Muscle Mechanics | Types of Contractions & Levers

All right, Ninja Nerds, in this video, we're going to continue on muscle mechanics part three. So if you guys are watching this, thanks again for sticking in there with us. We appreciate it. The main thing that we're going to try to cover in this video is we're going to specifically talk about two things. We're going to talk about isometric and isotonic contractions, and we're going to talk about how they're graphically represented, and we'll talk about physiological and anatomical examples in the body. The second thing that we're going to talk about is levers, the three classes of levers, and then examples of those in the body and their mechanical advantage and mechanical disadvantage. All right, so let's go ahead and get started on that. So let's say that you have two muscles here, two muscles and two graphs to correlate with those. Let's say that in this first muscle, I want to go for this first muscle, I want it to exhibit a specific type of contraction. And this contraction is called isometric contraction. Okay, so let's say that this muscle right here on the top is going to undergo a process called an isometric contraction. Well, let's decipher this word. What is iso and what does this metric mean? So, iso means same and metric is like a form of measurement. So, it's the same measure. So, what happens in an isometric contraction? Let's say that I have a fixed point. Let's say here I star this point here. Let's say this is the fixed point. Okay, that point right there is a fixed point. If that's the fixed point, let's say that this muscle tries to contract. contract and carry a load. So let's say, for example, I put, let's say that I'm trying to curl a 45 pound dumbbell, right? I'm sorry, 45 pound barbell with two 45 pound weights on both sides, right? And I'm trying to curl that. If I'm trying to curl that, and let's say that I try to curl that and I just get stuck in this position, I get stuck in this position. I'm generating a heck of a lot of tension and a lot of force, but the weight is not moving and the muscle isn't shortening. It's not actually going to be shortening and actually having the size. change. So because of that, it's staying the same size. It is not lengthening, nor is it shortening. It's staying at the same point. If that happens, that is an isometric contraction. So for example, if this muscle contracts, it can generate a whole lot of tension, but the muscle size after it contracts will not lengthen or shorten. So it stays the same. So again, isometric contraction, what are the things that we'll see? It can generate a lot of tension. A lot of tension can be generated. But here's the thing. Whenever you contract this, the force. So you know what? There's what's called the load. So let's say that I'm trying to lift a dumbbell. Let's say, for example, I take a 100-pound dumbbell. And I take that 100-pound dumbbell. and that's the load, that's the amount of resistance that's actually trying to push down with the force of gravity, or it's trying to push down. I'm going to try to exhibit a force that will move the dumbbell up. But let's say that the force that I generate is not enough to overcome. home the load that's pushing down towards the center of earth, right? With gravity. If that's the case, will the actual load move? No. So that is the concept of an isometric contraction. That the load, we can refer to it as the load force or the resistance, is greater than the muscle force. Okay, so we can say the load force All right, the resistance, the weight, that's a 100-pound dumbbell that's pushing down towards the actual center of the earth, right? Versus the muscle force, my biceps brachii and my brachialis muscles that are trying to contract. When they are trying to contract, they're trying to move the weight. But the amount of force that they generate is not enough to move the weight, so it stays the same size. So in other words, it does not lengthen. It doesn't lengthen. Nor does it shorten. It stays the same size. So stays the same. Okay, so these are the things I want you to get with isometric contraction. To recap it, the load force, the amount of weight, the 100-pound dumbbell is really, really heavy, right? It's trying to push down to the actual center of gravity. As it pushes down, you're trying to generate a force in your bicep, brachii, and brachialis to try to move the weight. But the load force is greater than the muscle force. When the muscle contracts, it can generate a lot of tension. But the actual muscle does not shorten, nor does it lengthen. It stays at the same size or same measure. Okay? That is this concept of isometric. What would that look like on a curve? Well, we said here... that this one can generate a lot of tension. I'm talking a lot. Let's say, for example, it generates up to, and I'm making this number up. I'm just doing it for example purposes. Let's say it's 10 newtons. Let's say it can generate 10 newtons. If this generates 10 newtons, and that's the maximal tension point, let's say that it starts here, and it works its way up to 10 newtons. It gets into this period of contraction, right? So that's the latent phase and it has that period of contraction. And when it reaches that point, it contracts, contracts, contracts, contracts. And then eventually what happens? It actually falls off, right? The tension starts decreasing and it starts moving back down to a resting point. And then it will go back into this latent phase, right? That's what's happening. And again, what is this point right here, this 10 newtons? Let's say that that is the maximal tension point. That is the maximal tension. Okay, so that's when you're trying to lift that 100 pound dumbbell. Alright, but how is that, how is that relatable to the length of the muscle? So again, we said that the length doesn't change. So let's say that I put a horizontal asthmatoid here. So I put a horizontal asthmatoid. And again, on the y-axis for this one, this one's tension, and the x-axis is our time. On this one, it is length. And on the x-axis, it is time. Let's see, here's my horizontal asthmatoid. And let's say that this represents the resting length. Okay, if this is representing the resting link, let's say originally, here it is, at this point here it's at rest. It's resting, right? But then we contract the muscle. If we contract the muscle, let's say that the length is actually increasing as you go up, right? So, for example, let's just say, for example, that at that point it's zero. And let's say that this is in meters, whatever. It's in meters, let's say that this is zero, two, four. 6 whatever right Let's say right. It's right around like 5.5 or something like that right? That's the length That is currently, but then whenever the muscle contracts is the length going to change no it doesn't lengthen nor does it shorten? So you shouldn't expect it to have a downward reflection, and you shouldn't expect it have an upward reflection It should stay a straight Okay, and this is what you would see on the graphical representation of an isometric contraction, okay? Now, let's talk about the next one. The next one is a little bit cooler. It's a little bit different. And it comes in two flavors in two different ways. This one is referred to as a isotonic contraction. Okay, before we talk about, well, actually, no, let's define the two types. There is two types here. The two types is going to be concentric. And the other one is going to be eccentric. So the other type is eccentric. Now when people think about lifting and isotonic contractions, they more commonly think about concentric contractions. Because what happens with isotonic contractions, let's say that I take a weight, a 50-pound dumbbell. It's a decently heavy, but let's say that 50-pound dumbbell, again, is exhibiting a what? It's exhibiting a downward force that's trying to pull my arm down from that elbow joint, right? But let's say that my biceps rake on my brachialis, I recruit enough muscle fibers that I can generate enough force and enough tension to overcome that weight load and move the weight. In other words, I'm shortening the muscle belly. As the muscle belly shortens, I'm generating a lot of tension, but I'm also moving the weight. That is an example of a concentric contraction. So a concentric contraction is when the muscle shortens. Let's write that down. So this is when the muscle shortens. Okay, now let's take, for example, the eccentric part. Let's take that same dumbbell. I'm at the peak point of contraction, and I contract the muscles. They're at the peak point of tension. I can't go beyond that point. And then let's say that I actually start relaxing, and I start giving, letting the muscle go down and down and down. If you guys have ever done like a preacher curl or something, it's really hard to resist the weight going down in a slow manner, right? And you're still generating tension. It's still generating a lot of tension, a lot of force, almost 50 times more. So the amount of force that you're generating as it's going down is still great. It's actually very, very strong. But an eccentric contraction is as the muscle is lengthening. So lengthening the muscle is an eccentric contraction. So this is when the muscle lengthens. Okay. So if the muscle lengthens, it's an eccentric contraction. If the muscle shortens, it's a concentric contraction. Remember, eccentric contractions aren't referred to as much, but they're equally important as a concentric contraction. They can actually generate more force than a concentric contraction. We'll talk about this when we talk about what's called the force-velocity curve. Okay, how this one can actually accommodate for a greater amount of force. Okay, another thing about isotonic contraction. What do we say? It can generate a lot of tension, but not as much tension as an isometric contraction. Okay, so it does generate a decent amount of tension. Decent amount of tension. But here's what's really important. We said that the load force was greater than the force of the load force. The muscle force in the isometric contraction. In this case, the load force, the weight, that 50 pound dumbbell, was less than the muscle force of my biceps, brachii muscle, and my brachialis muscle. In other words, I have enough force to move the load. So therefore, the muscle can shorten. Muscle shortens. Let's fix that L. And again, whenever the muscle is relaxing, it's going downwards and you're resisting the weight going downward, it can lengthen. Okay, so going down from bicep curl, as we were using in our example, muscle lengthens. But remember, as you're going up, you generate a lot of tension, but you can actually generate more tension on the way down. Another example of eccentric contractions is like, you know, whenever you're walking up a really, really steep hill. That's also an example of an eccentric contraction because you're stretching those calf muscles and causing micro tears, which again activates those myosatellite cells to come in and cause repair. All right, so let's see what this looks like. on an actual graph. So we said here, let's have, let's say they said, we said this one generates a lot of tension. This one doesn't generate as much tension. So it's not going to be at 10 newtons. Let's say for example, it's at like six newtons. So let's say at that point, point here it's about six newtons okay and once again let's say here's about zero and let's say here's about you know three if that's the case then when this muscle starts contracting muscles our muscles are always usually partially contracted because of muscle tone because of the reflex arcs so let's say that it's already having a little bit of force generated here right and it starts having this contractile phase so it goes into the contraction phase and it rises up and it hits this maximal tension point again what is their maximal tension at this point in order to move the actual muscle load. Maximal tension point, right? So if this maximal tension, or in other words, the amount of tension that you need to generate in order to overcome the actual load force, what will happen? It'll reach that point, and again, it'll, you know, generate some tension for a while, plateau, and eventually it'll go back down into the relaxation point, and then it'll go back into that latent phase, right? Now, let's say here we have over here our horizontal asthmatoid. Same thing. And this is our resting length. Let's say, for example, that the resting length for this one is, let's say that we go back off of this one. Let's say that this one was 6. Let's say that this one was actually going to be about 6 meters. Let's say that this point right here is about 4 meters. This one here is about 2 meters, you know, 1 meter, 0 meters, whatever. Okay? The whole point is this is the resting length. If this is the resting length and the muscle starts contracting, an isotonic contraction, it generates a lot of tension. What will that show on this actual length graph between the length-tension relationship? Okay, well then we know that in this part it's actually relaxing. So it's going to kind of stay the same here with the resting length. But then whenever it generates this tension, the muscle starts shortening. So what will happen to the length? It'll actually start decreasing. Let's say it drops down to about two. And then after that, it hits that point here where it's actually. actually staying in that plateau phase. But then what happens eventually? It goes back up as the muscle is starting to relax. And after it starts relaxing, it goes back into the resting length. That's what's happening to the actual length of the muscle. So the length of the muscle is decreasing as you are contracting the muscle. And then as the muscle starts relaxing, again, as you're going down, that's kind of the eccentric contraction, but it still has tension. Okay. As the muscle is contracting, it has a concentric contraction. And then as it starts relaxing, it starts having decreasing tension. And then the length starts actually going going back up towards resting length. And then again, it will plateau until another contraction occurs. This is the concept here with isometric and isotonic contraction. I hope that made sense, guys. So now what we're going to do is we're going to go over here and talk about levers for a little bit. Okay. Levers are really important. Well, first off, how do we define a lever? How do we define a lever? A lever is a rigid structure around which things can move. around a specific fixed point. So it's a rigid structure where things move around what's called a fixed point called the fulcrum. So how would we define this lever? A lever again is a rigid structure where movement occurs around a fixed point. Around a fixed point. And that fixed point that we're talking about. Is referred to. towards what's called a fulcrum. Okay, so before I actually start going into all the physiological examples of levers, Okay, so when we talk about levers, before we start getting into all the physiological examples of levers, let's first off do like a raw general diagram of the lever, and then we'll apply that to how that actually looks and how it functions in the human body. Okay, so first off, let's go with each class of levers. So there's three classes. There's class one levers. Okay, that's the first one we'll talk about. There's class two levers. And then there is the most common one, which is class three levers. Okay, let's go ahead and start talking about each one of these guys. Let me fix this into a roman numeral one so that we can see it consistent right here. Okay, so first thing I'm going to do is I'm going to draw a rod. I'm going to have just a straight rod here. So I have a rod here. And then let's say I put in the middle of the rod, I put this fixed point, which is called our fulcrum. All right, so there's my fulcrum. That fixed point right there is my fulcrum. That's the fixed point where things rotate around. Okay? Then let's say that I place a load on one end of this rod. Let's say I put it right here. So here's my load. I'll denote that with L. Now, whenever this load is actually sitting at this fixed point, it's trying to generate a force downwards. So when it generates a force, it's trying to generate a force that actually pushes downward. But you know there's this term called torque. What is torque? Well, torque is basically this rotational force, and it's defined as really the amount of force that's applied. from what's called the lever arm. And it is around an angle called sine theta. Let me explain what I mean by this. The load is exerting a force downwards. Let's denote this as a force that it's pushing downwards. The R is the distance from the fulcrum point. So from here to here, from this point here to this point here, that is my R. But since it's for the load, we call that the resistance arm or the load arm. Okay, so let's write that down. So this R is the distance here for this load so for the load right we can actually have it specifically the load torque is equal to the actual resistance arm or the load arm resistance arm times the actual force okay of the actual load so the force of the load But then, which way is this torque trying to push? It's trying to generate a direction going this way. It's trying to push this. Imagine this thing is trying to go like this. So the torque it's trying to generate is going in this direction. So that torque that it's trying to generate is in the counterclockwise direction. Now, what the person, what the human body tries to do is it tries to resist that torque. And it wants to produce a movement. Okay, well, if this torque, the load is pushing downward. Wouldn't I want to push this way so that the actual torque, I'll have a torque that goes clockwise? Yeah. So in other words, where would I want the force to be applied? I want it to be applied downwards on that point right there. So let's say that there's an effort force applied right here. Let's do that one in this maroonish color. Let's say that there's a force, an effort force. I'm going to call this the effort force. And that's applied at this point from a specific distance from the fulcrum. Okay, I know it's a lot of stuff, but it's going to make sense for the rest of the ones that we'll go over. This right here is trying to generate a torque, but the torque it's trying to generate is it's trying to push it this way. So which way is it trying to push it? It's trying to push it in the opposite direction. It's trying to generate a torque in the clockwise direction. Now, the point is, is which way will this lever move? Well, it depends upon which torque is greater. The greater the torque on this side, it'll move it this way. If the torque is greater on this side, it'll go this way. Well, how do we know which one's going to be greater? That's where we get into this term called mechanical advantage. Before we do that, let me explain one more thing. This one will also generate a torque. But what will his torque be? So let's call this the effort torque, just for the sake of it. We'll call it the effort torque. Okay? It's equal to its, you know, they call this distance here, it's r. but they call it more of what's called the force arm, because that's what you're trying to exert the force there. So they call this the force arm. And then we're going to multiply that by the actual effort force. Okay, why am I going over all of this stuff? And I'm going to explain why. If the load torque, let's say that I have my effort force. Force. If the effort force is greater, I have a greater distance from the fulcrum, what would that mean for R? For example, let's say that this one is actually, for example, I say it's 25 meters and let's say this one is 10 meters. Okay, well if I keep both of their forces the same, if both of the forces are the same, so for example, let's say for the resistance arm it's 10 meters times the actual what? The force load. Let's just say for this case it's 1, 1 newton. All right? And then for this one, this one is 25 meters for the actual force arm, the distance. And let's say that I keep the actual force the same, 1 newton. Then what is this one going to generate? This one will generate 25 in the form of torque, right, which is newton meters. And this one will generate what? This one will generate 10 newton meters for the torque. The whole concept is, is that if the force arm is farther away from the fulcrum, it has more power and you can generate more torque. So this is a mechanical advantage. So here's what we're going to get this relationship from. The whole relationship of this is, if the distance, which we're going to refer to this force arm as the distance. I'll put here D for the distance there. And the resistance arm also for the distance. If the, so here's the whole relationship that we really need to understand. If the force arm is greater than the actual resistance arm, which is just saying the distance to the fulcrum, will this be able to generate a lot of power? Yes. So this is meant for, I'm going to denote it MA, which stands for mechanical advantage. And if this lever is at a mechanical advantage, what is it going to be utilized for? It's going to be utilized primarily for power, for power movements. So this is utilized primarily for power movements. But if we take the opposite, so let's say that we take the opposing fact here. If the opposing fact is that the force arm is less than the resistance arm. Then what's going to happen? It'll be at a mechanical disadvantage. This won't be able to move the structure. So it's at a mechanical disadvantage. And it's no longer going to be able to generate a significant amount of power. It's going to be primarily utilized for speed. Okay, speed and direction. Okay, so again, let me just rephrase this real quick and then we'll go over the rest of the levers here. If the force arm is greater than the resistance arm, in other words, the distance from the fulcrum, if that amount of effort force, if the distance is actually greater than the amount of resistance or the amount of load that's being pushed down from that distance from the fulcrum, it's going to be at a mechanical advantage. It's going to generate power. the force arm, in other words, the distance that the effort force is being applied from the fulcrum is less than the resistance arm, which is the distance from where the load is being applied from the fulcrum point. It's in a mechanical disadvantage and it's not going to be for power, it's going to be for speed. Class one levers exhibit this type of capability. Okay, so this is an example of a class one lever. They can exhibit both power and they can exhibit speed. Now, let's do the next one. The next one class two levers, so let's say here If I want to put let's say I put my fulcrum at this point here, so now here's my fulcrum there's my fulcrum and Let's say that I want to put my force all the way out there, but before I do that Let's say I put my load here first. Let's say I put my load right here So here's the load and the load is pushing downwards right so that's the force that it's pushing down with. Here's the distance. So here's my resistance arm. Then let's say I apply an effort force. And the effort force, if this is pushing down, this will have to push. Again, what kind of direction, what kind of torque will this generate? It'll try to push it downwards this way. So this will generate a force. generate a torque in the what clockwise direction now I'm going to want to exhibit a force that can oppose that so I'm going to want to push this thing back up so this is trying to push it down I want this thing to push it up so I'm going to exhibit an effort force that's going to go up against this point here so I'm going to exhibit an effort force right here. Okay? So if I exhibit my effort force at that point there, it's going to try to generate a torque that's going this way. And that torque is going to be in the counterclockwise direction. It's going to try to oppose it. But here's the thing. Look at the distance. Holy mambo jambo. This sucker is super far away from the fulcrum. That is the force. If the force arm is a farther distance away from the fulcrum, what do we say? Force arm greater than the resistance arm? Oh, it's a mechanical advantage. These suckers are meant for power, okay? So this one, this lever, this second class lever, is primarily meant for power. Why? Because it is a mechanical advantage. The reason why is because it's at a mechanical advantage. That's it. See, once we develop this concept, it makes everything else easier. Okay, last one. Class 3 levers. Let's say I come down here. I have, again, this whole rod structure there. And I put my fulcrum again right here. But I'm going to be a little tricky. Here's my fulcrum. And let's say instead of me putting my load at the middle, I put it all the way down here at the end. So now the load is all the way down here at the end. And the force it's trying to exert is downwards. So therefore, whenever it's trying to exert that, it'll generate a torque that's trying to go in this direction. So that's a torque in the clockwise direction. Now, if I want to oppose that, I'm going to want to push opposite of that, right? I'm going to want to try to push upwards at this point right here. But I'm actually going to have it closer to the fulcrum. So let's say now I apply my effort force right here. Let's put my effort force. So here is my effort force. If that's the case, what kind of torque is it going to try to generate? It's going to try to generate a torque that moves it this direction. Counterclockwise, right? So it's going to try to generate a torque going in the counterclockwise direction. But again, let's look at the distances. Holy mambo jambo, look at this sucker right here. Look at the distance that this one has. Super far distance. So what happens to the resistance arm? Super far away. What about the actual force arm? Not very far away. Okay. What do we say? Let's go back to our little thing here. If the force arm is less than the resistance arm, it's at a mechanical disadvantage. It's not meant for power now. No. It's meant for speed. That's interesting now. So with this class 3 lever, what is it meant for? Class 3 levers are primarily meant for speed. Okay. Because they are at a mechanical... disadvantage. Alright, beautiful. So now we should understand the actual physics and biomechanics behind these actual levers. Class one levers, should have wrote this up here, sorry about that. It has both power and speed, right? So it's at both mechanical and mechanical, mechanical advantage and mechanical disadvantage. It all depends on how far that effort force is applied from the actual fulcrum. So it all depends upon the actual load arm or this force arm. I'm sorry, force arm. And then this is actually also going to be a factor too. So if this class one lever has a force arm greater than the resistance arm, that muscle will exhibit a mechanical advantage and be that lever. If the force arm is less than the resistance arm, then it'll actually be at a mechanical disadvantage and be for speed. So class one can exhibit both speed and power. Now let's go on to the physiological examples, okay? We're going to do like classical ones that most of you see in textbooks, right? So let's say here you got this guy with this Mississippi mud flap here, a little cool haircut. And he's got these muscles here in the back. So the posterior neck muscles, you know, like your spleen is capitis and your trapezius muscle, a lot of those muscles, right? And the function of those muscles is to extend the neck, right? So let's say that we look at this in a lever form. So let's say, where is the actual fixed point at? The fixed point is right here. Let's say that this is actually C1, you know, C2, C3, C4, C5, C6, C7, right? At C1, it articulates with the occipital condyles. So the articulation point right there, the atlantooccipital joint right there, that is our fulcrum. That's the pivot point. So let's say that's our fulcrum. Then our head is going to try to go downwards. It's going to try to go move our face, the anterior side. side of our face downwards. So where is the actual load being applied? It's being applied downwards. So that's the load force. It's the weight of your head, right? Pushing downwards with gravity. What do I need to do then? Well, this is trying to generate, let's go back to the torque concept. This is trying to generate a torque going where? Okay, counterclockwise. Well, we want the head to actually be pulled in the opposite direction. So which way do we want the actual head to go? We want it to go back. If we want the head to go back, which way do we want this actual torque to be generated? We'd want it to be generated in this direction. What is this direction here? This is the clockwise direction. Okay, now, if that's the case, then what... Muscles must be contracting. Those posterior neck muscles like the trapezius and the splenius capitis muscle. What are they going to try to do? They're going to try to generate an effort force that's pointing downwards. Okay, so when the muscle shortens, what happens? It pulls the actual head back, extends the neck, which lifts the anterior part of the face back up. That's an example of a class one lever. They're kind of rare though, so let's put that right up above it. This is a rare lever. You don't find many of these in the body. So kind of a rare lever. This lever and Class 2 levers are both rare. There's not too many examples of them in the body. Whereas Class 3 is the most common and the most abundant within the body. Okay, so let's keep going here. Let's go to this one. Okay, well where's the actual fulcrum? That's the first thing we want to identify. The fulcrum is this fixed point right here. It's when the foot is pushing into the actual ground. So you're trying to do a calf raise. You're trying to plantar flexion. If that's the fixed point, so this is my fulcrum. That's the fixed point. That's the fulcrum. Okay, well where's the load? It's our body weight trying to push down through the actual ankle joint. So if the load is right here, it's trying to push down. That's the load. That's trying to exhibit a downward force. So if it's trying to push downwards, think about this then. It's trying to push this downward. So it's trying to generate a torque going this way. It's trying to go down in this way, right? So what would that be? That would be going in the clockwise direction. So this would be a torque in the clockwise direction. I want to generate a torque going in the opposite direction. Okay, so if that's the case then, I'm going to want to generate a torque that's going in the counterclockwise direction. I'm going to want this torque to go in the counterclockwise direction. In order to resist this load force from pushing the ankle down, this ankle, the calcaneus right here, that point right there, instead of pushing it down, I need to have these gastrocnemius and soleus muscles here. I'm going to need them to contract and pull on that calcaneal tendon or the Achilles tendon and pull upwards. And this is going to be my effort force. Okay. And this is an example of a class two lever. So think about whenever you're trying to do calf raises. Plantar flexion with the gastrocnemius and the soleus muscles. Okay, the last one and the most common one is the class three levers. These are many, many examples in the body. For example, whenever you're thinking about your biceps, so contracting the biceps, doing flexion. Whenever you're doing chest flies, whenever you're doing front raises, side raises, knee extensions, I'm sorry, leg extensions, leg curls. All of those exercises involves class three levers. How does these class 3 levers function? Okay, let's look at this physiological example. Where's the fulcrum? It's at the elbow joint. Okay, so there is my fulcrum. That's my fixed point right there. Okay, where's the load? It's this hundred pound dumbbell trying to go downwards towards the actual center of the earth with gravity, right? So this is the load. This is the load and it's trying to push downwards. So in other words, what type of torque is it trying to generate? It's trying to generate a torque going in this direction. What kind of torque is that? That's a torque in the counterclockwise direction. Okay? Well, now, the biceps brachii muscle and the brachialis muscle, okay, when they attach, you know, they attach to the supraglenoid tubercle and the coracloid process, they help to be able to attach there. And what happens? Their insertion point around the radiotuberosity, right, they help to be able to move that up towards the origin. So when the muscle starts to contract, it exhibits an effort force that moves upwards. And if that effort force moves upwards, what is it going to do? It's going to move the load. But let's see what happens to the torque. So there's the effort force. We can put it right here in the bone. There's our effort force. So what happens to the torque? It's trying to push it this way. It's trying to oppose that. So if it's trying to do this action, this is going in the clockwise. I would want this to be torquing it in the clockwise direction, okay? To oppose that torque and to allow for the muscle to contract. And again, this is one of many examples. This is just an example of the biceps. But again, since this is the most common in the body, it could be the biceps, could even be, again, quadriceps muscles, hamstring muscles, deltoid muscles, pec muscles, a lot of those muscles are going to act as class three. levers. Whereas class one, there is one more example besides those posterior neck muscles, you can also think about the triceps. The triceps is another example of a class one lever. So besides the posterior neck muscles, you can also think about the triceps, just so that you guys know. All right Ningenerds, I appreciate you guys sticking in there with me. I really do. I hope all of this made sense. I know I say that a lot, but it really is our desire here at Ningenerd Science for it to really, really help you guys to make sense of these complex topics. I hope you guys enjoyed the video. If it did make sense and you guys liked it, please hit the like button, comment down in the comment section, and subscribe. Alright Ninja Nerds, as always, until next time.

The second thing that we're going to talk about is levers, the three classes of levers, and then examples of those in the body and their mechanical advantage and mechanical disadvantage. All right, so let's go ahead and get started on that. So let's say that you have two muscles here, two muscles and two graphs to correlate with those. Let's say that in this first muscle, I want to go for this first muscle, I want it to exhibit a specific type of contraction.

And this contraction is called isometric contraction. Okay, so let's say that this muscle right here on the top is going to undergo a process called an isometric contraction. Well, let's decipher this word.

What is iso and what does this metric mean? So, iso means same and metric is like a form of measurement. So, it's the same measure.

So, what happens in an isometric contraction? Let's say that I have a fixed point. Let's say here I star this point here. Let's say this is the fixed point. Okay, that point right there is a fixed point.

If that's the fixed point, let's say that this muscle tries to contract. contract and carry a load. So let's say, for example, I put, let's say that I'm trying to curl a 45 pound dumbbell, right? I'm sorry, 45 pound barbell with two 45 pound weights on both sides, right? And I'm trying to curl that.

If I'm trying to curl that, and let's say that I try to curl that and I just get stuck in this position, I get stuck in this position. I'm generating a heck of a lot of tension and a lot of force, but the weight is not moving and the muscle isn't shortening. It's not actually going to be shortening and actually having the size.

change. So because of that, it's staying the same size. It is not lengthening, nor is it shortening. It's staying at the same point. If that happens, that is an isometric contraction.

So for example, if this muscle contracts, it can generate a whole lot of tension, but the muscle size after it contracts will not lengthen or shorten. So it stays the same. So again, isometric contraction, what are the things that we'll see?

It can generate a lot of tension. A lot of tension can be generated. But here's the thing. Whenever you contract this, the force.

So you know what? There's what's called the load. So let's say that I'm trying to lift a dumbbell. Let's say, for example, I take a 100-pound dumbbell.

And I take that 100-pound dumbbell. and that's the load, that's the amount of resistance that's actually trying to push down with the force of gravity, or it's trying to push down. I'm going to try to exhibit a force that will move the dumbbell up. But let's say that the force that I generate is not enough to overcome. home the load that's pushing down towards the center of earth, right?

With gravity. If that's the case, will the actual load move? No. So that is the concept of an isometric contraction. That the load, we can refer to it as the load force or the resistance, is greater than the muscle force.

Okay, so we can say the load force All right, the resistance, the weight, that's a 100-pound dumbbell that's pushing down towards the actual center of the earth, right? Versus the muscle force, my biceps brachii and my brachialis muscles that are trying to contract. When they are trying to contract, they're trying to move the weight. But the amount of force that they generate is not enough to move the weight, so it stays the same size.

So in other words, it does not lengthen. It doesn't lengthen. Nor does it shorten.

It stays the same size. So stays the same. Okay, so these are the things I want you to get with isometric contraction. To recap it, the load force, the amount of weight, the 100-pound dumbbell is really, really heavy, right?

It's trying to push down to the actual center of gravity. As it pushes down, you're trying to generate a force in your bicep, brachii, and brachialis to try to move the weight. But the load force is greater than the muscle force.

When the muscle contracts, it can generate a lot of tension. But the actual muscle does not shorten, nor does it lengthen. It stays at the same size or same measure. Okay? That is this concept of isometric.

What would that look like on a curve? Well, we said here... that this one can generate a lot of tension.

I'm talking a lot. Let's say, for example, it generates up to, and I'm making this number up. I'm just doing it for example purposes. Let's say it's 10 newtons.

Let's say it can generate 10 newtons. If this generates 10 newtons, and that's the maximal tension point, let's say that it starts here, and it works its way up to 10 newtons. It gets into this period of contraction, right?

So that's the latent phase and it has that period of contraction. And when it reaches that point, it contracts, contracts, contracts, contracts. And then eventually what happens? It actually falls off, right? The tension starts decreasing and it starts moving back down to a resting point.

And then it will go back into this latent phase, right? That's what's happening. And again, what is this point right here, this 10 newtons? Let's say that that is the maximal tension point.

That is the maximal tension. Okay, so that's when you're trying to lift that 100 pound dumbbell. Alright, but how is that, how is that relatable to the length of the muscle? So again, we said that the length doesn't change. So let's say that I put a horizontal asthmatoid here.

So I put a horizontal asthmatoid. And again, on the y-axis for this one, this one's tension, and the x-axis is our time. On this one, it is length. And on the x-axis, it is time.

Let's see, here's my horizontal asthmatoid. And let's say that this represents the resting length. Okay, if this is representing the resting link, let's say originally, here it is, at this point here it's at rest.

It's resting, right? But then we contract the muscle. If we contract the muscle, let's say that the length is actually increasing as you go up, right?

So, for example, let's just say, for example, that at that point it's zero. And let's say that this is in meters, whatever. It's in meters, let's say that this is zero, two, four. 6 whatever right Let's say right.

It's right around like 5.5 or something like that right? That's the length That is currently, but then whenever the muscle contracts is the length going to change no it doesn't lengthen nor does it shorten? So you shouldn't expect it to have a downward reflection, and you shouldn't expect it have an upward reflection It should stay a straight Okay, and this is what you would see on the graphical representation of an isometric contraction, okay? Now, let's talk about the next one.

The next one is a little bit cooler. It's a little bit different. And it comes in two flavors in two different ways. This one is referred to as a isotonic contraction. Okay, before we talk about, well, actually, no, let's define the two types.

There is two types here. The two types is going to be concentric. And the other one is going to be eccentric. So the other type is eccentric.

Now when people think about lifting and isotonic contractions, they more commonly think about concentric contractions. Because what happens with isotonic contractions, let's say that I take a weight, a 50-pound dumbbell. It's a decently heavy, but let's say that 50-pound dumbbell, again, is exhibiting a what? It's exhibiting a downward force that's trying to pull my arm down from that elbow joint, right?

But let's say that my biceps rake on my brachialis, I recruit enough muscle fibers that I can generate enough force and enough tension to overcome that weight load and move the weight. In other words, I'm shortening the muscle belly. As the muscle belly shortens, I'm generating a lot of tension, but I'm also moving the weight.

That is an example of a concentric contraction. So a concentric contraction is when the muscle shortens. Let's write that down. So this is when the muscle shortens. Okay, now let's take, for example, the eccentric part.

Let's take that same dumbbell. I'm at the peak point of contraction, and I contract the muscles. They're at the peak point of tension.

I can't go beyond that point. And then let's say that I actually start relaxing, and I start giving, letting the muscle go down and down and down. If you guys have ever done like a preacher curl or something, it's really hard to resist the weight going down in a slow manner, right?

And you're still generating tension. It's still generating a lot of tension, a lot of force, almost 50 times more. So the amount of force that you're generating as it's going down is still great. It's actually very, very strong.

But an eccentric contraction is as the muscle is lengthening. So lengthening the muscle is an eccentric contraction. So this is when the muscle lengthens. Okay. So if the muscle lengthens, it's an eccentric contraction.

If the muscle shortens, it's a concentric contraction. Remember, eccentric contractions aren't referred to as much, but they're equally important as a concentric contraction. They can actually generate more force than a concentric contraction. We'll talk about this when we talk about what's called the force-velocity curve.

Okay, how this one can actually accommodate for a greater amount of force. Okay, another thing about isotonic contraction. What do we say? It can generate a lot of tension, but not as much tension as an isometric contraction. Okay, so it does generate a decent amount of tension.

Decent amount of tension. But here's what's really important. We said that the load force was greater than the force of the load force. The muscle force in the isometric contraction. In this case, the load force, the weight, that 50 pound dumbbell, was less than the muscle force of my biceps, brachii muscle, and my brachialis muscle.

In other words, I have enough force to move the load. So therefore, the muscle can shorten. Muscle shortens.

Let's fix that L. And again, whenever the muscle is relaxing, it's going downwards and you're resisting the weight going downward, it can lengthen. Okay, so going down from bicep curl, as we were using in our example, muscle lengthens.

But remember, as you're going up, you generate a lot of tension, but you can actually generate more tension on the way down. Another example of eccentric contractions is like, you know, whenever you're walking up a really, really steep hill. That's also an example of an eccentric contraction because you're stretching those calf muscles and causing micro tears, which again activates those myosatellite cells to come in and cause repair. All right, so let's see what this looks like.

on an actual graph. So we said here, let's have, let's say they said, we said this one generates a lot of tension. This one doesn't generate as much tension. So it's not going to be at 10 newtons. Let's say for example, it's at like six newtons.

So let's say at that point, point here it's about six newtons okay and once again let's say here's about zero and let's say here's about you know three if that's the case then when this muscle starts contracting muscles our muscles are always usually partially contracted because of muscle tone because of the reflex arcs so let's say that it's already having a little bit of force generated here right and it starts having this contractile phase so it goes into the contraction phase and it rises up and it hits this maximal tension point again what is their maximal tension at this point in order to move the actual muscle load. Maximal tension point, right? So if this maximal tension, or in other words, the amount of tension that you need to generate in order to overcome the actual load force, what will happen? It'll reach that point, and again, it'll, you know, generate some tension for a while, plateau, and eventually it'll go back down into the relaxation point, and then it'll go back into that latent phase, right? Now, let's say here we have over here our horizontal asthmatoid.

Same thing. And this is our resting length. Let's say, for example, that the resting length for this one is, let's say that we go back off of this one. Let's say that this one was 6. Let's say that this one was actually going to be about 6 meters. Let's say that this point right here is about 4 meters.

This one here is about 2 meters, you know, 1 meter, 0 meters, whatever. Okay? The whole point is this is the resting length.

If this is the resting length and the muscle starts contracting, an isotonic contraction, it generates a lot of tension. What will that show on this actual length graph between the length-tension relationship? Okay, well then we know that in this part it's actually relaxing. So it's going to kind of stay the same here with the resting length.

But then whenever it generates this tension, the muscle starts shortening. So what will happen to the length? It'll actually start decreasing.

Let's say it drops down to about two. And then after that, it hits that point here where it's actually. actually staying in that plateau phase. But then what happens eventually?

It goes back up as the muscle is starting to relax. And after it starts relaxing, it goes back into the resting length. That's what's happening to the actual length of the muscle. So the length of the muscle is decreasing as you are contracting the muscle. And then as the muscle starts relaxing, again, as you're going down, that's kind of the eccentric contraction, but it still has tension.

Okay. As the muscle is contracting, it has a concentric contraction. And then as it starts relaxing, it starts having decreasing tension.

And then the length starts actually going going back up towards resting length. And then again, it will plateau until another contraction occurs. This is the concept here with isometric and isotonic contraction. I hope that made sense, guys.

So now what we're going to do is we're going to go over here and talk about levers for a little bit. Okay. Levers are really important.

Well, first off, how do we define a lever? How do we define a lever? A lever is a rigid structure around which things can move. around a specific fixed point.

So it's a rigid structure where things move around what's called a fixed point called the fulcrum. So how would we define this lever? A lever again is a rigid structure where movement occurs around a fixed point.

Around a fixed point. And that fixed point that we're talking about. Is referred to. towards what's called a fulcrum.

Okay, so before I actually start going into all the physiological examples of levers, Okay, so when we talk about levers, before we start getting into all the physiological examples of levers, let's first off do like a raw general diagram of the lever, and then we'll apply that to how that actually looks and how it functions in the human body. Okay, so first off, let's go with each class of levers. So there's three classes.

There's class one levers. Okay, that's the first one we'll talk about. There's class two levers. And then there is the most common one, which is class three levers.

Okay, let's go ahead and start talking about each one of these guys. Let me fix this into a roman numeral one so that we can see it consistent right here. Okay, so first thing I'm going to do is I'm going to draw a rod. I'm going to have just a straight rod here. So I have a rod here.

And then let's say I put in the middle of the rod, I put this fixed point, which is called our fulcrum. All right, so there's my fulcrum. That fixed point right there is my fulcrum. That's the fixed point where things rotate around.

Okay? Then let's say that I place a load on one end of this rod. Let's say I put it right here.

So here's my load. I'll denote that with L. Now, whenever this load is actually sitting at this fixed point, it's trying to generate a force downwards.

So when it generates a force, it's trying to generate a force that actually pushes downward. But you know there's this term called torque. What is torque? Well, torque is basically this rotational force, and it's defined as really the amount of force that's applied. from what's called the lever arm.

And it is around an angle called sine theta. Let me explain what I mean by this. The load is exerting a force downwards. Let's denote this as a force that it's pushing downwards.

The R is the distance from the fulcrum point. So from here to here, from this point here to this point here, that is my R. But since it's for the load, we call that the resistance arm or the load arm. Okay, so let's write that down. So this R is the distance here for this load so for the load right we can actually have it specifically the load torque is equal to the actual resistance arm or the load arm resistance arm times the actual force okay of the actual load so the force of the load But then, which way is this torque trying to push?

It's trying to generate a direction going this way. It's trying to push this. Imagine this thing is trying to go like this. So the torque it's trying to generate is going in this direction. So that torque that it's trying to generate is in the counterclockwise direction.

Now, what the person, what the human body tries to do is it tries to resist that torque. And it wants to produce a movement. Okay, well, if this torque, the load is pushing downward.

Wouldn't I want to push this way so that the actual torque, I'll have a torque that goes clockwise? Yeah. So in other words, where would I want the force to be applied? I want it to be applied downwards on that point right there. So let's say that there's an effort force applied right here.

Let's do that one in this maroonish color. Let's say that there's a force, an effort force. I'm going to call this the effort force.

And that's applied at this point from a specific distance from the fulcrum. Okay, I know it's a lot of stuff, but it's going to make sense for the rest of the ones that we'll go over. This right here is trying to generate a torque, but the torque it's trying to generate is it's trying to push it this way. So which way is it trying to push it? It's trying to push it in the opposite direction.

It's trying to generate a torque in the clockwise direction. Now, the point is, is which way will this lever move? Well, it depends upon which torque is greater. The greater the torque on this side, it'll move it this way. If the torque is greater on this side, it'll go this way.

Well, how do we know which one's going to be greater? That's where we get into this term called mechanical advantage. Before we do that, let me explain one more thing. This one will also generate a torque.

But what will his torque be? So let's call this the effort torque, just for the sake of it. We'll call it the effort torque. Okay?

It's equal to its, you know, they call this distance here, it's r. but they call it more of what's called the force arm, because that's what you're trying to exert the force there. So they call this the force arm. And then we're going to multiply that by the actual effort force. Okay, why am I going over all of this stuff?

And I'm going to explain why. If the load torque, let's say that I have my effort force. Force. If the effort force is greater, I have a greater distance from the fulcrum, what would that mean for R?

For example, let's say that this one is actually, for example, I say it's 25 meters and let's say this one is 10 meters. Okay, well if I keep both of their forces the same, if both of the forces are the same, so for example, let's say for the resistance arm it's 10 meters times the actual what? The force load. Let's just say for this case it's 1, 1 newton. All right?

And then for this one, this one is 25 meters for the actual force arm, the distance. And let's say that I keep the actual force the same, 1 newton. Then what is this one going to generate?

This one will generate 25 in the form of torque, right, which is newton meters. And this one will generate what? This one will generate 10 newton meters for the torque.

The whole concept is, is that if the force arm is farther away from the fulcrum, it has more power and you can generate more torque. So this is a mechanical advantage. So here's what we're going to get this relationship from. The whole relationship of this is, if the distance, which we're going to refer to this force arm as the distance. I'll put here D for the distance there.

And the resistance arm also for the distance. If the, so here's the whole relationship that we really need to understand. If the force arm is greater than the actual resistance arm, which is just saying the distance to the fulcrum, will this be able to generate a lot of power?

Yes. So this is meant for, I'm going to denote it MA, which stands for mechanical advantage. And if this lever is at a mechanical advantage, what is it going to be utilized for?

It's going to be utilized primarily for power, for power movements. So this is utilized primarily for power movements. But if we take the opposite, so let's say that we take the opposing fact here.

If the opposing fact is that the force arm is less than the resistance arm. Then what's going to happen? It'll be at a mechanical disadvantage.

This won't be able to move the structure. So it's at a mechanical disadvantage. And it's no longer going to be able to generate a significant amount of power.

It's going to be primarily utilized for speed. Okay, speed and direction. Okay, so again, let me just rephrase this real quick and then we'll go over the rest of the levers here.

If the force arm is greater than the resistance arm, in other words, the distance from the fulcrum, if that amount of effort force, if the distance is actually greater than the amount of resistance or the amount of load that's being pushed down from that distance from the fulcrum, it's going to be at a mechanical advantage. It's going to generate power. the force arm, in other words, the distance that the effort force is being applied from the fulcrum is less than the resistance arm, which is the distance from where the load is being applied from the fulcrum point.

It's in a mechanical disadvantage and it's not going to be for power, it's going to be for speed. Class one levers exhibit this type of capability. Okay, so this is an example of a class one lever. They can exhibit both power and they can exhibit speed.

Now, let's do the next one. The next one class two levers, so let's say here If I want to put let's say I put my fulcrum at this point here, so now here's my fulcrum there's my fulcrum and Let's say that I want to put my force all the way out there, but before I do that Let's say I put my load here first. Let's say I put my load right here So here's the load and the load is pushing downwards right so that's the force that it's pushing down with. Here's the distance. So here's my resistance arm.

Then let's say I apply an effort force. And the effort force, if this is pushing down, this will have to push. Again, what kind of direction, what kind of torque will this generate? It'll try to push it downwards this way.

So this will generate a force. generate a torque in the what clockwise direction now I'm going to want to exhibit a force that can oppose that so I'm going to want to push this thing back up so this is trying to push it down I want this thing to push it up so I'm going to exhibit an effort force that's going to go up against this point here so I'm going to exhibit an effort force right here. Okay? So if I exhibit my effort force at that point there, it's going to try to generate a torque that's going this way. And that torque is going to be in the counterclockwise direction.

It's going to try to oppose it. But here's the thing. Look at the distance. Holy mambo jambo. This sucker is super far away from the fulcrum.

That is the force. If the force arm is a farther distance away from the fulcrum, what do we say? Force arm greater than the resistance arm?

Oh, it's a mechanical advantage. These suckers are meant for power, okay? So this one, this lever, this second class lever, is primarily meant for power. Why? Because it is a mechanical advantage.

The reason why is because it's at a mechanical advantage. That's it. See, once we develop this concept, it makes everything else easier.

Okay, last one. Class 3 levers. Let's say I come down here. I have, again, this whole rod structure there.

And I put my fulcrum again right here. But I'm going to be a little tricky. Here's my fulcrum. And let's say instead of me putting my load at the middle, I put it all the way down here at the end. So now the load is all the way down here at the end.

And the force it's trying to exert is downwards. So therefore, whenever it's trying to exert that, it'll generate a torque that's trying to go in this direction. So that's a torque in the clockwise direction.

Now, if I want to oppose that, I'm going to want to push opposite of that, right? I'm going to want to try to push upwards at this point right here. But I'm actually going to have it closer to the fulcrum.

So let's say now I apply my effort force right here. Let's put my effort force. So here is my effort force. If that's the case, what kind of torque is it going to try to generate? It's going to try to generate a torque that moves it this direction.

Counterclockwise, right? So it's going to try to generate a torque going in the counterclockwise direction. But again, let's look at the distances.

Holy mambo jambo, look at this sucker right here. Look at the distance that this one has. Super far distance. So what happens to the resistance arm? Super far away.

What about the actual force arm? Not very far away. Okay.

What do we say? Let's go back to our little thing here. If the force arm is less than the resistance arm, it's at a mechanical disadvantage. It's not meant for power now. No.

It's meant for speed. That's interesting now. So with this class 3 lever, what is it meant for? Class 3 levers are primarily meant for speed. Okay.

Because they are at a mechanical... disadvantage. Alright, beautiful.

So now we should understand the actual physics and biomechanics behind these actual levers. Class one levers, should have wrote this up here, sorry about that. It has both power and speed, right?

So it's at both mechanical and mechanical, mechanical advantage and mechanical disadvantage. It all depends on how far that effort force is applied from the actual fulcrum. So it all depends upon the actual load arm or this force arm. I'm sorry, force arm.

And then this is actually also going to be a factor too. So if this class one lever has a force arm greater than the resistance arm, that muscle will exhibit a mechanical advantage and be that lever. If the force arm is less than the resistance arm, then it'll actually be at a mechanical disadvantage and be for speed. So class one can exhibit both speed and power. Now let's go on to the physiological examples, okay?

We're going to do like classical ones that most of you see in textbooks, right? So let's say here you got this guy with this Mississippi mud flap here, a little cool haircut. And he's got these muscles here in the back.

So the posterior neck muscles, you know, like your spleen is capitis and your trapezius muscle, a lot of those muscles, right? And the function of those muscles is to extend the neck, right? So let's say that we look at this in a lever form. So let's say, where is the actual fixed point at? The fixed point is right here.

Let's say that this is actually C1, you know, C2, C3, C4, C5, C6, C7, right? At C1, it articulates with the occipital condyles. So the articulation point right there, the atlantooccipital joint right there, that is our fulcrum. That's the pivot point.

So let's say that's our fulcrum. Then our head is going to try to go downwards. It's going to try to go move our face, the anterior side. side of our face downwards.

So where is the actual load being applied? It's being applied downwards. So that's the load force. It's the weight of your head, right? Pushing downwards with gravity.

What do I need to do then? Well, this is trying to generate, let's go back to the torque concept. This is trying to generate a torque going where?

Okay, counterclockwise. Well, we want the head to actually be pulled in the opposite direction. So which way do we want the actual head to go?

We want it to go back. If we want the head to go back, which way do we want this actual torque to be generated? We'd want it to be generated in this direction.

What is this direction here? This is the clockwise direction. Okay, now, if that's the case, then what...

Muscles must be contracting. Those posterior neck muscles like the trapezius and the splenius capitis muscle. What are they going to try to do? They're going to try to generate an effort force that's pointing downwards.

Okay, so when the muscle shortens, what happens? It pulls the actual head back, extends the neck, which lifts the anterior part of the face back up. That's an example of a class one lever. They're kind of rare though, so let's put that right up above it.

This is a rare lever. You don't find many of these in the body. So kind of a rare lever.

This lever and Class 2 levers are both rare. There's not too many examples of them in the body. Whereas Class 3 is the most common and the most abundant within the body. Okay, so let's keep going here. Let's go to this one.

Okay, well where's the actual fulcrum? That's the first thing we want to identify. The fulcrum is this fixed point right here. It's when the foot is pushing into the actual ground.

So you're trying to do a calf raise. You're trying to plantar flexion. If that's the fixed point, so this is my fulcrum. That's the fixed point. That's the fulcrum.

Okay, well where's the load? It's our body weight trying to push down through the actual ankle joint. So if the load is right here, it's trying to push down. That's the load. That's trying to exhibit a downward force.

So if it's trying to push downwards, think about this then. It's trying to push this downward. So it's trying to generate a torque going this way. It's trying to go down in this way, right? So what would that be?

That would be going in the clockwise direction. So this would be a torque in the clockwise direction. I want to generate a torque going in the opposite direction.

Okay, so if that's the case then, I'm going to want to generate a torque that's going in the counterclockwise direction. I'm going to want this torque to go in the counterclockwise direction. In order to resist this load force from pushing the ankle down, this ankle, the calcaneus right here, that point right there, instead of pushing it down, I need to have these gastrocnemius and soleus muscles here. I'm going to need them to contract and pull on that calcaneal tendon or the Achilles tendon and pull upwards. And this is going to be my effort force.

Okay. And this is an example of a class two lever. So think about whenever you're trying to do calf raises.

Plantar flexion with the gastrocnemius and the soleus muscles. Okay, the last one and the most common one is the class three levers. These are many, many examples in the body. For example, whenever you're thinking about your biceps, so contracting the biceps, doing flexion. Whenever you're doing chest flies, whenever you're doing front raises, side raises, knee extensions, I'm sorry, leg extensions, leg curls.

All of those exercises involves class three levers. How does these class 3 levers function? Okay, let's look at this physiological example. Where's the fulcrum?

It's at the elbow joint. Okay, so there is my fulcrum. That's my fixed point right there. Okay, where's the load?

It's this hundred pound dumbbell trying to go downwards towards the actual center of the earth with gravity, right? So this is the load. This is the load and it's trying to push downwards.

So in other words, what type of torque is it trying to generate? It's trying to generate a torque going in this direction. What kind of torque is that? That's a torque in the counterclockwise direction.

Okay? Well, now, the biceps brachii muscle and the brachialis muscle, okay, when they attach, you know, they attach to the supraglenoid tubercle and the coracloid process, they help to be able to attach there. And what happens? Their insertion point around the radiotuberosity, right, they help to be able to move that up towards the origin.

So when the muscle starts to contract, it exhibits an effort force that moves upwards. And if that effort force moves upwards, what is it going to do? It's going to move the load.

But let's see what happens to the torque. So there's the effort force. We can put it right here in the bone. There's our effort force. So what happens to the torque?

It's trying to push it this way. It's trying to oppose that. So if it's trying to do this action, this is going in the clockwise.

I would want this to be torquing it in the clockwise direction, okay? To oppose that torque and to allow for the muscle to contract. And again, this is one of many examples.

This is just an example of the biceps. But again, since this is the most common in the body, it could be the biceps, could even be, again, quadriceps muscles, hamstring muscles, deltoid muscles, pec muscles, a lot of those muscles are going to act as class three. levers. Whereas class one, there is one more example besides those posterior neck muscles, you can also think about the triceps. The triceps is another example of a class one lever.

So besides the posterior neck muscles, you can also think about the triceps, just so that you guys know. All right Ningenerds, I appreciate you guys sticking in there with me. I really do. I hope all of this made sense. I know I say that a lot, but it really is our desire here at Ningenerd Science for it to really, really help you guys to make sense of these complex topics.

I hope you guys enjoyed the video. If it did make sense and you guys liked it, please hit the like button, comment down in the comment section, and subscribe. Alright Ninja Nerds, as always, until next time.

Transcript for:Muscle Mechanics | Types of Contractions & Levers

Transcript for:
Muscle Mechanics | Types of Contractions & Levers