The shoulder muscles

The shoulder muscles comprises of the three deltiod heads as well as the deeper rotator cuff group.

Good development of the shoulders can change the proportions of your physique.

Well developed shoulders draws attention to the upper body, creating an aesthetically pleasing taper to a narrower 'looking' waist.

Training should address all of the shoulder muscles via a variety of exercises as there is no single exercise that works the whole area.

Pay special attention to technique however as the shoulder muscles can be prone to injury quite easily especially if you are susceptible to shoulder injuries.

Remember to progressivly train the shoulders and do not handle weights you are not ready for, although this is good advice for all body parts it especially applies to the shoulders.

If you have suffered with rotator cuff injuries in the past, consult with a physiotherapist or medical proffessional for advice on strengthening these smaller muscles of the shoulder joint.

Lets look at the anatomy of the shoulder muscles:

Shoulder Muscles

Deltoid group

From the greek 'Delta' reflecting the geometrically triangular shape are the 'deltiods'. These comprise three distinct heads where each one serves a particular function:

1. Anterior Deltiod - front deltiod lifts the arm forwards and upwards.


2. Medial Deltiod - middle or outer deltiod lifts the arm away from the mid-line of the body to the side (abduction).


3. Posterior Deltiod- rear deltiod lifts the arm to the rear or draws the elbow backwards behind the shoulders.

Rotator cuff group

This group of muscles act to stabalize and strengthen the shoulder joint. They also act individually to move the humerus and upper arm.

1. Subscapularis - Holds the humerous (upper bone of arm) in the shoulder joint cavity.


2. Supraspinatus - Stabalizes shoulder joint


3. Infraspinatus - Holds the humerus in the gleniod cavity (shoulder joint 'socket')


4. Teres Mino - rotates the humerus laterally.

Complimentory Muscles

As the shoulder joint has the widest range of motion than any other joint in the body it is worth mentioning other muscles that assist the shoulder muscles in moving and stabalizing the shoulder and arm.

These muscles are of the pectoral girdle (chest and back muscles) as well as that of the core and the upper arms.

For example the Latissimus dorsi aids with arm adduction (moving the arm towards the body) as well as the pectoralis major.

Listed below are the complimentory muscles:

1. Latissimus Dorsi, aids adduction of arm - Back.
2. Trapezius, aids in the movement of the scapula (scapula-sometimes refered to as the shoulder blade) - Back.
3. Teres Major, extends and rotates the humerus (long bone of upper arm) medially - Back.
4. Levator Scapulae (deep muscle active in exercises such as the upright row) - Back
5. Rhomboid (Major and Minor) - Back.
6. Pectoralis Major, plays an important role in arm flexion and adduction - Chest.
7. Pectoralis Minor, draws the scapula forward and downward - Chest.
8. Strenocleidomastoid, aids as a stabalizing muscle (in exercises such as lateral raise) - Back/Neck.
9. Splenius, aids as a stabalizing muscle (in exercises such as lateral raise) - Back/Neck
10. Scalenes,aids as a stabalizing muscle (in exercises such as lateral raise) - Back/Neck
11. Bicep Brachii (short head), weak flexor of the arm at the shoulder joint, aids flexion - Arms
12. Tricep Brachii, forearm extension but also stabalizes the shoulder joint - Arms.
13. Coracobrachialis - Acts to flex the arm and adducts he humerus - Arms.