A BRIEF REVIEW OF THE TRAPEZIUS MUSCLE
Kinetic Control Accredited Tutor, Finland
Trapezius muscle is an important muscle for the function of the shoulder girdle, neck and thoracic spine as well as the ribs.
This muscle demonstrates unique anatomical, bio-mechanical and neurophysiological characteristics and also demonstrates specific functional changes in the presence of pain and pathology.
Some review points of the trapezius muscle:
Upper trapezius (or the clavicular part of trapezius) consists the fibres between the occiput and C7. It runs to the posterior border of the distal one third of the clavicle.
Middle trapezius (acromial fibres) runs from C7, T1 to the inner border of the acromion and along the entire length of the crest of the spine of the scapula.
Lower trapezius extends from T2 to T12 and attaches to the deltoid process of the scapula.
Nerve supply: from the accessory nerve, the ventral rami of third and fourth cervical nerves via cervical plexus.
Trapezius muscle is a multipennate muscle.
Fascicle mean length is 1 cm from occiput to C3 and 7-14cm from C3 to T12.
The fascicles from C3-C6, C7, and T1 comprise over 50% of the total physiological cross-sectional area, being the largest at the level of C7-T1.
Trapezius muscle demonstrates low threshold recruitment and low recruitment dominance in daily life (under 25% of maximal voluntary contraction).
Upper trapezius draws the clavicle backwards, medially and upwards at the sternoclavicular joint. It helps to control the neutral position of the scapula. It has some potential to produce movement to the cervical spine and contributes to the stability of the cervical spine.
Middle trapezius produces scapula retraction and external rotation, as well as drawing the clavicle and scapula backwards and medially together with upper trapezius allowing scapula upward rotation. It controls or resists scapula abduction and downward rotation.
Lower trapezius produces scapula upward rotation, external rotation, posterior tilt and depression. It controls or resists scapula elevation, abduction and downward rotation as well as controls the neutral position of the scapula.
Fiber type: in female and male predominance of type I fibers (male 65.5%, female 63,3%).
Trapezius muscle has feed forward activation.
In the presence of neck pain and dysfunction there is upper trapezius muscle fiber type changes from type I to type II, fatty infiltration and higher percentage of grossly hypertrophied type I muscle megafibers with poor capillarisation. There may be an increase or decrease of activation of upper trapezius with dysfunction and subjects in neck pain have difficulties to relax upper trapezius after task or exercise.
In the presence of shoulder pain and dysfunction there is an altered pattern of recruitment of trapezius muscle and delayed activation of middle and/or lower trapezius. Furthermore there is increased or decreased activity of upper trapezius while lower trapezius activity is increased. Depending on the movement dysfunction there is also trapezius muscle length-tension changes.
In summary trapezius muscle has both the local and global stabilising muscle functional role. Assessment of this muscle must include motor control dysfunction and retraining must include motor control low load low threshold exercises.
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