What weight should I use for rear delt flies?

Start with 5-15 pound dumbbells. The rear deltoid is a small muscle that responds better to lighter weights and perfect form than heavy loads. Most intermediate lifters use 10-20 pounds.

How often can I train rear delts?

You can train rear delts 2-4 times per week. They recover quickly and are often undertrained, so frequent stimulation helps bring them up to balance with your front and middle delts.

Should I feel rear delt flies in my upper back?

Yes, you should feel tension in your rear delts and between your shoulder blades. If you feel it in your neck or upper traps, reduce the weight and focus on initiating the movement from your shoulder blades.

What's the difference between rear delt flies and reverse flies?

These are the same exercise with different names. Both terms refer to the bent-over lateral raise movement that targets the posterior deltoid.

Can I do rear delt flies standing upright?

No, standing upright changes the movement into more of a lateral raise. The 45-degree forward lean is essential for properly targeting the rear deltoid fibers.

How to Do a Rear Delt Fly with Proper Form: Stop Making These 3 Mistakes

Master the rear delt fly with proper torso angle and squeeze cues. Learn why 45-degree forward lean and controlled tempo activate rear delts, not momentum.

The rear delt fly looks simple. Bend over, lift some dumbbells out to the sides, squeeze. But watch most people do it and you'll see why their rear delts stay underdeveloped while their traps take over.

How to do a rear delt fly with proper form: Stand with feet hip-width apart, hinge at the hips to create a 45-degree forward lean, hold dumbbells with arms slightly bent, lift weights out to shoulder height by squeezing shoulder blades together, then lower with control. The key is maintaining the torso angle and letting the rear delts—not momentum—drive the movement.

The rear delt fly targets the posterior deltoid, the often-neglected back portion of your shoulder. When done correctly, it also engages the middle traps and rhomboids. When done poorly, it becomes a sloppy trap exercise that does little for shoulder health or aesthetics.

Why Your Rear Delt Fly Form Probably Sucks

Most lifters make the same three mistakes that turn this isolation exercise into a momentum-driven mess.

Mistake #1: Standing too upright. If your torso is only slightly forward, you're not creating the angle needed to target the rear delts. The posterior deltoid works best when your arms move perpendicular to your torso. Stand upright and you're just doing an awkward lateral raise.

Mistake #2: Using too much weight. The rear delt is a small muscle. If you're using 25-pound dumbbells and swinging them up with your whole body, you're not training your rear delts. You're training your ego.

Mistake #3: Rushing the negative. The eccentric portion of the rear delt fly is where you build strength and control. Drop the weight fast and you're wasting half the exercise.

Step-by-Step Rear Delt Fly Technique

Here's how to nail the form every time:

Setup and Starting Position

Stand with feet hip-width apart, holding a dumbbell in each hand. Hinge at the hips until your torso is at roughly a 45-degree angle to the floor. Your knees should have a slight bend, and your back should maintain its natural arch.

Let the dumbbells hang straight down from your shoulders with your palms facing each other. Your arms should have a slight bend at the elbows—think of them as slightly curved steel rods that won't change shape during the movement.

The Lift Phase

Initiate the movement by squeezing your shoulder blades together. This isn't just a cue—it's the actual mechanism that drives the weight up. As you squeeze, your arms will naturally rise out to the sides.

Lift the dumbbells until they're roughly at shoulder height when viewed from the side. Your arms should form a straight line from dumbbell to dumbbell across your back. Don't lift higher than shoulder level—you'll just start recruiting other muscles.

The Squeeze and Lower

At the top, pause for a half-second and focus on the squeeze between your shoulder blades. You should feel tension in the back of your shoulders, not your neck or upper traps.

Lower the weight with control, taking 2-3 seconds to return to the starting position. Don't let the dumbbells drop—control the descent to maximize muscle activation.

What Muscles Does the Rear Delt Fly Work?

The rear delt fly primarily targets the posterior deltoid, but it's not working alone. Here's the full muscle breakdown:

Primary: Posterior deltoid (rear portion of the shoulder)
Secondary: Middle trapezius, rhomboids, infraspinatus
Stabilizers: Lower trapezius, serratus anterior, core muscles

The rear deltoid's main job is horizontal abduction—pulling your arm away from your body's midline when your arm is parallel to the floor. This is exactly what happens during a properly executed rear delt fly.

Common Rear Delt Fly Form Mistakes to Avoid

Using Your Neck and Upper Traps

If you feel this exercise in your neck or the top of your shoulders, you're lifting too heavy or not maintaining proper posture. The movement should originate from your shoulder blades, not your neck.

Changing Your Torso Angle Mid-Set

Some lifters start bent over but gradually stand up as the set gets harder. This shifts the emphasis away from the rear delts. Pick your angle and stick with it for the entire set.

Lifting Past Shoulder Height

More range of motion isn't always better. Once your arms reach shoulder height, additional lifting recruits the upper traps and reduces rear delt activation.

Using a Full Grip

Many lifters wrap their thumbs around the dumbbell handles, but this can create unnecessary tension in the forearms and biceps. Try a thumbless grip—let the dumbbells rest in your palms with your fingers draped over the handles.

Programming the Rear Delt Fly

The rear delt responds well to moderate weight and higher repetitions. Most lifters will use 10-20 pound dumbbells, even if they can bench press their bodyweight.

Start with 3 sets of 12-15 reps twice per week. The rear delt recovers quickly, so you can train it frequently without issues. I prefer placing rear delt flies at the end of a pull workout or as part of a shoulder finisher.

If you're training rear delts for the first time, expect some soreness in places you've never felt it before. The posterior deltoid is often severely undertrained, especially in lifters who focus heavily on pressing movements.

Variations and Progressions

Once you've mastered the basic dumbbell rear delt fly, these variations can add challenge and prevent adaptation:

Cable rear delt fly: Using cables provides constant tension throughout the range of motion. Set the cables at shoulder height and perform the same movement pattern.

Incline bench rear delt fly: Lie face-down on an incline bench set to 30-45 degrees. This variation locks in your torso angle and prevents cheating.

Single-arm rear delt fly: Perform one arm at a time while bracing yourself with the other hand. This allows you to focus on perfect form and address imbalances.

The rear delt fly isn't flashy, but it's essential for balanced shoulder development and long-term pressing strength. Master the basics first—proper torso angle, controlled tempo, and appropriate weight selection.

Your next workout should include rear delt flies if they're not already programmed. Start light, focus on the squeeze, and feel muscles you might have ignored for years finally start working."