The muscles of the anterior (front) upper arm are a complex group, but for the purpose of development and strength, they are often simplified into three distinct parts. The prominent, two-headed biceps brachii is complemented by a deeper, powerful muscle called the brachialis. Understanding how these different components work together is crucial for a well-rounded and effective fitness routine.
The Biceps Brachii: The Two-Headed Muscle
As its name suggests, the biceps brachii is a two-headed muscle that lies superficially on the front of the upper arm. Both heads originate from the scapula (shoulder blade) and insert via a common tendon onto the radius bone in the forearm. This arrangement allows the biceps to perform its dual functions at the elbow and shoulder joints. Both heads work together for powerful forearm supination (turning the palm up) and elbow flexion (bending the arm). However, the specific location and structure of each head mean they are targeted differently during certain movements, affecting the muscle's overall appearance.
The Long Head: Defining the Peak
The long head of the biceps is located on the outer portion of the upper arm, and its tendon runs through the shoulder joint. Its primary function, along with the short head, is elbow flexion and forearm supination. When properly developed, the long head is responsible for creating the visible “peak” of the bicep when the arm is flexed. Because its tendon crosses the shoulder joint, it is also involved in shoulder flexion, though this is a minor role. Exercises that can preferentially target the long head often involve movements where the elbow is behind the body, such as incline dumbbell curls.
The Short Head: Adding Width
The short head is positioned on the inner part of the upper arm. It originates from the coracoid process of the scapula and, when well-developed, contributes significantly to the overall width and thickness of the bicep when viewed from the front. The short head works with the long head to perform forearm supination and elbow flexion. To emphasize the short head, exercises that involve bringing the arms in front of the body, such as preacher curls or wide-grip barbell curls, are effective.
The Brachialis: The Third, Deeper Muscle
Lying beneath the biceps brachii is a separate but equally important muscle called the brachialis. It is often referred to as the “third part” because of its significant contribution to arm development. The brachialis originates on the front of the humerus (upper arm bone) and inserts onto the ulna (a bone in the forearm). Its sole function is to flex the elbow, making it the most powerful and consistent flexor of the elbow joint, regardless of whether the forearm is supinated or pronated. When well-developed, the brachialis pushes the biceps muscle upwards, giving the upper arm a fuller and wider appearance. Hammer curls and reverse grip curls are excellent exercises for targeting the brachialis.
Training for Comprehensive Arm Development
For a strong and well-developed upper arm, a training program should incorporate exercises that target all three components. Focusing solely on one type of curl will neglect a significant portion of your arm's strength and size potential. Incorporating a variety of movements and grip positions is the best way to ensure balanced growth and function.
Key exercises for targeting each part include:
- Long Head: Incline Dumbbell Curls, Drag Curls
- Short Head: Preacher Curls, Wide-Grip Barbell Curls
- Brachialis: Hammer Curls, Reverse Grip Curls
These exercises, combined with proper form and progressive overload, will lead to more comprehensive upper arm development, addressing both the peak and the width of your biceps.
The Anatomy of Arm Flexion: A Comparison Table
| Feature | Biceps Long Head | Biceps Short Head | Brachialis |
|---|---|---|---|
| Primary Location | Outer upper arm | Inner upper arm | Deep, underneath the biceps |
| Function | Elbow flexion, forearm supination, minor shoulder flexion | Elbow flexion, forearm supination | Pure elbow flexion |
| Visual Effect | Creates the bicep "peak" | Adds to bicep width | Pushes biceps up for a fuller look |
| Best Targeted By | Incline curls, drag curls | Preacher curls, wide-grip curls | Hammer curls, reverse curls |
| Origin | Supraglenoid tubercle of the scapula | Coracoid process of the scapula | Distal half of the humerus |
| Insertion | Radial tuberosity | Radial tuberosity | Ulnar tuberosity |
Conclusion: The Whole is Greater Than the Sum of Its Parts
So, when someone asks what are the three parts of your bicep?, the answer extends beyond the two-headed biceps brachii muscle. For comprehensive strength and aesthetics, it's essential to understand and train the long head, the short head, and the deeper brachialis muscle. By incorporating a variety of exercises that emphasize each of these components, you can achieve balanced muscle development, greater arm strength, and a more defined look. For deeper anatomical knowledge, consult resources from reputable institutions like the Cleveland Clinic. A holistic approach to arm training, focusing on all three parts, is key to maximizing your potential.
