Answer
The six movements at the shoulder joints that are most often cited are the following:
1a.. Extension . In this movement, as in all the others, several muscles ( agonists) a cooperate to
produce the movement:
1b. Prime mover(s) --Lattisimus dorsi,
1c. Antagonist-------Deltoid anterior
2a. Flexion:
2b. Prime mover(s)---Pectoralis major (upper)/ Deltoid anterior
2c. Antagonist--------Lattismus dorsi
3.a. Abduction:
3b.Prime mover(s)---Deltoid (middle)/supraspinatus
3c. Antagonist-------Llattisimus dorsi/ Pectoralis major(lower)
4a. Adduction:
4b. Prime mover.---- Pectoralis major(lower)
4c. Antaginist------ Deltoid (middle)
5a. Medial Rotation:
5b. Prime mover(s). --Pectoralis major/Deltoid(anterior)
5c. Antagonists----- Infraspinatus/Deltoid (post)
6a. Lateral Rotation:
5b. Prime mover(s)---Infraspinatus/Deltoid(posterior)
5c. Antagonist-------Deltoid (anterior)/Supraspinatus
Work Step by Step
There are more than six movements possible at the shoulder joint, but the six most often described are extension, flexion, abduction, adduction, medial (internal) rotation, and lateral (external) rotation.
Each movement is usually achieved by the cooperation of several muscles (agonists) and the
selection of a single prime mover is, in most cases, an arbitrary choice.
Extension: The following muscles ( agonists) cooperate in achieving extension: Latissimus dorsi,
teres major, pectoralis major(lower), and possibly deltoid(posterior),
The muscles ( antagonists) that oppose the muscles that effect extension include
deltoid( anterior), pectoralis major (upper part), coracobrachialis, and serratus anterior.
Flexion: The prime movers (agonists) that effect flexion are usually pectoralis major( upper part(,
deltoid anterior), serratus anterior and coracobrachialis. These agonists are usually opposed
by the following muscles, latissimus dorsi and pectoralis major (lower).
Abduction: The prime movers that effect abduction include deltoid (middle), supraspinatus,
pectoralis major(upper), serratus anterior-- and sometimes the trapezius.
Muscles that oppose the action of abduction include pectoralis major (lower).
latissimus dorsi, teres major, and teres minor.
Adduction. Adduction is movement towards the midline of the body and is effected by the joint
effort of the following muscles; Pectoralis major(lower), teres major, coracobrachialis,
latissimus dorsi, and pectoralis major. Some antagonists that oppose adduction are deltoid
(middle) and supraspinatus,
Medial Rotation; Medial rotation is brought about by the following muscles working together:
Pectoralis major, latissimus dorsi, deltoid ( anterior), subscapularis, and teres major. Muscles
that oppose medial rotation are infraspinatus, deltoid (posterior) and teres minor.
Lateral Rotation: This movement is produced by the cooperative action of the following muscles:
Infraspinatus, deltoid (posterior), teres minor, subscapularis. The group of antagonist of this
movement comprises pectoralis major, latissimus dorsi, deltoid (anterior) and supraspinatus
muscles.
Note: All these movement the very complex movements and often recruit the alliance and
assistance of other muscles like the biceps brachii, the brachialis and the trapezius in producing
various combinations of these movements.
