Decline Hammer Curl: How To, How Not To, and Benefits

Decline hammer curls are a variation of dumbbell hammer curls where the lifter lies chest down on an incline and the arms are suspended straight down toward the floor at the beginning of the curl.

They are almost identical in every way to spider hammer curls. The only difference between the two is that spider hammer curls can sometimes be performed from the vertical side of a preacher bench.

In comparison to the incline hammer curl, the lifter reclines back, letting the arms fall behind the torso, the arms are in front during a decline hammer curl. Both require a thumbs-up grip.

Where a spider hammer curl can be done standing, leaning against the angled side of a preacher bench, the decline hammer curl requires reclining, facing downward—a very slight difference between the two.

The grip and forward recline define the decline hammer curl.

Muscles Worked by Decline Hammer Curls

Decline hammer curls work the brachioradialis, the biceps brachii, and the brachialis in isolation. The brachioradialis is the upper arm muscle that adds thickness and height to the arm above, below, and around the elbow.

All three of these “biceps” muscles must work during decline hammer curls. It’s the orientation of the brachioradialis versus the direction of resistance that favors that single muscle.

The brachialis and biceps also must contribute but decline hammer curls feature the brachioradialis due to the grip orientation. The brachioradialis lies atop the forearm when the thumb is up where it directly opposes gravity.

If you were to turn the palms up, the brachioradialis would rotate to the outside of the arm, and not directly opposite resistance.

In that orientation, the biceps and brachialis would directly oppose gravity and for that reason contribute more overall force to the lift.

How to Do a Proper Decline Hammer Curl

You need dumbbells and an incline bench to do decline hammer curls correctly. Adjustable benches work well so that you can set the incline to adjust for your arm length.

1. Set the bench at an angle that keeps the dumbbells from touching the floor at the base of each repetition. If you’ve got long arms, you’ll need a higher angle. Which angle you select is completely up to you. If you have the option, pick an angle in the 45° to 60° range. Not too far forward and not too vertical either.
2. Select a dumbbell weight that permits strict form. They’ll be lighter than you think or might like.
3. Lie chest down on the incline bench. Take the dumbbells with you and use them to lower yourself onto the bench, then carefully lower them to a hanging position.
   • You can also leave the dumbbells on the floor and pick them up once you’re in position if you’re able to reach them.
4. Get a neutral grip on the dumbbell, thumbs are facing forward. (The thumbs should always face your  head as you curl.)
5. Bend at the elbow only, using only the anterior upper arm muscles to initiate and complete the rep. You can use one or two dumbbells.
   • You can do one arm solo.
   • You can do two hands simultaneously, or alternating.
6. Maintain tension throughout the entire set. Don’t relax the arms at the bottom of a rep. Do not let the wrists fall forward or backward.

How NOT to Do a Decline Hammer Curl

Lying forward on a bench makes the strict form easier as it removes the body’s ability to add momentum. Still, there are ways to ruin an otherwise perfectly good decline hammer curl.

Here are some common mistakes to avoid with decline hammer curls:

1. Hinging, not curling.

As with spider hammer curls, this is the most common error and one that’s easy to make if you’re not paying attention to your form. The upper arm should stay at 90° to the ground through the entire set.

• “Hinging” happens when the elbow moves backward as the fist curls up with the dumbbell. As its name suggests, the motion should look like hammering a nail.

2. Bench set too low

Bench set too low so that the weights touch the floor between reps. Dumbbells should be suspended at the ends of your arms at the bottom of a rep.

3. Wrong grip

Not maintaining the neutral, thumbs-up, grip. Your grip shouldn’t roll into palms-up at any point during the lift.

4. Using too much weight

Each rep should be executed smoothly and rhythmically. If you can’t move the weight by moving only the forearm, you’re using too much weight. You’ll be surprised how many benefits you’ll get from less weight and stricter form.

Benefits of Decline Hammer Curls

Decline hammer curls’ benefits arise from their ability to isolate the working muscles and prevent the addition of momentum by the trunk, legs, or shoulders.

Direction of Resistance

Gravity forces the arms to hang straight down as the lifter lies chest-down on the bench. That places the direction of resistance in proper orientation: in line with gravity. As the target muscles pull on the weight, they are acting directly against gravity.

The thumbs-up grip places the brachioradialis directly opposing direction of resistance, making this a terrific exercise to work for bulk on the top of the forearm and to add size around the elbow joint.

Ease of Isolation

If hinging (described above) can be avoided, decline hammer curls facilitate a very strict isolation arm exercise. Because the lifter must lie chest down, the legs and upper body can’t be used to swing the weight.

Cheating becomes a lot more difficult. Again, the only cheating that can be done is if the elbows are allowed to drift backward.

Low risk of Injury

You’ll need to use lighter weights than you could otherwise lift to do decline hammer curls correctly. And the thumbs-up grip positions the insertions of the biceps tendon under less tension.

There’s still some tension on the biceps because they are indeed working. They’re just not carrying the percentage of the load they would if a palms-up grip was employed.

Drawbacks

There are few if any drawbacks to the decline hammer curl. The only drawback that we can think of would be not having an angled bench-handy.