Hammer Curls: Muscle Activation, Benefits, and Biceps Development

Do Hammer Curls Work Long Head?

While hammer curls engage the entire biceps brachii, they do not primarily target or emphasize the long head. Instead, their unique grip and movement patterns place a greater emphasis on the brachialis and brachioradialis muscles, which are key for overall arm thickness and grip strength.

Understanding the Biceps Brachii

To fully grasp the mechanics of the hammer curl, it's essential to understand the anatomy of the upper arm muscles responsible for elbow flexion:

• Biceps Brachii (Long Head): Originates from the supraglenoid tubercle of the scapula (shoulder blade) and runs over the shoulder joint. Its position makes it more active in supinated (palms up) curling movements, especially when the shoulder is extended (e.g., incline curls).
• Biceps Brachii (Short Head): Originates from the coracoid process of the scapula. It lies medial to the long head and is more active in pronated (palms down) or neutral grip curls, and when the shoulder is flexed (e.g., preacher curls).
• Brachialis: Located deep to the biceps brachii, this muscle originates from the anterior surface of the humerus and inserts onto the ulna. It is considered the true elbow flexor, contributing significantly to all curling movements regardless of forearm position. Its action is purely elbow flexion.
• Brachioradialis: A prominent forearm muscle that originates from the lateral supracondylar ridge of the humerus and inserts near the wrist. It primarily acts as an elbow flexor, especially with a neutral grip (thumb up), and also assists in forearm pronation and supination back to a neutral position.

The Mechanics of the Hammer Curl

The hammer curl is distinguished by its neutral grip, where the palms face each other throughout the movement (like holding a hammer).

• Grip: This neutral (or "hammer") grip places the forearm in a position that optimizes the line of pull for the brachialis and brachioradialis.
• Movement Path: The exercise involves flexing the elbow, bringing the weights up towards the shoulders, and then lowering them with control. The key difference from traditional biceps curls is the constant neutral hand position.

Muscle Activation During Hammer Curls

Given the anatomical considerations and the unique grip of the hammer curl, here's how muscle activation typically plays out:

• Primary Movers:
  • Brachialis: This muscle is highly activated during hammer curls because its function is pure elbow flexion, unaffected by forearm rotation. The neutral grip removes the mechanical disadvantage the brachialis often experiences during supinated curls, allowing it to contribute maximally.
  • Brachioradialis: The neutral grip provides an optimal leverage point for the brachioradialis, making it a major contributor to the lift. This muscle is crucial for developing forearm thickness and grip strength.
• Secondary Movers:
  • Biceps Brachii (Both Heads): While the biceps brachii is certainly involved in elbow flexion during hammer curls, the neutral grip does not preferentially target the long head. In fact, the long head's role in supination is minimized, and its involvement in elbow flexion is shared significantly with the brachialis and brachioradialis. Neither the long nor short head is emphasized over the other in this movement.

Why the Neutral Grip Matters

The neutral grip alters the biomechanical advantage for different muscles.

• In a supinated grip (palms up, as in a standard biceps curl), the biceps brachii, particularly the long head, is in an optimal position to contribute to both elbow flexion and forearm supination.
• In a pronated grip (palms down, as in a reverse curl), the biceps brachii is at a mechanical disadvantage, and the brachialis and brachioradialis become the primary movers.
• The neutral grip of the hammer curl falls between these two extremes, creating an ideal scenario for the brachialis and brachioradialis to become dominant, while still engaging the biceps brachii.

Optimizing Biceps Development

To effectively target specific parts of the biceps and surrounding musculature, vary your curling exercises:

• To Emphasize the Biceps Long Head: Incorporate exercises that involve shoulder extension and forearm supination.
  • Incline Dumbbell Curls: The stretched position of the long head at the bottom of the movement increases its activation.
  • Close-Grip Barbell Curls: Can place more stress on the long head due to the angle.
• To Emphasize the Biceps Short Head: Focus on exercises that involve shoulder flexion or a more contracted position.
  • Preacher Curls: The arm position isolates the biceps and puts more stress on the short head.
  • Wide-Grip Barbell Curls: Can increase activation of the short head.
• To Emphasize Brachialis and Brachioradialis (and overall arm thickness):
  • Hammer Curls: Excellent for building these muscles and contributing to overall arm girth and grip strength.
  • Reverse Curls: Primarily target the brachialis and brachioradialis with a pronated grip.

Conclusion: The Value of Hammer Curls

While hammer curls do not specifically target the long head of the biceps, they are an incredibly valuable exercise for comprehensive arm development. They effectively build the brachialis and brachioradialis, contributing significantly to overall arm thickness, elbow flexion strength, and grip strength. Incorporating hammer curls into your routine ensures a well-rounded approach to upper arm musculature, complementing traditional biceps curls for a more complete physique and functional strength.