Hammer Curl vs Reverse Curl vs Zottman Curl: Which Builds Thicker Arms?

The biceps make up only one part of arm thickness — the brachialis (underneath the biceps) and brachioradialis (top of the forearm) contribute as much or more to apparent arm size when developed. Three curl variations specifically train these supporting muscles: hammer, reverse, and Zottman. Here's how each compares on muscle bias and how to combine them with standard curls.

Quick Answer

Run the hammer curl as your default for brachialis development — easiest to load heavy, accessible in any gym. Add the reverse curl as an accessory when forearm extensor development is a goal. Use the Zottman curl when you want one-rep efficiency that hits both flexors and extensors. Most arm programs benefit from running two of the three alongside standard supinated curls.

Side-by-Side Comparison

Hammer Curl

Stand or sit, dumbbells at your sides with palms facing each other (neutral grip), curl up keeping the palms in. The wrists don't rotate; the grip stays neutral throughout.

What it does well: Maximum brachialis loading. The brachialis sits underneath the biceps brachii — when developed, it pushes the biceps up and out, creating thicker apparent arm size from the side. The neutral grip puts the brachialis in its strongest mechanical position, which means hammer curls allow heavier loading than supinated curls.

The brachioradialis (the meaty muscle on the thumb-side of the forearm) also gets significant work because the neutral grip loads it directly. Hammer curls are one of the few mainstream exercises that build the brachioradialis without specific forearm work.

Where it falls short: Less direct biceps brachii work than supinated curls. The biceps still contributes — it's working at all elbow flexion angles — but its mechanical leverage is reduced compared to a palms-up curl. Lifters who need maximum biceps brachii growth shouldn't replace standard curls with hammer curls; they should add hammer curls as a complement.

Programming: 3 sets of 8–12 reps. See hammer curl and standing hammer curls.

Reverse Curl

Stand or sit, dumbbells or barbell in hands with palms facing down (pronated grip), curl up. The wrists stay pronated throughout — palms never rotate.

What it does well: Maximum forearm extensor loading. The pronated grip puts the brachioradialis and the forearm extensors (back of the forearm) in their strongest position, while the biceps brachii is in a mechanically weak position. This means the brachialis and forearm muscles do most of the work.

For lifters chasing the "thick forearm" look that's visible when the arm is held in pronated positions (typing, gripping a steering wheel, holding a phone), reverse curls are uniquely effective. The forearm extensors are also one of the most undertrained muscle groups in commercial gyms — most lifters do plenty of grip work (which trains the flexors) and almost no extensor work.

Where it falls short: Loading is meaningfully lower than hammer curls. The pronated grip is mechanically weak across the elbow, so working weight is typically 50–70% of your hammer curl weight. Heavy reverse curls can also strain the wrists and elbows because the grip position is structurally weaker.

Programming: 3 sets of 10–12 reps with moderate weight. See reverse curl and reverse-grip barbell bicep curls.

Zottman Curl

Stand or sit, start with dumbbells at sides palms forward (supinated, like a normal curl), curl up. At the top of the rep, rotate the wrists so palms now face down (pronated). Lower in the pronated position. At the bottom, rotate back to supinated. Repeat.

What it does well: One-rep efficiency. The Zottman curl trains the biceps brachii in the concentric (palms-up curl) and the brachialis + forearm extensors in the eccentric (palms-down lowering). This means each rep stimulates both muscle systems, which is useful when you want concentrated arm work in fewer total sets.

The eccentric portion is particularly valuable. Eccentric loading produces strong hypertrophy stimulus, and most lifters underuse it. The Zottman curl's pronated descent puts heavy eccentric load on the brachialis and forearm extensors — muscles that rarely get this kind of stimulus.

Where it falls short: Loading caps at moderate weight because the rotation slows the lift and adds technique complexity. The eccentric portion is also harder than the concentric — lifters who don't control the descent end up dropping the dumbbell rather than lowering it under tension, which kills the main benefit.

The other limitation is time per rep. The rotation phases add 1–2 seconds per rep, which means the same total volume takes longer to complete. For lifters with limited gym time, this can be a meaningful trade-off.

Programming: 3 sets of 8–12 reps with controlled rotation. See zottman curl.

What the Research Says

Direct comparisons between these three variations are limited, but the broader evidence on brachialis and forearm training points to two consistent findings:

1. Neutral and pronated grips bias the brachialis over the biceps brachii. EMG studies show hammer and reverse curls produce significantly higher brachialis activation than supinated curls. The biceps brachii activation is correspondingly lower.
2. Eccentric loading produces strong hypertrophy stimulus. Studies on eccentric vs concentric-focused training consistently show eccentric overload produces equal or greater hypertrophy at lower total volume. The Zottman curl's pronated eccentric exploits this directly.

Practical takeaway: pick based on what you're trying to grow. Brachialis + biceps thickness — hammer curl. Forearm extensors — reverse curl. Both flexors and extensors with one exercise — Zottman.

Combine With Standard Curls

None of these three replaces a supinated curl for biceps brachii development. The strongest arm program runs both types:

• Standard curl (barbell, dumbbell with rotation, or chin-up): trains biceps brachii heavily
• Hammer/reverse/Zottman: trains brachialis and forearms

Sample arm day:

1. Barbell curl: 3 sets of 8–10 reps (biceps brachii main lift)
2. Hammer curl: 3 sets of 10–12 reps (brachialis emphasis)
3. Reverse curl: 2 sets of 10–12 reps (forearm extensor accessory)

For more on the standard curl variations, see Cable Curl vs Barbell Curl vs Dumbbell Curl and Best Bicep Exercises Ranked.

How to Pick

Run hammer curls as your default if brachialis development is the priority and you want heavy progressive overload work alongside standard curls.

Run reverse curls if forearm extensor thickness is a goal, your forearms look flat from above, or you want a wrist-friendly alternative to other curls (some lifters with biceps tendinitis tolerate reverse curls well).

Run Zottman curls if you want one-rep efficiency, you're chasing both flexor and extensor stimulus in fewer sets, or you've plateaued on the other two and want a different stimulus.

Rotate variations across the week if you train arms twice. Sample week: Monday — barbell curl + hammer curl; Thursday — incline curl + reverse curl.

The Bottom Line

The three brachialis/forearm-biased curls all build arm thickness from a different angle than standard biceps work. Hammer curls win on loading and brachialis bias; reverse curls win on forearm extensor work; Zottman curls win on one-rep efficiency. Pick based on goal, run alongside standard curls, and the arms thicken in 8–12 weeks.

For more, see our Best Bicep Exercises Ranked hub, Cable Curl vs Barbell Curl vs Dumbbell Curl, and the bigger arms program.