Bicep curl
Dumbbell preacher curl
Works
Also works
Equipment
Unilateral (one side at a time)
How to do it
- Sit at the preacher bench, resting the back of your arm on the pad.
- Hold a dumbbell in one hand with your arm supported and palm facing up.
- Bend your elbow, bringing the dumbbell to your shoulder as you contract the biceps.
- Squeeze the biceps at the top without lifting your arm off the pad.
- Lower the dumbbell under control until your elbow is nearly extended.
Common mistakes
- Lifting the arm off the pad to assist
- Snapping the elbow into extension at the bottom, risking injury
- Using torso momentum
What the evidence says
Where you place the range matters more than how much range you use: with the same 50° range, training with the elbow extended (0°-50°) increased muscle thickness 8.9% versus 3.4% training with the elbow flexed (80°-130°), in untrained people.
Sato S, Yoshida R, Kiyono R, Yahata K, Yasaka K, Nunes JP, Nosaka K, Nakamura M. «Elbow Joint Angles in Elbow Flexor Unilateral Resistance Exercise Training Determine Its Effects on Muscle Strength and Thickness of Trained and Non-trained Arms». Frontiers in Physiology, 2021;12:734509. View the study
Preacher and incline curls don't compete, they split the arm: after 8 weeks in 63 women, the incline curl grew the proximal portion of the elbow flexors more, and the preacher curl grew the distal portion more.
Kassiano W, Costa B, Kunevaliki G, et al. «Distinct Muscle Growth and Strength Adaptations After Preacher and Incline Biceps Curls». International Journal of Sports Medicine, 2025;46(5):334-343. View the study
You don't need to squeeze all the way at the top: in 30 trained individuals, 8 weeks of partial repetitions in the lengthened half of the range produced muscle thickness increases similar to full range of motion.
Wolf M, Androulakis Korakakis P, Piñero A, et al. «Lengthened partial repetitions elicit similar muscular adaptations as full range of motion repetitions during resistance training in trained individuals». PeerJ, 2025;13:e18904. View the study
What isn't settled: "Taking the elbow behind you stretches the biceps more and grows it more" doesn't hold up: two trials that matched resistance profiles — preacher versus shoulder-extended cable curl, and cable curl at peak shoulder extension versus neutral — found no differences in total growth. Shoulder position seems to shift where the muscle grows, not how much. And for concentration, spider and Zottman curls there is no hypertrophy study at all: everything said about them is extrapolation.
Other variations
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