Flexibility vs Mobility

In the fitness industry, the term mobility has fast become popular and is generally defined as ‘active range of motion’ and has therefore been deemed desirable and important. Flexibility on the other hand is commonly referred to as ‘passive range of motion’ and is often seen as useless. Let's delve deeper into these two concepts to understand the nuances that set them apart.

What is flexibility (by definition)?

Simply put, flexibility is your joints ability to change position – so every form of movement requires some degree of flexibility, some just less than others. This makes it our overarching motor ability, as the other five (strength, endurance, speed, agility & coordination) can only be developed within our accessible range of motion. There are four main types of flexibility:

Static Passive Flexibility: This is what most people think of as flexibility – you’re relaxing in a stretch and here your joints are not moving & your muscles are not contracting.

Static Active Flexibility: This is similar to the above, your joints are still not moving but your muscles are now contracting. Think PNF stretching, Contract Relax (CR/CRAC), Pails & Rails.

Dynamic Passive Flexibility: Involves moving a joint through its full range of motion with the help of an external force, i.e. a physio. Here the joints are moving but your muscles aren’t contracting.

Dynamic Active Flexibility: This type, often confused with mobility, is the ability to move a joint through its range actively, using muscle strength. So here your joints are moving and you’re actively contracting your muscles. This can be anything from leg raises to running, sliding into the splits or lifting your arms overhead.

But then, what is mobility?

Contrary to popular belief, mobility is not your ability to actively move your joint through its full range of motion. Joint mobility refers to the intrinsic joint motions and the quality of those – as these are passive, we have no control over them. In the literature, the definition of mobility most commonly used is ‘the ability to move independently and safely through space’. It is the capacity to move the body through space effectively, performing tasks like getting out of bed, rising from the floor, or transitioning from one position to another seamlessly. That’s why things like wheelchairs, scooters and canes are called ‘mobility aids’.

So as you can see, the notion that flexibility is passive and mobility is active range of motion is slightly simplified and quite frankly, incorrect. Once I learned this, I told myself I would stop referring to mobility the way the industry is and start educating people on the true definitions. It bugs me that flexibility still gets written off so widely as ‘useless’, and given there are adequate definitions that are being used in scientific literature and research, I believe we should be using the correct terms. However, the term mobility is what people understand and while in fact it actually is dynamic active flexibility they’re referring to, I’ve accepted that it might be easier to stick with using the language they understand. But if you’ve read this far you’ll now know why I prefer to use the word flexibility over mobility when it comes to the ability to move your joints through their full ranges of motion. 

Stay flexy,
Kat