How is this different from a regular preacher curl?

The pad and arm path are the same, but the thumb stays up instead of the palm facing the ceiling, which takes away the biceps' job of turning the palm and gives the brachialis and brachioradialis more of the lift. A palm-up Dumbbell Single-Arm Preacher Curl keeps more of the focus on the biceps itself.

Why can I often lift more with a hammer grip?

The neutral forearm position is usually the strongest for bending the elbow. In a test of 85 healthy university students, elbow flexion force was highest with the thumb up and lowest with the palm down, so a slightly heavier dumbbell than on palm-up preacher curls is normal.

Should I lower the dumbbell all the way down?

Yes, lower until the arm is nearly straight, under control and without bouncing. In a study of untrained women doing seated dumbbell preacher curls, training only the bottom half of the range built more strength and more biceps size near the elbow than training only the top half, so the stretched part of the rep is worth keeping.

Is this better than a standing hammer curl?

Neither is better. They load the arm differently. The preacher version is strictest and hardest near the straight-arm position, while a standing Dumbbell Hammer Curl is hardest mid-range and lets you handle more weight, so many programs use both.

Should I start with my weaker arm?

Starting with the weaker arm and matching its reps on the stronger side is a simple way to keep both arms even. Do all reps on one arm before switching.

Dumbbell Single-Arm Hammer Preacher Curl

What Is the Dumbbell Single-Arm Hammer Preacher Curl?

Dumbbell Single-Arm Hammer Preacher Curl is an isolation exercise that primarily targets the biceps, working the brachialis and biceps brachii hardest while the brachioradialis in the forearm shares the lift. It is an intermediate-level movement performed one arm at a time on a preacher bench, with the palm facing in and the thumb pointing up throughout the rep.

The preacher pad fixes the upper arm in front of the body, so the shoulder cannot swing and the trunk cannot lean back to help the weight up. That makes it one of the strictest ways to train the elbow flexors, and the angled pad puts the most tension on them near the bottom of the curl, where the arm is close to straight. Working one arm at a time lets each side do its own share and makes it easy to spot a weaker arm.

The hammer grip changes the job compared with the palm-up Dumbbell Single-Arm Preacher Curl. The biceps is both an elbow flexor and a supinator, and with the thumb up it no longer has to turn the palm, so the brachialis and brachioradialis carry a larger share of the lift. A neutral forearm is also the position in which most people can produce the most elbow flexion force, so the load is often a little heavier than on the palm-up version.

It suits lifters who want more thickness through the upper arm and forearm, those who find palm-up curls uncomfortable on the wrist or elbow, and anyone who wants a strict curl that rules out cheating. Beginners should first get comfortable with a standing Dumbbell Hammer Curl, since the preacher position is weakest exactly where the arm is most stretched and a load that feels light standing can be hard to control at the bottom of the pad.

Muscles Worked

MuscleActivation

Biceps Brachii: Primary
Brachialis: Primary
Brachioradialis: High
Extensor Carpi Radialis: Medium
Flexor Carpi Radialis: Low
Flexor Carpi Ulnaris: Low
Deltoid: Minimal

Instructions

Adjust the seat so that, sitting tall with your feet flat on the floor, your armpit rests against the top edge of the pad.
Hold a dumbbell in one hand with a neutral grip, palm facing in and thumb pointing up, so the dumbbell hangs vertically.
Lay the back of that upper arm flat on the pad, from the armpit to just above the elbow, and lean your chest lightly against the top of the pad.
Start with the arm extended down the pad and the elbow slightly bent.
Curl the dumbbell up toward your face by bending only the elbow, keeping the thumb up and the wrist straight.
Keep the upper arm and elbow pressed into the pad as the forearm passes vertical.
Pause briefly when the dumbbell is near your chin and the elbow is fully bent.
Lower the dumbbell slowly along the same path until the arm is nearly straight, without dropping into a hard lockout.
Complete all reps on one arm, then switch sides.

Common Mistakes

Dropping into lockout
Letting the dumbbell fall the last part of the way puts a sudden stretch on the elbow at the point where the biceps is weakest.
Elbow lifting off the pad
Raising the elbow or shrugging the shoulder to finish the rep turns the curl into a front raise and takes work away from the elbow flexors.
Seat set too low
A low seat leaves a gap between the armpit and the top of the pad, so the upper arm cannot lie flat and the shoulder creeps forward.
Rotating the palm
Letting the palm turn up or down during the rep loses the neutral grip that defines this variation.
Bending the wrist
Curling or tipping the wrist to move the dumbbell shifts load away from the elbow flexors and strains the wrist.
Going too heavy
A weight that needs a body lean or a bounce at the bottom is too heavy for a strict single-arm curl.

Injuries

Dumbbell Single-Arm Hammer Preacher Curl is a low risk exercise when performed with proper technique. The weight is moderate, the upper arm is supported and only the elbow moves, so the main strain points are the front of the elbow, where the distal biceps tendon attaches, and the wrist, which has to hold the dumbbell level.

Most problems come from the bottom of the rep. With the arm resting on the angled pad, the elbow flexors are at their weakest and most stretched as the arm straightens, and letting the dumbbell drop into a fast, loaded lockout pulls hard on the distal biceps tendon. Lower under control, stop just short of a hard lockout, and pick a weight you can stop and reverse without bouncing. Keep the wrist straight and in line with the forearm rather than letting the dumbbell tip the hand down or to the side.

If the preacher position aggravates the elbow, go back to a standing Dumbbell Hammer Curl or a Cable Rope Hammer Curl, where the load is lighter near the straight-arm position. Progress by adding reps or slowing the lowering phase before adding weight.

Stop the set if you feel sharp or pinching pain at the front of the elbow, a sudden pop, or numbness or tingling into the hand, and get any pop with bruising or a change in the shape of the upper arm checked by a clinician.

Overview

Primary Focus: Biceps
Equipment: Dumbbell and bench
Modality: Strength
Difficulty: Intermediate

Alternative Exercises

Frequently Asked Questions

Q: How is this different from a regular preacher curl?: The pad and arm path are the same, but the thumb stays up instead of the palm facing the ceiling, which takes away the biceps' job of turning the palm and gives the brachialis and brachioradialis more of the lift. A palm-up Dumbbell Single-Arm Preacher Curl keeps more of the focus on the biceps itself.
Q: Why can I often lift more with a hammer grip?: The neutral forearm position is usually the strongest for bending the elbow. In a test of 85 healthy university students, elbow flexion force was highest with the thumb up and lowest with the palm down, so a slightly heavier dumbbell than on palm-up preacher curls is normal.
Q: Should I lower the dumbbell all the way down?: Yes, lower until the arm is nearly straight, under control and without bouncing. In a study of untrained women doing seated dumbbell preacher curls, training only the bottom half of the range built more strength and more biceps size near the elbow than training only the top half, so the stretched part of the rep is worth keeping.
Q: Is this better than a standing hammer curl?: Neither is better. They load the arm differently. The preacher version is strictest and hardest near the straight-arm position, while a standing Dumbbell Hammer Curl is hardest mid-range and lets you handle more weight, so many programs use both.
Q: Should I start with my weaker arm?: Starting with the weaker arm and matching its reps on the stronger side is a simple way to keep both arms even. Do all reps on one arm before switching.