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When I first started doing shrugs I assumed they would work my rear delts. They’re located next to the traps, which is the primary muscle being worked, so it only makes sense right?… Wrong.
Shrugs do not train the rear delts because the exercise mainly moves the shoulders straight up and down. This motion is known as scapular elevation and is not a function of the rear delts.
Still not convinced? Below I’ll compare the primary role of the rear delts to the anatomical motions of the shrug.
Table of Contents
Why Shrugs Won’t Build Your Rear Delts
Whether you perform shrugs with dumbbells, barbells, or cables the movements of the scapula will remain the same. The scapula will elevate and upwardly rotate, which moves the shoulder blades up and toward the ears. Your upper traps are the prime mover during these motions.
The rear delts are mainly responsible for horizontal shoulder abduction. This is when you move your arm behind your back while it’s raised in front of your chest. Horizontal abduction doesn’t occur during shrugs.
However, the rear delts do provide inferior glenohumeral stability, basically ensuring that the upper arm bone stays in place when shrugging. This is especially the case when the arms are abducted vertically, like in a shrug.
Essentially, the rear delts act as fixator muscles. Their responsibility while properly performing a shrug is to dynamically support the shoulder joint. This is not going to spark muscle growth. It only enables the upper trap muscles to work through the range of motion as effectively as possible.
One EMG study tested rear delt muscle activation across five exercises. The results showed similar recruitment of the rear delt with shrugs, upright rows, and lateral raises. Collectively all three use scapular elevation and upward rotation, again predominantly working the traps.
If you’ve been hitting upright rows hard lately and expecting your rear delts to grow, pause for a moment. I recommend you read my article on why they aren’t enough for building your rear delts.
The downfall of this study is that it was aimed specifically at women with chronic neck pain. They likely had weak traps, which is why there was more notable deltoid activation due to overcompensation.
Here’s a table showing the muscle-building functions of the rear delts compared to the motions utilized during shrugs:
| Rear Delt Functions | Functions of a Shrug |
|---|---|
| Horizontal Shoulder Abduction | Scapular Elevation |
| Shoulder Extension | Scapular Upward Rotation |
| External Rotation | Scapular Retraction (Minimal) |
As you can see the main functions of the rear delts don’t align with the shrug. One way to get potentially greater rear delt activation is by retracting the scapular while shrugging to promote external rotation.
This rotates the wrists to face forward as the shoulders retract and elevate. However, it’s still not going to breed significant gains in the size of your rear delts. Mainly because they’re a synergist of external rotation so it would need to be combined with horizontal abduction for optimal activation.
You’re better off sticking to reverse flys, which showed the most activation from the study I mentioned above.
Shrugging is just not going to promote growth in your deltoids. If anything focusing too heavily on shrugs will create imbalances between your upper back and shoulders.
Shrugs do not adequately work the three deltoid heads to spark muscle growth. The rear and side delts only act as joint stabilizers for the shoulders during the movement, allowing the trapezius to work more efficiently.
That’s not to say you shouldn’t do shrugs. Rather you should include a mix of isolation exercises for both your traps and delts.
Do Skiers for Your Rear Delts Instead of Shrugs
Dumbbell skiers are going to train your rear delts via shoulder extension. Looking back to the table above, this is a primary function of the muscle. So instead of trying to stubbornly recruit them with shrugs, do skiers and get an isolated and active contraction.
You can do them with a barbell, cables, or dumbbells while seated, standing, or with your upper body leaning on a bench for stability. The two biggest things to focus on are your torso and arm angle.
First, your torso should be nearly parallel to the ground. This will allow for greater mechanical tension, meaning more muscle growth.
Second, make sure you drive your arms back at an angle rather than keeping them tight to your body. This is because the rear delt muscle fibers are inserted on the back of the shoulder diagonally. By pulling with a back and out angle they’ll get a deeper contraction.
To perform dumbbell skiers:
- Sit on a flat bench with your feet flat on the floor, spread shoulder-width apart.
- Grab a set of dumbbells with your palms facing each other.
- Lean your upper body over your thighs with your arms extended toward the floor.
- Breathe in and raise your arms behind your torso, toward the ceiling.
- Stop when your arms are parallel to the floor and exhale.
- Lower the dumbbells toward the floor under control and repeat.
This is a single joint exercise and it’s best to perform high reps of 15-20 with light weight. The rear delts are partially slow twitch muscles, so this will provide a good pump.
Including skiers and shrugs in a back workout together will ensure both muscles receive stimulation. Plus, both exercises are low fatigue movements so you won’t have to worry about over training.
Common Mistakes and Fixes
- Turning the movement into a shrug:
- Squeezing your shoulder blades to assist the movement will shift focus onto the middle traps. This will make it look like a horizontal shrug, defeating the purpose of the exercise.
- Focus on swinging the weights back and up through your hands to minimize scapular retraction.
- Keeping the upper arms and elbows tucked in too much:
- Try to maintain a roughly 45-degree gap between your upper arms and the sides of your waist as you raise your arms.
- As I mentioned this will hit the rear delt fibers much more. Failing to do so will shift emphasis onto your lats.
Sample Workout With Shrugs and Rear Delt Skiers
Here’s how you could include shrugs and skiers as accessories in a back-focused workout. Notice that I placed the compound exercises (rows and pulldowns) toward the start as they work the rear delts and traps.
The purpose of the shrugs and skiers is to isolate those two muscles since they can be stubborn to grow.
- Bent-over barbell row: 3 x 8
- Lat pulldown: 4 x 12
- Dumbbell skiers: 3 x 20
- Dumbbell shrugs: 3 x 15
