The deltoid is the prime mover in shoulder abduction. It's two antagonists are the pectoralis major and the latissimus dorsi.
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.
Shoulder adductors. Abduction means moving away from the median plane of the body and adduction means moving towards the median plane of the body.
The latissimus dorsi and pectorals major are synergists for shoulder adduction
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.
Pectoralis moves the shoulder joint. It has a sternal and clavicular end , it helps in shoulder joint adduction, cross arm adduction and overhead. Adduction movement means bringing the shoulder towards midline
the antagonist of adduction is the pectoralis major
The major muscles involved in horizontal adduction or flexion is the anterior deltoid fibres, pectoralis major and minor. Bicep complex(bbicep brachii, brachioradialis and forearm flexor) comes into action as synergists, if the leverage is long.The antagonists of horizontal flexion is posterior deltoid fibres,teres major, minor, lats and the associated rotator cuff muscle(infraspinatus)
frontal
shoulder flexion shoulder adduction shoulder horizontal extension
There are four muscles used for horizontal adduction of the shoulder. These muscles are the pectorals major, middle deltoid, latissimus dorsi, and coracobrachilis.
Adduction of upper arm at the shoulder
The muscles that perform adduction to the shoulder include the pectoralis major, lattissimus dors, but these are the primary movers. The fixators that do adduction are the subscapularis and teres major.