What is a deltoid muscle?

The deltoid muscle, surrounding the shoulder, runs from the insertion of the trapezius, part of the clavicle and a portion of the scapula to the top of the upper arm (humerus). It helps flex and extend the shoulder, internally and externally rotate the shoulder, and bring the arms to the front and back of the body (think of performing a chest press and a row).
Rick Olderman
Physical Therapy
The deltoid muscle is the shoulder muscle originating from the clavicle (collar bone) and scapula (shoulder blade) and inserting onto the lateral portion of the humerus (upper arm bone). The front (anterior) fibers help flex the arm, lateral fibers help abduct the arm and back (posterior) fibers help extend the arm.
Fixing You: Shoulder & Elbow Pain: Self-treatment for rotator cuff strain, shoulder impingement, tennis elbow, golfer's elbow, and other diagnoses.

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Fixing You: Shoulder & Elbow Pain: Self-treatment for rotator cuff strain, shoulder impingement, tennis elbow, golfer's elbow, and other diagnoses.

The shoulders are a floating system on the trunk, held in place and moved by muscular control. The foundation of shoulder movement is the shoulder blade which has precise resting and moving...

Your deltoids, commonly referred to as the "delts,” are the muscles of the shoulder that sit just above your biceps where the arm connects to the body. The deltoid muscle is composed of 3 separate muscle divisions and resembles the shape of a triangle, which is how it got its name; delta means triangle in Greek. The anterior division, often referred to as the anterior deltoid, is located on the front of your shoulder just above the chest muscles. The middle division, often referred to as the medial deltoid, is located on the outside aspect of your shoulder. The posterior division, often referred to as the posterior deltoid, is located on the backside of the shoulder joint. Not each of the divisions of the deltoid are challenged with the same movements or exercises. Typically, the anterior and middle divisions of the deltoid will be emphasized during pressing movements/exercises to the front of the body and over the head, such as chest presses or dumbbell shoulder presses as well as during leverage movements such as flyes, front raises, lateral raises, and scaptions. The posterior division of the deltoid will be emphasized during pulling movements such as rows, pull-ups, pull-downs, and leverage movements like arm abduction (moving the arms from center away from the body), ball combo 1, and ball combo 2.

Continue Learning about Parts of the Muscular System

Parts of the Muscular System

Parts of the Muscular System

Your skeletal, smooth and cardiac muscles work together to keep your body running like a machine. Within this muscular system there are various parts, from muscle fibers to ligaments. You may know about hamstrings, quadriceps and ...

abdominal muscles, but there hundreds of muscles that move within your body. Some are involuntary, like parts of your digestive system, while you control others whenever you go for a walk or lift weights.
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.