Mobility and Stability in the Body
Mobility and stability go together like peanut butter and jelly! Mobility relates to movement. The ability of a joint to move freely through a given RANGE OF MOTION without restriction from surrounding tissues. Stability relates to control. The ability of surrounding soft tissue to support a join through its range of motion.
Mobility and stability of a joint work in unison. All joints of the body have a mobility and stability function – however, some are more mobile than stable and others are more stable than mobile. Generally, the ankle, hip, thoracic spine, shoulder joint and wrist are more mobile joints in the body. The degree of mobility of these joints depends on the factors such as ‘the architecture of the joint’, soft tissue length and neural control over surrounding muscle groups.
Lying in between these mobile joints are our relatively stable joints – the joints of the foot, knee, lumbar-pelvic region, scapular-thoracic articulation (shoulder blade connection to the ribcage), and the elbow. The stability of these joints depends on the joint structure, the myofascial network and, in some cases such as lumbar-pelvic region, the cavity pressure changes due to the breathing process.
The body has created this perfect balance between mobile and stable joints which alternate from the proximal to distal ends of the body. So once the body is stable in the right areas and mobile in the right areas, the body moves with ease and harmony.
However, when (for example) the scapulothoracic articulation which has a largely stability function and connects the scapulae to the ribcage, is weak; then the gleno-humeral (shoulder) joint becomes too unstable in its movement and injury becomes possible. Likewise, if a client suffers from osteoarthritis in the hip joint, the mobility of that joint becomes limited, the area above the joint (lumbar-pelvic area) which normally has a stability role, needs to then become more mobile to compensate. Hence, lower back pain becomes possible.
Therefore, it is important to know which joints of the body we need to move and which we need to stabilize. And where we need to stabilize to gain maximum mobility within a joint. Such as: stabilize the lumbar-pelvic area (including diaphragm, transverse abdominals, pelvic floor and multifidus) when we mobilize the hip joints.
If we look deeper into the joints themselves, we see that a joint has both a stability role and mobility role. For example, the joints of the spine have deep intrinsic muscles which cross each vertebra to stabilize it and allow it to move. Generally, the small, short muscles which lie closest to the skeletal structure of the joint act as deep intrinsic stabilizers for each joint. They contract at a low intensity (tonic contractions) for long periods of time. Such as Interspinalis, intertransversarii and rotatores which stabilize the spine. They have a small movement function, but their main function is to support and stabilize the spine.
Stability in a joint can also be achieved through dynamic stability of more superficial muscles which cross the joint (sometimes two joints) which are usually large, long and generally act as prime movers. The stability role comes from the antagonistic muscular control as the joint moves. ie: movement on one side of a joint means that stability is required on the opposite side of the joint. These contractions are phasic and are at a high intensity for short periods of time. So, this antagonistic stability is used for a specific movement patterns (with appropriate range of movement) for short periods of time.
The final aspect of mobility and stability to think about, is the importance of core stability for safe mobility.
CORE STABILITY: “maintaining support and control of the body as movement takes place. It does so by encouraging the recruitment of deep core muscles that help to control and stabilize movement.” (the Pilates Bible, L. Robinson, L. Bradshaw and N. Gardner, 2009)
Much of intrinsic stability is unconscious, however it is possible to train and improve stability within the body by consciously controlling the stability process (or proactively recruiting appropriate muscle groups). The ways we can do this is by:
- Good static and dynamic alignment through the movement process so the appropriate muscles are recruited. So the starting positions of an exercise as well as the way in which the exercise is executed is important in creating stability.
- Correct use of lateral breathing technique
- Degree of recruitment of the muscles for stability should be directly related to the challenge of the movement. Nothing more, nothing less. Therefore, ensure that the correct stabilizers are recruited.
Stability in a joint can also be achieved through dynamic stability of more superficial muscles which cross the joint (sometimes two joints) which are usually large, long and generally act as prime movers. The stability role comes from the antagonistic muscular control as the joint moves. ie: movement on one side of a joint means that stability is required on the opposite side of the joint. These contractions are phasic and are at a high intensity for short periods of time. So, this antagonistic stability is used for a specific movement patterns (with appropriate range of movement) for short periods of time.
(Cally Richardson)