Biceps
The biceps brachii, commonly referred to as the biceps, is a prominent two-headed muscle on the anterior (front) aspect of the upper arm. It is one of the most recognizable muscles in the human body and plays a crucial role in forearm movement and shoulder stability. The name "biceps" comes from the Latin words bis meaning "two" and caput meaning "head," referring to its two distinct proximal heads12.
Anatomy
The biceps brachii is a large, thick, fusiform muscle located in the anterior compartment of the arm. It consists of two heads that originate from the scapula and merge to insert on the radius1.
Long Head
The long head (caput longum) originates from the supraglenoid tubercle of the scapula, located within the shoulder joint capsule. Its tendon passes through the bicipital groove (also called the intertubercular sulcus) of the humerus and is enclosed in a synovial sheath. This head forms the lateral (outer) portion of the muscle belly when viewed from the front12.
Short Head
The short head (caput breve) originates from the coracoid process of the scapula, along with the coracobrachialis tendon. This head forms the medial (inner) portion of the muscle belly and is positioned more interiorly than the long head1.
Insertion
Both heads converge in the middle third of the upper arm to form a common muscle belly. Distally, the biceps inserts via a strong tendon onto the radial tuberosity of the radius bone. A secondary insertion comes from the bicipital aponeurosis (lacertus fibrosus), a broad fascial expansion that blends with the deep fascia of the forearm21.
Innervation
The biceps brachii is innervated by the musculocutaneous nerve, a terminal branch of the lateral cord of the brachial plexus. This nerve carries fibers from the fifth, sixth, and seventh cervical spinal roots (C5, C6, C7)1.
Functions
The biceps brachii is a multifunctional muscle that performs three primary actions12:
Forearm Supination
The biceps is the primary supinator of the forearm. It is most effective at supination when the elbow is flexed at 90 degrees. When combined with elbow flexion, the biceps provides powerful supination force for activities like turning a doorknob or screwdriver1.
Elbow Flexion
The biceps is a strong flexor of the elbow joint, particularly when the forearm is in a supinated position. However, the brachialis muscle is actually the primary elbow flexor when the forearm is in a neutral or pronated position. The biceps assists the brachialis and brachioradialis in elbow flexion1.
Shoulder Flexion
The long head of the biceps crosses the shoulder joint and assists in arm flexion. It also contributes to passive stabilization of the glenohumeral (shoulder) joint by helping to stabilize the humeral head within the glenoid fossa1.
The antagonist to the biceps is the triceps brachii, which extends the elbow1.
Best Exercises for Biceps
The biceps is targeted through various curl variations and pulling movements. Below are some of the most effective exercises for developing bicep strength and size1:
Barbell Curl
The barbell curl is a fundamental bicep exercise that allows for heavy loading. Using a shoulder-width or slightly wider grip emphasizes both heads of the biceps. This is one of the most effective mass-building exercises for the biceps1.
Dumbbell Curl
Dumbbell curls allow for independent arm training and a greater range of motion. The neutral (hammer) grip position targets the biceps differently and also engages the brachialis and brachioradialis muscles.
Preacher Curl
The preacher curl, performed on an inclined bench, provides maximal isolation of the biceps by eliminating momentum. This exercise is excellent for developing the bicep peak.
Incline Dumbbell Curl
Performing curls on an incline bench stretches the long head of the biceps across the shoulder joint, providing greater activation and development of this head.
Hammer Curl
The hammer curl uses a neutral grip (palms facing inward) and targets the biceps brachialis, brachioradialis, and both heads of the biceps equally.
Chin-Up
The chin-up (pull-up with an underhand grip) is one of the best compound exercises for building bicep strength and size, as it involves both elbow flexion and forearm supination.
Cable Curl
Cable curls provide constant tension throughout the movement, which can be particularly effective for muscle growth.
Clinical Significance
Biceps tendon injuries are relatively uncommon but can cause significant functional impairment if not properly treated34.
Distal Biceps Tendon Rupture
A distal biceps tendon rupture is a complete tear of the tendon that attaches the biceps to the radial tuberosity. This injury typically occurs in middle-aged men during activities involving forced extension of a flexed elbow4.
The incidence of distal biceps tendon rupture is approximately 2.55 per 100,000 patient-years, with over 95% of cases occurring in men between 40 and 60 years of age. The typical mechanism of injury is an eccentric (lengthening) contraction of the biceps while the elbow is forced into extension4.
Symptoms include sudden pain in the front of the elbow, a "popping" sensation, weakness in elbow flexion and forearm supination, and bruising or swelling. The biceps muscle belly may retract toward the shoulder, creating a visible deformity3.
Treatment depends on the patient's functional demands. Surgical repair is typically recommended for active individuals who require full strength in supination and flexion. Conservative treatment may be considered for older patients with lower physical demands, though it typically results in 30-40% loss of flexion strength and 40-50% loss of supination strength4.
Proximal Biceps Tendon Issues
The long head of the biceps is commonly involved in shoulder pathology, including biceps tendinitis, biceps instability, and SLAP (Superior Labrum Anterior and Posterior) tears. These conditions are often treated conservatively with physical therapy, anti-inflammatory medications, or in some cases, surgical intervention1.
Biceps tendonitis can cause anterior shoulder pain and is often associated with underlying rotator cuff pathology. Treatment typically involves rest, ice, NSAIDs, and physical therapy1.