The fundamental starting point of the physical therapy conceived by Francoise Mézières is the existence and action of what she termed a ‘Muscular Chain’ (MC).
A MC is a group of at least 2 polyarticular muscles (meaning they extend over a minimum of two joints) running in the same direction and overlapping like tiles on a roof without any interruption in the linkage. Where this occurs in the body, all the muscles in the chain are mutually dependent and behave as though they are a single muscle.
Mézières identified the existence of 4 MCs in the human musculature:
1. The dorsal MC
This is the first MC to have been discovered by Mézières. It is also the largest one and is made up of 25 muscles running from our skull, down our backs, the backs of our legs and right to our toes. It also includes the extensor (dorsiflexor) muscles of the foot and toes and, because of this, its action affects the front part of our lower leg up to the knee. Deformations of the toes, such as hallux valgus, are caused by the shortening of these elements of the dorsal MC.
2. The prevertebral MC or anterior chain of the neck
Whilst this consists of 3 relatively small muscles, it is nevertheless an important MC because it dictates the position of the head, which plays a central role in the integration of posture and movement. Problems with this MC can induce deformation in the cervico-dorsal area of the spine (the neck down to the fourth thoracic vertebra).
3. The antero-lumbar MC
This is made up of the iliopsoas muscle and the diaphragm. It pulls the pelvis forward and can also cause the concavity in the lower back to deepen.
4. The brachial MC
This runs from our shoulder to our finger tips. Apart from the short head of the muscle biceps brachii, all its muscles are flexors and pronators (pronation is a movement of inward rotation). The fact that the arms at rest are invariably slightly bent and rotated inwardly is evidence that the brachial MCs have too much tone.
The muscles belonging to MCs are:
Located mostly on the rear long axis of our bodies: they act therefore as postero-flexors (backward flexing). When they are too toned (and they nearly always are) they act to increase the two normal concavities in the spine (lordoses) and this is the primary distortion caused by shortened MCs.
Paired and symmetrical (apart from the diaphragm): they act as latero flexors (they bend the spine and the limbs sideways).
Oblique: they act therefore as rotators which means that they also twist the spine and limbs. This combination of anatomical characteristics means that too much tone in the muscles in the MCs distorts our body in 3D.
Due to the popularity of Mézières’ therapeutic approach, many bodyworkers jumped on the MC bandwagon. Mézières only found four MCs that fitted with her scientifically researched and strictly applied definition. Less meticulous bodyworkers have stretched Mézières’ theory so far as to find up to 20 by ignoring the parameters of Mézières’ definition. Other have wrongly extended the concept to other tissues and have described articular chains from an osteopathic perspective, fascial chains, and even acupuncture-orientated chains. These pseudo-chains suffer from too many missing links to be able to behave like the MCs discovered by Mézières.
The only true MCs are the ones discovered by Mézières.
The theory of MCs enabled Mézières to explain what she was observing in her patients, to then deduce some fundamental laws governing body mechanics and to devise her form of bodywork.