The Deltoid

The Deltoid is made up of three portions – the anterior, lateral and posterior heads. These heads lie over the glenohumeral joint and give the shoulder their rounded shape – boulder shoulders! One of the most important functions of the deltoid is stabilisation of the shoulder joint, preventing dislocation of the shoulder! It will also compensate for loss of strength in the rotator cuff too. 

• The anterior head of the deltoid originates from the lateral third, anterior surface of the clavicle. The primary function of the anterior head is shoulder flexion, and also aids in horizontal adduction.
• The lateral head originates from the acromion process scaupla, superior surface. The primary function of the lateral head is shoulder abduction. It’s also involved in movements such as lifting your arm and rotating it when the elbow is at a 90 degree angle.
• The posterior head originates from the spine of the scapula, posterior border. This head plays a key role in shoulder extension, horizontal abduction and external rotation of the shoulder.

All of the heads of the deltoid insert into the deltoid tuberosity on the humerus. The deltoid fascia is continuous with the brachial fascia and connects to the medial and lateral intermuscular septa. All heads also work together to produce abduction at the shoulder joint, and help lift the arm to the front, side and back. 

Now that we’ve done a quick whistle stop tour of the muscles and function of the deltoid, let’s look at how we strengthen the three heads!

How do we strengthen the Deltoid?

There are numerous exercises to choose from to strengthen the Deltoid, here are just a few (click on the exercises to see a demonstration):

Compound Exercises:

• Seated Dumbbell Shoulder Press
• Neutral Grip Shoulder Press
• Barbell Shoulder Press
• Machine Shoulder Press

Anterior Head:

• Seated Dumbbell Front Raise
• Cable Front Raise

Lateral Head:

• Dumbbell Lateral Raise
• Cable Lateral Raise

Posterior Head:

• Chest Supported Rear Delt Flye
• Cable Rear Delt Flye
• Face Pull

For overall shoulder development, include both compound exercises and an exercise to target each one of the heads of the Deltoid.