What Muscles Do Barbell Curls Work?

The barbell biceps curl is a weightlifting exercise that uses a barbell to target the biceps brachii muscles in the upper arms. Other muscles used in the move are the synergist muscles -- brachialis and brachioradialis -- and the stabilizer muscles -- the deltoids, the trapezius, the levator scapulae and the wrist flexors. Always choose a weight that is heavy enough to present a challenge but not so heavy that you cannot complete the set with proper form.

Proper Form

Stand with your feet hip-width apart and hold the barbell in an underhand grip, with your hands shoulder-width apart. Hold the bar at your thighs with your arms straight but not locked at the elbows. This is your starting position. Exhale as you flex your elbows to curl the weight up toward your upper chest. Pause at the top of the movement – when your forearms are as close to vertical as possible -- and then slowly lower the weight to the starting position as you inhale. This completes one rep. Keep your elbows against your sides for the entire movement. Do two sets of 12 to 15 reps.

Biceps Brachii

Shortened to “biceps,” these muscles are located at the front of your upper arms. They have two heads – the long head and the short head. The long head originates at the supraglenoid tuberosity of the scapula and inserts at the radius. The short head originates at the coracoid process on the scapula and inserts at the radius at the same place as the long head. The biceps are responsible for flexing the elbow, externally rotating the forearm, and flexing and transverse flexing the shoulder.

Synergist Muscles

Synergist muscles are those that assist another muscle during the course of a movement. When you perform a barbell curl, the brachialis and the brachioradialis muscles act as synergists. The brachialis is responsible for flexing the elbow. It originates at the anterior portion of the humerus and is inserted at the coronoid process of the ulna. The brachioradialis is also responsible for flexing the elbow. It runs from the lateral condoyle at the humerus to the styloid process of the radius.

Stabilizer Muscles

Stabilizer muscles are those that work to maintain a certain posture or fixate a joint, but they do not move during the exercise. During a barbell curl, the stabilizer muscles are the anterior deltoids, the upper and middle trapezius, the levator scapulae and the wrist flexors. The anterior deltoid is located at the front of the shoulder. The upper trapezius is the upper part of the shoulder at the back, and the middle trapezius is located just below the upper traps. The levator scapulae run from the top of the shoulder to the third or fourth cervical vertebra. The wrist flexors are located in the forearm and hand.