The bicep is one of the most iconic but misunderstood muscles, being far more complex than just a single muscle. Built from multiple heads and supported by crucial companion muscles, the biceps are a complex unit with diverse functions and appearance.
Whether you’re chasing bigger arms, better strength, or smarter training, understanding bicep anatomy is key to help you better target the correct muscles to increase strength and produce large, powerful-looking arms. In this article, we’ll break down the parts of the biceps and how to train each one more effectively.
Biceps Brachii Anatomy
The biceps brachii is the largest of the three muscles in the upper, forward-facing part of the arm. It’s a complex muscle with a long head and a short head. In addition to movement, it plays a critical role in supporting the humeral head within the shoulder joint. Let’s take a look at each head in more detail.
Long Head of the Biceps
The long head originates from the supraglenoid tubercle of the scapula (shoulder), then converges with the short head before tapering across the anterior aspect of the elbow to insert as a single tendon that attaches to the radial tuberosity just below the elbow. The long head is what we see as the bicep peak when we flex our arms. The appearance of that peak is primarily due to genetics, specifically the length of the muscle belly and tendon insertion points.
While the biceps brachii (long and short heads) play a primary role in elbow flexion and forearm supination, their role in shoulder movement is secondary. It’s important to note that the triceps brachii act as the biceps’ primary antagonist, working to extend the elbow. This muscular balance is key to smooth, controlled arm movements.
Shoulder actions like adduction and abduction are driven mainly by other muscles, particularly the anterior deltoid for flexion and abduction. The long head of the biceps does help to stabilize the shoulder joint, especially during overhead lifts, but it doesn’t produce abduction. As for adduction (bringing the arm towards the body), that role is mainly handled by the coracobrachialis, not the biceps.
Short Head of the Biceps
The short head also originates from the scapula, but this time to the coracoid process. After it converges with the long head and tapers across the anterior aspect of the elbow, it inserts as a single tendon to the radial tuberosity.
The short head is far less visible than the long head, but no less important, since it helps give more width to the bicep. The function of the short head is also primarily in elbow flexion, with lesser roles in shoulder flexion and adduction. In this way, it works somewhat opposite to the long head, since instead of abduction (away) from the trunk, it’s responsible for pulling the arm back towards the trunk (adduction).
Fun fact: Approximately 30% of people have variations in the origin of the bicep, with 2-5% of individuals having anywhere from 3 to 7 origin points instead of just 2.
Biceps Tendon and Insertion
While the two heads of the bicep merge and end in a single muscle belly, their tendons follow two distinct paths. The long head tendon runs through the shoulder joint and bicipital groove of the humerus, while the short head tendon travels beside the coracobrachialis tendon. They fuse lower down the arm, but in most people, the tendons remain separable.
Another fun fact: A small minority of the population has two tendons next to each other that both attach to the radius.
Related Muscles That Affect Bicep Appearance & Function
While the biceps brachii is the star of the show, it doesn’t act alone. Two other upper arm muscles affect how your biceps function and how they look. The other two are the brachialis and the coracobrachialis.
Brachialis
The brachialis is a vital muscle to understand since it supports and stabilizes the biceps brachii when your arm is flexed. You work the brachialis whenever you lift or lower your forearm—it produces 50-60% of flexion force, while the biceps contribute around 30-40%. However, this doesn’t mean the brachialis is stronger than the biceps; it’s simply more mechanically efficient for elbow flexion.
Targeting the brachialis with hammer curls, reverse curls, and neutral-grip lifts will help accentuate the peak of the biceps since it pushes on the biceps from below.
Coracobrachialis
The coracobrachialis crosses the shoulder joint, not the elbow, and plays a weaker role in shoulder joint flexion or adduction of the arm. Therefore, if you had an injured coracobrachialis, you’d likely still be able to perform overhead and pressing motions, though they could be more challenging.
How the Biceps Work
The biceps cross two joints, enable multi-plane movement, and assist with upper-body function. When they work together, their primary functions are:
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Elbow flexion: The biceps shortens concentrically while producing force to bend the elbow joint, bringing the forearm and upper arm closer together.
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Supination: Outward rotation of the forearm, rotating your palm upward (like turning a door knob). This is enabled in part by the 90-degree rotation of the muscle as it connects to the radius.
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Shoulder flexion: Lifting your arm in front of your body.
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Shoulder stabilization: Studies have shown that the long head plays a role in shoulder joint stability during movement, although it’s mostly passive support; primary stabilization comes from rotator cuff muscles.
Interestingly, the two heads often produce opposing movements:
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The long head assists in abduction (arm away from the body).
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The short head assists in adduction (arm toward the body).
This makes training both heads deliberately a smart strategy for full bicep development.
Bicep Training Tips for Targeting Both Heads
You don’t need 20 different curl variations, but you do need a smart plan. These training tips will help you isolate the long head, short head, and brachialis for optimal results when doing biceps exercises.
Varying Grip Width
One of the easiest ways to target different heads is by varying your grip width.
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When you do bar curls with a narrower grip, the long head on the outside of the arm is activated, enhancing the appearance of the peak.
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Using a wider grip enhances the activation of the short head, increasing the muscle's width, giving it a fuller-looking appearance.
You can also vary your grip width on a pull-up bar or during a calisthenics bicep workout, targeting each head separately.
Elbow Position
How you position your elbow during curls can also be used to target the different heads.
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Elbows slightly in front of your torso maximizes activation of the short head.
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Elbows in line with your torso make great long-head bicep exercises, as they maximize the long head's activation.
This also helps reduce shoulder strain while emphasizing different sections of the biceps.
Range of Motion
The range of motion is also important. The short head is more active in the latter part of a curl, while the long head is more active earlier in the range of motion. This means that you can selectively target each muscle easily by doing partial curls with dumbbells or on the Speediance Gym Monster 2.
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The bottom half of the curl to about 90 degrees is ideal for long head activation.
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The top half of the curl, from about 90 degrees to fully contracted, will result in better short head activation.
The Amount of Supination
Supination occurs at the radio-ulnar joint in the forearm when the palm is facing forward, while pronation is the movement that makes the palm face backward. Varying the amount of supination can also activate the different heads.
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Supinated grip (palms up): The long head is more active. For long head gains, try traditional curls with full palm-up rotation.
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Neutral or pronated position (palms in/down, thumbs forward): The short head and the brachialis are more activated. Try hammer curls or reverse curls for short head gains.
Work the Brachialis
As we mentioned before, the brachialis is a lesser-known but no less critical muscle located under the main belly of the biceps muscle. It’s responsible for increasing the bicep peak by pushing it upwards.
Flexing the arm with a neutral or pronated position in the forearm minimizes the bicep and maximizes the brachialis. Performing reverse or hammer curls can also be used to target the brachialis.
Frequently Asked Questions
What Are the Two Heads of the Biceps?
The biceps is a two-joint muscle consisting of a short head that originates at the coracoid process of the scapula and the long head, which originates at the supraglenoid tubercle of the scapula. Both groups converge and insert on the radial tuberosity of the radius.
Which Bicep Head Is Most Important?
While the long head is responsible for enhancing the bicep peak, it’s the short head that gives the bicep more width. Still, the brachialis beneath them both helps accentuate the peak by pushing up on the main mass of the bicep. So, in short, they are all important.
Train Biceps by Understanding Anatomy, Function, and Form
Understanding biceps anatomy guides smarter curls, improves symmetry, and accelerates arm growth. The biceps may seem like a single muscle, but a lot is happening beneath the surface. From the long head that creates that peak to the short head that adds width, each part of the biceps and surrounding muscles, like the brachialis and coracobrachialis, play a distinct and essential role.
With proper technique, you can target these different areas to build more powerful, better-shaped arms. By tweaking your grip, adjusting elbow position, and using targeted exercises for the long and short heads, as well as the brachialis, you can sculpt bigger, stronger, more defined arms while training smarter, not harder.
Ready to take your arm training to the next level? Explore all-in-one home training equipment like the Speediance Gym Monster 2 and Speediance Gym Pal to train smarter and more efficiently.
