The biceps brachii muscle is the most recognizable muscle group in the upper arm, composed of two distinct parts, or “heads,” which attach at different points on the shoulder blade. Developing a fuller look often involves emphasizing the inner portion of this muscle. This guide details the specific anatomy and training principles necessary to intentionally target and develop the short head of the biceps.
Understanding Biceps Anatomy and Function
The biceps brachii is named for its two origins, both arising from the scapula. The short head, which adds inner bicep width, originates at the coracoid process, lying closer to the body’s midline. The long head originates at the supraglenoid tubercle, positioning it on the outer part of the arm.
Both heads merge into a single muscle belly before inserting onto the radius bone in the forearm, sharing a primary function. Their main actions are elbow flexion (bending the arm) and forearm supination (rotating the forearm to turn the palm upward). The short head also assists in horizontal adduction.
The different attachment points allow changes in arm position to mechanically shift tension emphasis between the two heads. The short head is the inner head, and its development contributes to the arm’s overall thickness and width.
Biomechanical Principles for Short Head Activation
To selectively emphasize the short head, training methods must leverage its unique anatomical position and function relative to the long head. One primary method involves altering the hand position on a barbell or dumbbell, specifically using a wider grip than shoulder-width during curling movements. A wider grip can cause a slight external rotation of the humerus, which places the short head at a biomechanical advantage to bear the majority of the load.
Another method centers on the position of the elbow relative to the torso, specifically by introducing shoulder flexion, meaning the elbows are held in front of the body or supported. When the arm is positioned forward, the long head’s contribution is minimized because its tendon is slackened slightly, increasing the recruitment of the short head. This mechanical change effectively reduces the long head’s ability to generate maximum force, thereby transferring more work to the short head.
The concept of a supported elbow, such as using a preacher curl bench, is a powerful application of this principle. The supported angle forces the shoulder into a flexed position, mechanically isolating the biceps and making it difficult to use momentum. This setup ensures that the short head is heavily engaged throughout the curling motion. Furthermore, maintaining full forearm supination, or a palm-up grip, is consistently important across all movements to maximize overall biceps activation.
Essential Exercises for Short Head Development
The Preacher Curl is one of the most effective movements for targeting the short head because its setup directly applies the principle of shoulder flexion. When the upper arm rests on the angled pad, the long head is mechanically stretched at the shoulder joint, which limits its force production capacity. This limitation forces the short head to become the primary mover for elbow flexion, which is why studies suggest the preacher curl exhibits a bias toward the inner biceps.
To perform a Preacher Curl using an EZ-bar, an individual should ensure their armpits are pressed firmly against the top of the pad, minimizing the space between the arm and the bench. The movement involves fully extending the arms at the bottom for a deep stretch and then contracting powerfully until the forearm is vertical, without allowing the elbows to lift off the pad. This technique focuses tension entirely on the short head and the underlying brachialis muscle throughout the range of motion.
The Wide Grip Barbell Curl is another exercise that relies on the biomechanical principle of grip width to shift emphasis to the inner head. By gripping the barbell several inches wider than the shoulders, the arms are forced into a slightly externally rotated position. This external rotation favors the line of pull of the short head, helping to build the desired width and thickness of the arm.
When executing the Wide Grip Barbell Curl, the movement should be controlled, with the elbows staying relatively fixed at the sides, while the core remains braced to prevent the torso from leaning back. Slowly lowering the weight back to the starting position is equally important as the lifting phase, as the eccentric portion of the lift provides significant stimulus for muscle growth. Focusing on generating force through the pinky side of the hand can help reinforce the external rotation and further maximize the short head’s contribution.