Think Barbell Curls Build the Biggest Arms? MRI Scans Show These 3 Moves Trigger More Growth

If bigger biceps are a goal you’re after, traditional barbell curls may not necessarily be the best bang for your buck exercise. While a go-to staple in most arm workouts, traditional curls fail to provide much resistance at the bottom of the movement when the elbows are extended, and elbow flexors are in a lengthened position. And to get the most out of your bicep-building efforts, you also must program exercises that challenge the muscles at longer lengths, according to Menno Henselmans, a personal trainer and exercise scientist.

One 12-week study, published in the Journal of Sports Sciences, compared preacher curls and incline dumbbell curls. Participants trained one arm with preacher curls and the other with incline curls, and MRI scans revealed that preacher curls led to greater growth in the brachialis and brachioradialis. Comparatively, incline curls produced greater gains in the biceps brachii. While overall arm growth was similar between the two, each exercise helped develop different muscles.

For that reason, incorporating multiple curl variations into your training is the best approach. Henselmans considers preacher curls, incline dumbbell curls, and Bayesian curls to be the “holy trinity” of biceps growth, as each challenges the elbow flexors in a slightly different way. Learn how to do each below.

Related: An Exercise Scientist Claims You Only Need 30 Minutes a Week to Build Muscle. Try His 6-Move Upper Body Plan

Best Bicep Curl Variations, According to MRI Scans

How to Do Preacher Curls

1. Sit at a preacher curl bench and position the backs of your upper arms flat against the angled pad, holding an EZ bar or dumbbells with an underhand grip.

2. Start with your arms extended toward the floor, keeping a slight bend in your elbows.

3. Curl the weight toward your shoulders by bending your elbows, keeping your upper arms pressed against the pad throughout the movement.

4. Squeeze your biceps at the top, then slowly lower the weight until your arms are nearly fully extended.

How to Do Incline Dumbbell Curls

1. Sit on an incline bench set to roughly a 45- to 60-degree angle, holding a dumbbell in each hand with your arms hanging straight down.

2. Keep your back against the bench, palms facing forward, and shoulders relaxed.

3. Keeping your upper arms stationary, curl both dumbbells toward your shoulders by bending your elbows.

4. Squeeze your biceps at the top, then slowly lower the dumbbells until your arms are fully extended.

How to Do Bayesian Curls

1. Attach a single handle to a low cable pulley and stand facing away from the machine, holding the handle in one hand.

2. Step forward until your working arm is slightly behind your torso, allowing the cable to create tension through the biceps.

3. Keeping your upper arm stationary and elbow behind your body, curl the handle toward your shoulder.

4. Squeeze your biceps at the top, then slowly extend your arm back to the starting position, maintaining tension throughout the movement.

Related: Chris Bumstead Reveals the Back Workout That Won Him 6 Olympias Without Doing a Single Deadlift

Sources

• Menno Henselmans, personal trainer, via YouTube: The Best Curl for Bigger Arms According to MRI Scans

• Exercise-specific preferential hypertrophy of individual elbow flexor muscles after incline versus preacher dumbbell curl training. Journal of Sports Sciences, 2026

This story was originally published by Men’s Journal on Nov 9, 2026, where it first appeared in the Fitness section. Add Men’s Journal as a Preferred Source by clicking here.