The rear delt fly is an exercise that targets the deltoid muscles, specifically the posterior deltoids or rear delts. It is typically performed with dumbbells, but can also be done using a cable machine, a fly machine, or a pec deck machine. The exercise strengthens many of the upper body muscles, but mainly focuses on the deltoids. In addition to the rear delts, the exercise also engages the traps, rhomboids, and other small muscles in the upper back. Here are some benefits of the rear delt fly:

• Stronger Shoulders: The rear delt fly strengthens your shoulder muscles by developing your posterior deltoids. While this is an accessory exercise, the rear delt fly can boost your performance in compound exercises such as the overhead press, barbell bench press, and the deadlift.

• Improved Posture: The rear delt fly can help improve your posture by adding muscle engagement in the upper body to tighten your upper back muscles and prevent hunched over shoulders. The exercise also targets the core muscles which aids in maintaining a straight back for proper posture.

• Improved Shoulder Mobility: Moving the arms back from a hinged position aids the mobility of the shoulder joint, further aiding in preventing it from getting injured.

To perform the exercise, you can follow these steps:

1. Stand with your feet shoulder-width apart and hold a dumbbell in each hand.

2. Bend forward at the hips, keeping your back straight and your head up.

3. Raise your arms out to the sides, keeping your elbows slightly bent, until they are in line with your shoulders.

4. Squeeze your rear delts and slowly return to the starting position.

5. Repeat for 10-12 reps.

Its important to avoid common mistakes such as using heavy dumbbells, shrugging your shoulders, or relying on your traps to bring the handles back. Instead, grip the handles lightly and try to only use your rear delts to complete the exercise motion.