The biceps brachii muscle, which creates the visible mass on the front of the upper arm, is composed of two distinct sections. Many people use the concentration curl, a classic isolation movement, to build this muscle, but they often wonder if the exercise specifically targets the outer portion of the muscle. This article will explore the anatomy and biomechanics of the concentration curl to determine if it is an effective exercise for developing the long head of the biceps.
Biceps Anatomy: The Long Head vs. Short Head
The biceps brachii is a two-headed muscle, with each head originating from a different point on the scapula. The long head, which is positioned on the outside of the arm, originates from the supraglenoid tubercle, just above the shoulder joint. Because of this high attachment point, the long head crosses the shoulder joint, making its function highly dependent on arm position.
The short head, which lies on the inside of the arm, originates from the coracoid process of the scapula. Both heads merge to form a single muscle belly before inserting onto the radial tuberosity, just below the elbow. The long head is often associated with the visible “peak” of the biceps, while the short head contributes more to the muscle’s overall width.
The Mechanics of the Concentration Curl
The concentration curl is a single-joint exercise performed while seated, where the working elbow is braced against the inside of the thigh. This positioning serves to eliminate momentum and minimize the involvement of secondary muscle groups. By stabilizing the upper arm, the exercise forces the biceps brachii to perform the vast majority of the work.
The primary actions of the concentration curl are elbow flexion and forearm supination, which is the act of turning the palm upward. This movement isolates the biceps to an extreme degree. Studies have shown it to elicit some of the highest overall activation levels of the biceps brachii compared to other curling variations. The strict form ensures that the tension remains almost entirely on the target muscle.
Muscle Recruitment: Does Isolation Favor the Long Head?
Biomechanical principles suggest that to preferentially recruit a muscle head, it must be placed in a stretched position at the start of the movement. For the long head of the biceps, this means positioning the shoulder in extension, such as in an incline dumbbell curl. The standard concentration curl, with the elbow braced against the thigh, places the shoulder in slight flexion, which tends to slightly shorten the long head.
However, the concentration curl is widely regarded as a superior exercise for developing the bicep peak, which is heavily influenced by the long head. This is due to the extreme isolation and high overall activation it achieves, forcing both heads to work maximally with virtually no assistance. While the shoulder position may not provide the maximum stretch for the long head, the complete removal of momentum and the intense peak contraction make it a highly effective growth stimulus for the entire biceps complex.
Optimizing Form for Long Head Development
To maximize the recruitment of the long head during a concentration curl, subtle adjustments can be made to the body and grip position. Since the long head is most active when lengthened, leaning slightly further forward will allow the arm to hang more vertically and put the shoulder into a more neutral or extended position. This tweak provides a better stretch on the long head at the beginning of the curl.
Another modification is to perform the exercise using a neutral grip, often called a hammer concentration curl. This grip shifts some of the load from the biceps brachii to the brachialis and brachioradialis muscles. This can allow the long head to be relatively more stressed in its role as a stabilizer and elbow flexor. Focusing on a slow, controlled negative phase, where the weight is lowered slowly, can also extend the time under tension for the long head and enhance its development.