Flexibility Vs Mobility And How It Relates To Injury

A study was released in 2017 concluded that physical injuries are common among athletes competing in capoeira and bodybuilding, and that limited joint flexibility was a common trend.¹

For years, the terms flexibility and mobility has been used interchangeably for years. However, in recent years, the two terms have been pushed to be separated. My personal definition of the terms may vary from others, but in this blog post, I would define it to better explain the correlation between the two and their relation to the risk of injury.

Flexibility: the range your joint has when it is placed passively (or assisted) into that range.
Mobility: the range the individual has muscular control in moving into that range.

How this relates to injury
Well, if your flexibility is way further than your mobility, your body has a range that you have no muscular control over.

Therefore, should you ever be placed into a range that is beyond your mobility, the remaining structures to help stabilise you are your ligaments and bone structures. When you start stressing your ligaments and bone structures, that usually results in bad news (think tear, sprains and fractures).

Every human joint in the body is provided with a certain range it can move within. This range can be limited by structures such as other bones, muscles, or the joint capsule. This range forms your flexibility. Within this given range, you will have muscles that can move your joint throughout this range. How much you can use your muscles over the available range is your mobility.

To explain how you lose mobility from your flexibility – In general, most muscles work best in its mid-ranges. Placing a muscle at its inner or outer ranges will reduce its peak output. If a muscle is untrained in its furthest ranges, your body will essentially ‘forget’ about its ability in that range. After a long period of under-use, you would essentially get so weak in that range that you have now lost the mobility of that range.

What this would mean, is that although your joint has that range, you do not have the muscular control to use your limb in that range! If there is no muscle to hold the joint in that range, your ligaments or bones that limit that range will get stressed, and therefore can result in a tear or a fracture.

For example, an armbar in jujitsu occurs when an opponent places the elbow in a straight position, and tries to extend it past its limited range, therefore resulting in a tear, sprain or fracture of the structure that was limiting it.

If your mobility was matching your flexibility, the stressed will only be placed on the structure once it has gotten to the end of its range.

However, if say your mobility was five degrees from full extension, and you had no muscular control beyond that point, there will be a five degree range of motion of acceleration towards the end of range, therefore doing significantly more damage due to the increased force, where accelerations plays a huge part in generating.

Therefore, if you were in the unlucky position of being caught in an armbar, to minimise the risk, make sure your mobility range is as close to your flexibility as possible, ideally matching it!

Exercises to try:

Isometric exercises at the end of range: Get a joint into the end position, and work on holding that position. Challenge it further by adding resistance.
Range of motion exercises: Do an exercise to the very end of its range, rather than just working on the middle ranges.
1 Boguszewski et al. (2017) The use of functional physiotherapeutic tests to assess the risk of suffering physical injuries by men practicing capoeira and bodybuilding. Journal of Combat Sports and Martial Arts; 1(2); Vol. 8, 43-47

Physio-Logic see also here