The biceps brachii muscle, located on the front of the upper arm, is often the most recognizable muscle when discussing physique and strength. Many people who train their arms seek to develop a prominent, rounded mound when the muscle is flexed, commonly referred to as the “biceps peak.” Understanding which part of the muscle contributes to this peak is the initial step in purposeful training. The biceps muscle is structurally composed of two distinct sections, known anatomically as heads.
Biceps Brachii Anatomy: Understanding the Two Heads
The biceps brachii is a two-headed muscle, which is precisely what the term “biceps” means. These two sections are called the long head and the short head, named for the length of their tendons at the shoulder joint. The long head originates from the supraglenoid tubercle, a small bony projection on the scapula, and its tendon travels through the shoulder joint before connecting to the muscle belly.
The short head begins at the coracoid process of the scapula, a hook-like structure closer to the center of the body. Both heads merge to form a single, thick muscle belly in the upper arm. They insert distally via a single tendon onto the radial tuberosity of the radius, facilitating the primary functions of elbow flexion and forearm supination.
Identifying the Biceps Peak
The prominence known as the biceps peak is created by the development of the long head of the biceps brachii. When the muscle is contracted, the long head’s tendon path across the shoulder joint gives it a mechanical advantage for height. Its lateral (outer) position causes the muscle mass to bunch up and pull upward, resulting in the desired mountainous shape upon full flexion. The long head is what gives the biceps its height when viewed from the side.
The short head, situated more medially (inward), contributes primarily to the overall width and thickness of the arm. Developing the short head adds mass and fullness to the inner part of the biceps, pushing the muscle outward rather than upward. A fully developed bicep requires growth in both heads, but the long head is the specific driver of the peak’s height.
Movement Patterns for Long Head Emphasis
To selectively target the long head and encourage the development of a higher peak, training must focus on placing this head under maximum tension. The long head is maximally stretched when the shoulder is hyperextended, meaning the arm is positioned behind the torso. The incline dumbbell curl is a primary example, as sitting back on an inclined bench stretches the long head at the starting position, increasing its activation relative to the short head during the curl.
Another effective strategy involves manipulating the grip during curling movements. A neutral grip, such as in a hammer curl where the palms face each other, shifts the load toward the long head. This grip also heavily recruits the brachialis, an underlying muscle that pushes the biceps up, enhancing the peak appearance. Similarly, adopting a narrow grip on a barbell or EZ-bar curl places greater emphasis on the long head.
Concentration curls, performed with the elbow braced against the inner thigh, are also beneficial because they stabilize the shoulder and allow for a more intense peak contraction. This restricted position focuses on isolating the biceps and achieving a strong contraction. Incorporating exercises that utilize a close grip, a neutral grip, or a pre-stretched position is the approach to preferentially stimulate the long head for peak growth.
The Role of Genetics in Peak Height
While specific training techniques can optimize the development of the long head, the ultimate height of the biceps peak is largely predetermined by genetics. The most significant factor is the length of the muscle belly relative to the tendons. People with a shorter muscle belly have longer tendons, which causes the muscle tissue to bunch up when contracted.
This shorter muscle belly creates a noticeable gap between the end of the biceps muscle and the elbow joint when the arm is flexed, resulting in a naturally higher peak. Conversely, individuals with a longer muscle belly have shorter tendons, leading to a fuller, more evenly distributed muscle that extends closer to the elbow. This results in a bicep that appears flatter and less peaked, even when fully developed. Training can add mass to the existing structure, but it cannot alter the fixed points where the tendons insert into the bone.