Pain in the rear deltoid—the posterior shoulder muscle—during pressing movements is a common experience for lifters. This discomfort, often felt intensely during the bench press or overhead press, usually indicates a struggle with stability rather than a primary muscle strain. The pain signals that the muscle is being overloaded as it attempts to manage forces it is not prepared to handle. This overload typically results from a combination of technical errors and underlying muscular imbalance, requiring a targeted approach to correction.
The Role of the Rear Deltoid in Pressing Movements
The rear deltoid is responsible for shoulder extension and external rotation, movements that pull the arm backward and rotate it outward. While the larger chest and anterior deltoid muscles perform the pressing action, the rear deltoid’s primary function during a press is stabilization. It acts as a dynamic anchor, working to keep the head of the humerus, or upper arm bone, centered within the shoulder socket.
This stabilizing role prevents the shoulder from drifting excessively forward and internally rotating under load, especially at the bottom of the movement. If the rear deltoid is weak or fatigued, it fails to maintain this neutral, secure position. The resulting instability places undue stress on the joint capsule and surrounding connective tissues, which is interpreted as pain in the muscle’s location.
Identifying the Primary Causes of Pain
The pain often originates from a cycle of instability that forces the rear deltoid to overcompensate for other compromised structures. One primary issue is weakness in the rotator cuff, particularly the infraspinatus and teres minor, which are crucial for external rotation. When these smaller muscles cannot effectively stabilize the joint, the rear deltoid takes on an excessive workload to manage the rotational forces, leading to fatigue and pain.
Technical flaws during the movement dramatically increase this strain, a common one being excessive elbow flare during the bench press. Flaring the elbows outward creates a position of high internal rotation at the shoulder joint. This significantly increases the demand placed on the rear deltoid and rotator cuff to resist that rotation. This poor positioning can also lead to shoulder impingement, where tendons or bursa are pinched between the bones.
A separate but related issue is anterior humeral glide, where the head of the upper arm bone slides too far forward in the socket during the eccentric (lowering) phase. This is often exacerbated by a lack of proper scapular control or a rounded-shoulder posture. When the rear deltoid cannot effectively pull the arm bone back into a centered position, the resulting stress at the back of the joint manifests as pain.
Immediate Technique Adjustments to Reduce Strain
To alleviate acute pain during a pressing session, several immediate adjustments can be made to improve joint mechanics. Modifying your grip and elbow position is the most direct way to reduce stress on the posterior shoulder. Tucking the elbows slightly closer to the body, aiming for an angle of approximately 75 degrees relative to the torso, moves the shoulder into a less internally rotated and more stable position.
Key Adjustments
Focusing on controlling the tempo, especially the eccentric phase, is another powerful immediate fix. Consciously slow the lowering of the weight over two to three seconds to prevent the bar from being “dumped,” which eliminates high-velocity, uncontrolled forces on the shoulder joint. Other adjustments include:
- Narrowing the grip width slightly, as a very wide grip inherently increases the rotational demand on the shoulder stabilizers.
- Decreasing the range of motion to avoid the deepest, most vulnerable point of the press, stopping just short of maximal depth.
- Ensuring proper pre-tensioning before initiating the lift by actively retracting and depressing the shoulder blades to create a solid, stable base.
Corrective Exercises for Long-Term Shoulder Health
Addressing the pain requires dedicated accessory work to build strength and resilience in the posterior chain. Exercises that isolate the rear deltoid without heavy pressing load are essential, such as face pulls and bent-over dumbbell reverse flyes. These movements directly strengthen the posterior fibers and improve the motor control needed for shoulder external rotation and retraction.
Targeting the rotator cuff muscles, which directly support the rear deltoid’s stability work, is also necessary. Low-load exercises like side-lying external rotations with a light dumbbell or resistance band specifically strengthen the infraspinatus and teres minor. Performing these movements consistently helps ensure that the smaller, deeper stabilizers are functioning correctly before the larger pressing muscles engage.
Adequate thoracic spine mobility profoundly affects shoulder health, particularly during overhead movements. Limited mid-back extension forces the shoulder to compensate by moving into a less stable position. Simple mobility drills, such as thoracic extensions over a foam roller, can improve flexibility, allowing the shoulder blades to move correctly and reducing strain on the rear deltoid.