Dumbbell Side Plank With Rear Fly

upper back back dumbbell

Learn how to do the Dumbbell Side Plank With Rear Fly with proper form and technique. This dumbbell exercise primarily targets your Upper Back, with secondary emphasis on Shoulders, Core.

Dumbbell Side Plank With Rear Fly exercise demonstration showing proper form

How to Do the Dumbbell Side Plank With Rear Fly

Follow these steps to perform the Dumbbell Side Plank With Rear Fly with correct form:

1Start by lying on your side with your legs extended and stacked on top of each other.
2Place your forearm on the ground directly below your shoulder, keeping your elbow bent at a 90-degree angle.
3Hold a dumbbell in your top hand, with your arm extended straight down towards the ground.
4Engage your core and lift your hips off the ground, creating a straight line from your head to your heels.
5While maintaining the side plank position, lift the dumbbell up towards the ceiling, squeezing your shoulder blades together.
6Lower the dumbbell back down to the starting position.
7Repeat for the desired number of repetitions, then switch sides.

Dumbbell Side Plank With Rear Fly Muscles Worked

Primary

upper back

Secondary

shoulderscore

Exercise Details

Equipment: dumbbell
Body Part: back
Category: Extended

Muscles & Anatomy

This exercise combines lateral core stability with posterior shoulder isolation in a single challenging movement. The side plank forces the obliques, quadratus lumborum, and hip abductors to maintain a rigid lateral bridge while the top arm performs a rear delt fly. The instability of the side plank position means the posterior deltoid and rhomboids must work not only against the dumbbell's weight but also against the rotational force that the arm movement creates on the plank position. This anti-rotation demand recruits the deep core stabilizers more intensely than either exercise would in isolation. The rear deltoid's role is horizontal abduction — pulling the arm away from the body against gravity — while the obliques work continuously to prevent the hips from sagging.

Pro Tips for Better Results

1Establish a perfect side plank before attempting any arm movement. Body should form a straight diagonal line from feet to shoulders, hips elevated and stacked, no sag in the midsection. Only after confirming this position should you initiate the fly. A weak plank makes the exercise worthless for both the core and the rear delt.
2Lift the dumbbell slowly and with deliberate control — do not let the fly motion disturb the plank position. If your hips drop every time you raise the arm, use a lighter dumbbell and focus on anti-rotation core bracing. The goal is complete dissociation between the arm movement and the core position.
3Keep a slight bend in the flying arm's elbow throughout the movement. This reduces stress on the elbow joint and shortens the lever arm slightly, allowing the rear delt to work without the wrist and forearm creating excessive torque at the shoulder.

Common Mistakes to Avoid

✗ Hips sagging or rotating during the fly

Fix: Hip drop or rotation during the arm lift means the core is failing its anti-rotation task. Drop to a lighter dumbbell. The movement should look exactly the same with or without the fly — if the plank position changes during the arm movement, you've exceeded your current stability capacity and need to regress.

✗ Performing the fly too quickly

Fix: Rushing the dumbbell upward uses momentum and allows the core to relax momentarily during each rep. Use a 2-second raise and 3-second lower tempo. The slow eccentric is where the core is most challenged because the descending dumbbell creates a rotational pull that the obliques must resist continuously.

✗ Raising the dumbbell past vertical

Fix: Many people bring the dumbbell all the way up past vertical (arm pointing straight at the ceiling), which shifts load to the middle deltoid and trapezius. Stop the raise when the arm is approximately parallel to the floor or at 45 degrees above — this is where the rear delt is maximally activated.

✗ Not stacking the feet and hips properly in the side plank

Fix: Feet crossed or hips rotated forward reduces lateral core demand and makes the plank easier but less effective. Stack feet on top of each other and ensure the hips are perpendicular to the floor. This strict alignment makes the exercise substantially harder and ensures the obliques are working maximally.

How to Program the Dumbbell Side Plank With Rear Fly

Sets & Reps

2–3 sets of 10–15 reps per side. The combination of core stabilization and shoulder isolation means fatigue accumulates from two directions simultaneously. Keep rep ranges moderate and prioritize quality — this is not an exercise to grind through with heavy dumbbells. It works best as a finisher or accessory movement.

Frequency

2 times per week. The obliques and hip abductors recover relatively quickly, but the shoulder stabilization demand adds recovery requirements for the posterior capsule. Spacing sessions 48 hours apart is sufficient. This exercise fits naturally in full-body sessions or at the end of upper body days.

Where to Place It in Your Workout

Position as a core and accessory finisher at the end of a workout. The side plank rear fly is too demanding on stabilization systems to perform early in a session when heavy compound movements are still to come. It works well as part of a shoulder health or core finisher circuit.

How to Progress

Progress by mastering the plank stability before increasing dumbbell weight. The test is whether the plank position is identical with and without the fly. Once stability is established, increase dumbbell weight by 2.5 lbs. An intermediate progression is to switch from a stacked foot position to a single-leg raised foot position before adding weight.

Variations & Alternatives

Side Plank with Hip Dip

Remove the fly and instead focus solely on lowering and lifting the hips in the side plank position. Isolates the obliques and quadratus lumborum without any shoulder involvement. A useful regression when building the core stability prerequisite for the full side plank rear fly.

Prone Rear Delt Raise

Lying face-down on a flat or incline bench, raise both dumbbells out to the sides simultaneously. Trains the same rear delt muscles without any core stability demand. A useful alternative for trainees who want to focus purely on rear delt development before adding the plank complexity.

Side Plank with Cable Rear Fly

Perform a side plank beside a cable machine at low height, using the cable for the fly instead of a dumbbell. The cable provides constant tension through the full range of motion including the bottom, where a dumbbell provides minimal resistance. More demanding on the rear delt but requires careful positioning.

Related Exercises

Frequently Asked Questions

What muscles does the Dumbbell Side Plank With Rear Fly work?

The Dumbbell Side Plank With Rear Fly primarily targets your Upper Back. Secondary muscles worked include Shoulders, Core. This makes it an effective exercise for developing your back.

What equipment do I need for the Dumbbell Side Plank With Rear Fly?

The Dumbbell Side Plank With Rear Fly requires dumbbell. Make sure your equipment is properly set up and you have enough space to perform the movement with full range of motion.

How do I perform the Dumbbell Side Plank With Rear Fly with proper form?

Start by start by lying on your side with your legs extended and stacked on top of each other.. Place your forearm on the ground directly below your shoulder, keeping your elbow bent at a 90-degree angle. Hold a dumbbell in your top hand, with your arm extended straight down towards the ground. Focus on controlled movement throughout the entire range of motion. See the full step-by-step instructions above for complete form guidance.

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