Hi folks, welcome to this video on types of contractions or contraction types, whichever you prefer. There are three main types of muscular contractions that can take place that could be an answer to a question in the paper and they're isometric, concentric and eccentric as we've got there. Isometric, concentric and eccentric contractions. So we're going to go through each of those, what they basically mean and a few of the key terms that could confuse you in the heat of the exam or make you panic a little bit in the heat of the exam.
So just trying to simplify it as much as we can. Let's start in the middle with a concentric contraction. The key thing about a concentric contraction is the muscle shortens as it contracts.
And we use concentric contraction when we want to accelerate an object or your own body. When you want to get something moving, it is due to a concentric contraction. If we look at the picture associated with that, I know we always seem to do bicep kale, but you know there's plenty of pictures of it. So what's happening there is as that...
weight is being lifted in this direction the muscle is bulging and it bulges because it shortens so every time you contract your muscles to how big they are you are shortening that muscle so that is it a concentric contraction the thing that we are accelerating in this instance is the weight now the thing is could you get asked about a bicep curl because we keep banging on about it in all these different videos yeah you could but it's unlikely you're more than likely to get asked about a sports movement So when are you likely to see a concentric contraction? What does acceleration mean? Anytime you're getting yourself or an object moving, that is going to be a concentric contraction. Anytime you jump, kick, run, throw, lift, tackle, shoot, head something, drive towards something or someone, they are concentric contractions taking place. They are accelerating you, your body, an object.
over a certain distance or into somebody else or a certain height or whatever it is. Concentric contractions in sport are by far the most common because we are always trying to do something quicker, hence why we're trying to accelerate, move something, whatever it is. So they are a very, very common type of contraction. Now, in contrast, an eccentric contraction is where the muscle lengthens.
But the key thing here is under tension. to decelerate you or an object. Now, do not confuse this with a stretch. Yes, when you stretch a muscle, that is also lengthening, but an eccentric contraction is still a contraction.
The muscle still has tension in it. So as we've seen here, this person has done the bicep curl. The bicep has concentrically contracted.
It's shortened to lift and accelerate it. What we are now trying to do is we are going to lower that same dumbbell back to the ground i gravity is going to want to pull it down we're going to let gravity pull it down but under control under tension so this bicep is now extending it's getting longer but it's doing it under our control under tension now a little thing i use to remember or identify whether it's an eccentric contraction i remember that eccentric to earth Hey, hey. If I am lowering something down to the ground, including myself, the downward phase of a press-up, the downward phase of a squat, if I'm lowering that dumbbell back towards the ground because I've finished lifting it, I've finished that rep. That is an eccentric contraction. Gravity always wants to pull things down and always will pull things down to planet Earth. If you let gravity pull something down to Earth at its natural rate, things will smack into the ground very, very quickly.
What we do is we do eccentric contractions to lower it. Think about jumping for an attacking header in a sport. As you land, if your quadriceps didn't do an eccentric contraction, you would just smash into the ground.
Your quadriceps will lengthen, your knees will bend as your quadriceps lengthen under tension as they perform an eccentric contraction to control the rate at which you go down to the F. So you don't go into the F too quickly, so you don't collapse entirely. Alright, so eccentric contractions are ones that take place to decelerate you or something down and the way to remember it is eccentric to F. They are not as common.
in sport and with sporting examples as concentric contractions. If you don't think that person is slowing something down or lowering it down or something like that, then it is, you know, if they're accelerating, it's a concentric contraction. Only if they are lowering, decelerating, eccentric to F is an eccentric contraction.
Now just a quick bit of terminology, just because they can be a little bit like this. These are both isotonic contractions. Both this one. and this one. Concentric and eccentric contractions are isotonic.
Iso meaning same tonic tension or speed, whichever you prefer. Just a little bit of terminology. If they ask you which type of isotonic contraction is taking place, it's basically a posh way of saying, is this a concentric or an eccentric contraction?
That's just their way of doing it. The reason I say that is because we're now coming up to a bit of a new term, that one being isometric and it's very easy to get isotonic and isometric confused but isotonic are either concentric or eccentric contractions and isometric is its own little thing so let's have a look at that. An isometric contraction is where there is a contraction of the muscle but there is no change in length so with this picture here this person has been asked just to hold that weight in that fixed position don't lower it don't raise it That bicep is now performing an isometric contraction. Iso, as it did down here, meaning same, but whereas tonic meant tension or speed, metric, where we get the word metre from, means length.
So isometric, the muscle contracts, but there's no change in muscle length. They're very rare in sport. There are only a few times you are going to see an isometric contraction, and that is when our athletes are doing that.
They are staying still. stationary or in a fixed position. Now if you think about gymnastics, when they're asked to hold that crucifix position or hold a handstand position or something like that, that's an example of isometric contractions.
Equally, someone like Usain Bolt or any sprinter, when they're on the start line in the set position in the blocks, they're not allowed to move at all, otherwise it would trigger a false start. Same with the swimmers, people like Adam Peaty and Jazz Carlin, people like that. So they've got to hold isometric contractions.
Yes, there are lots of examples of isometric contractions, but if you think the bulk of sports, you're moving. You're doing something. You're trying to move yourself or move your opponent or move an object. So it's much more common to see concentric contractions in sport. Less common is eccentric contractions, the lowering, but they definitely do happen.
But the least common is isometric contractions. So you need to know about these three different contraction types, what happens to muscle length and where you are likely to see them.