The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. “Shoulder joint” typically refers to the glenohumeral joint, which is the major joint of the “shoulder,” but can more broadly include the acromioclavicular joint. In human anatomy, the shoulder joint comprises the part of the body where the humerus attaches to the scapula, the head sitting in the glenoid fossa[disambiguation needed.The shoulder is the group of structures in the region of the joint.
The shoulder has greatest range of motion of any joint in the body. Because of this mobility, it is at risk for injury or degenerative problems. The bones of the shoulder are the humerus (upper arm bone), clavicle (collar bone), and scapula (shoulder blade). The head of the humerus bone (the ball) is lined with cartilage that glides over the shoulder socket (also known as the “glenoid cavity”). The clavicle attaches the shoulder to the rib cage and holds the shoulder out from the body. The scapula is a large triangular bone located on the back side of the upper body, and it is connected to the clavicle through the acromioclavicular (AC) joint.
The front delts play a major assisting role in chest training, and even receive some degree of stimulation from biceps and triceps exercises like barbell curls and dips. Because of all the ancillary work they receive, front delts are often an overdeveloped item on many physiques. Over time, this can even lead to posture problems, as the person tends to adopt a ‘slumped forward’ stance. The medial, or side head, abducts the arm, meaning that it brings the arms out and away from the midline of the body. The side heads are only activated to a significant level when trained using specific isolation movements. Finally, the posterior, or rear head, extends the arm and produces external rotation. The rear delts are very much involved in back training movements such as chins and rows.