The long head of the biceps is one of two muscle bellies that make up the biceps brachii, the prominent muscle on the front of your upper arm. It’s called the “long” head because its tendon takes a longer path than its partner, starting deep inside the shoulder joint and traveling through a groove in the upper arm bone before joining the short head to form the single muscle you see and feel. This unique route through the shoulder makes the long head important not just for arm strength but for shoulder stability, and it also makes the tendon vulnerable to a specific set of injuries.
Where the Long Head Attaches
The long head tendon originates from a small bony bump at the top of the shoulder socket called the supraglenoid tubercle, along with the rim of cartilage (the labrum) that surrounds the socket. The tendon’s fibers attach to the posterior (back) side of the labrum in virtually all people. A study of 101 shoulders found that 83% had a predominantly posterior attachment, and not a single shoulder showed a purely anterior one. This consistent posterior anchoring point matters because damage where the tendon meets the labrum is the basis of SLAP tears, a common shoulder injury.
From that origin inside the joint, the tendon runs forward and exits through the bicipital groove, a channel between two bony prominences on the upper arm bone. The tendon is held in place there by a sling of fibers formed mainly by the subscapularis tendon (part of the rotator cuff), with contributions from the supraspinatus tendon and the coracohumeral ligament. For the tendon to slip out of this groove, those restraining fibers have to tear first.
At the other end, both heads of the biceps merge into a single tendon that inserts on the radial tuberosity, a bump on the forearm bone near the elbow. The long head attaches to the upper portion of this bump, while the short head attaches slightly further down and toward the front.
Long Head vs. Short Head
Although the two heads work together, their distinct attachment points give them slightly different mechanical advantages. The short head originates from a bony projection on the front of the shoulder blade (the coracoid process) and never enters the shoulder joint itself. Because of this, the short head acts purely on the elbow and forearm, while the long head crosses both the shoulder and the elbow.
Biomechanical analysis shows the short head is the stronger elbow flexor, generating about 15% more flexion force relative to its load at 90 degrees of bend. The long head, by contrast, is relatively more efficient at supination (rotating your palm upward) when the forearm is already in a palm-up position. When your forearm is in a neutral or palm-down position, the short head actually supinates more efficiently. So the two heads trade off depending on your arm’s position, which is why varying your grip during curls changes which head works harder.
Its Role in Shoulder Stability
In a healthy shoulder, the long head’s contribution to overall shoulder movement and stability is relatively small. The rotator cuff muscles do most of the work keeping the ball of the upper arm bone centered in the socket. But the long head becomes significantly more important when the rotator cuff is damaged or weakened. Ten studies in a large scoping review demonstrated a shoulder-stabilizing role for the long head tendon, and six studies confirmed it acts as a depressor of the humeral head, pulling the ball of the arm bone downward to prevent it from riding up in the socket.
A study of seven patients whose long head tendon was absent found measurably more upward migration of the arm bone in the shoulder compared to intact shoulders. In people with rotator cuff tears, the long head essentially picks up the slack, helping to keep the joint aligned during movement, particularly at low angles of arm elevation (below about 30 degrees). This is one reason surgeons think carefully before cutting or detaching the long head tendon during shoulder surgery.
Common Injuries and How They Feel
The long head tendon is the most frequently injured part of the biceps, largely because of its exposed path through the shoulder joint and the bicipital groove. Problems range from chronic tendon irritation to partial tears to complete ruptures.
Tendinopathy (chronic irritation and degeneration) typically causes pain at the front of the shoulder that worsens with overhead reaching or lifting. It often develops alongside rotator cuff problems rather than in isolation, because the same overhead motions that strain the rotator cuff also load the long head tendon.
A complete rupture of the long head tendon produces a distinctive visual sign: the muscle belly slides downward toward the elbow, creating a ball-shaped bulge in the lower part of the upper arm. This is called a “Popeye” deformity because it resembles the cartoon character’s exaggerated forearm. The rupture itself may feel like a sudden pop or snap, followed by bruising and a dull ache. Most people with a complete long head rupture lose only modest arm strength because the short head and the brachialis (a deeper elbow flexor) compensate well. Older adults who aren’t highly active sometimes opt to leave it alone.
SLAP tears occur where the tendon anchors to the labrum at the top of the shoulder socket. These injuries cause deep shoulder pain, clicking or catching sensations, and pain with overhead throwing or lifting. They’re common in athletes who perform repetitive overhead motions.
Surgical Options and Recovery
When conservative treatment (rest, physical therapy, anti-inflammatory measures) fails to resolve long head tendon problems, two main surgical options exist. A tenodesis detaches the tendon from its origin inside the shoulder and reattaches it to the upper arm bone, preserving muscle length and cosmetic appearance. A tenotomy simply cuts the tendon free without reattaching it. The tenotomy is a simpler procedure with a faster initial recovery, but it carries a higher chance of the Popeye deformity and some loss of supination strength.
Full recovery from a tenodesis typically takes four to six months. Physical therapy starts about two weeks after surgery and continues for several months. People who have an open (non-arthroscopic) tenodesis tend to return to sports somewhat faster than those who have it done arthroscopically.
Training the Long Head
Because the long head crosses the shoulder joint, its fibers are stretched more when your arm is behind your body and shortened more when your arm is in front. This means exercises that position the arm behind the torso place greater tension on the long head specifically.
Incline dumbbell curls are the classic example. Sitting on a bench set to about 45 to 60 degrees with your arms hanging straight down behind your torso stretches the long head at the start of each rep, forcing it to work through a larger range. Two technique points matter: keep your elbows pointing straight down (don’t let them drift forward as you curl), and expect to use lighter weight than you would for a standard curl. The stretched starting position makes the exercise significantly harder.
Other movements that emphasize the long head include drag curls (where you pull the bar up along your body, keeping elbows behind you) and any curl performed with a narrow, supinated grip. Hammer curls and wide-grip curls, by comparison, shift more work to the short head and the brachialis. If your goal is building the peak of the biceps, the long head is the muscle you’re targeting, because it sits on the outer portion of the arm and contributes most to that rounded shape when viewed from the side.