Hammer Curl: Muscles Targeted, Benefits, and Proper Technique

What Head Does the Hammer Curl Target?

While the hammer curl engages both heads of the biceps brachii for elbow flexion, its unique neutral grip primarily emphasizes the brachialis and brachioradialis muscles, which are key elbow flexors.

Understanding the Hammer Curl

The hammer curl is a popular strength training exercise designed to build muscle in the upper arms and forearms. Unlike a traditional bicep curl where the palms face up (supinated grip), the hammer curl employs a neutral grip, meaning your palms face each other throughout the movement, as if you were holding a hammer. This seemingly subtle change in grip significantly alters the muscular emphasis, making it a distinct exercise with unique benefits for arm development.

Primary Muscles Targeted by the Hammer Curl

While the question specifically asks about the "head" targeted, implying the biceps brachii, it's crucial to understand that the hammer curl's neutral grip shifts the primary focus to other powerful elbow flexors.

• Brachialis: This is arguably the most emphasized muscle during a hammer curl. The brachialis lies directly beneath the biceps brachii and is a pure elbow flexor, meaning its sole function is to bend the elbow, regardless of forearm rotation. When the forearm is in a neutral position, the brachialis gains a mechanical advantage, allowing it to contribute significantly to the lifting force. Developing the brachialis can contribute to overall arm thickness, pushing the biceps brachii outward.
• Brachioradialis: This muscle, located in the forearm, runs from the upper arm bone (humerus) to the radius (the larger forearm bone). It is most active as an elbow flexor when the forearm is in a neutral (hammer) grip. The hammer curl places the brachioradialis in an optimal position to contribute substantially to the lift, making it a key target for building forearm size and strength.
• Biceps Brachii (Long and Short Heads): While the hammer curl doesn't primarily target the individual "heads" of the biceps brachii in the same way a supinated curl does, both the long head and short head are still actively involved in elbow flexion. However, the biceps brachii also plays a significant role in forearm supination (turning the palm up). By removing the supination component with a neutral grip, the hammer curl reduces the emphasis on the biceps' supination function, allowing the brachialis and brachioradialis to become more dominant. So, while the biceps still work, they are not the primary target for all their functions.

In summary, while both heads of the biceps brachii are involved in the hammer curl, the exercise is more renowned for its profound impact on the brachialis and brachioradialis.

Why the Neutral Grip Makes a Difference

The key to understanding the hammer curl's unique muscle activation lies in the biomechanics of the neutral grip:

• Altered Mechanical Advantage: The neutral grip places the brachialis and brachioradialis in a more mechanically advantageous position to exert force during elbow flexion. These muscles are less influenced by forearm rotation compared to the biceps.
• Reduced Biceps Supination Role: The biceps brachii is a powerful supinator of the forearm. When you perform a traditional bicep curl with a supinated grip, the biceps is actively engaged in both elbow flexion and supination. By maintaining a neutral grip, you remove the supination demand, thereby shifting a greater percentage of the elbow flexion work to the brachialis and brachioradialis.
• Greater Forearm Engagement: The brachioradialis, a significant forearm muscle, is optimally recruited in a neutral grip, leading to enhanced forearm development.

Benefits of Incorporating Hammer Curls

Adding hammer curls to your routine offers several advantages:

• Comprehensive Arm Development: By targeting the brachialis and brachioradialis more directly, hammer curls help build more well-rounded and proportional arm musculature, contributing to overall arm thickness and strength that traditional bicep curls might miss.
• Improved Grip Strength: The nature of holding dumbbells with a neutral grip engages the forearm flexors and grip muscles effectively.
• Enhanced Functional Strength: Stronger brachialis and brachioradialis muscles contribute to better performance in activities requiring pulling and lifting, as well as sports.
• Reduced Strain on Biceps Tendons: For some individuals, the supinated grip of traditional curls can place stress on the biceps tendon. The neutral grip can be a more comfortable alternative.

Proper Hammer Curl Technique

To maximize effectiveness and minimize injury risk, proper form is paramount:

• Starting Position: Stand tall with a dumbbell in each hand, arms extended by your sides. Your palms should face your body (neutral grip).
• Execution: Keeping your upper arms stationary and elbows tucked close to your body, slowly curl the dumbbells upwards towards your shoulders. Focus on squeezing your target muscles.
• Peak Contraction: Pause briefly at the top of the movement when your forearms are roughly perpendicular to the floor, ensuring a strong contraction.
• Controlled Descent: Slowly lower the dumbbells back to the starting position, maintaining control throughout the entire range of motion. Avoid letting gravity take over.

Common Mistakes to Avoid

• Using Momentum (Cheating): Swinging the weights up by leaning back or using your hips reduces the work done by your arm muscles. Use a weight you can control.
• Flaring Elbows: Keeping your elbows tucked in helps isolate the target muscles. Letting them flare out can put undue stress on the shoulder joint.
• Incomplete Range of Motion: Not fully extending your arms at the bottom or not curling high enough at the top limits muscle activation and growth.
• Lack of Control: Dropping the weights quickly on the eccentric (lowering) phase misses out on a crucial part of muscle building.

Conclusion

While the hammer curl does involve both heads of the biceps brachii, its primary distinction and benefit lie in its ability to powerfully engage the brachialis and brachioradialis muscles due to the neutral grip. Incorporating hammer curls into your training regimen is an excellent strategy for achieving comprehensive arm development, contributing to greater arm thickness, strength, and overall functional fitness. Focus on proper technique to harness the full potential of this valuable exercise.