Complete Guide to the Deltoids

The deltoid also Referred to as Deltoids is a triangular muscle located on the shoulder that consists of three distinct portions or “heads” – the anterior (front), lateral (middle), and posterior (rear) heads. Each head has very specific functions and contributes to overall shoulder movement and stability. Recent science has shown seven neuromuscular segments of the deltoid muscle.

There are three of them in the anterior head, one in the anatomical middle head, and another three in the posterior head of the deltoid. The shoulder is the most mobile joint in the body and can operate many planes of movement. However, it does this with the help of the rotator cuff and in this article, we are only going to break down the deltoid functions. Let’s get started!

Functions and Movement

• Shoulder Flexion: The anterior deltoid raises the arm forward. It is responsible for any movement where your arm is moving forward. The anterior deltoid is activated to a high degree on pushing and pressing movements.
• Shoulder Abduction: The lateral deltoid is crucial for lifting the arm to the side (abduction). If you’ve spent any amount of time in the gym, I’m sure you’ve heard of lateral raises. The purpose of that movement is to train the lateral deltoid as it contributes a great deal to shoulder width. In most movements, the trapezius muscle will also aid with this abduction.
• Shoulder Extension: The posterior deltoid contributes to moving the arm backward (extension). Therefore, it is constantly in balance with its antagonist brother, the anterior deltoid.
• And of course, this also means that together the 3 delts work hard to provide stability to the entire shoulder joint.

You can test this out with a simple experiment! Just stand up with a straight posture with your hands on your sides and raise your arm out in front of you. That’s shoulder flexion by the anterior deltoid. Now with your arm still in front of you, bring your arm backward until it is parallel with your body. That’s Extension. Bring your hands to your hips and raise them again and you will have experienced abduction, all 3 movements of the deltoid.

Utilization of the Deltoids

The shoulder joint and muscles are some of the most important in your body. The deltoid is actively engaged in various daily activities, such as reaching overhead, lifting objects, and performing pushing or pulling motions. For this reason, the shoulder can withstand a lot of damage as it is a highly vascularized muscle, meaning it has an extensive network of blood vessels. This is important for nutrient delivery and muscle function.

The deltoid inserts onto the deltoid tuberosity, a bony prominence on the humerus, and is innervated by the axillary nerve. While there are plenty of fast twitch muscle fibers in your deltoids, it is primarily a slow twitch muscle, unlike its pressing counterparts, the chest and triceps. In heavy lifters and most gym-goers, the anterior deltoid is usually overemphasized, leading to imbalances in the entire shoulder. This is not ideal since the deltoids contribute a great deal to posture with the anterior deltoid commonly being much stronger and tight while the rear delt is neglected leading to rounded shoulders.

Final Thoughts

And that’s all there is to it. Shoulders, meaning not just deltoids but the muscles surrounding the rotator cuff, are vital to human ability. So it goes without saying that learning how they work and then strengthening them through their entire R.O.M (range of motion) is one of the best ways to feel better genetically and relieve pain and stiffness. Finding exercises that do exactly this now become a must but don’t worry we have the answers for training your entire shoulder in just a couple of movements. Thanks for reading, and be sure to read our comprehensive guide to the Chest & Shoulders!