Dumbbell Preacher Curl

What the dumbbell preacher curl actually trains

A dumbbell preacher curl is a single arm biceps isolation exercise in which the upper arm rests flat on an angled pad while you curl a dumbbell from full extension to full flexion.

The biceps brachii does most of the work, both heads together, with the brachialis underneath contributing throughout and the brachioradialis assisting a little given the supinated grip.

The pad is the whole exercise. By fixing the upper arm at an angle in front of your torso, it does two things at once.

The first is that it makes cheating impossible. The elbow cannot travel, the torso cannot swing, and the shoulder cannot help. What lifts the dumbbell is elbow flexion and nothing else.

The second, and more interesting, is that it moves the hardest part of the curl to the bottom. With the upper arm angled forwards and downwards, the forearm is closest to horizontal when the elbow is nearly straight, so the resistance peaks in the stretched position and falls away as you approach the top.

That is the opposite of a spider curl, which is hardest at the top, and it is the only meaningful difference between them. Preacher, spider and incline curls are one movement with the resistance peak parked in three different places. Nobody needs all three.

If you want a reason to prefer this one, it is that loading a muscle in a lengthened position has some evidence behind it. Pedrosa and colleagues found partial ranges performed at long muscle lengths produced more favourable hypertrophy than the same partials performed short. That points mildly towards the preacher rather than the spider.

The single arm version adds one more thing. Working one side at a time makes side to side differences visible, lets you give the weaker arm the same number of hard reps as the stronger one, and lets the hand rotate freely as it curls.

Setting up and executing

Set the preacher bench seat so the top of the pad meets your armpit when you sit down. This is the setup decision that matters. If the pad sits lower than that, you slide forwards and the position falls apart.

Sit with your feet flat and lay one upper arm flat along the pad, from armpit to elbow.

Take the dumbbell with a supinated grip and rest your free hand on the top of the bench or your thigh.

Let the arm straighten completely at the bottom. Do not rush this position or bounce out of it.

Curl the dumbbell up towards your shoulder, keeping the upper arm and shoulder pressed into the pad throughout, and squeeze for a beat near the top.

Lower over about three seconds back to full extension, pause briefly, and repeat. Finish all the reps on one side before swapping.

The mistakes that cost you the most

Bouncing out of the bottom is the fault to take seriously. The stretched position is where the elbow is under most tension and where the exercise earns its keep, and dropping into it under load is how preacher curls get their reputation for irritating elbows. Lower slowly, arrive gently, and start the next rep with muscular effort rather than a rebound.

Not straightening the arm is the opposite error and just as wasteful. Pallares and colleagues found full range training produced better strength and hypertrophy outcomes than partial range work, and on a preacher curl the missing range is the loaded stretch, which is the best part.

Lifting the shoulder off the pad shortens the lever and lets the front delt take over. If the shoulder is peeling away as you curl, the weight is too heavy.

A seat set too low is the setup version of the same problem, because you end up perched forward with the armpit above the pad and no support at all.

And too much weight is more obvious here than anywhere else. The bottom position is mechanically weak, so an honest preacher weight is well below what you use standing. That is the point, not a failure.

Sets, reps and rest by goal

For muscle gain, three sets of eight to twelve per arm with sixty seconds rest. For strength, three sets of six to ten with ninety seconds. In a fat loss phase, three sets of twelve to twenty with forty five seconds.

Slow the descent to about three seconds. On a preacher the eccentric ends in the most stretched position, so control has a practical purpose here beyond the training effect.

Schoenfeld and colleagues found a dose response between weekly hard sets and hypertrophy. For arms the useful reading is that total weekly curl volume drives the result, not the specific curl, so six to twelve hard sets a week across everything you do is a sensible target.

Refalo and colleagues found stopping a rep or two short of failure produces comparable growth to going all the way, which is worth applying here because the failure rep on a preacher curl is the one where the shoulder lifts off the pad.

Where it fits in your split

At the end of a session, after the heavy pulling.

On push, pull and legs it goes on pull day after the rows and pulldowns. On an upper and lower split it belongs at the end of the upper sessions. On a bro split it is the main biceps movement on arm day. On a full body programme it is optional work at the end.

If you are going to run only one seated curl variation, this is a good one to keep, because it loads the stretched position and forces strict technique in a single setup. Adding a spider curl alongside it is close to pointless, since you would be doing the same movement with the difficulty moved from one end of the range to the other.

A better companion is a hammer or reverse curl, which loads the brachialis and brachioradialis in a way a supinated curl does not.

Variations worth knowing

The barbell preacher curl uses both arms at once on an EZ or straight bar, which is faster and allows more total load, at the cost of letting the stronger arm carry the weaker one.

The machine preacher curl fixes the arc and adds a seat, which makes it the easiest version to take to genuine failure without a spotter or a dropped dumbbell.

The cable preacher curl runs from a low pulley and keeps tension more even through the range, which softens the very hard bottom position some elbows dislike.

The spider curl is the mirror image, hardest at the top rather than the bottom, and is the one to swap to when you want a hard contraction instead of a loaded stretch.

The incline dumbbell curl loads an even longer biceps position by letting the arms hang behind the torso.

And the hammer preacher curl keeps the palm neutral on the pad, shifting a share of the work onto the brachialis and brachioradialis.

What the evidence says

Marcolin and colleagues compared electromyographic activity of the biceps brachii and brachioradialis across three curl variants and found the differences were modest, which is a good reason to treat curl selection as a matter of preference rather than strategy.

Pedrosa and colleagues found partial range training performed at long muscle lengths produced more favourable hypertrophy than the same work at short lengths, which is the strongest available argument for a preacher curl over a spider curl.

Schoenfeld and Grgic reviewed range of motion and muscle development and concluded that full range training is generally at least as good as partial work, with lengthened positions carrying particular value.

Pallares and colleagues found full range training beat partial range training for strength and hypertrophy, supporting complete extension at the bottom of every rep.

Liao and colleagues reviewed unilateral against bilateral resistance training and found broadly comparable strength outcomes, which means the single arm format here is about attention and symmetry rather than a superior stimulus.

Schoenfeld and colleagues found a dose response between weekly hard sets and hypertrophy, and Refalo and colleagues found stopping short of failure produces comparable growth, which together set the volume and effort targets.

Common questions

Preacher curl or spider curl?

They are the same movement with the hard part at opposite ends. The preacher loads the stretched bottom position, the spider loads the contracted top. The evidence on long muscle lengths leans slightly towards the preacher, so if you only keep one, keep this. Doing both in the same session is redundant.

Why does the preacher curl bother my elbows?

Usually because the bottom is being reached too fast or with too much weight. The stretched position is where the tendon is under most tension, so drop the load, lower over three seconds and arrive at full extension under control rather than dropping into it.

Should I use dumbbells or a barbell?

Dumbbells if you want each arm to do its own work and the hand to rotate freely, which also exposes side to side differences. A barbell if you want to save time and move more total weight. Neither is meaningfully better for growth.

Do I need to go all the way to a straight arm?

Yes, that is the part of the range that makes this exercise worth choosing. Stopping short leaves out the loaded stretch and turns the preacher curl into a slightly awkward version of every other curl.

How much weight should I be using?

Considerably less than your standing curl, which surprises people the first time. The pad removes every source of assistance and puts peak resistance where you are weakest, so a smaller dumbbell doing strict work is exactly what the exercise is for.