There are many reasons postural dysfunction can occur as well as distortion in the muscle slings although we are increasingly seeing the dysfunction caused by poor movement patters at a young age due to sedentary lifestyle patterns. Ageing can also cause significant bone changes, joint changes and muscle changes leading to dysfunctional postures. Injury or immobilization of a limb can cause compensatory movements at joints, while fatigue without adequate recovery can also cause changes in movement. All lead can lead to postural dysfunction.
Clients who spend many hours of the day in prolonged postures i.e. sitting at computers and at a desk, driving for long periods or sitting in meetings result in a significant shortening and lengthening of associated muscles, e.g. sitting postures. When specific muscles become habitually shorter their length tension-relationship becomes compromised. This in turn decreases their force production and alters their relationship with their antagonist muscles producing muscle imbalances caused by a neural insufficiency. Muscle can become tight and short or weak and long.
There are many causes of postural syndromes including postural syndromes that can be caused by tight/short and or weak/long muscles. Some of which are the upper cross syndrome, the lower cross syndrome, the pronation distortion syndrome and synergistic dominance. Over the next few parts of this article we are going to discuss the dysfunctions and learn a little more about it. Lets start with ‘Synergistic Dominance”
Synergistic Dominance
Synergistic dominance is a neuromuscular occurrence in which synergist muscle (helper muscle) overcompensates and takes over the primary role of the agonist (prime mover) muscle because the intended prime mover is short, tight and or weak and becomes inhibited. Whilst this allows a joint action to take place it can cause imbalances and faulty movement patterns.
Let’s discuss the mechanism; Every movement has a “prime mover” (e.g., glutes for hip extension) and “synergists” (e.g., hamstrings at the hip). When the prime mover is short, tight or weak, fatigued, or inhibited, the body adapts by redirecting the workload to the synergist to accomplish the task.
How! When a tightening or shortening develops in a strong muscle it causes a reciprocal inhibition in its antagonist (opposing) muscles. The resulting inhibition of the antagonist muscles can lead to a decrease in neural activation of the opposing muscles contributing to further muscle imbalances. As these agonist muscles become shorter and stronger and their antagonists becomes weaker (loss of strength), other synergist muscles within the muscle group become dominant, causing altered movement patterns. This is synergistic dominance. For example, in the case where a client sits for long periods the hip flexors are in a shortened position and may become short and tight which causes a shutting down or inhibition of the opposing antagonist muscle which are the gluteal muscles (reciprocal inhibition and neural insufficiency). Since the gluteal muscles are no longer working correctly the body may compensate i.e when hip extension is needed as the neural system fails to activate glute max sufficiently it will begin to recruit the hamstrings (synergistic dominance) and the low back muscles to assist the gluteal muscles in hip joint extension. This can lead hamstrings to become dominant at the hip and tighten leading to postural and movement pattern dysfunction. As the hamstring is responsible for flexion of the knee and is now dominant at the hip this can cause over recruitment of the gastrocnemius as the knee flexor and can cause the gastroc to shorten and tighten. This effect of synergistic dominance can cause a tightening of the lower posterior chain and postural dysfunction. Remember this all started because of a shortened, tight and or weak hip flexor.
The Consequences: Because synergists are designed for assistance, not primary movement at the joint in question, this dominance forces the synergist to carry a heavier load than intended. Over time, this leads to muscle fatigue, tightness, altered movement patterns, and an increased risk of injury (such as chronic strains or referred pain)
The Solution: As movement practitioners and exercise specialists you need to correct the dominance by reversing the principle i.e if a muscle is short, release it and mobilise it, if it is weak strengthen it and so on. Understand the anatomical/biomechanical dysfunction and reverse the principles.
Look out for section two next week on upper and lower cross syndrome.