The close grip EZ bar curl is a popular isolation exercise designed to increase the size and strength of the upper arm musculature. This movement uses a specialized EZ (or cambered) bar, which features an undulating shape that allows the hands to rest in a semi-supinated position, intermediate between a palms-up and a neutral grip. The close grip variation specifies holding the bar on the innermost curves, placing the hands closer together than shoulder-width. This combination of grip width and bar design significantly changes the muscle recruitment pattern compared to a standard straight bar curl.
Targeting the Biceps Brachii
The primary muscle targeted by this exercise is the biceps brachii, the two-headed muscle on the front of the upper arm responsible for flexing the elbow and supinating the forearm. While both heads of the biceps—the long head (outer) and the short head (inner)—are always active during any curl, the close grip EZ bar curl places a greater emphasis on the long head. The long head is responsible for the peak or height of the biceps muscle, originating from the scapula and running along the outside of the upper arm.
The close grip forces the arms into a more internally rotated position, which increases the stretch and tension placed on the long head of the biceps. This manipulation of the grip width prioritizes development in that specific area. The biceps brachii is the main engine for the curling motion, contracting concentrically as the weight is lifted toward the shoulders. Focusing on a powerful squeeze at the top of the movement helps maximize the contraction.
Forearm and Stabilizer Engagement
Although the biceps brachii is the main mover, several other muscles work as crucial assistants during the close grip EZ bar curl. The brachialis, a broad muscle located deep beneath the biceps, is heavily involved in pure elbow flexion and is activated regardless of the hand position. Since the EZ bar places the hands in a semi-supinated position, it increases the engagement of the brachialis compared to a fully supinated straight bar curl.
The brachioradialis, a prominent muscle of the upper forearm, also plays a role as an elbow flexor. This muscle is engaged when the forearm is in a semi-supinated or neutral position, which is the grip angle provided by the EZ bar’s curves. Other muscles, such as the anterior deltoids and the core muscles, work isometrically to stabilize the body and prevent unwanted momentum during the lift.
How the EZ Bar and Close Grip Alter Muscle Focus
The unique design of the EZ bar and the choice of a close grip work together to shift the muscular focus of the exercise. The close grip positions the hands inward, which mechanically increases the demand on the long head of the biceps, helping to develop the muscle’s peak. This is the fundamental difference between this variation and a wide grip, which would place greater emphasis on the short head.
The wavy, cambered shape of the EZ bar allows the wrists to remain in a slightly more natural, semi-supinated angle than a straight bar. This reduced strain on the wrist and elbow joints prevents lifters from compensating for discomfort. It allows them to fully concentrate tension on the intended muscles: the biceps, brachialis, and brachioradialis.