Place two dumbbells on the floor, one on each side of a flat bench.
Lie prone (on your front) on the bench and grasp a dumbbell in each hand.
Spread your legs on the floor for support.
Keeping your elbows slightly bent, exhale as you raise the dumbbells out to the sides.
Hold for a count of two.
Inhale as you lower the dumbbells to the starting position in a controlled manner.
Repeat for the prescribed number of repetitions.
Comments and tips
Ideally, the bench should be elevated to allow the dumbbells to hang straight down without touching the floor.
You can use either a neutral grip (palms facing inward), as in the illustration, or a supinated grip (palms facing upward). Avoid using a pronated grip (palms facing downward) because there is a greater risk of shoulder impingement.
To target your posterior deltoid and avoid the involvement of your latissimus dorsi, your upper arms must rise perpendicular to your torso (i.e. directly out to the sides).
To target your posterior deltoid and minimize the involvement of your lateral deltoid, your torso must be horizontal. That’s why the bench must be flat and not inclined.
This exercise is also known as the lying dumbbell rear lateral raise, the lying dumbbell rear delt raise, and the lying dumbbell rear delt fly.