But what's the difference between a preacher curl and an incline dumbbell curl?
This comparison pits each exercise against the other across three categories—biomechanics, muscle growth, strength gains—so that you can decide which one is right for you and your weight lifting ambitions.
Incline curls vs preacher curls: Biomechanics
It's well documented that incline curls provide more consistent resistance than preacher curls.  This means that your biceps have to work harder during the set, which provides a more robust hypertrophy stimulus.
Incline curls also emphasize the long (outer) head of the biceps more than preacher curls because they have you lift the weight with your shoulders extended behind your torso.
Conversely, preacher curls prioritize the short (inner) head of the biceps by having you curl with your arms in front of your body. Compared to incline curls, preacher curls provide less consistent muscle tension because they pose a significant challenge for the biceps at the start of the concentric (near full elbow extension) but much less when the biceps are nearing full contraction.
Both exercises are highly conducive to maintaining the proper form. For starters, the preacher pad helps your arms to stabilize the weights, so it's much harder to cheat the weight up with your shoulders.
Incline curls don't benefit from a support pad. However, they do place your shoulders in a weak position, which means that they can't contribute much force towards lifting the weight; hence your biceps have to perform the majority of the lifting.
Incline curls vs preacher curls: Muscle growth
Since each exercise emphasizes different regions of the biceps, one isn't better than the other for stimulating hypertrophy.
Incline curls are better for bringing up the long head, whereas preacher curls are more effective at emphasizing the short head.
The best choice depends on your physique; do you need more long head or short head development?
On the other hand, you could make a case for incline curls being superior for muscle growth because they provide more consistent tension levels than preacher curls.
Ultimately, since your biceps can only get so big, both movements will likely result in the same development over the long term providing that you pair your training with an appropriate diet and good recovery. But for maximizing muscle growth over the short term, incline curls have a slight edge over preacher curls.
Incline curls vs preacher curls: Strength gains
Since preacher curls are compatible with barbells, they naturally enable you to lift heavier weights than incline curls. This, in turn, lets you overload your biceps with more resistance and potentially achieve faster rates of both strength development and muscle growth. 
However, as we established, preacher curls are easier than incline curls because they don't maximally challenge your biceps throughout the entire repetition. Instead, preacher curls pose the most challenge in the first phase of the concentric portion of the rep (near elbow extension).
Based on this line of reasoning, you could argue that preacher curls are worse than incline curls for strength gain because the biomechanics of the exercise puts less tension on your biceps despite enabling you to lift heavier weights.
Related Exercise: Kettlebell incline curls
Is it necessary to do both exercises?
You can build muscle without doing both exercises. However, by working your biceps from a variety of angles, you'll naturally recruit a broader range of muscle fibers and stimulate greater hypertrophy.
Still, you don't necessarily have to do these two exercises. Preacher curls and incline curls make good choices because they each emphasize different regions of the biceps.
But you can also click the link to learn the difference between hammer curls and preacher curls if you want to work on your other arm muscles like the brachialis and brachioradialis.
Which movement should you perform first in the workout?
Since incline curls are more challenging than preacher curls, it makes sense to start with them. However, if you're focusing on gaining strength by training with barbells, then beginning your workout with preacher curls also makes good sense.
Essentially, whichever exercise you deem most important to achieving your goals is the one that you should do first. For me, that's incline curls because they force the biceps to work harder.
If you're short on equipment or train at home, then you can see our guide to performing preacher curls without a bench.
Preacher curl vs incline curl: The verdict
As you discovered, you don't have to choose either the preacher or incline curl; you can do both. However, if you don't have the time or desire to perform two different exercises, then doing incline curls is your best bet.
Unlike preacher curls, incline curls emphasize the biceps long head, which is an area that many lifters need to improve and which can build an impressive bicep peak when well developed.
Incline curls also provide more consistent muscle tension by challenging your biceps throughout the entire range of motion.
I hope that you enjoyed our incline curls vs preacher curls comparison. Both exercises have their place in a weight lifting routine, but if you can only do one, then I recommend making incline curls your primary movement.
- Oliveira, L. F., Matta, T. T., Alves, D. S., Garcia, M. A. C., & Vieira, T. M. M. (2009). Effect of the shoulder position on the biceps brachii emg in different dumbbell curls. Journal of Sports Science and Medicine, 8(1), 24–29. https://pubmed.ncbi.nlm.nih.gov/24150552/
- Suchomel, T. J., Nimphius, S., Bellon, C. R., & Stone, M. H. (2018). The Importance of Muscular Strength: Training Considerations. Sports Medicine, 48(4), 765–785. https://doi.org/10.1007/s40279-018-0862-z