Key takeaways: Incline vs Preacher Curls: What a New MRI Study Found
- When comparing incline vs preacher curls, incline curls favored biceps growth: 22.1% versus 18.9% with preacher curls.
- Preacher curls favored brachialis and brachioradialis growth, but the study did not assess all forearm muscles.
- Total elbow flexor growth showed no statistically significant difference. This does not establish that the exercises are equivalent.
Incline vs Preacher Curls: What Grew More?
Most lifters assume every curl variation stimulates the arm flexors identically. However, earlier studies on incline vs preacher curls evaluated muscle thickness at only a few sites or tested short occlusion protocols (da Silva Vendruscolo et al., 2024; Kassiano et al., 2025; Zabaleta-Korta et al., 2023). Consequently, those localized measurements could not capture changes across full three-dimensional muscle volume (Balshaw et al., 2026).. In a 2026 study in the Journal of Sports Sciences, Kobayashi and colleagues compared the two dumbbell curls and tracked muscle growth over 12 weeks (Kobayashi et al., 2026).
What the study found about incline vs preacher curls
The study included 21 adults who had not been doing regular strength training. Each person trained one arm with incline curls and the other with preacher curls. They trained twice a week for 12 weeks.
The researchers used MRI scans to measure the size of three muscles that help bend the elbow: the biceps, the brachialis, and the brachioradialis.
| Muscle measured | Incline curl growth | Preacher curl growth | Which showed more growth? |
|---|---|---|---|
| Biceps | 22.1% | 18.9% | Incline curl |
| Brachialis | 17.1% | 21.1% | Preacher curl |
| Brachioradialis | 13.5% | 17.6% | Preacher curl |
| All three muscles combined | 17.6% | 19.2% | No clear difference |
In short, the incline curl led to slightly more biceps growth. However, the preacher curl led to more growth in the other two muscles. When the researchers added the three muscles together, they did not find a clear difference between the exercises (Kobayashi et al., 2026).
How the tested curls were done
For the incline curl, the shoulder sat behind the body. For the preacher curl, the upper arm rested in front of the body on a support. In both curls, participants turned their palms up and bent and straightened the elbow.
That matters because the study tested these specific setups—not every version of an incline or preacher curl. It also did not test a workout that combined both curls.
What lifters can take from incline vs preacher curls
Both curls helped grow the muscles measured in the study. If you want to focus on the biceps, the incline curl may have a small edge. If you want to focus on the brachialis or brachioradialis, the preacher curl may be a useful choice.
Still, this was a small study of adults who were new to regular strength training. The results may not apply in the same way to experienced lifters. Also, the study did not test whether doing both curls in one program leads to more growth.
The main takeaway: incline and preacher curls both grew the elbow-bending muscles, but the pattern of growth differed. This study does not show that one curl is best for everyone.
Study Limitations to Consider
While this investigation utilized gold-standard MRI imaging, several limitations warrant careful consideration:
- Untrained Participants: The subjects were recreationally active young adults without prior resistance training experience. Well-trained bodybuilders might experience smaller absolute percentage gains.
- Combined Biceps Heads: The MRI protocol assessed total biceps brachii volume rather than isolating the long head from the short head.
- Absence of Failure: Sets were terminated strictly at 10 repetitions rather than taken to absolute muscular failure, though loading was progressively updated across the 12 weeks.
FAQs
Which is better for biceps in incline vs preacher curls?
Incline dumbbell curls produced greater whole-biceps growth in this study: +22.1% versus +18.9% with preacher curls (Kobayashi et al., 2026). However, the difference was modest, and both exercises stimulated substantial biceps hypertrophy.
Did preacher curls build more forearm muscle?
Preacher dumbbell curls produced greater growth in the brachioradialis (+17.6% vs. +13.5%). However, researchers did not measure other forearm muscles, so this finding applies specifically to the brachioradialis rather than the entire forearm.
Did either exercise produce more total arm growth?
Total measured elbow flexor volume showed no statistically significant difference between incline and preacher curls (+17.6% vs. +19.2%, p = 0.134). Both movements proved effective for overall mass.
Should you combine incline and preacher curls in the same routine?
Combining both movements is a practical strategy to target all three elbow flexors, but this study tested each arm separately and did not evaluate a combined training routine.
What bench angle was used for incline curls?
The study positioned the shoulder at approximately 50° of extension relative to the torso, which does not directly correspond to a specific bench angle setting.
Reference
- Balshaw, T. G., Funnell, M. P., McDermott, E. J., Maden-Wilkinson, T. M., James, L. J., & Folland, J. P. (2026). Ultrasound muscle thickness is a poor index of criterion magnetic resonance imaging measures of resistance training-induced muscle growth. Medicine & Science in Sports & Exercise. https://doi.org/10.1249/MSS.00004078
- da Silva Vendruscolo, L., Brendon, H., Hevia-Larrain, V., Aihara, A. Y., & de Salles Painelli, V. (2024). Similar regional hypertrophy of the elbow flexor muscles in response to low-load training with vascular occlusion at short versus long muscle lengths. Sports Health: A Multidisciplinary Approach, 17(5), 1036–1043. https://doi.org/10.1177/19417381241287522
- Kassiano, W., Costa, B., Kunevalki, G., Lisboa, F., Stavinski, N., Prado, A., Tricoli, I., Francsuel, J., Lima, L., Nunes, J., Ribeiro, A. S., & Cyrino, E. S. (2025). Distinct muscle growth and strength adaptations after preacher and incline biceps curls. International Journal of Sports Medicine, 46(5), 334–343. https://doi.org/10.1055/a-2517-0509
- Kobayashi, Y., Maeo, S., Eihara, Y., Ono, M., Sato, M., Sugiyama, T., Kanehisa, H., & Isaka, T. (2026). Exercise-specific preferential hypertrophy of individual elbow flexor muscles after incline versus preacher dumbbell curl training. Journal of Sports Sciences. Advance online publication. https://doi.org/10.1080/02640414.2026.2741751
- Zabaleta-Korta, A., Fernández-Peña, E., Torres-Unda, J., Francés, M., Zubillaga, A., & Santos-Concejero, J. (2023). Regional hypertrophy: The effect of exercises at long and short muscle lengths in recreationally trained women. Journal of Human Kinetics, 87, 259–270. https://doi.org/10.5114/jhk/163561
