{"schemaVersion":1,"id":"en-anatomy-biceps-brachii","type":"anatomy","pillar":"body","locale":"en","translationGroupId":"anatomy-biceps-brachii","slugPath":"body/muscles/biceps-brachii","title":"Biceps brachii","shortTitle":"Biceps","summary":"The biceps brachii sits on the front of the upper arm and crosses both the shoulder and the elbow. It flexes the elbow, but its most specific function is supination of the forearm.","level":"beginner","estimatedMinutes":8,"synonyms":["biceps","biceps brachii","front of the arm","elbow flexor"],"blocks":[{"id":"b1","type":"heading","level":2,"text":"Where the biceps brachii is located","anchor":"where-the-biceps-brachii-is-located"},{"id":"b2","type":"paragraph","content":[{"kind":"text","value":"The biceps brachii forms the well-known relief on the front of the upper arm. It is thinner than it looks: beneath it lies the brachialis, deeper, which supplies a large share of the force of elbow flexion. The biceps is a biarticular muscle, meaning that it crosses both the shoulder and the elbow."}]},{"id":"b3","type":"heading","level":3,"text":"Origins","anchor":"origins"},{"id":"b4","type":"paragraph","content":[{"kind":"text","value":"Its two heads both start on the shoulder blade, but at points far apart."}]},{"id":"b5","type":"list","ordered":false,"items":[[{"kind":"text","value":"The long head arises from the supraglenoid tubercle, above the socket of the shoulder joint. Its tendon crosses the joint and then runs down the intertubercular groove of the humerus."}],[{"kind":"text","value":"The short head arises from the tip of the coracoid process, a bony prominence at the front of the shoulder, which it shares with the coracobrachialis."}]]},{"id":"b6","type":"heading","level":3,"text":"Insertion","anchor":"insertion"},{"id":"b7","type":"paragraph","content":[{"kind":"text","value":"The two heads merge into a single muscle belly that continues as a tendon attached to the radial tuberosity, a bump on the radius just below the elbow. A fibrous expansion, the bicipital aponeurosis, leaves that tendon and spreads into the fascia of the forearm."}]},{"id":"b8","type":"heading","level":3,"text":"Innervation and palpable landmarks","anchor":"innervation-and-palpable-landmarks"},{"id":"b9","type":"paragraph","content":[{"kind":"text","value":"Innervation comes from the musculocutaneous nerve, from roots C5 and C6. The muscle belly can be felt over the whole front of the upper arm; its terminal tendon stands out at the crease of the elbow when the arm is flexed against a resistance."}]},{"id":"b10","type":"heading","level":2,"text":"What the biceps brachii does","anchor":"what-the-biceps-brachii-does"},{"id":"b11","type":"paragraph","content":[{"kind":"text","value":"Its attachment on the radius, a bone that rotates on itself, gives the biceps a function the other elbow flexors do not have."}]},{"id":"b12","type":"list","ordered":false,"items":[[{"kind":"strong","value":"Supination of the forearm"},{"kind":"text","value":": it turns the palm upward. This is its most powerful action, and it is greatest when the elbow is flexed."}],[{"kind":"strong","value":"Elbow flexion"},{"kind":"text","value":": it brings the forearm toward the upper arm, in partnership with the brachialis."}],[{"kind":"strong","value":"Shoulder flexion"},{"kind":"text","value":": a modest action, produced mainly by the short head."}]]},{"id":"b13","type":"definition","term":"Supination","definition":"Rotation of the forearm that turns the palm of the hand upward, bringing the radius back parallel to the ulna. The opposite movement is called pronation.","alsoKnownAs":["outward rotation of the forearm"]},{"id":"b14","type":"paragraph","content":[{"kind":"text","value":"This double function explains why the position of the hand changes how an elbow flexion feels: with the palm up, the biceps is in its most favourable configuration; with the palm down, it loses its supinator role and the brachioradialis takes a more visible share of the work."}]},{"id":"b15","type":"heading","level":2,"text":"Seeing the biceps in motion","anchor":"seeing-the-biceps-in-motion"},{"id":"b16","type":"scene3d","sceneId":"grand-dorsal-tirage","title":"The biceps during a pull","intro":"The scene follows the arm through a pulling movement. The biceps shortens as the elbow closes, while the latissimus dorsi brings the arm toward the trunk. Without the 3D, the idea is simple: the biceps pulls the radius upward, which closes the elbow and turns the palm toward the face.","initialStepId":"step-2","accessibility":{"textAlternative":"A three-dimensional diagram of the trunk seen from behind, arms raised diagonally overhead as at the start of a vertical pull. The ribcage, the spine, the pelvis, both shoulder blades, both humeri and the forearms are shown in bone tones, with a small dark sphere marking each shoulder joint. In terracotta, latissimus dorsi forms a wide fan on each side, spreading from the lower back and iliac crest and narrowing as it rises to the top of the humerus. The trapezius is split into three bands — upper towards the shoulder, middle towards the spine of the scapula, lower rising from the mid back — and biceps brachii runs along the front of the arm. A two-and-a-half-second animation brings the humeri back alongside the trunk in adduction while the shoulder blades descend and latissimus dorsi shortens. The volumes are stylised: this is a teaching diagram, not an exact anatomical reconstruction.","structures":[{"label":"Latissimus dorsi","description":"A broad fan arising from the spinous processes of the lower thoracic and lumbar vertebrae, the thoracolumbar fascia, the iliac crest and the last three or four ribs. All its fibres converge on the bicipital groove of the humerus: it pulls the arm down, back and towards the trunk.","href":"/en/body/muscles/latissimus-dorsi"},{"label":"Shoulder blade","description":"A flat bone gliding over the back of the ribcage, with no direct joint to the spine. In a pull it depresses and rotates downwards: without that motion the humerus jams against the acromion and the range gets paid for elsewhere.","href":"/en/movements/vertical-pull"},{"label":"Trapezius","description":"Its three portions pull the shoulder blade in three directions: the upper elevates it, the middle draws it towards the spine, the lower depresses it. In a vertical pull, the lower portion is the direct partner of latissimus dorsi.","href":"/en/body/muscles/trapezius"},{"label":"Biceps brachii","description":"Two heads arising from the scapula and inserting on the radial tuberosity. It flexes the elbow and supinates the forearm: in a pull it shortens the distance between hand and shoulder while latissimus dorsi moves the arm.","href":"/en/body/muscles/biceps-brachii"},{"label":"Insertion on the humerus","description":"The tendon of latissimus dorsi attaches in the floor of the bicipital groove, at the very top of the humerus. A wide origin across the whole lower back and a narrow insertion high on the arm: that convergence is what gives the muscle its fan shape.","href":"/en/body/muscles/latissimus-dorsi"}],"steps":[{"id":"charpente","title":"Three parts to connect","body":"A pull connects the hand to the pelvis through three moving parts: the humerus, the shoulder blade gliding over the ribcage, and the spine acting as the fixed point. Latissimus dorsi is the only muscle to span almost that whole path, from pelvis to arm."},{"id":"origine-large","title":"A very wide origin","body":"Latissimus dorsi anchors across almost the whole lower back: the lower thoracic and lumbar spinous processes, the thoracolumbar fascia, the iliac crest and the lowest ribs. That origin surface is what gives it its strength, and why a pull is felt all the way down to the pelvis."},{"id":"insertion-etroite","title":"A narrow insertion","body":"All those fibres converge into a flat tendon attached in the floor of the bicipital groove of the humerus. Wide below, narrow above: the pull concentrates on a single point of the arm, which makes it strongly directional — downwards and backwards."},{"id":"tirage","title":"The pull","body":"The humeri leave the overhead position and adduct back alongside the trunk while the shoulder blades depress and rotate downwards. Latissimus dorsi shortens, the lower trapezius holds the blade down and the elbow bends: arm motion and shoulder-blade motion cannot be separated."},{"id":"trapezes-et-biceps","title":"Trapezius and biceps","body":"The lower trapezius depresses the shoulder blade, the middle trapezius draws it towards the spine, and biceps brachii flexes the elbow to bring the hand closer to the shoulder. A pull is never an isolated back exercise: it is coordination between arm, shoulder blade and spine."}],"license":"Z-Anatomy et BodyParts3D — CC-BY-SA 4.0"}},{"id":"b17","type":"heading","level":2,"text":"The movements it takes part in","anchor":"the-movements-it-takes-part-in"},{"id":"b18","type":"paragraph","content":[{"kind":"text","value":"The biceps accompanies every pulling movement. In the "},{"kind":"link","value":"vertical pull","href":"/en/movements/vertical-pull","external":false},{"kind":"text","value":", it flexes the elbow while the "},{"kind":"link","value":"latissimus dorsi","href":"/en/body/muscles/latissimus-dorsi","external":false},{"kind":"text","value":" draws the arm down. In the "},{"kind":"link","value":"horizontal pull","href":"/en/movements/horizontal-pull","external":false},{"kind":"text","value":", it works the same way, with a contribution that depends on the grip used."}]},{"id":"b19","type":"paragraph","content":[{"kind":"text","value":"It is also involved in everyday carrying tasks, where its supination function serves to orient the hand before flexion even begins."}]},{"id":"b20","type":"heading","level":2,"text":"Related structures","anchor":"related-structures"},{"id":"b21","type":"heading","level":3,"text":"Synergists","anchor":"synergists"},{"id":"b22","type":"list","ordered":false,"items":[[{"kind":"text","value":"The brachialis, lying beneath the biceps, is the most consistent flexor of the elbow because its attachment on the ulna makes it indifferent to rotation of the forearm."}],[{"kind":"text","value":"The "},{"kind":"link","value":"brachioradialis","href":"/en/body/muscles/forearm","external":false},{"kind":"text","value":" contributes to flexion, especially when the forearm is in an intermediate position."}],[{"kind":"text","value":"The "},{"kind":"link","value":"latissimus dorsi","href":"/en/body/muscles/latissimus-dorsi","external":false},{"kind":"text","value":" and the "},{"kind":"link","value":"trapezius","href":"/en/body/muscles/trapezius","external":false},{"kind":"text","value":" create the shoulder and shoulder blade movement that makes the pull possible."}]]},{"id":"b23","type":"heading","level":3,"text":"Antagonists","anchor":"antagonists"},{"id":"b24","type":"list","ordered":false,"items":[[{"kind":"text","value":"The "},{"kind":"link","value":"triceps brachii","href":"/en/body/muscles/triceps-brachii","external":false},{"kind":"text","value":" and the anconeus extend the elbow."}],[{"kind":"text","value":"The pronator teres and the pronator quadratus produce pronation, the opposite action to supination."}]]},{"id":"b25","type":"heading","level":2,"text":"What the 3D model simplifies","anchor":"what-the-3d-model-simplifies"},{"id":"b26","type":"callout","tone":"limit","title":"A muscle rarely on its own","content":[[{"kind":"text","value":"The scene puts the biceps in the foreground, whereas elbow flexion is shared work. The brachialis, lying deep, is not visible but takes part in every repetition; crediting the movement entirely to the biceps is a simplification."}],[{"kind":"text","value":"The biceps is also a muscle with marked anatomical variation. A supernumerary head is described in part of the population, and the length of the muscle belly relative to the tendon changes clearly from person to person. The model shows the most common arrangement, not an individual anatomy."}]]},{"id":"b27","type":"heading","level":2,"text":"Sources","anchor":"sources"},{"id":"b28","type":"sourceList","title":"Key sources","referenceIds":["standring2020","neumann2016"]},{"id":"b29","type":"shapierAction","actionId":"exercises-curl-biceps","label":"See the biceps curl exercise","description":"Performing the biceps curl step by step is done in Shapier; Body Lab only explains why this elbow flexion movement recruits the biceps.","webTarget":"https://shapier.app/en/exercises/curl-biceps","appTarget":"shapier://exercises/curl-biceps"},{"id":"b30","type":"quiz","title":"Check my understanding","questions":[{"id":"q1","prompt":"What is the most specific action of the biceps brachii?","choices":[{"id":"q1c1","label":"Supination of the forearm","correct":true,"explanation":"Turning the palm upward is its most powerful action, greatest with the elbow flexed, and the other elbow flexors cannot do it."},{"id":"q1c2","label":"Elbow flexion","correct":false,"explanation":"It is indeed one of its functions, but it is shared with the brachialis and is in no way specific to the biceps."},{"id":"q1c3","label":"Shoulder flexion","correct":false,"explanation":"It exists, but the page describes it as a modest action, produced mainly by the short head."}]},{"id":"q2","prompt":"Which muscles supply the force of an elbow flexion?","choices":[{"id":"q2c1","label":"The biceps and the brachialis, together","correct":true,"explanation":"The page notes that the deeper brachialis supplies a large share of the force and takes part in every repetition."},{"id":"q2c2","label":"The biceps alone","correct":false,"explanation":"That is the impression given by the visible relief of the arm, but crediting the whole flexion to the biceps is presented as a simplification."},{"id":"q2c3","label":"The triceps brachii","correct":false,"explanation":"It is the antagonist: it extends the elbow instead of flexing it."}]},{"id":"q3","prompt":"What changes when an elbow flexion is done with the palm down?","choices":[{"id":"q3c1","label":"The biceps loses its supinator role and the brachioradialis does more work","correct":true,"explanation":"The page explains that with the palm down, the brachioradialis takes a more visible share of the work."},{"id":"q3c2","label":"Nothing, hand position makes no difference","correct":false,"explanation":"The page says the opposite: hand position changes how an elbow flexion feels."},{"id":"q3c3","label":"The biceps becomes more effective","correct":false,"explanation":"Its most favourable configuration is the opposite: palm up, where it can play its supinator role."}]}]},{"id":"b31","type":"relatedContent","title":"Read next","targetIds":["en-anatomy-forearm","en-anatomy-latissimus-dorsi","en-anatomy-triceps-brachii"]}],"relations":[{"type":"produces-movement","targetId":"en-movement-vertical-pull"},{"type":"produces-movement","targetId":"en-movement-horizontal-pull"},{"type":"uses-structure","targetId":"en-anatomy-latissimus-dorsi"},{"type":"next-step","targetId":"en-mechanism-how-muscle-grows"}],"authors":["equipe-editoriale-shapier"],"reviewers":["Thanh Chau"],"references":[{"id":"standring2020","authors":"Standring S","year":2020,"title":"Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition","source":"Elsevier","kind":"book","url":"https://shop.elsevier.com/books/grays-anatomy/standring/978-0-7020-7705-0"},{"id":"neumann2016","authors":"Neumann DA","year":2016,"title":"Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation, 3rd edition","source":"Elsevier","kind":"book","url":"https://shop.elsevier.com/books/kinesiology-of-the-musculoskeletal-system/neumann/978-0-323-28753-1"}],"review":{"publishedAt":"2026-08-02","reviewedAt":"2026-08-02","reviewDueAt":"2027-08-02","evidenceLevel":"established"},"limitations":["The brachialis, lying beneath the biceps and the main flexor of the elbow, does not appear distinctly in the 3D scene.","The path of the long head tendon in the groove of the humerus is drawn schematically, without the sheath or the capsule that surround it.","Anatomical variation is common for this muscle, in particular a third head found in part of the population."],"seo":{"title":"Biceps brachii — anatomy, heads and role in supination","description":"Origins, insertion and actions of the biceps brachii, its supination function, its synergists and the pulling movements that recruit it.","canonicalPath":"/en/body/muscles/biceps-brachii","image":"/og/en/anatomy-biceps-brachii.png"},"app":{"offlineEligible":true},"version":1}