Targeting the Rear Deltoid
The rear deltoid (posterior) head sits to the back of the shoulder, and assist in supporting the shoulder joint during many lifts and presses, but is mostly isolated during the raising of the arms towards the back of the body.
Aesthetically, the rear deltoids help towards greater shoulder side and density, and can make a big difference to how the back looks, when the rear deltoids, traps, and upper back are all well developed.
Usually left towards the end of a workout (perhaps due to their lack of not being as visible as other muscles groups, as well as the limited exercises used to develop them. Often a weaker muscle group for many, especially given the over involvement of the anterior (front) deltoids during many arm curl and pressing-type movements, the rear deltoids should be prioritized early on in the workout.
The rear (posterior) deltoids are often the least developed of the 3 shoulder heads, and may need to be prioritized early on within your shoulder workout to help encourage further development.
The Rear Delt Technique
Many compare this movement to the reverse of a chest-fly exercise, with the arms moving in an arc-like position, (similar to how wings flap), raising a weight/resistance upwards (when in a bent forward position), or behind (when in a standing position), with the posterior deltoid best being isolated and involved.
To perform a bent over rear delt dumbbell raise, stand with feet shoulder-width apart, and tilt forwards at the waist, keeping your back straight and your hips pushed back to counterbalance the weight (this is the same position you might get into for a barbell row or concentration curl).
Holding a dumbbell in each hand (not too heavy), let the arms hang but with a slight bend in the elbow (if the arms are straight, then the triceps will become involved to a greater degree), and then focus on squeezing your shoulder blades together as you raise your arms out to the side of you, in an arc-like movement.
Briefly pause when your arms are parallel to the floor, or you are unable to raise your arms any higher without needing to bend at the elbow.
Slowly resist the weight back down, reversing your arms back towards the starting position.
Seated Bent Over Rear Delt Dumbbell Flys
If the standing rear deltoid raise is either uncomfortable or the technique may require some practice, you can modify it so as to perform it seated. Sat on the end of a bench, tilt forwards at the waist so that your arms can hang just in front of you.
Still with your back straight, raise your arms up to the side so that you can feel the rear deltoids contract towards the top of the movement. This particular variation requires a strict movement, so your weight may need to be adjusted to be able to perform it correctly with full effect.
(You may need to increase the height of the bench seat if possible, and even put something under your feet, to ensure your arms can raise freely at full length (with a slight bend at the elbow), without touching the floor at the bottom of the rep).
Pronated Incline Bench Rear Delt Flys
An even stricter movement than the seated rear delt flys, as this version supports your whole torso, so that only your rear delts are really being involved to raise the arms out to the side.
Set the incline bench at an angle so it’s about 45-degrees from a flat position. Lay chest-forward onto the bench, so that you can use your feet to support yourself on the floor (some prefer to sit on the bench seat and lean forwards on the bench, whilst others prefer to stand with their legs straight, and lean forwards on the bench. This is more of a personal preference).