Biceps Brachii: Anatomy, Functions, Training, and Injuries of the Long and Short Heads

What is the Biceps Long Head and Short Head?

The biceps brachii muscle, located on the front of the upper arm, is comprised of two distinct heads—the long head and the short head—which originate from different points on the scapula and converge to insert into the forearm, collectively performing elbow flexion and forearm supination.

Anatomy of the Biceps Brachii

The term "biceps" literally means "two heads," accurately describing the structure of this prominent muscle in the anterior compartment of the upper arm. Both heads originate from the scapula (shoulder blade) and converge into a common tendon that inserts into the radius bone in the forearm.

• The Long Head (Caput Longum):

  • Origin: This head originates from the supraglenoid tubercle of the scapula, a small bony protrusion just above the glenoid cavity (the shoulder joint socket).
  • Path: Its tendon is unique in that it passes through the shoulder joint capsule and descends within the intertubercular groove (bicipital groove) of the humerus. This intra-articular path gives the long head a significant role in shoulder stability.
  • Course: It then runs superficially down the arm, medial to the deltoid, before joining the short head.
  • Appearance: Due to its lateral position, the long head contributes significantly to the "peak" or height of the biceps muscle when flexed.

• The Short Head (Caput Breve):

  • Origin: This head originates from the coracoid process of the scapula, a hook-like projection on the anterior aspect of the scapula.
  • Path: Its origin is extra-articular (outside the shoulder joint). It runs inferiorly and laterally, lying medial to the long head.
  • Course: It joins the long head approximately midway down the humerus.
  • Appearance: Positioned more medially, the short head contributes more to the overall width and thickness of the biceps muscle.

• Common Insertion:

  • Distally, the long and short heads unite to form a single, powerful tendon, the biceps tendon, which primarily inserts onto the radial tuberosity of the radius bone.
  • A broad aponeurotic sheet, the bicipital aponeurosis, also extends from the biceps tendon to the fascia of the forearm, providing additional stability and protecting underlying structures.

Primary Functions of the Biceps Heads

While both heads work synergistically to perform the primary actions of the biceps brachii, their distinct origins allow for subtle differences in their contribution, particularly in specific joint positions.

• Elbow Flexion: This is the most recognized function. Both heads powerfully bend the elbow, bringing the forearm closer to the upper arm. The biceps is most effective as an elbow flexor when the forearm is supinated.
• Forearm Supination: The biceps is the most powerful supinator of the forearm (turning the palm upwards). This action is particularly strong when the elbow is flexed at 90 degrees. The oblique pull of the biceps tendon on the radial tuberosity facilitates this rotational movement.
• Shoulder Flexion (Long Head Emphasis): Due to its origin on the supraglenoid tubercle and its path through the shoulder joint, the long head of the biceps assists in flexing the shoulder joint (lifting the arm forward) and contributes to stabilizing the humeral head within the glenoid cavity, especially during overhead movements. The short head has minimal, if any, direct action on the shoulder joint.

Distinguishing Roles and Contributions

While it's impossible to completely isolate one head from the other during standard exercises, understanding their anatomical differences allows for strategic exercise selection to emphasize specific areas for development or rehabilitation.

• Emphasis on the Long Head: Exercises that place the shoulder in extension (arm behind the body) or that involve a more neutral to pronated grip can subtly increase the stretch and, therefore, the activation of the long head.

  • Incline Dumbbell Curls: Lying on an incline bench places the humerus into extension, stretching the long head at the shoulder joint, potentially increasing its recruitment.
  • Hammer Curls: While primarily targeting the brachialis and brachioradialis, the neutral grip can also provide a unique stimulus to the long head.
  • Narrow Grip Curls: A slightly narrower grip on a barbell curl might emphasize the long head more.

• Emphasis on the Short Head: Exercises that place the shoulder in slight flexion (arm in front of the body) or involve a wider grip can subtly increase the activation of the short head.

  • Preacher Curls: The fixed position of the arm in front of the body, often with a wide grip, can place a greater stretch on the short head at its origin, potentially emphasizing its contribution.
  • Wide Grip Barbell Curls: A wider grip can shift some emphasis to the short head.
  • Concentration Curls: Performed with the elbow supported and slightly in front of the body, these can also target the short head effectively.

Practical Application for Training

For comprehensive biceps development, a variety of exercises that target both elbow flexion and forearm supination, and vary arm positions, is recommended.

• Incorporate Diverse Grips: Supinated (underhand), pronated (overhand), and neutral (hammer) grips all place different demands on the biceps and synergistic muscles.
• Vary Arm Position: Include exercises where the arms are:
  • Behind the body (shoulder extension): E.g., Incline Curls (emphasizes long head).
  • In front of the body (shoulder flexion): E.g., Preacher Curls (emphasizes short head).
  • Close to the body: E.g., Standing Barbell Curls (balanced development).
• Focus on Full Range of Motion: Ensure complete extension at the bottom and full contraction at the top of each repetition to maximize muscle fiber recruitment and development.
• Control the Eccentric Phase: The lowering (eccentric) phase of a curl is crucial for muscle growth and should be performed slowly and controlled.

Common Injuries and Considerations

Understanding the anatomy of the biceps heads is also vital for injury prevention and rehabilitation.

• Biceps Tendinopathy: Inflammation or degeneration of the biceps tendon, often near the shoulder (long head) or elbow (distal biceps tendon).
• Biceps Tears: Can occur at the origin (proximal tear, often long head) or insertion (distal tear). Proximal long head tears are common, leading to a "Popeye" deformity where the muscle belly bunches up.
• Importance of Proper Form: Using excessive weight or improper technique can place undue stress on the biceps tendons and surrounding joints, increasing the risk of injury.

Conclusion

The biceps brachii, with its distinct long and short heads, is a fascinating and functionally important muscle. While both heads work in concert for most actions, their unique anatomical origins allow for subtle variations in activation based on joint position and exercise selection. A well-rounded training program that incorporates a variety of movements and grip positions will ensure comprehensive development of both heads, contributing to both strength and aesthetics of the upper arm. Understanding these anatomical nuances empowers fitness enthusiasts and professionals to design more effective and targeted training strategies.