Core Stability Intro
This article is an introduction to the concept of core stability.
Core stability has been recommended for results as diverse as injury management and prevention; to increased sporting performance or a more toned appearance.
Runners could benefit from training of the core muscles, so future articles will focus on stability issues specific to runners.
But first, what is core stability and what are the benefits?
In order to understand the role of the core muscles it's worthwhile first examining some muscle anatomy and function.
Muscles can be grouped into various roles. Broadly speaking they form 3 layers – each one having a specific role to play.
The deepest layer consists of small muscles which span a single joint. They are often referred to as 'Local muscles' or the 'Inner Core'.
These muscles are too short to generate actual movement. They are responsible for increasing mechanical stiffness and they control excessive translation movements at a joint. Think of these as ‘Joint Controllers’
They also provide information to the central nervous system regarding joint position, range and rate of movement. That is, they send information about where the body is moving in space.
They fire in anticipation of movement to protect the joint and work in the background of all functional tasks.
In the trunk the local system can be thought of as a cylinder.
Transversus abdominus forms the walls as it wraps around the abdomen and via connections to the thoracolumbar fascia it attaches to each spinal segment individually. The roof is formed by the diaphragm and the floor is formed by the pelvic floor. In front of and behind the spinal column, deep fibres of psoas and multifidus also have segmental attachments
The next 2 layers form the 'Global Muscle System' and this system is responsible for producing and controlling movement.
The middle layer (the deepest of the global system) is often termed the 'Outer Core' or the 'Global Stabilisers'.
These muscles tend to span 1 joint and are oriented obliquely.
They have a higher proportion of type I fibres and are best designed to assist postural holding / alignment and control / decelerate movement, especially in the rotation plane. Examples include gluteus maximus and gluteus medius at the pelvis, abdominal obliques in the trunk and serratus anterior at the shoulder.
The outermost layer are made up of long, multijoint muscles termed the 'Global Mobilisers'.
They have a higher proportion of type II fibres and are best designed to generate high force and speed in the power (forward / back) plane during high load activities. Examples include the quadriceps and hamstrings.
The significance of understanding these muscle roles is that with poor posture, a predictable pattern of muscle dysfunction occurs:
1. The Global Stability muscles of the outer core become elongated and so become less efficient at generating tension during postural tasks and low level tasks. In an effort to assist this system, the Global Mobilisers become dominant. This results in a bracing pattern which can lead to pain.
2. Trauma can also lead to restrictions to movement and set up the above muscle imbalance
3. The presence of pain sets up the same imbalance pattern as well as alteration in, the Local Muscle System. It develops a delay in reflex firing in anticipation of movement and so movements are accompanied with more joint translation than is ideal. Uncontrolled translation, repeated over time, has been proven to cause recurrent episodes of pain.
4. Repetitive actions in training such as distance running can re-enforce this muscle imbalance.
The next article will look at common muscle imbalances in runners.