Preacher Curls vs Bayesian Cable Curls: Which Loads the Biceps Better?

If you want one answer to the preacher curl vs bayesian curl debate: both grow the biceps, and the best head-to-head trial found no significant difference between them. The Bayesian curl keeps the cable pulling through the whole rep, while the preacher curl is hardest in the stretch and eases off near the top. That is a real mechanical difference, but so far it has not translated into clearly different muscle growth.

This article sits under our guide to range of motion and stretch-mediated hypertrophy. Here we do the narrow face-off. For single-exercise deep dives, see Bayesian cable curls and preacher curls for the distal biceps.

What is the difference between a preacher curl and a Bayesian curl?

Both exercises are elbow flexion. What changes is where your shoulder is and how the resistance pulls on the arm.

Preacher curl. Your upper arm rests on a pad in front of you, so the shoulder is flexed (arm pointing forward). This blocks swinging and keeps the biceps working on a fixed arm position.

Bayesian cable curl. You stand facing away from a low pulley and hold the handle behind you with the shoulder slightly extended (arm behind the torso). The cable pulls you backward, so your biceps have to resist from a lengthened position and keep pulling throughout.

Shoulder position matters because the biceps brachii crosses both the shoulder and the elbow. Moving the shoulder changes how stretched the long head is at the start of the curl. We cover that angle in long head vs short head biceps and shoulder position.

What does the resistance curve look like?

Resistance on the elbow is not the weight itself. It is the weight multiplied by how far the line of pull sits from the elbow joint (the lever arm). When the forearm is horizontal, that lever arm is longest. When the forearm is vertical, it shrinks.

On a free-weight preacher curl, the load usually feels heaviest in the stretched half of the range and fades toward the top, where the forearm is nearly vertical. One trial describes the barbell preacher curl as applying greater torque when the elbows are extended and the biceps are stretched (Nunes et al., 2020). Exactly where the peak lands depends on the bench angle and your grip position, so treat the common “peak at 90 degrees” line as a rough rule of thumb.

A cable that pulls from behind you changes the direction of the load as you curl, which tends to keep resistance more even across the range. That is the logic behind the “constant tension” label.

What does the research say about preacher vs Bayesian curls?

There is one direct trial, and it is small, so read it as a first data point rather than a verdict.

The head-to-head trial (2025). Fifteen young men trained for 10 weeks, twice a week, doing 3-5 sets of 8-12 reps. One arm did a unilateral cable curl with the shoulder flexed (preacher), the other did a cable curl with the shoulder extended (Bayesian). The researchers deliberately matched the resistance profiles. Both arms gained muscle thickness across the biceps proximal, mid and distal regions, and in the brachialis, with no significant differences between them. Biceps thickness rose about 6-7% on the preacher arm and about 9% on the Bayesian arm. Strength rose about 28% versus 37% (Attarieh et al., 2025). The authors concluded that shoulder angle did not seem to affect hypertrophy or strength gains when resistance profiles are matched.

Two caveats matter. First, both exercises were cable-based, so this trial does not tell you whether a dumbbell preacher curl differs from a Bayesian curl. Second, the sample was 15 young men, so we do not know how well the result carries over to women, older lifters or very advanced trainees.

Where in the range to load the biceps. Other trials looked at the lengthened side directly:

• Cable preacher versus barbell preacher in 35 young adults (10 weeks): strength rose in both, with greater gains for the barbell version only at the longer muscle length, and biceps thickness grew similarly (7% vs 8%) (Nunes et al., 2020).
• Dumbbell preacher curls trained in the initial range (extended elbow) versus the final range in 19 young women: the initial range produced greater growth at 70% of biceps length (distal), similar growth at 50%, and a larger 1RM gain (Pedrosa et al., 2023).
• Incline versus preacher curls in 38 women (9 weeks): only the preacher group’s distal region grew significantly, but there were no significant differences between groups or regions (Zabaleta-Korta et al., 2023).
• Incline versus preacher dumbbell curls in 21 untrained adults, measured with MRI over 12 weeks: biceps growth was greater after incline (+22.1% vs +18.9%), brachialis and brachioradialis grew more after preacher, and total elbow flexor growth did not differ (Kobayashi et al., 2026).

Why do these results not line up neatly? The studies used different exercises, ranges, sexes, training backgrounds and measurement methods (ultrasound versus MRI). Some are tiny, and several used untrained people, who tend to grow from almost any reasonable program. A 2020 systematic review of range of motion studies concluded that research on the upper limbs is limited and conflicting (Schoenfeld and Grgic, 2020).

The practical read: the stretched half of the curl may matter for the distal biceps, the exact exercise probably matters less, and no trial has shown a clear winner. For the incline comparison, see our dedicated piece on incline curls vs preacher curls.

Preacher vs Bayesian curl at a glance

	Preacher curl	Bayesian cable curl
Shoulder position	Flexed (arm forward on pad)	Extended (arm behind torso)
Where it feels hardest	Stretched half, fades near the top	Fairly even, with the stretch under load
Biceps long head stretch	Less	More
Equipment	Preacher bench plus dumbbell, EZ bar or cable	Single cable pulley, low
Cheating risk	Low, the pad blocks swing	Low if you stay still, but the cable can pull you out of position
Best for	Strict, simple stretched-range work	Keeping tension all the way up

How do I program both without hurting my elbows?

The stretched start of both curls puts load on the biceps and its tendon in a long position, so ease into them.

1. Start light. Use a weight you can control for 10-12 reps with a 2-3 second lowering phase. Add load slowly over weeks.
2. Control the bottom. Do not drop into the stretch or bounce out of it. A fast, uncontrolled bottom puts a sudden load on the biceps tendon in its longest position.
3. Use a comfortable range. Stop short of full lockout if the elbow or inner biceps complains. A slightly shorter range you can repeat beats a deep one that irritates you.
4. Rotate them. A sensible week might use preacher curls in one arm session and Bayesian curls in the other, rather than stacking both in one workout.
5. Count the volume. Many lifters do well on roughly 6-12 hard biceps sets a week including rows and pulldowns, though response varies. Our training volume calculator helps you keep track, and direct vs indirect arm volume shows how rows count.
6. Mind effort. Finish most sets with about 1-3 reps left, and save the hardest set for the end. The RIR and RPE calculator can help you gauge it.

Which should you pick?

• Beginner or gym with no cables: dumbbell preacher curls. Strict, simple and well supported by the trials above.
• Intermediate wanting more stretch and constant pull: add the Bayesian curl on one session a week.
• Elbow or shoulder cranky: pick the version that causes no pain and use a shorter range. If neither works, drop curls for a couple of weeks and use rows and pulldowns as your biceps work.
• Plenty of equipment: alternate them across the week. Variety costs nothing, and the trial data do not show one as clearly better.

When should you see a doctor?

Soreness in the biceps after new exercises is normal. These signs are not, and deserve a medical assessment:

• Pain at the front of the elbow or inner biceps that persists or worsens over a couple of weeks
• A sudden pop or sharp pain in the arm during a curl, especially with bruising or a change in the shape of the biceps
• Numbness, tingling or weakness in the arm or hand

If elbow pain is already a pattern, read our guide to distal biceps tendonitis and golfer’s elbow. This article is not a diagnosis, and a physio or doctor can examine the arm in person.

The bottom line

The Bayesian curl is a clever way to keep a cable pulling on the biceps through the whole rep, and the preacher curl is a strict way to load the stretched half. The one trial that compared them while matching the resistance profile found similar growth. Use both if you like variety, pick one if you do not, and spend your effort on progressive overload, enough weekly sets and pain-free technique. For the bigger picture, pair your arm work with our free push, pull and legs plans.