When you are dancing, being able to connect your mind to your body is incredibly important. It might sound odd, but think about it. Your muscles move because your brain directs them to. If you have a better understanding of what your muscles are doing as you perform a certain movement, you can direct your mental energy to better achieve your intentions. For this reason, I thought it would be useful to explain three types of muscle contractions for dancers so you can visualise what your muscles are doing when you move.
3 types of muscle contractions
Concentric contraction
This is the type of muscle contraction that you might think of when you think of using a muscle. Think of doing a bicep curl with a hand weight (not that we do this in dance, but it’s a useful illustration).
In a bicep curl, you hold a weight in your hand, and then move the hand towards the shoulder. To achieve this movement, your bicep muscle (the one on the inside of your upper arm) shortens and, depending on how big your muscles are, bulges.
The muscle ‘bulges’ because it is getting shorter and thicker. This ‘shortening’ of the muscle is a concentric contraction.
If we think about a dance example, pointing the foot (the correct name is ‘plantar flexion’) you will notice that your calf muscle bulges. This is the concentric contraction. You’ll also notice the same thing when you rise onto the balls of your feet (going onto demi-pointe).
You can also think of it as movement ‘toward the centre’. There is visible joint movement in the direction of the primary muscle.
When you do a bicep curl, you bring your hand in towards your body, towards the bicep.
When you stretch your quadricep in ‘stork stretch’, you flex (bend) your knee, bringing your foot closer to the centre, towards the hamstring on the back of your upper leg.
Eccentric contraction
The opposite of a concentric contraction is an eccentric contraction. It is when the muscle lengthens, and moves away from the centre of the body and the primary muscle. In the bicep curl example, the bicep is the ‘primary muscle’, the one doing most of the work.
When you control the movement as you extend your arm, you are performing an eccentric contraction and controlling the speed at which you lengthen the bicep. So one way to think of it is that an eccentric contraction of a muscle slows down the rate of movement.
Think of a grand battement or high kick with a controlled lowering of the leg. As you lift the leg, your hip flexors and quadriceps contract concentrically. As you lower down with control, these same muscles are performing an eccentric contraction, to stop the limb just dropping to the floor. In the grand battement or high kick example, it generally feels easier to lift the limb with a powerful concentric contraction, but it feels difficult to lower it slowly and carefully.
Are you with me so far? Both of these types of contraction are called isotonic (also known as dynamic), which means the length of the muscle changes when it contracts.
Isometric contraction
The third type of muscle contraction that I’d like to tell you about today is isometric contraction. This is when the muscle contracts, but doesn’t change length.
What the …? I hear you thinking.
This is the type of muscle contractions that occurs when you are holding a position. Think of holding your leg out to seconde position, turned out, without moving. Both the quadriceps and hamstrings will be working hard, but not moving. They are undergoing an isometric contraction.
Holding any position, whether it is an arabesque in ballet, or a plank in contemporary dance, involves isometric contraction of the muscles involved.
Examples of contraction during dance movements
High kick
If you are in a jazz class and you do a high swish kick to the side you are working the hamstrings and quadriceps. Of course this movement involves a lot more than just those two muscle groups, but for the sake of simplicity, I’m going to ignore what is happening in the rest of the leg and body.
As you kick the leg and the foot moves up into the air, your quadriceps (on the front of your leg) shorten (concentric contraction). They are the agonist, or movers. At the same time, your hamstrings lengthen. They are the antagonist. As you lower your leg, the quadriceps undergo an eccentric contraction. In other words, they lengthen with control, and the hamstrings shorten.
If at the height of the kick you want to hold your leg instead of letting it lower, both muscles will stay the same length (isometric contraction).
When I think of this I imagine a kind of rope and pulley system. As you lower your leg, it’s like the quadriceps are a rope and you are gradually letting out the length to lower the leg, instead of just letting it flop. This is not anatomically correct, of course, but it’s an image that helps me a lot in thinking about that descent stage of the kick.
Landing from a jump
When you land from a jump, the hip and knee extensors and the 'ankle plantar flexors'* contract eccentrically to slow down the downward motion of the body, which helps to reduce the impact of landing. I like to think of this as being like shock absorbers on a car. These muscles effectively reduce the impact of the landing on your ankle, knee and hip joints.
* plantar flexion is when you pull your toes towards the shin – often just called flexing the foot by dancers
The examples I’ve given above grossly simplify the complex interplay of muscles that happens when we dance, as there are many muscles involved in most movements in the human body. But even if you don’t know much about the different muscles in your body, you can feel the part of your body that is working. You might be able to feel the muscles on one side of your leg, arm, or torso contracting and shortening, and the opposite muscles extending as you go into a movement. Also be aware of the muscles that just shortened contracting eccentrically to control the pace of the reverse movement.
As you start to become more aware of how your muscles are working, which ones are shortening and lengthening, you’ll start to feel more control over your body and movement.
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