People often use the terms mobility and flexibility interchangeably, however there is a distinction between these two words. To understand the difference let’s first define what mobility and flexibility are!
What is Mobility?
Mobility is defined as the degree to which an articulation (where two bones meet) can actively move before being restricted by surrounding tissues (ligaments, tendons, muscles, etc.). This is otherwise known as the range of uninhibited movement around a joint. For example, active stretching or various exercises such as an arm circle or a squat pattern will be an indication of mobility through various moving joints.
What is Flexibility?
Flexibility is defined as the ability of a muscle or muscle groups to lengthen passively through a range of motion. The flexibility of muscle tissue will determine the amount of passive joint range of motion you possess (there are individual exceptions to this, such as a boney block or arthritis). For example, stationary stretching like a seated sit and reach will be an indication of your hamstring flexibility.
So we can see by definition that the difference between the two lies within the activity of the muscle or muscle groups; the former being active motion and the latter being passive.
Why is it important to have mobility and flexibility?
The importance of both of these qualities are multifaceted and intertwined. From injury prevention to joint health to the ability to stay physically active throughout your life.
Perhaps the most important reason for working on flexibility and mobility is the deterrence and mitigation from injury or damage to body tissues and structures. Common injuries such as sprains, strains and tears caused by slips, trips or falls could be diminished or avoided by having more tissue flexibility or joint mobility to handle different stressors and forces. Our muscles and bones understand the language of force and injury occurs when the force is greater than what the tissue can handle (also known as tissue capacity). Decreasing tissue stiffness allows for a ‘bend but not break’ quality.
Imagine you are walking outside on the sidewalk during the winter and come across a patch of ice. You slip and your leg slides out from under you going forward forcing you into a forward split position. If your hamstrings are overly tight and your hip mobility is limited you are susceptible to some pretty nasty injuries whereas someone who possesses adequate mobility and flexibility to withstand this slip and manage the body’s sudden positioning could walk away unscathed.
The next prevailing reason these two qualities are of great importance is maintenance and improvement of joint health. Unfortunately, the human body is inherently lazy. You know the saying: “if you don’t use it, you lose it”. This is true when talking about the body's mobility and flexibility. Our bodies over time will deem unused ranges of motion as unnecessary and thus our tissues will stiffen due to inactivity. Stiffening will lead to decreased mobility and flexibility. Subsequently, if we lose range of motion in a specific joint we also greatly reduce the fluid supply to that joint. The fluid is vital as it brings fresh blood flow and nutrients to that joint to keep it healthy. Think of our joints as gears and the fluid as oil. If you grease those gears they will not rust!
Think about the amount of time the majority of society spends in a seated position: in a car, at work, on the couch and at the dinner table. It adds up to a lot of sitting. If the hips never have the opportunity to move and express their full range of motion that could lead to hip and/or low back tightness and loss of mobility. This loss can create further and more serious issues such as arthritis, bursitis and possibly even the need for joint replacements later in life.
It is a slippery slope when it comes to the loss of mobility and flexibility. If you are able to maintain joint health throughout your life, while avoiding or mitigating injury, you are more likely to be able to express more movement for longer. There is a laundry list of benefits as to why it is so important to be able to express movement throughout one's life but being able to exercise later into life is perhaps the greatest benefit of maintaining these two qualities. Having less barriers to exercise, in this case joint health and previous injuries, will lead to an increased probability that one will remain physically capable as they age and decrease the likelihood of sedentary behaviors and issues.
With some exceptions, most humans are born with excellent movement capabilities and maintaining those proficiencies are a piece of the puzzle to living a long and healthy life.