There are two types of muscle contractions–isotonic and isometric. What your muscle is doing during the movement determines why type of muscular contraction is happening. In isotonic contractions, your muscle moves from shortening to lengthening. With isometric contractions, the muscle length stays constant throughout. By learning how your body is using your muscles, you can get more out of your workouts.
Isotonic contractions are further divided into two groups: concentric contractions and eccentric contractions. This is because whatever you do to your muscle (whether it’s shortening or lengthening), it must be undone for you to return to neutral.
Concentric contraction happens when the muscle shortens. For example, let’s look at the yoga pose Malasana. Strength trainers will refer to this pose as a squat.
Think about the quadriceps, the muscles on the front of your thigh. When they are in neutral, your knee is straight. As the knee bends, the quadriceps lengthen, and as the knee straightens, the quadriceps shorten.
To do Malasana (or a squat), you start in a standing position, engage your core, and bend deeply at the knees. You may hold for a period of time at the bottom of this range of motion, or you might straighten your knees to come back up. When you are at the bottom of your squat and you start straightening your knees, your quadriceps are working concentrically.
Eccentric contraction happens when the muscle lengthens. So, let’s return to our example with Malasana. You start in a standing position, and start to bend your knees. As your knees bend, you are lengthening the quadriceps. Therefore, the movement from standing to squatted is an eccentric contraction of the quadriceps.
In squats, it’s true that the primary muscle targeted is the quadriceps. However, the quadriceps are not the only muscles working. Think of the steps that you take when you do Malasana. Before your knees even start bending, you engage your core muscles.
Because your core muscles (your transverse abdominis, internal obliques, and external obliques) don’t change length, this is what is known as an isometric contraction. Isometric contraction is when a muscle is working but does not change length.
If you think about it, Pilates and yoga are filled with isometric contractions because we frequently stabilize with core muscles before we ask the body to move. Think of the isometric muscle work in The Hundred, Heel squeeze, Tadasana, and Dandasana.
Although isometric exercises don’t have the glamour of isotonic exercises, some people believe that isometric contractions are actually more effective at building strength. Take a look at your favorite Pilates exercises and yoga poses to learn how to incorporate isometric contractions in your workouts.
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Pay attention to how you’re using your muscles. What do you think your most used muscle is? Let us know in the comments below.