Rear Delt Flys: Optimal Grip, Biomechanics, and Technique

What is the best grip for rear delt flys?

For optimal isolation and biomechanical efficiency in the rear delt fly, the neutral grip (palms facing each other) is generally considered superior, as it aligns most effectively with the posterior deltoid's fiber orientation while minimizing synergistic muscle involvement.

The Crucial Role of the Posterior Deltoid

The posterior deltoid, often referred to as the rear delt, is a vital component of a healthy, functional, and aesthetically balanced shoulder girdle. While the anterior (front) and medial (side) deltoids often receive more attention in training, a strong and well-developed posterior deltoid is critical for:

• Shoulder Health and Stability: It plays a key role in stabilizing the glenohumeral joint, particularly during overhead movements and deceleration.
• Posture: Weak rear delts can contribute to protracted (rounded) shoulders and poor upper back posture.
• Injury Prevention: Balancing the strength of the anterior and posterior deltoids helps prevent common shoulder injuries, such as impingement.
• Performance: Essential for movements involving pulling, throwing, and any activity requiring shoulder extension and external rotation.

Understanding Rear Delt Anatomy and Function

The posterior deltoid originates from the spine of the scapula and inserts into the deltoid tuberosity of the humerus. Its primary actions include:

• Horizontal Abduction: Moving the arm away from the midline of the body in the horizontal plane (e.g., the "fly" motion).
• External Rotation: Rotating the humerus outwards.
• Extension: Moving the arm backward.

The rear delt fly specifically targets the horizontal abduction function, making grip choice paramount for maximizing its effectiveness.

Common Grip Variations for Rear Delt Flys

When performing rear delt flys, whether with dumbbells, cables, or a machine, three primary grip variations are commonly employed:

• Neutral Grip (Hammer Grip): Palms face each other throughout the movement.
• Pronated Grip (Overhand Grip): Palms face down (or rearward when seated).
• Supinated Grip (Underhand Grip): Palms face up (or forward when seated).

Biomechanics of Each Grip

The choice of grip significantly influences the biomechanical path of the humerus and the recruitment patterns of the surrounding musculature.

• Neutral Grip (Palms Facing Each Other)

  • Shoulder Position: This grip naturally places the humerus in a more externally rotated or neutral position. This alignment is highly congruent with the primary fiber orientation of the posterior deltoid, allowing for a direct line of pull during horizontal abduction.
  • Muscle Activation: Maximizes the activation of the posterior deltoid by directly engaging its primary function. It also tends to minimize the involvement of the biceps brachii and other synergistic muscles, allowing for greater isolation.
  • Joint Stress: Often considered the most shoulder-friendly grip, as it avoids excessive internal rotation or impingement risk often associated with a pronated grip, especially under load.

• Pronated Grip (Palms Facing Down/Rearward)

  • Shoulder Position: This grip can encourage internal rotation of the humerus, particularly at the end range of motion. While the posterior deltoid still contributes to horizontal abduction, this internal rotation can alter the line of pull and potentially increase stress on the shoulder joint, especially for individuals with pre-existing shoulder issues.
  • Muscle Activation: While still activating the posterior deltoid, there can be increased recruitment of the medial deltoid, upper back muscles (rhomboids, trapezius), and potentially a greater tendency for the biceps to assist if form breaks down.
  • Joint Stress: May increase the risk of impingement for some individuals due to the internally rotated position, especially if the elbows are kept locked or the movement is performed with heavy weights and poor control.

• Supinated Grip (Palms Facing Up/Forward)

  • Shoulder Position: This grip places the humerus in an externally rotated position. While external rotation is a function of the posterior deltoid, the supinated grip for a fly motion often leads to significant biceps brachii involvement.
  • Muscle Activation: The biceps, being a strong supinator and elbow flexor, can become a dominant mover, turning the exercise more into a reverse curl or a compound pulling motion rather than an isolated rear delt fly. This can significantly detract from the intended rear delt isolation.
  • Joint Stress: Generally not considered high risk for shoulder impingement, but the increased biceps involvement reduces the specificity of the exercise for the posterior deltoid.

The "Best" Grip: A Biomechanical Perspective

Based on the biomechanical analysis, the neutral grip (palms facing each other) stands out as the most effective grip for rear delt flys.

• Optimal Fiber Alignment: It aligns the humerus in a way that directly engages the posterior deltoid's primary function of horizontal abduction, allowing for a more focused and efficient contraction of the target muscle.
• Reduced Synergistic Involvement: By minimizing the recruitment of the biceps and other assisting muscles, the neutral grip ensures that the posterior deltoid is the primary mover, maximizing its growth stimulus.
• Shoulder Health: This grip promotes a more natural and safer shoulder joint position, reducing the risk of impingement or undue stress, making it suitable for a wider range of individuals and for consistent training.

While the pronated grip can be used, especially with lighter weights and meticulous form to avoid internal rotation, it is generally less optimal for direct rear delt isolation and carries a slightly higher risk for shoulder discomfort compared to the neutral grip. The supinated grip is largely inefficient for rear delt fly isolation due to excessive biceps involvement.

Optimizing Your Rear Delt Fly Technique

Regardless of the grip chosen, proper technique is paramount for effective and safe rear delt training.

• Mind-Muscle Connection: Actively focus on squeezing your rear delts to initiate and control the movement. Visualize your shoulder blades spreading apart slightly as you bring the weights out, and then feel the contraction in the posterior deltoid as you reverse.
• Controlled Movement: Avoid swinging the weights or using momentum. The movement should be slow and controlled, especially during the eccentric (lowering) phase, to maximize time under tension.
• Scapular Stability: While the rear delt fly is primarily a glenohumeral joint movement, maintaining slight scapular retraction and depression can provide a stable base. However, avoid excessive scapular retraction, which can shift the emphasis to the rhomboids and mid-back.
• Elbow Position: Maintain a slight, consistent bend in your elbows. Locking them out can put undue stress on the joint, while too much bend can turn the movement into a row, engaging more of the lats and biceps.
• Resistance Profile: Cable machines often provide a more consistent tension profile throughout the entire range of motion compared to dumbbells, which can be advantageous for rear delt isolation.

Conclusion

For individuals seeking to maximize posterior deltoid activation, promote shoulder health, and achieve balanced shoulder development, the neutral grip is the recommended choice for rear delt flys. It offers superior biomechanical alignment, minimizes synergistic muscle recruitment, and reduces the risk of shoulder impingement. Prioritize impeccable form, controlled movements, and a strong mind-muscle connection to unlock the full potential of this crucial exercise for a robust and resilient shoulder girdle.