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Trapezius and Levator Scapulae
Shoulder extension is controlled by: Long head of the triceps, the last, and the teres major
Because shoulder horizontal adduction is performed when the arm is horizontal position (i.e., the elbow is level with shoulder) and adduction is movement toward the center of the body, shoulder horizontal adduction is performed primarily by pectoralis major and anterior deltoid, with an assist by latissimus dorsi.
Prime mover is the bicep and the antagonist is the tricep.
Triceps Brachii - it is the only muscle fleshing out the posterior humerus; its three heads arise from the shoulder girdle and proximal humerus, and it inserts into the olecranon process of the ulna. It is a powerful prime mover of elbow extension.triceps brachii
.. Masseter - prime mover of jaw closure - elevates the mandible ... External intercostals - with 1st rib fixed by scalene muscles - pull ribs toward one
Do you mean flexion and (abd)uction?? If so, the prime mover would be the deltoid muscle with many smaller muscles assisting. If you are in fact meaning flexion and adduction, the prime mover would be the pectoralis major and the latissimus dorsi with many smaller muscles assisting.
The prime muscle differs depending on the degree of abduction. From 1 to 20 degrees it is the supraspinatus muscle, from 20 to 90 degrees it is the deltoid and from 90 degree and above the action is done by that rotate the scapula (trapezius and serratus anterior).
The movement of the scapula is largely determined by the position of the shoulder girdle as a whole. As a "floating bone" the scapula is often at the mercy of the more fixed extremities and can be acted upon by several different muscles simultaneously. That being said, the prime mover responsible for scapular depression is the trapezius (specifically the lower fibers). Other muscles which act as stabilizers or synergists in scapular depression and eventual scapular protraction are the subscapularis, the serratus anterior and the lower fibers of latissimus dorsi.
The trapezius muscle extends from the upper back to the back of the neck. Its main functions are to support the arm and to move the shoulder blade.
The Gastrocnemius (calf muscle) is the primary mover. The Synergist (or assistor) muscle is the Soleus.
Antagonist: Controls movement, opposite of prime mover Prime Mover: Main muscle that is directly responsible for movement Synergist: Aids in movement of muscle