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  • Writer's pictureSarah and Martin Moesgaard

Flexibility: Defined

In this article we share our working definition of, "Flexibility," the different ways in can be expressed, and examples of modalities and exercises that train flexibility. For more on, How is Mobility training is different from Flexibility training, we have an article coming very soon.

Why define Flexibility?

A note on why any of this might be interesting or important. As you'll see in the sweet little graphic below, Flexibility isn't one thing. And it isn't trained in one way. Depending on your genetics, lived experiences, and goals, you might find that one way of thinking about and/or training flexibility, works better for you than another. If you are, for example, someone who does a lot of active dynamic training already, but you haven't seen the gains in flexibility that you would like, or are feeling "stuck," you may want to consider trying passive static flexibility training, ie getting some Thai Bodywork.

It is also nice, when working with a personal trainer, coach, or therapist, to have some language to put to your thoughts: "Why is my trainer asking me to do the same Horse Stance I did last week? I said I wanted more open hips, but this seems like a lot of WORK?! Why aren't we stretching?" Having a clear understanding of the terms in this article can help you communicate more clearly with your fitness professionals. It can also you get good search results if you are looking for flexibility programs online, and help you articulate for yourself where you are, where you want to be, and how to get there.

Flexibility is..

Flexibility is a joint's ability to move to the end of its normal range, or how far a joint can flex, extend or rotate; also known as, Range of Motion. As we discussed recently in our article, Mobility: Defined, the most important word in that sentence is, "normal." What is normal for one person is not necessarily normal for someone else. Depending on body structure, the demands placed on the joint, lived experiences, like injuries and hand dominance, etc., a particular joint's normal range is unique. Even within one body, normal range of motion can be very different from one side to the other. For example, the shoulder of your non-dominant hand probably has a greater range of motion than that of the other since your dominant side tends to be slightly more muscular as a result of being used more often.

Flexibility is a joint's ability to move to the end of its normal range of motion.

The 4 Expressions of Flexibility

Before we dive further into the different ways flexibility can be expressed, we need to define a few more terms:

1. Active Flexibility

For our purposes, we'll say Active Flexibility involves the contraction of a muscle somewhere in the body. It could be the same muscle being stretched. It could be the muscles who does the opposing job; the antagonist. But somewhere in the body a muscle is contracting to help us achieve more flexibility.

2. Passive Flexibility

Conversely, we'll use Passive Flexibility to refer to a flexibility demand where the muscle is being asked not to contract. Again, it could be the whole body being asked to relax, or it could be just one muscle or group.

3. Static Flexibility

We'll use the term Static to mean a joint is not in motion. So, the body could actually be moving slightly in a particular direction, ie. toward the ground in a gravity-driven stretch. But the joints are still. And again, we are sometimes referring to the joints around the muscle in question, and sometimes referring to joints throughout the whole body. Most likely, we are using Static to mean the whole body is being asked to be still.

4. Dynamic Flexibility

You can probably see where this is going... We'll use Dynamic to mean a joint is in motion. Probably, we are talking about the joints directly related to the muscle or muscle group whose flexibility is being tested.

Whew! Does that take you back to middle school anatomy class, or what?!

For a deeper dive into how we use these definitions to generate guiding questions and design Mobility Training routines, see our article, "How Can I Improve My Mobility?" which lays out a step by step system for building your own Mobility Training program.

How the parts work together

Now, when we think about these four Expressions of Flexibility on two continuums, like this, we see four somewhat different ways of training flexibility emerge:

*Note: These are not 100% distinct - they are continuums and there are many places where the lines blur and the expressions overlap. The diagram above is meant only as a tool to help us organize our thoughts around Flexibility.

A good example of an Active Dynamic Expression of Flexibility you might be familiar with is a Long Stride Lunge: muscles are being asked to contract while the joints are in motion. Another good example is Vinyasa Yoga, where we are flowing from one pose to another continuously.

A Horse Stance Hold is an example of an Active Static Expression of Flexibility because the muscles are being asked to contract to pull us deeper into the stretch, but the joints are being asked to remain still. Ashtanga Yoga is an example of a training system where this is mostly true. Even though the series is punctuated with flows, the major poses are held for several breaths while the muscles contract and pull us deeper and deeper into the stretch. Proprioceptive Neuromuscular Facilitation (PNF), or Contract-Relax stretching as it is sometimes called, is another expression of Active Static Flexibility because the muscle being stretched contracts while held in a stretch.

Passive Static Flexibility is Expressed in stretches where gravity does the work, muscles are relaxed, and the joints are still, for example, lying in a Supine Twist stretch, or as in most of the poses of Yin Yoga. Using a foam roller, therapy balls, or massage techniques are ways of increasing flexibility through Passive Static Expression - even though the body as a whole may be in motion, the joints around the muscle being stretched are not moving and the the muscles itself is being as to relax.

When we let gravity do the work, and ask the joints to move while the muscles stay relaxed, we see a Passive Active Expression of Flexibility, as in a Jefferson Curl or the way Thai Bodywork works to improve flexibility in the body.

We hope this helps organize your understanding of flexibility and gives you some language to use when working with fitness professionals, when searching for inspo online, or just for your own love of movement. For the next installment in this series, find Mobility vs. Flexibility and more at our website.

We are currently working on more articles about Mobility, Flexibility, and Functional Movement. Let us know what articles or topics you'd like to see - what does Flexibility mean to you? Does our definition miss something crucial? Find us on social or email us at

If you are interested in having a flexibility or mobility program designed specifically for you and your needs, contact us at and let's chat.

Train Smart. Move Well. Play Hard, friends.


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