Mastering the Lateral Shoulder Flye

How to build the shoulders you've always wanted

May 24, 2026

In this article:

Shoulder growth discussion
Shoulder width anatomy
Medial delt lateral flye tips and tricks

Truth: total growth to your shoulder muscles inevitably increases your overall width. If you want wider shoulders, focus on multiple forms of overhead pressing first, as compound exercises are always going to be king for foundational growth.

Contrary to the beliefs of some, two things can be true at once. In this case, the second truth is that, aside from compound exercises, isolation exercises play an undeniable role in muscular development.

While compound overhead pressing builds your shoulder growth base layer, it never hurts to apply that shoulder-widening finishing touch by focusing in on the medial deltoids. This focused medial deltoid work is exactly what this article is about.

Why the Medial Deltoids?

Shoulders, otherwise known as the deltoids, commonly called delts, are made up of three main parts:

Front/Anterior Deltoid
Middle/Medial/Lateral Deltoid
Rear/Posterior Deltoid

To build a great set of shoulders, you’ll need complete development. To build your widest set of shoulders, you’ll need jacked medial delts.

When viewed from the front, the anterior delts provide size and fullness to the majority of the shoulder area, but the medial delts provide valuable added width, which is what this article is focused on.

If you look carefully, you can see in the diagram above that the medial delt protrudes past the front delt, creating a wider frame. That contribution of width is also seen from the rear.

When viewed from the side, it’s clear that developed front and rear delts will add total thickness to the shoulder area, while the medial delt makes up the visual majority.

The medial delts are clearly a high-value muscle group when building an impressive upper body and they also contribute to a commanding physical presence. There’s an old Pontiac Grand Prix commercial and their slogan was ‘Wider is Better!’ I agree.

Making Them Grow!

The medial delts are responsible for raising your arms to your sides. In more technical terms, the function of the medial deltoid is arm abduction. Broken down to its most simplistic form, hypertrophy-focused training is:

Knowing what movement a muscle is responsible for.
Repeating that movement with resistance applied.
Increasing the level of resistance over time.

What's the Difference Between Abduction and Adduction? (Biomechanics) | Machine Design

Let’s break this down for our specific situation.

We already know the medial delts are responsible for arm abduction.
In the gym universe, if someone abducts their arm with resistance applied, they’re doing the exercise known as the lateral shoulder flye.
Now the only thing that’s left is to work hard and increase the level of resistance over time.

4 Common Lateral Raise Mistakes and Fixes - Muscle & Fitness

Here are a few important tips to make sure you’re working the medial delts when hitting those lateral flyes:

Try to reach as far away from your body as possible while raising the weight. Doing this will reduce trap involvement because you’re relying more on the deltoids to raise the weights and not the traps.

There shouldn’t be much shrugging going on during lateral flyes and if you think about getting the weight as far away from your body as possible as you raise it up, it’ll keep shrugging to a minimum.

Keep your palms facing down towards the floor. You’ll notice that as you fatigue during a set of lateral flyes, your hands want to rotate into the ‘thumbs up’ position. This is because your medial delts are tiring and your body is naturally trying to recruit the front delts for backup.

Rotating to the thumbs up position increases the involvement of the front delts. Since you’re not doing laterals for front delt activation in this case, keep those palms facing down.

Maintaining a slight forward lean during lateral flyes tends to help with medial delt activation. This slight lean keeps you from leaning back as you lift the weights, which would shift focus to the front delts.

Leaning back is also just contributing to poor lateral flye form in general.

Along with my three tips above, I’m including video tutorials for a handful of lateral flye variations. Don’t limit yourself to the classic dumbbell lateral flye; mix it up!