The insertion is an arch-like structure with strong anterior and posterior fascial connections flanking an intervening tissue bridge.

[10] These neuromuscular segments are supplied by smaller branches of the axillary nerve, and work in coordination with other muscles of the shoulder girdle include pectoralis major and supraspinatus.

The anterior deltoid also works in tandem with the subscapularis, pecs and lats to internally (medially) rotate the humerus.

They are not utilized significantly during strict transverse extension (shoulder internally rotated) such as in rowing movements, which use the posterior fibers.

An important function of the deltoid in humans is preventing the dislocation of the humeral head when a person carries heavy loads.

The function of abduction also means that it would help keep carried objects a safer distance away from the thighs to avoid hitting them, as during a farmer's walk.

To stop this compressing against the undersurface of the acromion the humeral head and injuring the supraspinatus tendon, there is a simultaneous contraction of some of the muscles of the rotator cuff: the infraspinatus and subscapularis primarily perform this role.

Muscle atrophy may result from various causes, including aging, disuse, denervation, muscular dystrophy, cachexia and iatrogenic injury.

Conversely, deltoideal acromial enthesopathy is likely a hallmark of seronegative spondylarthropathies and its detection should probably be followed by pertinent clinical and serological investigation.

This reflects the need to strengthen the shoulders, particularly the rotatory cuff, in knuckle walking apes for the purpose of supporting the entire body weight.