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When all its fibers contract simultaneously, the deltoid is the prime mover of arm abduction along the frontal plane. The arm must be medially rotated for the deltoid to have maximum effect. [13] This makes the deltoid an antagonist muscle of the pectoralis major and latissimus dorsi during arm adduction.
If the shoulder is laterally (externally, outwardly) rotated, the anterior deltoid becomes the prime mover of the glenohumeral joint, the posterior deltoid de-activates, and the middle head assists. By bending at the waist or leaning against a bench, the line of pull created allows the lateral deltoid to be isolated to a higher degree.
It is thus opposed to adduction. Upper limb. Arm and shoulder. of arm at shoulder (raising arm) [1] [2] Supraspinatus 0-15; Deltoid 15-90; Hand and wrist
Adduction is an anatomical term of motion referring to a movement which brings a part of the anatomy closer to the middle sagittal plane of the body. Upper limb [ edit ]
Abduction and adduction of the shoulder (frontal plane). Abduction is carried out by the deltoid and the supraspinatus in the first 90 degrees. From 90-180 degrees it is the trapezius and the serratus anterior. Adduction is carried out by the pectoralis major, latissimus dorsi, teres major and the subscapularis.
The teres minor (Latin teres meaning 'rounded') is a narrow, elongated muscle of the rotator cuff.The muscle originates from the lateral border and adjacent posterior surface of the corresponding right or left scapula and inserts at both the greater tubercle of the humerus and the posterior surface of the joint capsule.
The arms have the same orientation relative to the ground as in the "shoulder fly" which is done to target the lateral deltoid. The difference is that the angle of the torso changes, and the change in the shoulder's rotation and angle of movement relative to the body means the lateral head is a synergist rather than the prime mover.
Shoulder anatomy, front view Shoulder anatomy, back view The rotator cuff is an anatomical term given to the group of four muscles and their tendons that act to stabilize the shoulder. [ 3 ] These muscles are the supraspinatus , infraspinatus , teres minor and subscapularis and that hold the head of the humerus in the glenoid cavity during ...