Incline Dumbbell Curls vs Preacher Curls: Lengthened Stretch vs Shortened Resistance

The incline dumbbell curl vs preacher curl debate has a short answer: neither wins outright. In the one direct MRI comparison, incline curls grew the biceps brachii a little more, preacher curls grew the muscles underneath it a little more, and total elbow flexor growth came out about the same.

That matters because most “best biceps exercise” advice treats them as rivals. They are better seen as two different ways to load a stretch. This article sits inside our wider guide to range of motion and stretch-mediated hypertrophy, so we will focus on the mechanics of these two curls and what the evidence does and does not say.

What is actually different between the two curls?

Your biceps brachii crosses two joints. It flexes the elbow and, via the long head, it also crosses the shoulder. That means where your upper arm sits changes how stretched the muscle is before you even start curling.

In an incline curl, you sit back on an angled bench and let the arms hang behind your torso. The shoulder is extended, so the long head is already stretched across the shoulder when the elbow is straight.

In a preacher curl, your upper arm rests on a pad in front of you. The shoulder is flexed, which slackens the long head at the shoulder. The elbow still goes into a deep stretch at the bottom, but the shoulder is not contributing.

The same logic is behind the overhead triceps work. In a 2023 study of 21 adults, overhead cable extensions grew the triceps long head more than neutral-arm extensions (+28.5% vs +19.6%), even with lighter loads (Maeo et al., 2023). The biceps version of that idea is the incline curl. Whether it gives the same payoff is the question the next section answers.

What does the research say about incline vs preacher curls for growth?

Only one study I could find has put the two head to head with MRI. In 2026, Kobayashi and colleagues had 21 untrained adults train one arm with incline dumbbell curls and the other with preacher dumbbell curls for 12 weeks (70% of 1RM, 5 sets of 10 reps, twice a week) (Kobayashi et al., 2026). They measured the volume of the biceps brachii, brachialis and brachioradialis.

The results:

• Biceps brachii: +22.1% after incline vs +18.9% after preacher (Hedges’ g = 0.33).
• Brachialis: +17.1% after incline vs +21.1% after preacher (g = 0.50).
• Brachioradialis: +13.5% after incline vs +17.6% after preacher (g = 0.47).
• Total elbow flexors: +17.6% vs +19.2%, not a significant difference.

The authors summarised it as small-to-moderate, exercise-specific differences, with limited influence on total elbow flexor growth and on where along the muscle the growth occurred.

Is the biceps lengthened position better for growth?

The idea behind the incline curl is that training at long muscle lengths drives extra growth. The broader literature is promising but not settled.

A 2020 systematic review of range of motion studies found a full range helped lower body hypertrophy, while upper limb research was limited and conflicting, so strong practical conclusions were not possible. It also noted that the response may differ by muscle (Schoenfeld and Grgic, 2020).

More recently, a trial in 30 resistance-trained people trained one arm with lengthened partials and the other with full range for 8 weeks. Elbow flexor and extensor thickness grew similarly, with Bayes factors giving moderate support for no difference (Wolf et al., 2025). The authors suggest emphasising the stretched position, through a full range or lengthened partials, when size is the goal.

Then there is the regional question. A 2025 Bayesian meta-analysis of 12 studies in young adults found trivial differences in regional hypertrophy between training at longer and shorter mean muscle lengths, and the authors warned that the length differences between conditions were relatively small (Varovic et al., 2025).

So what do we do with this? The studies are not contradicting each other as much as asking different questions. The Kobayashi and Maeo trials changed where the muscle sits and found some differences. The meta-analysis pooled mostly small manipulations and found little. A cautious takeaway: loading the stretch is a reasonable way to train, but it is not a magic trick, and you should not drop every other curl variation for it.

Why the preacher curl can still be a great choice

The preacher pad does two useful things. It fixes your upper arm in place, so you cannot swing your torso or drift the elbow. And it moves the hardest part of the load into the stretched half of the rep for most setups.

The resistance curve of a free weight follows simple geometry. A dumbbell feels heaviest when your forearm is closest to horizontal. On an angled preacher pad, that point falls in the lower half of the movement, then the load fades as the hand comes toward the shoulder. On an incline curl, the forearm starts hanging straight down, so the first few degrees feel easier, and the load builds through the middle. Both patterns depend on bench angle and where you place your elbow, so treat them as general principles rather than exact numbers.

One 2009 EMG study compared standing and preacher curls at low loads (25-40% of 1RM) in 20 healthy people. Muscle activity, heart rate and perceived exertion were lower in the preacher version at 40% 1RM by the 20th repetition (Oliveira and Goncalves, 2009). I would not read much into that for growth, since those were light, short-term loads and EMG is not a measure of muscle gain. It simply fits the idea that the pad changes how the movement feels and is executed.

For more on the preacher side, see preacher curls and peak tension for the distal biceps and how it compares to Bayesian cable curls.

How to do incline dumbbell curls properly

Set the bench at roughly 45-60 degrees (a common coaching range, not a research-defined optimum). Sit back with your head and shoulders against the pad and let the dumbbells hang with palms facing forward.

1. Keep your elbows just behind your torso. If they drift forward, you lose the stretch you came for.
2. Curl without rocking your shoulders off the bench.
3. Lower slowly until your elbow is almost straight.
4. If your front shoulder feels pinched at the bottom, raise the back pad or reduce the load.

For a closer look, our guide on incline dumbbell curls and shoulder extension covers setup in more detail, and long head vs short head biceps explains why the head-targeting claims are often overstated.

Incline curl vs preacher curl: quick comparison

Factor	Incline dumbbell curl	Preacher curl
Shoulder position	Extended, behind torso	Flexed, in front on a pad
Biceps stretch	Across shoulder and elbow	At the elbow only
12-week MRI result (untrained)	Biceps brachii +22.1%	Brachialis +21.1%, brachioradialis +17.6%
Cheating risk	Low, as long as your back is on the bench	Low, the pad blocks swinging
Typical limiter	Front shoulder comfort	Elbow and tendon comfort at the bottom
Best for	Loading the biceps stretch	Strict, repeatable elbow flexion

How to pair them in a week

You do not need to over-plan this. Here is a simple structure that follows the evidence we have without pretending it is more precise than it is.

• Pull day A: incline dumbbell curls, 3 hard sets of 8-12.
• Pull day B: preacher curls, 3 hard sets of 8-12.
• Take sets within 1-3 reps of failure, and add reps before you add weight.
• Count your rows and pulldowns too. They train the biceps, so more curl sets are not always better. Our training volume calculator helps you tally weekly sets, and the pull day plan shows where curls fit.

If you want a third option, see hammer curls for the brachialis and brachioradialis, which train the two muscles that grew more in the preacher arm.

What if you only have one option?

On a basic gym floor in India, a bench and a pair of dumbbells is often all there is. That is enough. Choose the curl that you can load progressively, that does not hurt, and that you will do consistently. A comfortable, progressed curl beats a “perfect” one you avoid.

When to see a doctor

Mild muscle soreness after curls is normal. Sharp pain at the front of the elbow or in the crease, a sudden pop, visible bruising, or a bulge in the upper arm after a heavy rep are not. Persistent pain that lasts more than a week or two, or arm weakness, should be checked by a doctor or sports physiotherapist. I cannot diagnose anything from a description, and you should not train through it.

Bottom line

For the incline dumbbell curl vs preacher curl question, the best current evidence says both build the elbow flexors well, with small differences in which muscle benefits most. If you can only do one, pick the one you can progress comfortably. If you can do both, you get a more complete set of stimuli. For the bigger picture, return to the pillar guide on range of motion and stretch-mediated hypertrophy, or compare functional anatomy of the arm flexors.