How many reps of the single-arm preacher curl should you do per arm when you are new to the exercise?

Train each arm for 3 sets of 8 to 10 reps, always starting with the weaker arm and matching whatever it can do on the stronger side, not the other way around.

What can replace the single-arm preacher curl with no preacher bench?

A single-arm concentration curl, bracing the back of the upper arm against your inner thigh, gives the same one-arm-at-a-time isolation with just a bench and a dumbbell.

What is the single-arm preacher curl good for, and when is it not the right choice?

It's corrective work for side-to-side strength differences and a good finisher after your main pressing and curling. It's a poor choice as a primary mass-building exercise, since the light, controlled loads it demands limit how heavy you can go.

Intermediate

Single-Arm Preacher Curl

Working one arm at a time on the preacher bench lets you pour all of your focus into a single biceps and iron out side-to-side differences that a bar can hide. The braced upper arm kills momentum and locks the shoulder in flexion, so the short head and the tough bottom of the curl take the load. Use it as a corrective or a strict finisher after your main pressing and curling.

Equipment: Bench, Dumbbell
Body part: Biceps
Type: Strength
Browse by muscle: Biceps Brachii Short Head
Browse by movement: Elbow Flexion

How to do it

1
Set the preacher pad so its top edge sits just under your armpit.
2
Rest the back of one upper arm flat on the pad and hold a dumbbell underhand.
3
Let the arm extend to nearly straight at the bottom of the pad.
4
Curl the dumbbell toward your shoulder by flexing the elbow.
5
Squeeze at the top, then lower slowly until the arm is almost straight.
6
Finish the reps, then switch arms.

Tips

Never bounce out of the stretched bottom; that near-straight position is vulnerable.
Keep the whole upper arm glued to the pad instead of letting the elbow lift.
Match reps and tempo on both arms so the weaker side is not shortchanged.

Variations

Common mistakes

The free hand braces hard against the bench or your knee, quietly adding a second point of leverage that a single-arm exercise is supposed to remove.
The torso twists toward the working arm at the top of the rep, letting rotation finish what the biceps couldn't.
Whichever arm feels weaker gets fewer total sets over time because it's harder to push through, which locks in the imbalance this exercise exists to fix.
Rushing the weaker arm's set to catch up with the stronger arm's rep count trades quality for a number that doesn't matter.
Once one arm's set ends, resting only a few seconds before starting the other side carries fatigue across and makes the comparison between sides meaningless.

Frequently asked

How many reps of the single-arm preacher curl should you do per arm when you are new to the exercise?: Train each arm for 3 sets of 8 to 10 reps, always starting with the weaker arm and matching whatever it can do on the stronger side, not the other way around.
What can replace the single-arm preacher curl with no preacher bench?: A single-arm concentration curl, bracing the back of the upper arm against your inner thigh, gives the same one-arm-at-a-time isolation with just a bench and a dumbbell.
What is the single-arm preacher curl good for, and when is it not the right choice?: It's corrective work for side-to-side strength differences and a good finisher after your main pressing and curling. It's a poor choice as a primary mass-building exercise, since the light, controlled loads it demands limit how heavy you can go.

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