The close grip EZ bar curl is an isolation exercise that primarily works the biceps, with particular emphasis on the long (outer) head. It also recruits two important supporting muscles: the brachialis, which sits underneath the biceps, and the brachioradialis, the thick muscle running along the top of your forearm. Together, these three muscles handle all the work of bending your elbow against resistance.
How Grip Width Changes Which Part of the Biceps Works Harder
Your biceps has two distinct portions: a long head on the outer side of your arm and a short head on the inner side. Using a narrower than shoulder-width grip shifts more of the workload onto the long head. This is the portion most visible when you flex from the side, and it contributes to the “peak” shape many people train for. A wider grip, by contrast, shifts emphasis toward the short head, which adds width when viewed from the front.
The close grip also allows for a slightly greater range of motion since your hands are closer together, which can increase the stretch on the biceps at the bottom of each rep. That added stretch may translate to more total muscle activation per rep compared to a wider hand position.
The Brachialis and Brachioradialis
While the biceps gets top billing, two other muscles do real work during this exercise. The brachialis sits directly beneath the biceps and assists with elbow flexion regardless of how your forearm is rotated. Building the brachialis pushes the biceps up from underneath, making your upper arm look thicker overall.
The brachioradialis runs from just above your elbow down into your forearm. It gets pulled into the movement partly because of the EZ bar’s angled grip, which places your hands in a semi-supinated position (palms angled slightly inward rather than facing straight up). Research from Marcolin and colleagues found that EZ bar curls produced significantly higher brachioradialis activation than dumbbell curls through both the lifting and lowering phases. So if forearm development matters to you, the EZ bar has a measurable advantage over dumbbells for that muscle.
Why the EZ Bar Shape Matters
A straight barbell forces your wrists into full supination, meaning your palms face directly upward throughout the curl. That position creates more stress on the wrist joint, especially under load. The EZ bar’s W-shaped camber angles your grip inward, reducing that strain considerably. If you have any wrist tightness or limited mobility, you’ll notice the difference immediately.
There is a tradeoff. Full supination with a straight bar activates both functions of the biceps more completely, which is why some research from Coratella and colleagues found slightly higher biceps activation with a straight bar compared to an EZ bar. In practice, the difference is modest, and many lifters find they can use heavier loads or train more frequently with the EZ bar because their wrists aren’t a limiting factor. For most people, that consistency matters more than a small edge in peak muscle activation.
Form That Keeps Tension on the Biceps
The biggest mistake people make is letting their elbows drift forward or flare outward during the curl. Once your elbows move away from your sides, your shoulders start absorbing work that should go to your biceps. Pin your elbows to your ribs and keep them there for the entire rep. The only joint moving should be your elbow.
Shoulder position matters too. If you hunch forward or let your shoulders roll inward, you reduce biceps engagement and add unnecessary stress to your shoulder joint. Pull your shoulder blades back and down before you start your set, brace your core, and maintain that posture throughout. The EZ bar naturally reduces internal shoulder rotation compared to a straight bar, which makes it a more comfortable option for people with shoulder sensitivity.
Control the lowering phase. Letting the bar drop quickly wastes half the rep. EZ bar curls produced greater muscle activation during the eccentric (lowering) phase compared to dumbbell curls in EMG testing, but only if you actually resist gravity on the way down. Aim for a two to three second descent on every rep.
One more detail: stop the curl when your hands reach about shoulder height. Curling higher than that shifts the load from your biceps to your front deltoids, which defeats the purpose of an isolation exercise.
Sets, Reps, and Loading
For muscle growth, 3 to 4 sets of 8 to 12 reps at roughly 65 to 75 percent of your max is the standard recommendation. The close grip EZ bar curl is best used as an accessory movement rather than a primary lift, so place it after your heavier compound work like rows or chin-ups.
Because this is a single-joint exercise, progressive overload doesn’t need to come exclusively from adding weight. You can add a rep to each set, slow down your tempo, or add a brief pause at the top of the curl where the biceps is fully contracted. Small, consistent increases in difficulty over weeks will drive growth without forcing you to compromise your form with a weight that’s too heavy to control.
How It Compares to Other Curl Variations
Concentration curls produce the highest overall biceps activation of any curl variation, making them the go-to choice if pure biceps isolation is your priority. Hammer curls (palms facing each other) generate the highest brachioradialis activation, so they’re better for building forearm mass specifically. The close grip EZ bar curl sits in a productive middle ground: strong biceps activation with meaningful brachialis and brachioradialis involvement, all in a wrist-friendly package that lets you load heavier than most dumbbell variations.
If you’re choosing between a close grip and a wide grip on the EZ bar, the close grip is generally the better pick for long head development and overall range of motion. Wide grip curls place more stress on the elbow joints, which can become an issue at higher loads or volumes. Using both grip widths across different training sessions covers both heads of the biceps thoroughly.