Facts about shoulders

Note: To understand this article fully you need to know basic Anatomy of the human body.

Your shoulder muscles persists of 3 parts. Anterior (front) middle, and Posterior (back).
This is crucial to know considering handstands movements, and the health of your shoulders in particularly.

Anterior Deltoids (front side)

Anterior Deltoids are involved in shoulder abduction when the shoulder is externally rotated. And supports your pectorals (chest) when pressing.

Middle Deltoids

Elevates your arm sideways. When used simultaneously with anterior and posterior it levitates the arm forward. 

Posterior Deltoids (backside)

The posterior deltoid is the primary shoulder hyperextensor, moreso than the long head of the triceps which also assists in this function.

Support of the shoulder

To support your arm up to your shoulders you got what we call Rotator Cuffs (these are the muscles infraspinatus, supraspinatus, teres minor and subscapularis)

People tend to stress the importance of “pulling your shoulders back” position in weight lifting and such sports for a reason. Also regarding to handstands this is very important.
I’ll draw a picture for you. If you pull your shoulders back you’re engaging a set of muscles that each and everyone has it’s own job. Read carefully.

This happens on contraction (pulling shoulders back)

- The rhomboids minor raise and approximate the scapulae (shoulder blades)

- The rhomboids major does the same as the minor

- The infraspinatus engage the humerus in external rotation

- The teres minor does the same as the infraspinatus

- The posterior deltoid pulls the arm posterios making it engage the humerus in a external rotation

- Simultaneous contraction of both trapezius pulls the head back and up and brings the shoulder blades closer together by pulling the shoulders backward.

- The teres major lowers the arm and pulls the shoulder and the arm posterior.

- The latissimus dorsi lowers the arm and  pulls the shoulder and the arm backward.

Watch picture below for clarification

Click to enlarge

 

 

 

 

 

 

 

 

Quote from Wikipedia:
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. The major joint of the shoulder is the glenohumeral joint, which “shoulder joint” generally refers to. 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. The shoulder is the group of structures in the region of the joint.

Read the whole article from Wikipedia  here