Hammer Curls vs Preacher Curls vs Concentration Curls: Which Builds Bigger Arms?

Walk into any gym and you’ll see all three: someone doing hammer curls by the dumbbell rack, someone on the preacher bench, someone sitting with an elbow braced against their thigh. They’re all curls, but they don’t do quite the same job. Here’s what each one is good for — and why the best arm routine usually uses more than one.

A quick bit of anatomy

The front of your upper arm isn’t one muscle. The biceps is the one everyone thinks of, but underneath it sits the brachialis, and running down your forearm is the brachioradialis. All three help bend your elbow, and changing your grip and arm position shifts how much each one works. Bigger-looking arms come from developing all of them — the brachialis in particular pushes the biceps up and makes the arm look thicker from the side.

Hammer curls

How: Hold dumbbells with your palms facing each other — like holding a hammer — and curl them up without rotating your wrists.

What it targets: The neutral grip shifts more of the work onto the brachialis and brachioradialis, so hammer curls build arm thickness and forearm size more than a standard curl does.

Why do it: It’s also usually the strongest curl variation, so it’s easy to progress, and it’s comfortable for people whose wrists don’t like a palms-up grip.

Watch out for: Swinging. If your body is rocking to get the weight up, it’s too heavy.

Preacher curls

How: Sit at a preacher bench with the back of your upper arms resting on the angled pad, then curl a barbell, EZ-bar or dumbbell up from nearly straight arms.

What it targets: The pad locks your upper arm in place, so you can’t cheat with your shoulders or body. All the work stays on the biceps, and the hardest part of the movement is near the bottom, when your arm is almost straight.

Why do it: It’s a strict, controlled way to work the biceps through a long range of motion.

Watch out for: Dropping the weight at the bottom. That fully stretched position puts a lot of stress on the elbow — lower slowly and don’t bounce out of it. Go lighter than you would on a standing curl.

Concentration curls

How: Sit on a bench, lean forward, brace the back of your working arm against the inside of your thigh, and curl a single dumbbell up towards your shoulder.

What it targets: It’s the strictest isolation of the three. A small 2014 study commissioned by the American Council on Exercise compared eight biceps exercises and found concentration curls produced the highest biceps muscle activation of the group.

Why do it: Strong mind-muscle connection, and you can’t cheat. Good as a finisher.

Watch out for: Ego. It’s meant to be done with a light dumbbell and a hard squeeze at the top.

So which builds bigger arms?

None of them on its own. The research on muscle growth points to total weekly volume and working close to failure mattering more than any single “best” exercise. What these three give you is coverage: hammer curls for thickness, preacher curls for a strict long-range biceps stretch, concentration curls for a hard finishing squeeze.

A simple arm routine

Once or twice a week, after your main lifts:

1. Hammer curls — 3 sets of 8–12 reps
2. Preacher curls — 3 sets of 10–12 reps
3. Concentration curls — 2 sets of 12–15 reps per arm

Add a triceps exercise in between if you want balanced arms — the triceps make up more of your upper arm’s size than the biceps do.

Not every gym has a dedicated preacher bench, so it’s worth checking before you sign up. Browse gyms near you and look at their photos for the equipment you need.