Hammer Curls: Build Bigger Arms With This Underrated Exercise

If you only do one curl variation, make it the hammer curl.

Standard bicep curls get all the attention, but hammer curls are quietly the better arm builder for most people. They hit the biceps, the brachialis (the muscle underneath the biceps that pushes them up and makes your arms look bigger), and the brachioradialis (the meaty part of your forearm). One exercise, three muscle groups.

Here's everything you need to know about doing them right.

What Makes Hammer Curls Different

A regular bicep curl uses a supinated grip — palms facing up. A hammer curl uses a neutral grip — palms facing each other, like you're holding a hammer. This grip change shifts the emphasis.

With palms facing each other, your brachialis and brachioradialis do more work relative to the biceps. The biceps still work hard, but the load is distributed more evenly across the elbow flexors. The result: thicker arms from every angle, not just a bicep peak when you flex.

The brachialis sits under the bicep and literally pushes it up when developed. If you want arms that look big in a T-shirt (not just during a flex), you need brachialis development. Hammer curls deliver that.

How to Do Hammer Curls

Starting Position

Stand with feet hip-width apart, a dumbbell in each hand
Arms at your sides, palms facing your thighs (neutral grip)
Shoulders back, chest up, core braced

The Curl

Curl the dumbbells up by bending at the elbow
Keep your palms facing each other throughout — don't rotate
Bring the dumbbells up to shoulder height or until your forearms are fully contracted
Squeeze at the top for a beat

The Lowering

Lower under control — 2 to 3 seconds on the way down
Fully extend your arms at the bottom without swinging
Don't let momentum carry the dumbbells — reset before each rep

Key Form Points

Elbows stay pinned. Your elbows should stay close to your sides and shouldn't drift forward during the curl. If they're moving forward, you're compensating.
No swinging. If you need to swing your torso to lift the weight, it's too heavy.
Wrists stay neutral. Don't let your wrists bend forward or backward. Keep them straight and rigid.

Common Mistakes

Swinging the Weight

The most common mistake. People grab too-heavy dumbbells and use their whole body to swing them up. This turns an arm isolation exercise into a full-body momentum exercise. Lower the weight. Your arms should do the work, not your back.

Elbows Drifting Forward

When your elbows come forward as you curl, you shorten the range of motion and reduce tension on the target muscles. Pin your elbows to your sides. If they drift, you've lost the rep.

Rushing the Eccentric

The lowering phase is where a huge amount of muscle growth stimulus happens. If you drop the weight after the top of each rep, you're throwing away half the exercise. Control the descent. Every inch of the lowering counts.

Going Too Heavy

Hammer curls are an isolation exercise. They don't need to be heavy to be effective. If you can't do 8 clean reps without swinging, drop the weight. Ego curling builds nothing but joint problems.

Variations

Alternating hammer curls: Curl one arm at a time. Lets you focus on each side and use slightly heavier weight per arm.

Cross-body hammer curl: Curl the dumbbell across your body toward the opposite shoulder instead of straight up. Shifts more emphasis to the brachialis and the long head of the bicep.

Rope hammer curl (cable): Using a rope attachment on a cable machine provides constant tension throughout the range. Great for finishing sets.

Incline hammer curl: Sit on an incline bench (30–45 degrees). The incline stretches the bicep more at the bottom, increasing the growth stimulus.

Preacher hammer curl: Using a preacher bench eliminates all momentum and isolates the brachialis hard.

Programming Hammer Curls

For arm growth:

3–4 sets of 10–15 reps
60 seconds rest between sets
Controlled tempo: 1 second up, 2–3 seconds down
Squeeze at the top

In your program: Place hammer curls after your heavier compound pulling (rows, pull-ups) or as part of an arm day. They pair well with tricep work in supersets.

Frequency: Arms can handle high frequency. Hammer curls 2–3 times per week with moderate volume per session works well for most people.

Why Form Matters on Curls

People think curls are too simple to mess up. They're not. Swinging, elbow drift, and partial reps are everywhere, and they all reduce the stimulus your arms receive. Clean reps with moderate weight build bigger arms than sloppy reps with heavy weight. Every time.

If you're serious about arm development, film a set occasionally and watch it back. Gymscore can analyze your form and catch the compensations you don't feel — the slight swing, the elbow drift, the shortened range of motion. Small form fixes lead to big arm gains over time.

The Bottom Line

Hammer curls should be a staple in your arm training. They build the biceps, brachialis, and forearms in one movement, and they're easier on the wrists than supinated curls for many people. Use a neutral grip, pin your elbows, control every rep, and watch your arms grow.