Barbell biceps curl muscles worked

Every role here is for this technique: standing, underhand grip at shoulder width, elbows kept at the sides, from straight arms to fully bent.

What muscles does the barbell biceps curl work?

The prime movers of the barbell biceps curl are biceps brachii and brachialis. They produce elbow flexion. The synergists are brachioradialis and pronator teres. Eight stabilizers hold joints and segments still, among them the anterior deltoid, the wrist and finger flexors, and the erector spinae. The roles follow Kendall et al. (2005) and Neumann (2017).

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Joint actions and their prime movers

The joint actions of the barbell biceps curl and the prime movers that produce each
Joint action	Prime movers
Elbow flexion	Biceps brachii and brachialis

Every muscle by role

A prime mover produces the lift’s main joint action against the load; a synergist assists that action, or adds a secondary action the lift needs; a stabilizer contracts mostly isometrically to hold a joint or a segment still. A role describes what the muscle does in the technique above, not how hard it works or how much it grows.

Prime movers 2

Prime movers in the barbell biceps curl, with what each does
Muscle	What it does here
Biceps brachii	Elbow flexion with the forearm turned up
Brachialis	Elbow flexion

Synergists 2

Synergists in the barbell biceps curl, with what each does
Muscle	What it does here
Brachioradialis	Elbow flexion
Pronator teres	Elbow flexion

Stabilizers 8

Stabilizers in the barbell biceps curl, with what each does
Muscle	What it does here
Anterior deltoid	Keeping the upper arm from swinging back
Wrist and finger flexors	Holding the wrist straight and gripping the bar
Erector spinae	Stopping the trunk leaning back
Rectus abdominis	Bracing the trunk against the load
External oblique	Bracing the trunk and resisting rotation
Internal oblique	Bracing the trunk and resisting rotation
Transversus abdominis	Raising abdominal pressure to stiffen the trunk
Upper trapezius	Holding the shoulders level under the bar

Lowering and lifting

What the prime movers of the barbell biceps curl do in each half of a rep
Phase	What the prime movers do
Lowering	Biceps and brachialis lengthen as the bar comes down
Curling	They shorten to bend the elbows

Where these prime movers also work

Biceps brachii: prime mover in the bent-over barbell row, pull-up, chin-up and lat pulldown.
Brachialis: prime mover in the bent-over barbell row, pull-up, chin-up and lat pulldown.

Sources

Kendall et al., Muscles: Testing and Function, 5th ed. (2005)
Neumann, Kinesiology of the Musculoskeletal System, 3rd ed. (2017)

The cited studies that measured muscle activity used electromyography, and a larger signal need not mean more force or more growth (Vigotsky et al. (2018), Front Physiol 8:985). The roles draw on those studies for which muscles a lift involves and how two lifts differ, never to rank one muscle against another.

See these muscles in 3D

Visualiser · Biology Muscles Worked by Exercise 3D Explorer Choose a lift and a real body lights its prime movers, synergists and stabilisers, front and back, with the same muscles in 3D. Visualiser · Biology Muscle Origin, Insertion and Action Explorer Paint a muscle’s origin and insertion on real 3D bones, or click a bone to see what attaches to it.