The posterior deltoid, often called the rear deltoid, is one of the three heads of the shoulder muscle group. Situated on the back of the shoulder, it originates from the spine of the scapula and inserts on the humerus. Its primary mechanical actions are shoulder extension (pulling the arm backward) and horizontal abduction (moving the arm away from the body’s midline). Training this muscle is important for maintaining optimal shoulder health and functional movement. Developing the rear deltoids helps stabilize the shoulder joint, improves posture by counteracting the tendency to slouch forward, and contributes to the aesthetically rounded appearance of the shoulder.
Isolating the Rear Deltoid
Targeting the rear deltoid specifically can be challenging because larger muscles like the trapezius and rhomboids often take over the movement. To focus on the smaller posterior head, exercisers must prioritize form and muscle activation over lifting heavy weights. Using a slow, controlled tempo and avoiding momentum ensures the rear deltoid performs the work throughout the entire range of motion. This focus on the “mind-muscle connection” is more important than the load lifted, as excessive weight engages the larger back muscles.
The direction of the pull and the hand position are also important for isolation. When executing movements like flyes or pulls, the goal is to drive the elbows backward and outward, aligning with the rear deltoid’s function of horizontal abduction. Maintain a slight bend in the elbow, but initiate the movement by contracting the rear shoulder muscle, not by bending the arm. Focusing on leading the movement with the pinky finger or the back of the hand is helpful. This subtle cue encourages external rotation, a secondary function of the rear deltoid, maximizing engagement while minimizing the contribution of the upper trapezius.
Avoiding excessive scapular retraction is another technique to keep tension localized to the rear deltoid. While it may seem intuitive to “squeeze the shoulder blades together,” over-retracting the scapulae heavily recruits the rhomboids and mid-back. Instead, maintaining a slightly rounded or protracted shoulder position at the start of the exercise can help place more mechanical tension directly onto the rear deltoid. The overall execution should resemble separating the arms horizontally rather than performing a traditional back row, which engages the lats and central back muscles.
Key Exercises for Rear Deltoid Development
The most effective movements for developing the rear deltoid isolate its primary functions: horizontal abduction and external rotation. Electromyography (EMG) studies show that isolation exercises are superior to most compound back movements for direct rear deltoid activation. Incorporating a variety of angles and resistance types ensures comprehensive development.
The Reverse Pec Deck Fly is an outstanding isolation movement because it mechanically locks the body into position, minimizing assistance from other muscles. Press the chest firmly against the pad, and adjust the seat height so the hands are roughly level with the shoulders. The movement involves pressing the arms backward and outward, focusing on a strong contraction of the rear shoulder muscles at peak tension. Since the machine provides constant tension and stability, it allows for maximal focus on the muscle connection.
Face Pulls are highly regarded because they combine horizontal abduction and external rotation, addressing two distinct functions of the muscle. Using a cable machine with a rope attachment, set the pulley at or slightly above shoulder height. Pull the rope toward the face, aiming for the forehead or ears, while actively pulling the hands apart. This hands-apart action drives the external rotation component, which is beneficial for shoulder health and strength balance.
A versatile free-weight option is the Bent-Over Dumbbell Lateral Raise, also known as the reverse dumbbell fly. To perform this, bend the torso until it is nearly parallel to the floor, aligning the resistance line of the dumbbell with the muscle fibers. Starting with the dumbbells hanging straight down, raise the arms out to the sides with a slight bend in the elbow, stopping once the arms reach horizontal. Because gravity dictates the tension profile, resistance is highest at the top of the movement. Control the descent fully.
Integrating Rear Deltoid Work into Your Training Schedule
Since the rear deltoid is a relatively small muscle with excellent recovery capabilities, it responds well to higher training frequencies and moderate volume. Training the rear deltoids two to three times per week is often recommended to maximize growth, contrasting with larger muscle groups that require longer recovery. For intermediate lifters, aiming for six to twelve sets of direct rear deltoid work per week is a common starting point for noticeable gains.
The rep ranges for rear deltoid work are typically higher than those used for compound lifts. Sets of 10 to 20 repetitions, or even 20 to 30 repetitions, are effective because the muscle is well-suited for endurance and responds to the metabolic stress of higher volume training. Using lighter weights for these higher rep ranges also makes it easier to maintain the specific isolation cues, preventing the larger back muscles from dominating the lift.
Strategic placement of rear deltoid work within the training session can enhance results. Because this muscle is often underdeveloped, performing rear deltoid exercises early in a workout, such as before heavy pressing or rowing movements, is advantageous. Placing these isolation movements at the beginning of the session ensures the muscle receives attention while energy levels are high, allowing for maximal focus and quality of execution. This prioritization helps correct the common imbalance where the stronger anterior deltoids receive the majority of work.