of a quick review, you can take a look at this, and this will also come up when we talk through they exercise prescription framework. But muscle setting, remember, those are, like those low load isometrics, and so you're essentially just going to have them contract the muscle, hold it for six seconds, and then they usually do about 10 reps. [00:14:14] And again, there's no load added. This is just tighten up your quads, hold it, release it. Then we've got active range of motion, which typically is just okay, let's move this so if it's shoulder flexion, let's move your shoulder in and out of shoulder flexion for 30 seconds. [00:14:33] And again, this is not about load, this is about joint mobility. And both of these, the isometrics and the range of motion, they can help with sort of clearing out swelling as well. So the muscle contraction and the joint movement can help move edema and swelling. And then finally, this early stage muscle activation it's very similar to our muscle endurance, but you're doing a slightly lower load and usually fewer sets. [00:15:04] But again, this is kind of that transition stage where you've done your isometrics, you've done your active range of motion, and now you're getting ready for more typical exercise. And then, once again, motor control, we will come back to this when we talk about things like balance training. [00:15:21] But mostly whatever motor control activity you're doing, you need lots of reps because it's more of a learning than necessarily a physiological component. [00:00:05] >> This lecture is specifically going to look at how we adapt exercise for different needs, and also how we progress or regress depending on the patient or client's performance. The dosing for an exercise depends on the individual's fitness level as well as the ultimate outcome goal, for example, for folks who are new to exercise or coming at a really low level. [00:00:32] So this might be patients who've not been exercising, or maybe patients who've recently gotten off a bed rest restriction. It tends to be that one set of that eight to 12, which is kind of that hypertrophy range, is going to be sufficient for them to make progress in the first couple of weeks. [00:00:51] For individuals who have more experience, or for these new folks, once they've made progress, once they get comfortable with an exercise, you need to start thinking about, do I increase the load? Do I change my dosing? For example, if you started an individual on this one set of eight to 12 reps at this kind of lighter to moderate load, and they've made progress. [00:01:16] Now you want to think about, do I want to dose this? Do I want to focus more on muscular endurance? In which case, we might keep the weight that increase it to 15 or 20 reps. Or maybe we want to move towards more muscular strength, in which case we drop the number of reps. [00:01:32] Maybe we only do six or eight reps, but we start adding heavier loads. This, as we get further along, the concept of periodization in training comes along. So if you're working with really high level folks, periodization, essentially is intentional variation within your training. So that the body is always adapting to new loads and new forms of loading, so it continues to make progress. [00:01:59] One of the key principles of resistance training, which really is a principle of fitness, exercise in general, is the SAID principle. Essentially specific adaptation to impose demands. So what this says is, not only, is it the muscle you're training that's going to respond? For example, if you do bicep curls, your bicep is what's going to adapt, but the adaptation is also related to things like the speed, the load and the range of motion. [00:02:30] So for example, if you have someone doing squats, but they're only doing very partial range squats, so they're only squatting maybe 20 degrees into flexion, they're only going to gain benefits in that range. The other thing about our specificity is the rate that we load. So for example, if you are rehabbing a sprinter who's had a hamstring strain, as you progress them, you're going to have to work on fast eccentric contractions. [00:03:03] Because that's how the hamstring works in sprinting. The other thing is that we also, as we progress, we move from just general loading to more specific movement patterns. So for example, if you're rehabbing a runner who's had a knee injury, you can't just do isolated glute exercises and isolated quad exercises. [00:03:24] You need to move them into patterns that are relevant for running. So, always think specific, especially in rehab. The more that your exercise or activity can match the patient's goal, the better it's going to translate into real life. So when it comes to making modifications and modifications to an exercise can be made either to make it more challenging what we would consider a progression. [00:03:56] Or to make it easier, what we would consider a regression. There's multiple different ways that you can adapt the exercise. Some of this will depend on what resources you have. Some of this will also depend on what are you trying to move the patient towards. So one simple thing to do is to change the external torque. [00:04:16] This is something we think about often, right? We increase the weight, right? That's just increasing the load, when the patient can do squats with 20 pounds we give them 30 pounds, that is an example of changing the external torque. Haven't changed anything about the movement, you just put more load and that increases the torque. [00:04:35] Now for some exercises, it makes more sense to change the external lever arm. And the demonstration that we have over here with planks is a perfect example, right? The load or resistance force in a plank is always body weight. So when you change position in a plank, you're not changing your body weight because that doesn't happen. [00:04:58] But you'll notice, and if you haven't played with this, try out this progression. Do a plank against the wall, then do a plank on a table like this, then do a knee plank, then do a full plank. It gets harder as you go through those. What did you change? [00:05:15] You didn't change the resistance or the load. You changed the length of the lever arm that your trunk muscles are working with. We'll definitely play with this more in person. You might also change the mode of resistance, because different modes of resistance provide changes in load in different places. [00:05:35] So for example, you might start doing squats where they're using a heavy resistance band. In that case, as they move to the extension phase of the squat, the band is getting stretched. The longer a band gets stretched, the more resistance it creates. So if you want more resistance at the end range of movement, you might use a resistance band. [00:05:57] So this is something I want you to always think about, the mechanics of what you're doing. Three typical types of load we use are resistance bands, free weights like dumbbells, and cables. Each of those changes its load through the range in different ways because of either changing lever arms. [00:06:17] Or changing, for example, with the resistance band, changing the force exerted by the band because of the lengthening. So, that is something very common that we do, is we get somebody started on an exercise, and when that gets easy, then we just want to increase the external torque. Another way to change an exercise. [00:06:37] And again, this can be to make it more challenging, or less challenging, is to change the base of support. So, one of the things obviously is you can make a base of support wider. And that should make the exercise more stable and a little less challenging or you make it narrower. [00:06:54] A simple example of this would be doing squats. If somebody is having challenge with the balance aspect of a squat, taking them to a wider turned out stance will give them a bigger base of support. Or moving them to tandem stance or even moving to a single leg stance is going to increase the level of challenge. [00:07:15] And we see similar things, right, with our planks. If you go from two feet on the ground to one foot on the ground, you've changed your base of support, and you change the level of challenge. Now you can also change the base of support, which changes your level of stability by changing the surface. [00:07:33] So, oftentimes we start folks on a very stable surface, right? That might be a solid surface like the table or the floor. And then we may, as they need to adapt to more uncertainty in regular life, we might move them to unstable surfaces. Like a foam pad or a wobble board. [00:07:52] Or in the case of our planks, we might move them up onto something like a physio ball. You also can think about the stability coming from the question of is it compliant? Does it give like a phone pad, or is it firm, like standing on the ground? As you know from your balance practice, standing on a compliant surface requires more stabilization from your muscles, which increases the challenge of the exercise. [00:08:18] Once again, how do you modify the exercise for your specific patient? It is going to depend on what they need to do, what goals are they trying to get back to, and what does that movement pattern look like? Another way to change an exercise is to change the speed of movement. [00:08:38] Now, different speeds of movement can be more advantageous or disadvantageous in different settings. Sometimes moving faster allows momentum and makes something easier. But there's other times, especially if you're working at a high load, where moving faster requires more muscle contraction. So, usually we start folks with a moderate velocity. [00:09:02] But depending on what they need to do, we need to move that velocity towards what they're going for, for example. And I'll tell you, I've seen this done wrong in the clinic. You have a client recovering from a calf strain who is a runner. If you only have them do calf raises with body weight at a moderate velocity in the clinic. [00:09:23] You can get them to a point where they are totally pain free with that, they're pain free with walking, the moment they start running that calf strains again. You didn't train the right velocity. You also probably didn't train the right load. So you've gotta think about matching velocity ultimately to the patient's goal. [00:09:40] Now the other part about speed of movement is to think about that angular velocity of the joint. So in other words, is the movement isometric? Is it concentric? Is it eccentric? Because that is also going to affect things. So, to come back to the sprinter with a hamstring strain, you better be working on high load, high velocity, eccentric hamstring contractions. [00:10:09] Because that's how hamstrings work in sprinting, and that's where they usually get strained. So you always want to think about what is the goal activity. And finally, there's lots of different ways to change the complexity of movement. Oftentimes, again, in rehab, we start folks with very simple, single joint activities, a quad set, a single bicep curl, a plantar flexion with the TheraBand, very simple, very isolated. [00:10:39] Great for focusing in on the muscle, getting it going, maybe getting the joint moving, but not terribly functional. So we usually will start with single joint simple and move to multi-joint as we progress. Same thing goes for planes, right? When you're doing a single joint exercise normally we're working in one plane, right? [00:11:00] Plant our dorsiflexion, just in that sagittal plane. Life tends to happen in multiple planes, so we might move into exercises that require moving in more of a rotational movement or in some sort of an oblique plane. And then we also can talk about isolation versus functional activity. Do I train my patients solely on a leg press, or do I start working them into step ups and lunges and activities that more so mimic our daily activity? [00:11:33] For a lot of patients, this is actually true for athletes as well as for our neurological patients. Single task versus multi-task. So doing the same step up can become much more challenging if you are asked to be reacting to something at the same time or reading something or catching a ball. [00:11:53] And that applies across the continuum of our patients. An open versus a closed environment, right? A safe corner of the clinic is a closed environment. There's nothing to distract you, there's nothing happening. The soccer field during a game is a very open environment. So for example, if you're trying to help a patient recovering from an ACL reconstruction that wants to go back to playing soccer. [00:12:20] You're going to start in closed environment exercises, because you want to make sure they have that stability and control. But you need to progress to a busier environment, to things going on, distractions, decision-making, all of those things, because that's where they ultimately need to go. And that really ties into our last thing, is that your progression of exercises needs to be moving towards the sport specific or functional specific, doesn't have to be sport. [00:12:52] Maybe it's somebody who's had a stroke and wants to go back to gardening, right? There's a lot of complexity in gardening. Thinking about the activity and that environment. So what kind of surfaces? Is it a busy environment? Is it a quiet environment? If you can think about all of these different ways to progress and exercise, you're going to be able to go from day one to discharge with a really thought out plan for your patient. [00:00:05] >> This session is going to focus on how the body responds to our specifically resistance exercise, both in terms of the short-term and the long-term. Some of the quickest changes that happen with resistance training are neural adaptations. What this means is as someone starts a weightlifting program or any kind of resistance building program, you see progress within the first week, and that is due to increased recruitment. [00:00:36] One of the things is that your body starts to recruit more of fast twitch motor units. Which if you remember, fast twitch or type 2 fibers are the ones that are more about power and speed as opposed to your type 1s that have more endurance, so that allows your muscle to start generating more force. [00:00:54] What we really see is within those first six weeks or so, most of the strength gains are due to that neural recruitment. One of the things that we will see in the clinic a lot, is that oftentimes our patients are weak because their nerves are inhibited due to the injury. [00:01:15] You'll learn a lot more about this, but a lot of times joint swelling will inhibit the nerves to the muscles around that joint. Which is why our neuromuscular electric stimulation or e-stim, as we call it a lot, like those pictured in here, is really helpful. Because it kind of detours or bypasses some of the nerve pathways and allows that innervation to go straight to the muscle. [00:01:42] So quite frequently, when somebody is either post op or post acute injury, we will use electric stim on certain muscles to start that recruitment phase. Now, once somebody can recruit that muscle on their own, there's really no need for the electric stim, that's a whole other story in the sports world. [00:02:03] Because once they can recruit on their own, they're actually going to gain more by using their own recruitment to work the muscle especially in terms of translating to function. But the key take home is there is a lot of neural adaptation that happens in response to resistance training. Since we're working the muscle with resistance training, there's obviously some key adaptations that happen at the muscular level itself. [00:02:29] Number one, right, this is why a lot of people live, they want hypertrophy. That is an increase in the number of contractile proteins within a fibril, right? There may be little bits of what we call hyperplasia, which is an increase in number of fibers. But in a normal functioning human, the majority of muscle adaptation and muscle size change is due to hypertrophy. [00:02:55] Now, when you're working with certain folks, there's some other really great benefits, one of those is increased insulin sensitivity. The whole issue of insulin resistance has been kind of a huge thing, and that's right, that's the primary issue in type II diabetes. Well, muscular adaptations and increased muscular training improves the sensitivity of the muscle to insulin. [00:03:22] Which essentially means that the muscle will then take up the sugar with less insulin circulating, which really is part of what helps with managing type II diabetes. So it's one of the things if somebody is totally inactive sedentary with type II diabetes, they can sometimes make a big change just by starting general activity. [00:03:43] Doesn't have to be extreme, basic couple days of strength training and some walking. The other part and this is important for athletes is when you strength train, when you resistance train, you increase the glycogen storage in the muscles. So here's a couple of things, you going to catch I'm not a diet fan, this is part of why low carb diets cause rapid weight loss but they would not be recommended for an athlete. [00:04:12] Because on a low carb diet the first thing you're losing is that muscle glycogen. Which you lose you store water with glycogen, so yeah, you're going to lose weight, but it's not weight that you wanted to lose. So anyway, the other thing is muscle glycogen, right, we hear a lot of talk about this for our endurance athletes. [00:04:31] The more glycogen you have stored in your muscles, the longer you can go before your body has to shift to other energy sources. So that is a great reason for pretty much anyone to be doing resistance training, including folks like long distance runners. So all of the tissues in our body are very responsive to loads, bone is no exception. [00:04:55] And this is something that we've probably all become quite familiar with, is all the stuff about doing loading exercise. Whether that's impact exercise or weightlifting strength training for bone mineral density. And what we really know is that really needs to be happening early in life and continuing. Now, the interesting stuff about the bone response is the bone responds better to a higher strain rate, right? [00:05:24] That's a faster contraction and a higher magnitude, higher force of loading. So in other words, power training, jump training, plyometric training, that is all stuff that is great for your bone. And interestingly enough, they've actually done studies on kind of middle aged and older women, not individuals with osteoporosis, more on contraindications later. [00:05:49] But with folks who are starting to lose bone density, and they've gotten them into a jump training or a power training program and actually seen improvements in bone density. So that really comes to this last part is that bone loading is important for the prevention and management of osteopenia and osteoporosis. [00:06:08] And this translates not only to women, this is for men as well, and it starts early in life. Because you lay down the bone through your adolescent years, and then, you want to keep it, you don't want to lose it, as you're going through your 20s, 30s and 40s. So, this is something that's really important, and it can often help some of our patients, especially older patients, maybe more resistant to doing loading and training. [00:06:34] And helping them to see the connection to bone health may help motivate them. So as we've been seeing, every type of tissue responds to loading, so tendons and ligaments, which as you'll recall, are our dense, regular connective tissue. They respond to loading by increasing the number and the diameter of their collagen fibrils. [00:06:56] Remember, collagen fibrils are like the rope part that makes tendons and ligaments strong and be able to pull. It also increases the number of cross links which helps to make them more stable. And so that is why as you start to talk pathologies, any kind of tendon injury, loading is your number one piece of your rehab. [00:07:19] Starting with isometric, progressing through, and there's a lot of research on eccentric loading around tendons. But the number one thing is you need that load, but it needs to be progressive, right? The reason the person got the injury was they loaded too much when the tissue wasn't ready. [00:07:36] So our job as a PT is to progressively reload the tissue at a rate that gives it time to adapt. Cartilage also needs that loading and unloading, so as you recall from anatomy, cartilage is kind of like a sponge. It doesn't have a blood supply, so it needs this compression and unloading to get the diffusion of nutrients. [00:08:00] Now, the other thing is just like all of these other tissues, there's collagen fibers and glycoproteins in cartilage, and regular loading with appropriate unloading and rest. So we're talking about appropriate training load can increase the thickness of cartilage. So, that's another one, right, there's a lot of myths out there that things like walking and running and exercising are going to give you arthritis. [00:08:28] Actually it's exactly the opposite, if you do appropriately dosed exercise throughout your life, it's going to help to protect your joints surfaces. And finally, even our cardiovascular system has adaptations to resistance training. What we will see is the majority of the cardiovascular responses are acute, which means your system increases cardiac output during exercise. [00:09:00] This makes sense, you're using more muscles, you need more nutrients going to those muscles. You need to clear waste products, so you need to be increasing circulation to the muscles, so your heart's gotta pump more volume. And so that's what we see, we get increased blood flow to the working muscles. [00:09:18] That's where we see vasodilation in the working areas, and that's where you're getting more nutrients brought in and more waste products cleared. Now, when it comes to the chronic, and when we mean chronic, we mean like long-term, right? The acute, this is what happens in the moment you're exercising, which is one, right? [00:09:38] You're going to see doing strength training, especially doing heavy load, your heart rate increases, because that's part of increasing that cardiac output. Now, in the long-term, a really important thing to know is that resistance training does not have an adverse effect on aerobic power. So things like, VO2 max, lactate threshold, all of those performance concepts that an endurance athlete, runner, cyclist, skaters. [00:10:07] Any of the folks that do endurance activity, strength training does not have an adverse impact. This is important because for a long time runners were really adverse to doing strength training because they thought it would have a negative impact and it would make them too bulky. Anyway, we know now that running is actually a power activity, right? [00:10:29] Every time you're pushing off that's a little jump, and so runners benefit hugely from strength training and it actually only makes them better in the cardiovascular round. However, there are no long-term adaptations for heart rate or blood pressure. So unlike cardiovascular training, aerobic training, which is going to help to lower resting heart rate, lower resting blood pressure, we don't really see any change. [00:10:55] No good change, no bad change, right, doesn't go up, doesn't go down, just nothing changes. So that's an important thing because you can have somebody who does have elevated blood pressure. You can have them do resistance training, and it's not going to make a long-term increase in their blood pressure. [00:11:13] They'll need to be doing other things like cardiovascular training to help lower it. But you're not going to in the long-term raise blood pressure by doing exercise.