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The Deltoid Muscle


The Deltoid Muscle

Multipennate is defined as a muscle that has several tendons with fibers running diagonally between them, similar to a feather. The deltoid is an example. Superficially capping the shoulder, the deltoid is divided into three parts: anterior, middle, and posterior.

The proximal front fibers begin on the clavicle, the middle on the acromion process of the scapula, and the back on the spine of the scapula, all coming together as the deltoid muscle belly gives the shoulder its round shape. The distal attachment is joined together on the humerus at the deltoid tuberosity. When all three sections contract simultaneously they abduct the arm, bringing it out from the side and up in the frontal plane.

Most lifting movements involve the deltoids. The fun happens when trying to decipher the differences. The anterior deltoid can flex the arm, while the posterior extends it. These are opposite actions in the same plane (sagittal), which seems impossible in the same muscle. However, the location, or path of the fibers, explains it. The front deltoid can also inward rotate while the posterior outward rotates, and can horizontally adduct while the posterior horizontally abducts. The middle deltoid is the least complicated; it only abducts, synergistic with the supraspinatus muscle.

Such a complicated muscle also acts as a shock absorber, protecting the shoulder from impact. It does not act on any joint other than the shoulder. Since it is so visible, it is a popular muscle in the weight room.


Deltoid Stretching Exercise;




  • Stand upright and place one arm across the body.
  • Bend the arm at 90 degrees and pull the elbow towards the opposite shoulder.
  • Keep the upper arm parallel to the ground. 



Trigger Points in the Posterior Deltoid Muscle

Here we explain where trigger points can be found in the posterior deltoid muscle;




Trigger Points in The Posterior Deltoid Muscle 









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