Flexibility is the foundation of every movement we make with our body. With the uprise of social media over the years, many people are now using these platforms as their main source of health and fitness information, which has lead to the word being used interchangeably with other, incorrect, terms. In this post, I will be defining flexibility, how flexibility relates to movement in the human body, clarifying definitions of commonly used phrases such as ‘mobility’ and ‘range of motion’ and explaining why they are not synonymous with flexibility, and the four types of flexibility.
When you hear the term ‘flexibility’, you often think of stretching or a body moving past the typical range of motion. Simply put, the Oxford dictionary defines flexibility as the ability to bend easily without breaking, the ability to be easily modified and willingness to change or compromise. I emphasise the word ability, as that’s exactly what flexibility is; an ability. Or more specifically; a motor ability, which contributes to your ability to move your body.
When we apply the dictionary definitions of the word flexibility to the human body, it defines the ability of the joint and the limb attached to it to change position in a three-dimensional space. This ability is measured by Range of Motion (ROM). So in other words, flexibility is the ability for joints to change position which is then measured by ROM – they are NOT the same thing.
Another term I mentioned in the introduction that is often used synonymously with flexibility is Mobility. Shumway-Cook and Woollacott define mobility as the ability to move freely and independently from one place to another. Flexibility, alongside the other motor abilities strength, speed, endurance, agility and coordination, contributes to our mobility. As mobility is an emergent phenomena from the interaction of our motor abilities, it is not possible to directly train mobility and therefore, flexibility and mobility cannot be used interchangeably.
When defining the type flexibility occurring in the human body, we must describe two things. 1) Is the joint moving or not moving (Dynamic or Static)? And 2) Are the muscles working or relaxing (Active or Passive)?. Any conscious movement made is an example of Dynamic Active Flexibility. For example, a grand battement in ballet. If the joint is moving but the muscles responsible for moving the joint are not contracting, then this is Dynamic Passive Flexibility. An example of this is being stretched by a partner. If the joint is not moving but the muscles responsible for moving the joint are contracting, this is Static Active Flexibility. For example, a ballerina holding an attitude. And lastly, if the joint is not moving and the muscles responsible for moving the joint are also not contracting, this is Static Passive Flexibility. This is the type of flexibility displayed when we are sitting in splits and is often thought of as being the only type of flexibility.
To summarise, flexibility is the ability to bend easily without breaking and is much more than just a Static Passive action in the body. It should not be defined as a ‘passive range of motion’, nor should it be used interchangeably with the terms mobility and range of motion.
Molly Toner 