The hammer curl is a neutral-grip dumbbell curl that builds thicker arms — you curl with the palms facing in, like swinging a hammer. Here's how to do it with good form, the muscles it works, the mistakes to avoid, and how to program it.
The hammer curl is a neutral-grip biceps isolation exercise that works the biceps brachii, brachialis and brachioradialis (a forearm muscle). You hold the dumbbells with palms facing in and curl without rotating the wrist, keeping the upper arm still. Because the neutral grip shifts extra work to the brachialis and forearm, hammer curls are a favorite for adding arm and forearm thickness on top of standard biceps training.
The hammer curl is an isolation lift for the elbow flexors, but the neutral grip changes the emphasis. The biceps still works, and the brachialis and brachioradialis pick up more of the load than they would in a supinated curl.
| Role | Muscles | What they do in the lift |
|---|---|---|
| Primary mover | Biceps brachii | Flexes the elbow to curl the weight up in a neutral grip |
| Assisting | Brachialis | Sits under the biceps and works hard with the palm facing in |
| Assisting | Brachioradialis | Forearm muscle heavily recruited by the neutral grip |
| Stabilizers | Wrist flexors, shoulder | Keep the wrist neutral and the upper arm fixed in place |
Step-by-step form for the standing neutral-grip hammer curl. Pick a weight you can lift with strict form and no torso swing.
If you want to train the same pattern with a different emphasis or equipment, these are the common swaps:
The hammer curl fits at the end of any upper-body, pull or arm day. General starting points:
| Goal | Sets × reps | Notes |
|---|---|---|
| Arm size | 2–4 × 8–15 | Moderate load, controlled tempo, train close to failure on the last set |
| Forearm thickness | 3–4 × 10–15 | Neutral grip, slow lowering, keep the wrist steady throughout |
| Frequency | 1–3× / week | Progress by adding a rep or small increment when you hit the top of the range |
Hammer curls pair well with a supinated dumbbell curl and a barbell curl for loaded biceps work. Read up on RPE to gauge how hard each set should feel.
Log every hammer curl set — weight, reps, and an RPE value — in LiftHero, and it charts your progressive overload and flags personal records so you can watch your arms grow over the weeks. You can add warm-up sets, supersets and rest-timer holds, then drop the curl into a saved routine so it's ready the next time you train. LiftHero records what you log; it doesn't diagnose your form.
The neutral grip works the biceps brachii along with the brachialis and the brachioradialis in the forearm. That extra emphasis on the brachialis and forearm helps build overall arm thickness.
A regular dumbbell curl supinates the palm to face up and emphasizes the biceps. A hammer curl keeps the palm facing in the whole time, shifting more work to the brachialis and brachioradialis.
Yes. The neutral grip recruits the brachioradialis, a forearm muscle, more than a supinated curl does. Hammer curls are a common choice for adding forearm and upper-arm thickness.
Both work. Curling both arms together saves time; alternating lets you focus on one side and keep form strict. Cross-body hammer curls emphasize the brachialis further.
For arm size, about 8–15 reps across 2–4 working sets. Keep the movement strict and controlled and train close to failure rather than chasing heavy weight.
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This guide is educational and not medical advice. Consult a qualified coach or medical professional before starting or changing a training program.
By Meitar Lazimi, founder of LiftHero · Last updated July 9, 2026.