What is the inner and outer bicep? An anatomical and exercise guide

October 2, 2025 •

4 min read

Did you know the bicep is actually comprised of two distinct muscle heads, not just one? Understanding this fundamental anatomical fact is key to building well-proportioned, powerful arms. This guide explains exactly what is the inner and outer bicep, and how to train them effectively.

Quick Summary

The 'inner bicep' refers to the short head, located on the medial side of the upper arm, while the 'outer bicep' is the long head, positioned on the lateral side. These two heads work together but can be emphasized individually with specific grip and arm position variations.

Key Points

Two Heads: The bicep is composed of two distinct parts: the short head (inner) and the long head (outer), which have different origins on the shoulder blade.
Inner Bicep (Short Head): Found on the medial side of the arm, the short head is targeted with wide-grip or arms-in-front exercises, contributing to the muscle's width.
Outer Bicep (Long Head): Located on the lateral side, the long head creates the bicep's peak and is emphasized with narrow-grip or arms-behind-the-body movements.
Variable Training is Key: To ensure balanced development, incorporate a variety of exercises that manipulate your grip and arm position to activate both heads effectively.
Aesthetic vs. Function: The long head gives the bicep its height (peak), while the short head adds to its overall thickness. Both are essential for balanced aesthetics and functional strength.
Proper Form is Paramount: Using controlled movements and focusing on the correct form prevents injury and ensures you are targeting the intended muscle head for maximum benefit.

Demystifying the Biceps Brachii: The Two-Headed Muscle

The term "biceps" comes from the Latin for "two heads," a fitting name for this key muscle group. The biceps brachii is composed of two distinct parts that work together to flex the elbow and supinate the forearm. Often, exercisers refer to these as the 'inner' and 'outer' bicep, but their official names are the short head and the long head. Both heads originate from different points on the shoulder blade (scapula) but converge into a single tendon that inserts into the radius bone of the forearm.

This two-part structure means that while all bicep exercises engage both heads to some degree, subtle adjustments in your technique can place more emphasis on one head over the other. Understanding this is crucial for anyone looking to correct muscle imbalances, improve arm aesthetics, or enhance functional strength.

The Anatomy of the Inner Bicep (Short Head)

The short head is located on the inside of your upper arm, closer to your torso. It originates from the coracoid process, a small, hook-like bony projection on the scapula. Due to its position, the short head is more involved in movements where your arm is in front of your body or when using a wide grip. Developing the short head contributes to the overall width and thickness of your biceps, giving them a more massive appearance, especially when viewed from the front.

Exercises to Target the Short Head:

Wide-Grip Barbell Curls: Holding the barbell with a grip wider than shoulder-width places greater emphasis on the short head. Maintain a controlled motion without using momentum.
Concentration Curls: Performed while seated, this exercise effectively isolates the bicep. Resting your elbow against your inner thigh prevents cheating and forces the short head to do the majority of the work.
Preacher Curls: Using a preacher bench to pin your upper arm eliminates shoulder involvement and allows for maximum isolation. A wider grip on the EZ-bar can further focus on the short head.
Spider Curls: This movement involves lying face down on an incline bench, allowing your arms to hang straight down. The position minimizes momentum and promotes a strong contraction in the short head.

The Anatomy of the Outer Bicep (Long Head)

The long head is on the outside of the upper arm, running along the bicep's peak. It originates from the supraglenoid tubercle, a small bump at the top of the shoulder socket. The long head is more active in movements where your arm is positioned behind your body or when using a narrow grip. A well-developed long head is what creates the coveted "peak" or height of the biceps, giving your arm a more prominent and defined look from the side.

Exercises to Target the Long Head:

Hammer Curls: Performing curls with a neutral grip (palms facing each other) primarily targets the long head and the brachialis muscle underneath. This also adds overall arm thickness.
Incline Dumbbell Curls: Lying back on an incline bench places your arms behind your body, putting the long head in a pre-stretched position. This leads to a greater range of motion and an intense stretch at the bottom of the movement.
Narrow-Grip Barbell Curls: A grip closer than shoulder-width, with your elbows tucked, will force the long head to bear more of the load.
Cable Curls (Rope Attachment): The constant tension from the cable machine can be highly effective. Using a rope attachment with a neutral grip and curling can isolate the long head.

Comparison Table: Inner (Short) Head vs. Outer (Long) Head


Feature	Inner Bicep (Short Head)	Outer Bicep (Long Head)
Location	Medial (inside) part of the upper arm	Lateral (outside) part of the upper arm
Origin	Coracoid process of the scapula	Supraglenoid tubercle of the scapula
Aesthetic Result	Contributes to the width and thickness	Creates the bicep's peak and height
Optimal Grip	Wide grip (barbell), neutral to supinated	Narrow grip (barbell), neutral grip (hammer)
Arm Position	Arms in front of the torso	Arms behind the torso
Best Exercises	Wide-Grip Curls, Preacher Curls	Incline Dumbbell Curls, Hammer Curls

How to Balance Your Bicep Training

For balanced and complete development, it is vital to incorporate a variety of exercises that target both the long and short heads. Simply doing standard barbell curls won't achieve the best results, as this primarily works both heads simultaneously without emphasizing one over the other. The key is to include variations that alter your grip and arm position, forcing each head to take on a larger role.

Additionally, don't neglect the other muscles of the upper arm, such as the brachialis and brachioradialis. Training these can contribute to overall arm size and strength, and even help 'push' the biceps up, further enhancing their peak and appearance. Consistency and proper form are far more important than lifting heavy weights. Listen to your body and focus on the mind-muscle connection to maximize your results.

For more in-depth scientific explanations of muscle physiology and anatomy, an excellent resource is the National Center for Biotechnology Information (NCBI) at https://www.ncbi.nlm.nih.gov/.

Conclusion

The notion of an "inner" and "outer" bicep is a common gym term that refers to the short and long heads of the biceps brachii. While they function as a single unit, their distinct origins and insertions mean they can be preferentially stimulated through exercise selection and technique adjustments. By diversifying your bicep routine to include a mix of wide-grip, narrow-grip, and neutral-grip exercises, you can ensure comprehensive development and build impressive, well-proportioned arms. Remember, balanced training is the fastest path to achieving your fitness goals.

Frequently Asked Questions

While it's anatomically impossible to completely isolate one bicep head from the other, specific exercises can change the emphasis. By adjusting your grip and arm position, you can make one head work harder than the other, allowing for targeted development.

The main difference lies in their origin and position. The long head originates outside the shoulder joint and contributes to the bicep's peak, while the short head originates inside the shoulder joint and adds to the bicep's width.

Exercises that place your arms behind your body and use a narrow or neutral grip are most effective. Incline dumbbell curls and hammer curls are two of the best options for emphasizing the long head and building a better bicep peak.

To focus on the inner bicep (short head), you should use a wide grip and perform exercises that keep your arms in front of your body. Wide-grip barbell curls, preacher curls, and concentration curls are excellent choices for adding width to your biceps.

Yes, absolutely. A wider-than-shoulder-width grip tends to place more stress on the short (inner) head, while a narrower-than-shoulder-width grip puts more emphasis on the long (outer) head.

Yes, for balanced strength, aesthetics, and injury prevention, it is important to train both heads of the biceps. Over-emphasizing one head over the other can lead to muscle imbalances.

Pay attention to which area of the muscle you feel contracting most. For example, during wide-grip curls, you should feel the contraction more on the inner part of your bicep. Conversely, with narrow-grip or hammer curls, you will feel it more prominently on the outer part.