📖 Read-only demo. All content is browsable; accounts, saved progress, and quizzes need the full app — run it locally from GitHub.

Skip to content
ArmsSource-checked

Biceps brachii

Biceps brachii

Pronunciation: BY-seps BRAY-kee-eye

Simplified side view of the upper arm showing the two-headed biceps brachii on the front of the humerus and the three-headed triceps brachii covering the back of the humerus, down to the elbow.
Arms — biceps brachii and triceps brachii (simplified). A beginner-level schematic of the upper arm's opposing muscle pair: biceps brachii and triceps brachii.
Illustration: Anatomy Learning Platform (original) · CC0-1.0 (public domain dedication)

For beginners

The 'biceps' most people picture when they think 'arm muscle' — it bends your elbow and is especially strong when your palm faces up, like in a classic dumbbell curl.

Show the advanced explanation

Because it is also a strong supinator, grip/wrist orientation changes how much the biceps contributes to a curl: a palm-up (supinated) curl emphasizes it more than a neutral-grip hammer curl, which shifts more work to the brachialis.

Structure & function

Location
The well-known two-headed muscle on the front of the upper arm.
Origin
Two heads from the scapula (long head: above the shoulder socket; short head: the coracoid process).
Insertion
Radial tuberosity of the radius.
Main action(s)
Flexes the elbow, supinates the forearm (turns the palm up — its strongest action), and assists shoulder flexion.
Joint(s) crossed
Elbow joint, shoulder joint (and the proximal radioulnar joint, for supination)
Movement plane
sagittal (flexion); transverse (supination)
Innervation
Musculocutaneous nerve (C5–C6)
In daily movement
Bringing a cup to your mouth, carrying a bag with the palm facing up, and turning a doorknob or screwdriver.
In exercise
Prime mover of elbow flexion in curls, most effective when the forearm is supinated (palm up).
Commonly confused with
Its two heads are sometimes thought to be separately trainable; in practice both heads act together and cannot be meaningfully isolated from each other with exercise selection.
Common misconceptions
'Curls alone build a complete arm' overlooks the triceps, which makes up more of the upper arm's mass than the biceps.

Exercises that use this muscle

As a primary mover

As a secondary / stabilizer

⚠ Safety note

A sudden pop with a bulge lower in the arm ('Popeye deformity') can indicate a torn biceps tendon and needs prompt medical evaluation.

Sources

“The biceps brachii flexes the elbow and supinates the forearm, and assists shoulder flexion.”

Anatomy and Physiology 2e — OpenStax, Rice University · Ch. 11.5 Muscles of the Pectoral Girdle and Upper Limbs

Peer-reviewed textbook · License: CC BY-NC-SA 4.0 · Last checked 2026-07-19

Quiz me on the Biceps brachii

Sign in to bookmark this and save notes.