 Hey everybody, Dr. O here. This video we're going to talk about the different types of muscle contractions. So we always talk about lifting weights, but we never talk about the fact that lots of muscle contractions lead to no lifting or no movement at all. And also we have to lower the weights that we lifted. So we're going to talk about these different types. So real quickly, all muscle contractions that can be broken down into isometric, isotonic, then there is also something called isokinetic, but that takes specialized equipment like Cybex machines. So isometric is going to mean same length. So muscle is going to contract, but it's not going to change in length, meaning it's not going to get longer or shorter. So there's not going to be any movement. Isotonic means same tension, same tone. These are going to be the type of muscle contractions where there is a change in length. And we'll look at how we break those apart, whether the muscle is getting shorter or longer. Just because I brought it up, isokinetic means same speed. So there are special equipment that will allow you to lift weights at a set speed. So when you're feeling really strong, you'll be lifting heavier weights at that speed. As you weaken, the weights will get lighter. And like I mentioned, it takes specialized equipment to do that. So let's not worry about that. So let's jump in here. And first we'll talk about isometric contractions. These are going to be contractions where there's no movement. So when you think again, when you think of contractions, you probably do think of movements, but imagine how many muscles have to contract. Like just me sitting here, if you standing up, right, it would take a couple of hundred muscles easily for you to stand still, right? So think about all your postural muscles. That's what I think of with isometric contractions. Now there are, like if I take my hands and I press them together here, this is an isometric contraction. I'm contracting the same muscles that I would in my chest and my arms is if I was doing a push-up. But since there's no movement, it's an isometric contraction. But generally think of your postural muscles and how much muscle contraction it takes to sit or stand still. And you would see that for most people, unless you're very physically active, isometric contractions would be the most common type of contractions that you would have, especially if you were standing a lot. So that is your isometric contractions where muscle contracts but does not change in length, so there is no movement. So next we have, there are two types of isotonic contractions. So you have to know these terms as well. And that would be concentric contractions, which you see right here. And the next slide will show you eccentric contractions. So both of them, there is a change in muscle length, so there is going to be movement. So make sure you note this, concentric contractions, muscles contract and get shorter, eccentric contractions, muscles contract and get longer. So here let's look at the concentric contraction first. This would be called the lifting phase of a movement. So if the muscles are contracting and getting shorter, it's because you're like in this situation, this man is lifting the weights, he's curling, he's doing the bicep curls, he's picking the weight up, so it's called the lifting phase. Same thing as if you're doing a push-up when you're pushing off the floor, that would be concentric contractions. So these are also called positives. So the lifting phase of a movement and the positive phase of a movement are two terms you might see when someone's talking about concentric contractions. So muscles are contracting and getting shorter. When we talk about the action of a muscle, what it actually does, we usually are talking about a concentric contraction. The last type then we have are the eccentric contractions where while a muscle is contracting, it's getting longer. So this would be called the lowering phase of a movement. Notice how this guy here in the picture is putting the weight down. He's lowering the weight back to his side. Or if you're doing push-ups, as you lower yourself to the floor, that would be eccentric contractions. So this is called the lowering phase of the movement and then also this is called negatives. So if you spend much time in the gym, there are negatives. For example, if you want to use negative or eccentric contractions when you're lifting weights, you might have, let's say you're doing a bench press, you might have spotters that actually help you lift the weight and you just lower it on your own. Now the reason you do that is because eccentric muscle contractions are where most of the muscle damage comes from. I think that makes sense. The muscles are while they're contracting, they're being pulled apart. So every so often you might want to do this, but this could lead to a lot of muscle damage, but if you're trying to get bigger and stronger and more explosive muscle damage and the repair from that damage is actually what you need. So, all right, so just to review, we have the isometric contraction. There's no change in muscle length, so no movement. Think postural muscles. And then we have the two types of isotonic contractions with a con-center contraction and muscles contracting while getting shorter. So you're lifting a weight or doing a positive movement. E-center contractions, muscles are contracting while getting longer. So you're lowering a weight or doing a negative movement. So those are all the different types of muscle contractions that you need to know. Have a wonderful day. Be blessed.